Been using tube amps for 25 yrs and never truly understood how they work just loved the sound. Your series on tubes is second to none! Thank you so much for posting this and sharing your knowledge, it is appreciated. Looking forward to more.
I have a mk2 deville ( made in mexico) I fitted a fromel supreme kit ,and changed all the valve sockets to gold ceramic .I usually set the bias a 68 mv ,I also recently changed the first ax12 to a at12 ,this has made the volume much more controllable
Rob, was looking for a simple video for biasing a Vibrolux and came upon this one. Since I purchase tubes like I'm sure many below from you all, I was happy to find this video. Very well presented, clear to understand and a great help for dummies like myself. Thank you.
Excellent instruction. Just got a HRDV 410 and walked through the steps. Fantastic result. Beautiful cleans for days and very silent even with single coils. Thanks very much.
G'day Rob, I hope you've been well in this time of crisis. I'm 11 years or more late on this, but I guess it's better late than never. Amongst most of the Biasing for the Hot Rod Deluxe I've seen, I decided to follow yours because it is the most clear (visually plus the audio & explanations) I've just done my Hot Rod today .. with 101% confidence thanks to you. Just one thing which I thought is super important, for those non-techo's like me. .... that's the detailed settings of the multimeter. I had to go over your video a few times to be sure. Where you set the multimeter to "Volts" to take the reading of the plate behind the Bias adjust knob, but mentioned very little about changing the multimeter to mV when setting the actual Bias while at the same time looking at the mV readings. I was lucky I saw the different settings showing on the video for your multimeter and so followed. In my case every detail of the procedure is important. Hope this will help you help us (non-techos) for future video releases. Stay well and all the best. ru
Great video! Very helpful and informative. I've had my Deville for probably 10 years and I was never 100% happy with the gain/overdrive channel. It sounded.......raspy.....not smooth at all. I installed a Fromel kit, which made things better....but still....something wasn't quite right. I had the amp serviced/biased/etc. Again.....better, but not quite 'there'. So I found your video and did as you suggested. The bias was set at 58-59, and the blue trimmer was epoxied in place. I powered-off and carefully trimmed the epoxy. I set the bias to 68 (the alleged 'sweet spot'), let it warm-up and took it for a spin. Much better! I was more satisfied with the gain....definitely an improvement. I also thought the clean channel had improved as well.....I could hear a difference. I kicked the bias up to 70 and I'm happy with it. Looking forward to next band rehearsal.
Hi! great tutorial! I have a question, I have a old hot rod deluxe made in USA and I would like to know what are the valves you recomend me. I would like to change all of them. Thanks from Spain!
hey, yes, all the solder connections are fine. I just thought it was strange that i couldn't get it under 73mV but i made a call to the store and they said it's perfectly normal. They offered me to return them in if i wanted, so they could give me another pairbut as you said 73mV is a nice value. Great vid by the way! nicely explained for electronica noobs (like me)
Thanks dude, great video, very well spoken and nicely put together! I'm just about to change the tubes on my Blues Deville and I hope I goes as smoothly as your video!
Good. Point taken. I just bought a fender hotrod deville that had a very loud microphonic howl, seemed to be the first valve in line of the 3 small ones, was going to buy a complete new set, but then I just swapped the first to around absolutely perfect now. A good hint to try first.
Very Good Explanation! Glad you mentioned safety. Too bad for the Test Point - the PCB should have a Tip Probe socket for holding the DMM's probe. To minimize the chance of getting an electrical shock (although not UL approved/tested) I wear the Black thicker Mechanics "Nitrile Gloves". Love 6L6 amps like the Deville (I have a Peavey ValveKing 2x 6L6). A dab of Nail Polish or RTV/Silicone keeps the pot from moving after being set.
Very informative and to the point. Thanks for sharing.. Mighty fine guitar playing as well. That's how my amp used to sound. I repaired a cracked solder joint at the "foot switch" connector, but now I find there's something not right with the far right, small(pre-amp) tube. A friend tested my tubes by removing them, then stuck new tubes in thew sockets(1 by 1). That's when I noticed he wasn't quite somber enough to be doing this test. He either bent the pins and/or caused damage at the connection. I realized this when it popped and cut in and out as I barely wiggled the the tube. Are the tube pins worth messing with till they fit again(If that's the only damage) or should I just replace them with new tubes?
At 1:23 you say to not touch anything without first discharging the amp. How is this done? Will simply turning it off and unplugging your amp discharge it after a period of time?
Mike Lowrey Well, probably, after a month.. I'm tempted to say "if you have to ask, don't do it." - Not to be snarky, but because it's actually dangerous. A power resistor is used to discharge the power supply filter caps. There's a lot of videos about it. If in doubt, take it to your tech.
I made a wand out of a cheap screwdriver, alligator clip and a 1k resistor. Alligator clip lead is soldered to the resistor, resistor to the Clip the alligator clip to the chassis, touch the end of the screwdriver to the positive end of one of the filter caps. That will usually discharge most caps in less than 10 seconds. They will discharge after turning the amp off while the cathodes are still hot enough to emit electrons. But don’t rely on that alone before sticking your hands in there. Plus, it only works if the tubes are installed, if you’re testing something with the tubes pulled, those caps will hold a charge for quite a while.
Great video, well done! I own a HotRodDeluxe and this thing is always frying tubes. I took it to a tech who claimed to have biased it correctly but two days later at a gig I only had one 6L6 working, glowing extremely bright amber, distorted badly on the clean channel (I only use the clean channel) until it died all together. This was back in '05. I have a tech friend install new tubes 'bout a year ago and bias it, and it distorted again. I bought new tubes and I'll use your vid to DIY. Thx
Hi Rob, Tube Depot, Just a little FYI, the ribbon connectors on the Deville can come loose and this will cause issues with the amp and performance of. El Paso Tube amps on RUclips did a video about this problem, worth a view. Discharge filter caps first when working on amps, use only one hand when hooking up meter. Also see Uncle Doug on YT, very knowledgeable. Take care, C.
Thanks Rob for the info. Can you suggest what practical brand of KT88 tube good for this dyna mk3 in terms of quality but not much expensive like the three choices below from your TubeDepot: 1. Sovtek 2. Electro-Harmonix 3. JJ/Tesla so what about these 3 NOS respective cathode currents then? Is 70mA still safe or they are just between 45mA - 60mA?
