Boyuurange Reisong A12: Follow up on Final Mods.
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- Опубликовано: 29 сен 2024
- So today I am doing on a follow up video of the finished amp after both channels are modified. And no, repeating the mods on the second channel doesn't undo the positive changes we saw modifying the first channel... I've had dozens of emails at this point thanking me, explaining how much better it now sounds.
Another good thing to come out of this video is: I am able to show measurably what I already knew from previous testing, the PSVane tubes these come with are junk. It was the first thing I changed and I never used them again. And no, just replacing these tubes isn't going to fix this amp, it still will sound crappy, just maybe a little less crappy.
This A12 amp is sold on Amazon for just under $500 and for many folks this is their first taste of a tube amplifier. I plan to do a complete video series, critically testing this and exploring ways to improve the sound just like I did on the A50 amp. I know a lot of people own these and like them, I'm curious how they actually perform!
The schematics and BOM can be found here: www.skunkiedes...
Hi Skunkie, I wish I could give you a hug right now! Today I finished doing all the mods to the BRZHIFI A20 / Reisong A10 PCB version. I had to lower the EL34 cathode resistor to 150 Ohms as my plate voltages are lower. I measure 267V Plate-to-cathode and 13.8V on the cathode resistor. This sould get me around 93% dissipation. Not onyy is the sound VERY clean right now, I can listen at lower volumes as the low and high frequency response has resolved nicely now. When measuring the dB in my room it is a good 8dB lower now. My nieghbours are very grateful. I did not know this little amp could put out this sound! Still does not beat my Thule IA60 in terms of sheer power, but damn does it sing. I might actually sell my solid state amp now. Thank you for your work! That disspiation did you get on the EL34? kind regards!
Thanks for everything you do on your channel. There’s always gonna be naysayers and people with ugly attitudes, but then again, everyone’s an expert. I’m merely an audio,/HiFi/vinyl obsessed hobbyist, and it’s unfortunate some people feel they’re done learning. Thanks again, and Merry Christmas! 🎄🎶💜🔊✨
Not in a position to do the mods as A10 and 12 are too £££ in uk to jusify it. Would rather start your 300b amp build instead. Totally appreciate your mods though. And the work put in. I don't know why people find this so hard to understand. You are offering them the means of getting a great amp for not much money. If I could get one cheap in uk or if I had one already I would be modding it for sure using your research and design. Merry Christmas.
A most wonderful festive season to you & yours! You're a great instructor for showing how everything is put together and the rational for doing so. Hardly in any way longwinded!
Wow, thank you!
Just finish the mod on my A10 with stock tubes, the difference is more clean power compared to the triode modded version. I will eventually buy new tubes but for now, I'm very happy. You are the best.
I watched all the A12 mod videos and finally finished my amp. I upgraded to Sovtek 5AR4, JJ EL34L and Genalex Gold Lion 12AX7 (regular) tubes. I also used 620K p-t-p feedback. I am running this amp to 1986 Klipsch La Scala speakers with the AL crossover. This is my first tube amp and first mod attempt. I don’t have measuring equipment, just my ears. Before mods, I thought the amp sounded very raspy and grainy. High frequency sounds were harsh and fatiguing. After mods I can definitely hear much cleaner and clearer vocals and more pronounced and pleasing dynamic range with improved bass. I would like to thank Skunkie Designs for all the time and effort you put into fixing this amp and creating the videos. I will definitely