Hi, fantastic video! I have this same amp and at now I know do the bias adjustment in my HRD 2x12". But I would like to know which is the plate voltage of this HRD for calculate the 100% of bias value and 70% also. I thing this value varies from each same amp and I would like to know how measure this value. Please, if it's possible to you, make a video explaining how to measure the HRD 2x12" plate voltage value!!! Thanks
thanks, I also tapped the reverb tank and could hear the springs through the speakers so thats working ok, it was bad timing too cause my Wampler tweed 57 pedal had just came in the mail and I was itching to try er out. Still in Awe over how many tools and tube accessories you have on the tubedepot store, wouldnt mind getting one of the 18 Watt british amp Kit sometime in the future.
Yeah, that makes some sense. After I watched your vid, I perused other utube biasing vids, and all the techs were touching the tubes and viewers were commenting the same thing I said to you (I guess I'm not as alone as I thought in my old thinking). It would be so cool if you could demystify this old wives tale by doing an unbiased test (no pun intended) using two sets of matched power tubes, one totally filthy, and one spotless.
got the new JJs in the mail today and checked em out by swapping one position at a time, swapped V3 nothing put the original in. tried V2 still nothing, tried V1 which I suspected and got a low volume fuzzy tone even on 12, so I put another one of the JJs in the V2 position and she jumped back to life with even more tone, put the last new one in just to complete the set and i figure ill hang on to the one good one for emergencies till i get a few spares, Thanks again for your help
Awesome video, just what I was looking for. Recently picked up one of these babies used. It played fine for a day or so then started doing some heavy volume fluctuating. The jewel light also fluctuated but not always in synch with the volume trouble. I popped the back off and checked the connections as Rob did in the video and they looked solid. It's my first tube amp and don't want to assume anything. Would a good first step be to pick up some new power tubes and pop them in?
I so wanted to be a guitar god ... but sadly my playing has always been well below the "god" rating. Therefore, I had to find a real job ... enter electronics tech.
I bought my DeVille 2/12 in 1996 and I've never adjusted the bias level... the original Fender tubes burnt out in 1998 and I replaced them with a set of tubes from a guy I found in the Nickel Ads in Portland Or. They've never gone bad and still work to this day! I'd be interested to see what the bias level is set to?
Hi Fantastic video I plan to change my tubes watching this video as I have a hot rod deville. Last time I played the sound was getting fuzzy and losing power. Do you suggest any different tubes to the ones originally in the deville? another question. How do I know if the pre amp tubes need changing also? Im I correct in saying you changed the power tubes only in this video? is it the same method for pre amp tubes? Thanks. sorry for long message Cheers
Nik, installing EL34 tubes in the Hot Rod DeVille would require modifying the amp. If you want a close EL34 sound, I recommend trying the JJ 6L6 as these have a very compressed, low vacuum sound ... very similar to an EL34.
Shoes EL34's draw more current which means they need a sturdier OT (more ma headroom in the output transformer) and higher screen resistor values, and sometimes also different bias resistors depending on if they can be biased with the trim pot (if the value is in the range of the pot). Sometimes you can get away with just swapping them but common screen resistors for 6L6 is 470ohm resistor and EL34's for better with 1K or 1.5K resistors. You can see in this video that even at max range, this bias pot didn't have much throw and would be hard to run EL34's in.
Shoes Both the power transformer and output transformer would have to be replaced to put EL34's in this amp, along with changing the screen grid resistors as well as changing some of the wiring on the tube sockets, which isn't very easy since their PCBs.
+Alva Goldbook one of my tube amps (and only one out the 30+ I own) a Carvin MTS 3212 has a switch to select between using EL-34 or 6L6GC tubes. it says in the owners manual that it has different taps on the transformers and different resistors and different heater loads. Either way the amp has some great tones. This amp also has a switch that literally shuts off two of the power tubes to drop from 100w to 50w. but that's another story. you will almost certainly damage the amp if you use the EL-34 instead of the 6L6 where specified, but what would happen if you use a 6v6, the JJ seams to have very similar specs, . Could I get my Blues Deville 410 to break up at much more usable volumes? Just wondering?
Mitchel Young Yes, you can use 6V6s as a drop in replacement for 6L6s in a Fender Blues Deville, but you would have to rebias the amp. It may even require a modification of the bias supply circuit. I've heard of many people doing this with these amps, but do NOT use some vintage NOS 6v6 tubes, as they would most certainly get fried, and possibly damage your amp. Rather, you should stick with the more sturdy modern production JJ 6v6s which are designed to handle such abuse. Another way to tame the volume of the amp is to use an attenduator. Those can be pricey. One trick that worked pretty well for me was plugging into the 2nd input jack and removing 2 of the 10 inch speakers from the amp. I'm thinking I might just put a new baffle in my Hot Rod Deville 410 and replace it with 2 12 inch speakers. The fewer the speakers, the less the volume. You'd be surprised by just how effective this little trick is. Just make sure you have your remaining speakers wired up correctly.
Hey Rob I really appreciated the video as I just bought a Blues Deluxe and it looks like the tubes are in same configuration. I have a lot of noise coming from the middle 12AX7, do I need to bias them as well as the 5U's if so is there are similar reference point and and adjustable potentiometer for the other side? Really appreciate the video, going to save me some money. Oh yah the noise goes away when I put pressure on the tube so maybe a quick solder is all that's needed.
Brilliant vid and pickin ! The lad just picked up a HR Deluxe ii ....fantastic sound except the power tubes are noisy on some low notes. Gonna try some damper rings but if that doesn't work then may be putting your instructions to use soon with a pair of new tubes.
Hi Rob, I have the same amp as enrique , a 1980 Fender Twin Reverb 135 for which I just bought a whole new set of matched tubes, preamp and power tubes (SED Winged C 6L6) ,(a replacement package expressly for the Twin from tubestore),Do I have to proceed necessarily with changing the resistor since I have not a technician ready at hand in the short period? Or can I go on without particular problems in terms of sound or amp efficiency and postpone the replacement. Thanks
@TubeDepotTV i knew it was a legacy because of the bridge and the tremolo arm.... they´re just the best guitars for me, i have the legacy special model, and also have a deville amp... awesome combination... excelent tutorial i am about to do this to my amp, greets!
this was very informative, cleared up a few things for me. cheers mate much appreciated p.s guitar playing at the end was killer, should upload a video with just you jammin
Nice vid, never had seen all this biasing thing ......Btw, I also have a Fender Deville with Sovtek tubes but one of the preamp's is microphonic so I'm thinking of buying new ones. Which preamp tubes would you recommend for this amp? Thanks
Good video, nice guitar playing ! I just replaced all the tubes on my brothers Deville, looking at the back of the amp, the left power tube looks like it never comes on, the amp still plays and seems strong. Could this be the solder connection you were talking about, or else what may be causing this ? Thanks !
Great vid just subscribed glad to find someone who can explain step by step for a D.I.Y. saved me money. I have the blues deluxe reissue is this similar process as well?
Hello Rob. I'm an owner of the Hot Rod Deluxe ( 12 inch speaker ) and the amp is the smaller brother of the Deville but looks prett much the same inside. I'm living in Holland so our current is 230V AC unlike the 110V in the states. Does that make any difference in biasing the power tubes? I read somewhere that you recommend 70mv for a Hot Rod Deluxe. Is this a safe value for my amp. I appreciate it that you took the time to explain this ! Thanks
Wow! You made it look easy. I have a question. I have a Hot Rod Deluxe. I put new JJ power tubes in and the started rattling shortly after. The guy at JJ said it's because I have a combo and the amp vibration is the cause. What do you think? Also what replacement tubes do you recommend? I play rock, blues, country.
Hi Rob, Like the video. Good solid and easy to follow. I have just changed to TAD 6L6 tubes and during biasing could not get less than 61mV at the bias test point (highest voltage pot would go was -60V, which gave me 61mV at the bias test point). I therefore backed off the pot voltage until I got 70mV as the bias voltage. Is there large tolerances between amps, or should they all be able to get 60mV without having the pot at max counterclockwise Regards, Allan
@TubeDepotTV Looks like one of the preamp tubes was a little loose! Thanks for all the help, do you guys ship to Canada and if so, can you ship via USPS?
@TubeDepotTV Thanks man. I just got JJ 6l6gc's and a tung sol 12ax7 for the V1 spot and two electro harmonix for the V2 and V3 preamps. Sounds great even without biasing it yet. Which leads me to my next question: I have an analog multimeter, any idea what setting it should be on? AC or DC? 500, 250, 50V?
Hello! I am new with tube amps and I am planning to buy one. The amp I am planning to buy also has 2 power tubes. Is this method you showed is alwasy the same? 1. Turn the tripmot full counterclockwise while in standby mode 2. Turn the amp on (switch it out of bypass) and set the voltage to the desired amount while touching the sowder spot of the powertube? What do you recommend when replacing with different tubes? Does the safe voltage remain the same? Thank for you reply in advence!
Thank you so much for your video mate! Can you please tell me why did you need to read negative voltage before you read positive also do you only bias when changing power amp tubes or also when changing preamp tubes! Many thanx
Nice demo! I have the same amp and it has been great aside from one issue. Is the volume knob on your amp extremely sensitive? There seems to just be a fraction of a degree between inaudible and glass-shattering loud with mine. Is there an easy way to either adjust this or perhaps replace some hardware to distribute and voltages a bit more evenly? Thanks!
when you said "there's a newer model", i suppose you were talking about the hotrod deville 3 ? as far as gettin new tubes, i'm gonna check out your catalogue see if there's any special custom sets for the 212 deville.. Thx once again for you answers and kindness.
Hi - the bias test point on my recently acquired (used) Hot Rod Deville 410 won't go past 30 mV even with the bias pot turned all the way clockwise. I have all the volumes down, power on and standby off, and 30 mV is the actual reading (I didn't divide by 2). I only have the tubes that came with the amp. Is there any explanation you can think of? Nice playing!
Hi, I have the same issue with my Hot Rod Deluxe. Not as low as your readings but the maximum reading I get is 59mV's. To get a setting so I'm not burning up my tubes I have to set it at 30mV's, which is about halfway. So far I haven't found out why my readings are a lot lower than Fender and others recommend.
I had a burned out 470 ohm resistor and probably bad power tubes. There are two 470 ohm resistors - one going to each power tube (I think coming off pin 3 - you can see the pin numbers if you look on the white plastic that the power tube plugs into, from inside where the ciruit boards are). I got some 1 watt 470 ohm resistors (xicon) from Mouser.com and replaced the tubes. Now I was able to bias my amp to 66mV. I found the answer to my own question in this article: www.maxxplay.us/img/hrdx/How%20to%20Bias%20&%20Biasing%20FAQ.pdf
Sal Alexander Thanks for the reply, much appreciated. I've changed my tubes, had same problem with previous pair also, so next step will be to check the resistors. Thanks again.
Sal Alexander - You likely have an amp issue. There is likely an open component or poor solder connection. A qualified amp tech needs to look at your amp.
Hey there thank you for your speedy response. so I seem to have found out the source of the issue, and I'd thought I'd share what I found. The speaker jack was plugged into the ext. speaker output on the chassis. someone must have plugged it back in incorrectly. does that sound like that would cause that kind of volume drop?
hi rob,,i checked the HTfuse looks ok.b4 all this happen about a month ago i noticed that the amp making a cracking & hissing sound when a i check the amp one of the tube is blinking..i wanted to know if the amp will still create sound even if one of the tube died? i just want to know b4 i buy a new pair of tube..thnks very mch ,,
@TubeDepotTV thanks a lot! I ended up settling at 70mV, messed with it back and for for a while and 70 just seemed to be a good middle ground where i got the best tone without killing my tubes
Question? Is it normal to hear a buzzing sound coming from the upper PCB board on the Fender 410 Deville? It sounds as though it might be coming from one of the large grey capacitors. Thank You, Matt
I have a Jet City JCA20H 20w 2xEL84 head. It doesn't have the nifty test point on the pcb. I saw a video here that showed how to bias it with a multimeter and I'd just like to verify the procedure before I make any adjustments. They suggest to check the plate voltage which is supposed to be around 350VDC (mine was 370VDC), then check the milliAmperes at each tube and plug those numbers into the following equation: 11.5watts x (600 / [PlateVDC]) = X [milliAmperes].
Great video! I noticed the volume level on my 212 has dropped a ton (I'll have it maxed and it's lower than bedroom level). Do you think this is a power tube issue? Is there a common way to test if thats the case?
Hi Rob! Thanks for the great manual for replacing the power tubes on the DeVille. I've the same amp (only difference: I've got the 4x10" version) and recently I replaced my 6L6 tubes. Now I've got a question: My other amp is a Fender Twin Reverb Reissue from 1992 and would ask you for a replacement manual for the power tubes there. Same as on the Deville? As far as I know the Twin has also a BIAS knob. What are the measure data for the BIAS there?
thank you for the great videos as always.Sir i have question,I have hammond 291AEX 240 euro power transformer,but the primary has two black wires not like us version ,in this case when i connect to champ 5F1push pull pot.do i have make sure which is hot and return or i can connect any of these two leads switch and fuse?any help really do appreciate.
Hi Rob! I follow your tips in my deville 2x12 and all ok.Now I wanna try with a pair of TAD Tubes 6V6GT-STR. Can you tell me the save level on test point for these tubes? Maybe a good video like this....This would be good!!...(Very people interested). Thank you!!
this one is very informative..i want 2 ask a question regarding my sound city sc30 amp..after i used the amp in a jam session i turn it on the next day but theres no sound coming out , there is a power & the tube is glowing ok but no sounds..i also check the speaker 7 its ok..do u think my tubes worn out alrady thats why thers no sounds or somthing else?dnt know much about tubes hope u can a help me...thanks very much..mike frm glasgow
Hi..thanks for the response..I checked my Blues deluxe and it did have a test point ..I went and bought a multimeter at the hardware store. The meter he sold me only had a 2000 milivolt setting..not a 200mV like shown in a lot of these videos..He told me that was ok and the meter would measure 0-2000 mV..Is that correct in your opinion?
hi again..the power tube,yes there is a sound coming out in the drive channel but its very very low i cant barely hear it not unless put my ear close enough to the speaker,i also found out that one of the 2 filament of one of the preamp tube is not glowing..my friend told me it might be the pre amp tube not the power tube because the volume will pass to the preamp section b4 power..is this true..thnk u very mch on ur advice i really appriciate it..
Is there any chance of salvaging a pulled PCB trace leading to the power tube socket? I'm fairly confident with soldering, and I have 18 gauge solid core wire I've used to replace bad traces in guitar pedals. I think my concern is long-term sustainability. It seems like once the solder mask is pulled, the copper trace continues to deteriorate pull off the board. I assume the only alternative would be a lot of work around hand wiring the traces off those finicky ribbon connectors.
Hi...I'm a layman so I need to ask a question...do these parameters (approx. 60mV) work for any brand of power tube? The original ones that came on my Hot Rod are two 6L6GC GT and I want to exchange it for two JJ 6L6GC. So the ideal parameter is still about 60mV? Thank you so much
i have a Hot Rod Deluxe. I picked it up used, and swapped out all the tubes today. 2 brand new mesa boogie 6l6 for power, and 2 groove tube 12ax7-r for the pre. Since it's used, and i don't have the manual, any advice about what to bias to? Close to 60 like the deville? Already gave the new tubes a quick test, sounds much better.
hi Tube Depot, i have a problem with my marshall TSL 122 combo, one day i turned on the amp to play and it has no sound, all channels working, all leds working, power tubes glowing (6l6GC), the only thing i noticed is that the preamp tubes are not glowing like before (less glowing), i dont know what could be the reason for no sound, can you help me?. THANKS.
hi rob,i need ur advice please help..i mistakenly plug the footswitch to the speaker output of my amp. both channel are not working anymore its just hum coming out from the speaker i dont know if i blown the tubes or i shorted something else..tnx..
I used this most excellent of all tutorial's in 2015 for biasing my new Fender Dot Rod Deville III 410. I deliberately set the Ma to only 57-59 Ma to prolong tube life. Now I have been wondering to my self if this is too cold and did I sacrifice tone. I can not get power tube break up at any volume and when it's at full volume I get that "ice pick" pain in my ears it's so loud. I think I shall re-bias to the 60 Ma and maybe change V1 to the 12AT7 which has 60% as much gain as the 12AX7 which has 100%. The available Pre Amp tubes have these gain factors: 12AX7 100% 5751 70% 12AXT7 60% 12AY7 45% 12AV7 41% 12AU7 19% Changing tubes is not difficult so I may even set the bias as high as 70 Ma or 80 Ma just as rob mentioned. If the amp then sounds warmer to my ears it will be worth the cost of purchasing new tubes sooner. After all I did not purchase the amp to save money but rather to enjoy the tone of a fine amplifier. He, he, as usual I outsmarted myself with the too cold re-bias from the factory settings of 60 Ma. Live and Learn! Thanks again Rob for your video, for re-biasing/bias of a Fender Deville it's the best one on You-Tube!
I've got a Blues Deville, the reissue and I think the newer version of that, so the inside looks pretty much the same as the Deville here. I can see the bias pot and test point in the same position. The only thing I can't figure out for sure is whether or not it has the same recommend bias of 60mV. Is it? Where do they hide this information in the specs, or can you derive it from something else?
I have a acquired a fender De Ville 410 and we used it while having a practice it sounded a bit distorted, and after an hour we had a rest and whilst we were sat down it did a few pops. Have you any idea what could cause this please.
Been using tube amps for 25 yrs and never truly understood how they work just loved the sound. Your series on tubes is second to none! Thank you so much for posting this and sharing your knowledge, it is appreciated. Looking forward to more.
Best explanation ever... Happened to be the first video I clicked on, what luck. You have just saved me hours of my life! Thanks for that!
I have a mk2 deville ( made in mexico) I fitted a fromel supreme kit ,and changed all the valve sockets to gold ceramic .I usually set the bias a 68 mv ,I also recently changed the first ax12 to a at12 ,this has made the volume much more controllable
This video was so helpful. Replaced the tubes in my Fender Blues Deluxe reissue. Worked great! Thank you!
Same test point on the blues deluxe? Service manual for deluxe is different.
MAds
Rob, was looking for a simple video for biasing a Vibrolux and came upon this one. Since I purchase tubes like I'm sure many below from you all, I was happy to find this video. Very well presented, clear to understand and a great help for dummies like myself. Thank you.
Excellent instruction. Just got a HRDV 410 and walked through the steps. Fantastic result. Beautiful cleans for days and very silent even with single coils. Thanks very much.
G'day Rob, I hope you've been well in this time of crisis. I'm 11 years or more late on this, but I guess it's better late than never. Amongst most of the Biasing for the Hot Rod Deluxe I've seen, I decided to follow yours because it is the most clear (visually plus the audio & explanations) I've just done my Hot Rod today .. with 101% confidence thanks to you. Just one thing which I thought is super important, for those non-techo's like me. .... that's the detailed settings of the multimeter. I had to go over your video a few times to be sure. Where you set the multimeter to "Volts" to take the reading of the plate behind the Bias adjust knob, but mentioned very little about changing the multimeter to mV when setting the actual Bias while at the same time looking at the mV readings. I was lucky I saw the different settings showing on the video for your multimeter and so followed. In my case every detail of the procedure is important. Hope this will help you help us (non-techos) for future video releases. Stay well and all the best.
ru
Great info and sick blues at the end. Love it
Great video! Very helpful and informative. I've had my Deville for probably 10 years and I was never 100% happy with the gain/overdrive channel. It sounded.......raspy.....not smooth at all.
I installed a Fromel kit, which made things better....but still....something wasn't quite right.
I had the amp serviced/biased/etc. Again.....better, but not quite 'there'.
So I found your video and did as you suggested. The bias was set at 58-59, and the blue trimmer was epoxied in place.
I powered-off and carefully trimmed the epoxy. I set the bias to 68 (the alleged 'sweet spot'), let it warm-up and took it for a spin.
Much better! I was more satisfied with the gain....definitely an improvement.
I also thought the clean channel had improved as well.....I could hear a difference.
I kicked the bias up to 70 and I'm happy with it. Looking forward to next band rehearsal.
Most excellent straight forward biasing video ever.
Hi! great tutorial! I have a question, I have a old hot rod deluxe made in USA and I would like to know what are the valves you recomend me. I would like to change all of them. Thanks from Spain!
Nice video man! Very informational and easy-to-follow 👍
Great video! Kudos for mentioning the connections.
Excellent video production and clear instruction, thank you!
Thanks for this awesome video! I just bought a deville and this video is a big help!
hey, yes, all the solder connections are fine. I just thought it was strange that i couldn't get it under 73mV but i made a call to the store and they said it's perfectly normal. They offered me to return them in if i wanted, so they could give me another pairbut as you said 73mV is a nice value. Great vid by the way! nicely explained for electronica noobs (like me)
Thanks so much for making this video. Great explanation and instructions.
Thanks dude, great video, very well spoken and nicely put together!
I'm just about to change the tubes on my Blues Deville and I hope I goes as smoothly as your video!
Good.
Point taken.
I just bought a fender hotrod deville that had a very loud microphonic howl, seemed to be the first valve in line of the 3 small ones, was going to buy a complete new set, but then I just swapped the first to around absolutely perfect now.
A good hint to try first.
Very Good Explanation! Glad you mentioned safety. Too bad for the Test Point - the PCB should have a Tip Probe socket for holding the DMM's probe. To minimize the chance of getting an electrical shock (although not UL approved/tested) I wear the Black thicker Mechanics "Nitrile Gloves". Love 6L6 amps like the Deville (I have a Peavey ValveKing 2x 6L6). A dab of Nail Polish or RTV/Silicone keeps the pot from moving after being set.
Hi. OK understood now, I'd got milliamps on my mind.
Got the right measurement now.
Thank you for all your help.
Brilliant.
wonderful presentation!!! breath of fresh air!!!!!!
Awesome. One of the best vids on youtube.
Very informative and to the point. Thanks for sharing.. Mighty fine guitar playing as well. That's how my amp used to sound. I repaired a cracked solder joint at the "foot switch" connector, but now I find there's something not right with the far right, small(pre-amp) tube. A friend tested my tubes by removing them, then stuck new tubes in thew sockets(1 by 1). That's when I noticed he wasn't quite somber enough to be doing this test. He either bent the pins and/or caused damage at the connection.
I realized this when it popped and cut in and out as I barely wiggled the the tube. Are the tube pins worth messing with till they fit again(If that's the only damage) or should I just replace them with new tubes?
I don't know much about amps,I'd rather watch your playing.I like it,U teach?
At 1:23 you say to not touch anything without first discharging the amp. How is this done? Will simply turning it off and unplugging your amp discharge it after a period of time?
Mike Lowrey Well, probably, after a month..
I'm tempted to say "if you have to ask, don't do it." - Not to be snarky, but because it's actually dangerous.
A power resistor is used to discharge the power supply filter caps.
There's a lot of videos about it.
If in doubt, take it to your tech.
I made a wand out of a cheap screwdriver, alligator clip and a 1k resistor. Alligator clip lead is soldered to the resistor, resistor to the Clip the alligator clip to the chassis, touch the end of the screwdriver to the positive end of one of the filter caps. That will usually discharge most caps in less than 10 seconds.
They will discharge after turning the amp off while the cathodes are still hot enough to emit electrons. But don’t rely on that alone before sticking your hands in there. Plus, it only works if the tubes are installed, if you’re testing something with the tubes pulled, those caps will hold a charge for quite a while.
That's some purty good playin at the end Rob!
Great video. Cool guitar playing too. I thought these amps had 2 speakers.
Great video, well done! I own a HotRodDeluxe and this thing is always frying tubes. I took it to a tech who claimed to have biased it correctly but two days later at a gig I only had one 6L6 working, glowing extremely bright amber, distorted badly on the clean channel (I only use the clean channel) until it died all together. This was back in '05. I have a tech friend install new tubes 'bout a year ago and bias it, and it distorted again. I bought new tubes and I'll use your vid to DIY. Thx
Hi Rob, Tube Depot, Just a little FYI, the ribbon connectors on the Deville can come loose and this will cause issues with the amp and performance of. El Paso Tube amps on RUclips did a video about this problem, worth a view. Discharge filter caps first when working on amps, use only one hand when hooking up meter. Also see Uncle Doug on YT, very knowledgeable. Take care, C.
excellent video and kudos for providing safety review . . . very important!
thank you for your wonderful comment.
Thanks Rob for the info.
Can you suggest what practical brand of KT88 tube good for this dyna mk3 in terms of quality but not much expensive like the three choices below from your TubeDepot:
1. Sovtek
2. Electro-Harmonix
3. JJ/Tesla
so what about these 3 NOS respective cathode currents then?
Is 70mA still safe or they are just between 45mA - 60mA?
thanks for the help I lowered my bias as low as it can go 30. now its playable beyond 1
Excellent instruction. Can this similar bias adjustment be done on the Fender 410 blues Deville reissue, 2005 model?
I just got onw for my son 👍, can you clean the tone pots when you remove the backing plate?
Hi, fantastic video! I have this same amp and at now I know do the bias adjustment in my HRD 2x12". But I would like to know which is the plate voltage of this HRD for calculate the 100% of bias value and 70% also. I thing this value varies from each same amp and I would like to know how measure this value. Please, if it's possible to you, make a video explaining how to measure the HRD 2x12" plate voltage value!!! Thanks
thanks, I also tapped the reverb tank and could hear the springs through the speakers so thats working ok, it was bad timing too cause my Wampler tweed 57 pedal had just came in the mail and I was itching to try er out. Still in Awe over how many tools and tube accessories you have on the tubedepot store, wouldnt mind getting one of the 18 Watt british amp Kit sometime in the future.
Holy shit thank God for this video!!! So well explained!!🙌🏻🙌🏻🙌🏻
Yeah, that makes some sense.
After I watched your vid, I perused other utube biasing vids, and all the techs were touching the tubes and viewers were commenting the same thing I said to you (I guess I'm not as alone as I thought in my old thinking). It would be so cool if you could demystify this old wives tale by doing an unbiased test (no pun intended) using two sets of matched power tubes, one totally filthy, and one spotless.
got the new JJs in the mail today and checked em out by swapping one position at a time, swapped V3 nothing put the original in. tried V2 still nothing, tried V1 which I suspected and got a low volume fuzzy tone even on 12, so I put another one of the JJs in the V2 position and she jumped back to life with even more tone, put the last new one in just to complete the set and i figure ill hang on to the one good one for emergencies till i get a few spares, Thanks again for your help
Hi Rob,
What's the correct Cathode current of "each" of the Dynaco MK3's KT88? is it 70mA?
TIA.
Awesome video, just what I was looking for. Recently picked up one of these babies used. It played fine for a day or so then started doing some heavy volume fluctuating. The jewel light also fluctuated but not always in synch with the volume trouble. I popped the back off and checked the connections as Rob did in the video and they looked solid. It's my first tube amp and don't want to assume anything. Would a good first step be to pick up some new power tubes and pop them in?
Very nice video and it's just not right that your top technician can play the guitar like that. Very impressive.
I so wanted to be a guitar god ... but sadly my playing has always been well below the "god" rating. Therefore, I had to find a real job ... enter electronics tech.
I bought my DeVille 2/12 in 1996 and I've never adjusted the bias level... the original Fender tubes burnt out in 1998 and I replaced them with a set of tubes from a guy I found in the Nickel Ads in Portland Or. They've never gone bad and still work to this day! I'd be interested to see what the bias level is set to?
Hi Fantastic video
I plan to change my tubes watching this video as I have a hot rod deville.
Last time I played the sound was getting fuzzy and losing power.
Do you suggest any different tubes to the ones originally in the deville?
another question. How do I know if the pre amp tubes need changing also?
Im I correct in saying you changed the power tubes only in this video?
is it the same method for pre amp tubes?
Thanks. sorry for long message
Cheers
Nik, installing EL34 tubes in the Hot Rod DeVille would require modifying the amp. If you want a close EL34 sound, I recommend trying the JJ 6L6 as these have a very compressed, low vacuum sound ... very similar to an EL34.
I would think that EL34s would merely require re-biasing. All octal-pin tubes use the same plug and socket.
Shoes EL34's draw more current which means they need a sturdier OT (more ma headroom in the output transformer) and higher screen resistor values, and sometimes also different bias resistors depending on if they can be biased with the trim pot (if the value is in the range of the pot). Sometimes you can get away with just swapping them but common screen resistors for 6L6 is 470ohm resistor and EL34's for better with 1K or 1.5K resistors. You can see in this video that even at max range, this bias pot didn't have much throw and would be hard to run EL34's in.
Shoes Both the power transformer and output transformer would have to be replaced to put EL34's in this amp, along with changing the screen grid resistors as well as changing some of the wiring on the tube sockets, which isn't very easy since their PCBs.
+Alva Goldbook one of my tube amps (and only one out the 30+ I own) a Carvin MTS 3212 has a switch to select between using EL-34 or 6L6GC tubes. it says in the owners manual that it has different taps on the transformers and different resistors and different heater loads. Either way the amp has some great tones. This amp also has a switch that literally shuts off two of the power tubes to drop from 100w to 50w. but that's another story. you will almost certainly damage the amp if you use the EL-34 instead of the 6L6 where specified, but what would happen if you use a 6v6, the JJ seams to have very similar specs, . Could I get my Blues Deville 410 to break up at much more usable volumes? Just wondering?
Mitchel Young Yes, you can use 6V6s as a drop in replacement for 6L6s in a Fender Blues Deville, but you would have to rebias the amp. It may even require a modification of the bias supply circuit. I've heard of many people doing this with these amps, but do NOT use some vintage NOS 6v6 tubes, as they would most certainly get fried, and possibly damage your amp. Rather, you should stick with the more sturdy modern production JJ 6v6s which are designed to handle such abuse. Another way to tame the volume of the amp is to use an attenduator. Those can be pricey. One trick that worked pretty well for me was plugging into the 2nd input jack and removing 2 of the 10 inch speakers from the amp. I'm thinking I might just put a new baffle in my Hot Rod Deville 410 and replace it with 2 12 inch speakers. The fewer the speakers, the less the volume. You'd be surprised by just how effective this little trick is. Just make sure you have your remaining speakers wired up correctly.
Hey Rob I really appreciated the video as I just bought a Blues Deluxe and it looks like the tubes are in same configuration. I have a lot of noise coming from the middle 12AX7, do I need to bias them as well as the 5U's if so is there are similar reference point and and adjustable potentiometer for the other side? Really appreciate the video, going to save me some money. Oh yah the noise goes away when I put pressure on the tube so maybe a quick solder is all that's needed.
Brilliant vid and pickin !
The lad just picked up a HR Deluxe ii ....fantastic sound except the power tubes are noisy on some low notes. Gonna try some damper rings but if that doesn't work then may be putting your instructions to use soon with a pair of new tubes.
Thanks man!!! Does this go the same for the 4x10 model?
Hi Rob, I have the same amp as enrique , a 1980 Fender Twin Reverb 135 for which I just bought a whole new set of matched tubes, preamp and power tubes (SED Winged C 6L6) ,(a replacement package expressly for the Twin from tubestore),Do I have to proceed necessarily with changing the resistor since I have not a technician ready at hand in the short period? Or can I go on without particular problems in terms of sound or amp efficiency and postpone the replacement. Thanks
Great Video! Is there a Marshall JTM 45 video like this? That would be cool!
@TubeDepotTV i knew it was a legacy because of the bridge and the tremolo arm.... they´re just the best guitars for me, i have the legacy special model, and also have a deville amp... awesome combination... excelent tutorial i am about to do this to my amp, greets!
this was very informative, cleared up a few things for me.
cheers mate much appreciated
p.s guitar playing at the end was killer, should upload a video with just you jammin
Nice vid, never had seen all this biasing thing ......Btw, I also have a Fender Deville with Sovtek tubes but one of the preamp's is microphonic so I'm thinking of buying new ones. Which preamp tubes would you recommend for this amp? Thanks
Good video, nice guitar playing !
I just replaced all the tubes on my brothers Deville, looking at the back of the amp, the left power tube looks like it never comes on, the amp still plays and seems strong.
Could this be the solder connection you were talking about, or else what may be causing this ?
Thanks !
Great vid just subscribed glad to find someone who can explain step by step for a D.I.Y. saved me money. I have the blues deluxe reissue is this similar process as well?
Hello Rob. I'm an owner of the Hot Rod Deluxe ( 12 inch speaker ) and the amp is the smaller brother of the Deville but looks prett much the same inside. I'm living in Holland so our current is 230V AC unlike the 110V in the states. Does that make any difference in biasing the power tubes? I read somewhere that you recommend 70mv for a Hot Rod Deluxe. Is this a safe value for my amp. I appreciate it that you took the time to explain this ! Thanks
Wow! You made it look easy.
I have a question. I have a Hot Rod Deluxe. I put new JJ power tubes in and the started rattling shortly after. The guy at JJ said it's because I have a combo and the amp vibration is the cause. What do you think? Also what replacement tubes do you recommend? I play rock, blues, country.
Oh ok! Thank you for the quick reply! Your video was very informative and helpful!
Hi Rob, Like the video. Good solid and easy to follow. I have just changed to TAD 6L6 tubes and during biasing could not get less than 61mV at the bias test point (highest voltage pot would go was -60V, which gave me 61mV at the bias test point). I therefore backed off the pot voltage until I got 70mV as the bias voltage. Is there large tolerances between amps, or should they all be able to get 60mV without having the pot at max counterclockwise
Regards,
Allan
@TubeDepotTV Looks like one of the preamp tubes was a little loose! Thanks for all the help, do you guys ship to Canada and if so, can you ship via USPS?
@TubeDepotTV Thanks man. I just got JJ 6l6gc's and a tung sol 12ax7 for the V1 spot and two electro harmonix for the V2 and V3 preamps. Sounds great even without biasing it yet. Which leads me to my next question: I have an analog multimeter, any idea what setting it should be on? AC or DC? 500, 250, 50V?
Hello!
I am new with tube amps and I am planning to buy one.
The amp I am planning to buy also has 2 power tubes.
Is this method you showed is alwasy the same?
1. Turn the tripmot full counterclockwise while in standby mode
2. Turn the amp on (switch it out of bypass) and set the voltage to the desired amount while touching the sowder spot of the powertube?
What do you recommend when replacing with different tubes? Does the safe voltage remain the same?
Thank for you reply in advence!
thanks rob, and thanks for posting! great vid!
Great vid, clear and to the point. thanks for that
Very good video. How do you bias an amp that doesn't have the test point, say like a 64 blackface with an AB763 circuit?
Thank you so much for your video mate! Can you please tell me why did you need to read negative voltage before you read positive also do you only bias when changing power amp tubes or also when changing preamp tubes! Many thanx
Does the same info here apply to a blues junior? And just to make sure, preamp tubes can be replaced w/o biasing? Thank you....
Nice demo! I have the same amp and it has been great aside from one issue. Is the volume knob on your amp extremely sensitive? There seems to just be a fraction of a degree between inaudible and glass-shattering loud with mine. Is there an easy way to either adjust this or perhaps replace some hardware to distribute and voltages a bit more evenly? Thanks!
when you said "there's a newer model", i suppose you were talking about the hotrod deville 3 ? as far as gettin new tubes, i'm gonna check out your catalogue see if there's any special custom sets for the 212 deville.. Thx once again for you answers and kindness.
Hi - the bias test point on my recently acquired (used) Hot Rod Deville 410 won't go past 30 mV even with the bias pot turned all the way clockwise. I have all the volumes down, power on and standby off, and 30 mV is the actual reading (I didn't divide by 2). I only have the tubes that came with the amp. Is there any explanation you can think of? Nice playing!
Hi, I have the same issue with my Hot Rod Deluxe. Not as low as your readings but the maximum reading I get is 59mV's. To get a setting so I'm not burning up my tubes I have to set it at 30mV's, which is about halfway. So far I haven't found out why my readings are a lot lower than Fender and others recommend.
I had a burned out 470 ohm resistor and probably bad power tubes. There are two 470 ohm resistors - one going to each power tube (I think coming off pin 3 - you can see the pin numbers if you look on the white plastic that the power tube plugs into, from inside where the ciruit boards are). I got some 1 watt 470 ohm resistors (xicon) from Mouser.com and replaced the tubes. Now I was able to bias my amp to 66mV. I found the answer to my own question in this article:
www.maxxplay.us/img/hrdx/How%20to%20Bias%20&%20Biasing%20FAQ.pdf
Sal Alexander Thanks for the reply, much appreciated. I've changed my tubes, had same problem with previous pair also, so next step will be to check the resistors. Thanks again.
Sal Alexander - You likely have an amp issue. There is likely an open component or poor solder connection. A qualified amp tech needs to look at your amp.
Fender56 You likely have an amp issue. There is likely an open component or poor solder connection. A qualified amp tech needs to look at your amp.
Hey there thank you for your speedy response. so I seem to have found out the source of the issue, and I'd thought I'd share what I found. The speaker jack was plugged into the ext. speaker output on the chassis. someone must have plugged it back in incorrectly. does that sound like that would cause that kind of volume drop?
hi rob,,i checked the HTfuse looks ok.b4 all this happen about a month ago i noticed that the amp making a cracking & hissing sound when a i check the amp one of the tube is blinking..i wanted to know if the amp will still create sound even if one of the tube died? i just want to know b4 i buy a new pair of tube..thnks very mch ,,
@TubeDepotTV thanks a lot! I ended up settling at 70mV, messed with it back and for for a while and 70 just seemed to be a good middle ground where i got the best tone without killing my tubes
Question? Is it normal to hear a buzzing sound coming from the upper PCB board on the Fender 410 Deville? It sounds as though it might be coming from one of the large grey capacitors. Thank You, Matt
I have a Jet City JCA20H 20w 2xEL84 head. It doesn't have the nifty test point on the pcb. I saw a video here that showed how to bias it with a multimeter and I'd just like to verify the procedure before I make any adjustments. They suggest to check the plate voltage which is supposed to be around 350VDC (mine was 370VDC), then check the milliAmperes at each tube and plug those numbers into the following equation: 11.5watts x (600 / [PlateVDC]) = X [milliAmperes].
Great video! I noticed the volume level on my 212 has dropped a ton (I'll have it maxed and it's lower than bedroom level). Do you think this is a power tube issue? Is there a common way to test if thats the case?
Hi Rob! Thanks for the great manual for replacing the power tubes on the DeVille. I've the same amp (only difference: I've got the 4x10" version) and recently I replaced my 6L6 tubes.
Now I've got a question: My other amp is a Fender Twin Reverb Reissue from 1992 and would ask you for a replacement manual for the power tubes there. Same as on the Deville? As far as I know the Twin has also a BIAS knob. What are the measure data for the BIAS there?
Really good. Keep on rockin.....
Great video - Do you know if this is the same in the Fender Blues Deluxe?
and wich multimeter did you use?
Great video. Should the bias level be set differently for different brands of tubes or is 60 generally a safe bet?
thank you for the great videos as always.Sir i have question,I have hammond 291AEX 240 euro power transformer,but the primary has two black wires not like us version ,in this case when i connect to champ 5F1push pull pot.do i have make sure which is hot and return or i can connect any of these two leads switch and fuse?any help really do appreciate.
Excellent. Thank you for your time and incredibly helpful reply. I really appreciate it.
Hey, excellent video! Very informative. Would the Hot Rod Deluxe be the same way, but set at 40v instead of 60v? or would it also be 60v?
Hi Rob!
I follow your tips in my deville 2x12 and all ok.Now I wanna try with a pair of TAD Tubes 6V6GT-STR.
Can you tell me the save level on test point for these tubes?
Maybe a good video like this....This would be good!!...(Very people interested).
Thank you!!
this one is very informative..i want 2 ask a question regarding my sound city sc30 amp..after i used the amp in a jam session i turn it on the next day but theres no sound coming out , there is a power & the tube is glowing ok but no sounds..i also check the speaker 7 its ok..do u think my tubes worn out alrady thats why thers no sounds or somthing else?dnt know much about tubes hope u can a help me...thanks very much..mike frm glasgow
it's Bob from Brookwood Leather : )
Otaypanky is my alter ego ~
Have a great 2013
Hi..thanks for the response..I checked my Blues deluxe and it did have a test point ..I went and bought a multimeter at the hardware store. The meter he sold me only had a 2000 milivolt setting..not a 200mV like shown in a lot of these videos..He told me that was ok and the meter would measure 0-2000 mV..Is that correct in your opinion?
Hi.
Why is the power tube guard missing.
Good info by the way.
hi again..the power tube,yes there is a sound coming out in the drive channel but its very very low i cant barely hear it not unless put my ear close enough to the speaker,i also found out that one of the 2 filament of one of the preamp tube is not glowing..my friend told me it might be the pre amp tube not the power tube because the volume will pass to the preamp section b4 power..is this true..thnk u very mch on ur advice i really appriciate it..
Is there any chance of salvaging a pulled PCB trace leading to the power tube socket? I'm fairly confident with soldering, and I have 18 gauge solid core wire I've used to replace bad traces in guitar pedals. I think my concern is long-term sustainability. It seems like once the solder mask is pulled, the copper trace continues to deteriorate pull off the board. I assume the only alternative would be a lot of work around hand wiring the traces off those finicky ribbon connectors.
Hi...I'm a layman so I need to ask a question...do these parameters (approx. 60mV) work for any brand of power tube? The original ones that came on my Hot Rod are two 6L6GC GT and I want to exchange it for two JJ 6L6GC. So the ideal parameter is still about 60mV? Thank you so much
i have a Hot Rod Deluxe. I picked it up used, and swapped out all the tubes today. 2 brand new mesa boogie 6l6 for power, and 2 groove tube 12ax7-r for the pre. Since it's used, and i don't have the manual, any advice about what to bias to? Close to 60 like the deville? Already gave the new tubes a quick test, sounds much better.
hi Tube Depot, i have a problem with my marshall TSL 122 combo, one day i turned on the amp to play and it has no sound, all channels working, all leds working, power tubes glowing (6l6GC), the only thing i noticed is that the preamp tubes are not glowing like before (less glowing), i dont know what could be the reason for no sound, can you help me?. THANKS.
hi rob,i need ur advice please help..i mistakenly plug the footswitch to the speaker output of my amp. both channel are not working anymore its just hum coming out from the speaker i dont know if i blown the tubes or i shorted something else..tnx..
I used this most excellent of all tutorial's in 2015 for biasing my new Fender Dot Rod Deville III 410. I deliberately set the Ma to only 57-59 Ma to prolong tube life.
Now I have been wondering to my self if this is too cold and did I sacrifice tone. I can not get power tube break up at any volume and when it's at full volume I get that "ice pick" pain in my ears it's so loud.
I think I shall re-bias to the 60 Ma and maybe change V1 to the 12AT7 which has 60% as much gain as the 12AX7 which has 100%.
The available Pre Amp tubes have these gain factors:
12AX7 100%
5751 70%
12AXT7 60%
12AY7 45%
12AV7 41%
12AU7 19%
Changing tubes is not difficult so I may even set the bias as high as 70 Ma or 80 Ma just as rob mentioned. If the amp then sounds warmer to my ears it will be worth the cost of purchasing new tubes sooner. After all I did not purchase the amp to save money but rather to enjoy the tone of a fine amplifier. He, he, as usual I outsmarted myself with the too cold re-bias from the factory settings of 60 Ma. Live and Learn!
Thanks again Rob for your video, for re-biasing/bias of a Fender Deville it's the best one on You-Tube!
I tried 2 different 12AT7's and at volume over 4 1/2 the amp made a strange noise. I have decided my amp only want's 12AX7's.
I've got a Blues Deville, the reissue and I think the newer version of that, so the inside looks pretty much the same as the Deville here. I can see the bias pot and test point in the same position. The only thing I can't figure out for sure is whether or not it has the same recommend bias of 60mV. Is it? Where do they hide this information in the specs, or can you derive it from something else?
I have a acquired a fender De Ville 410 and we used it while having a practice it sounded a bit distorted, and after an hour we had a rest and whilst we were sat down it did a few pops. Have you any idea what could cause this please.
Fantastic presentation!
Thanks ...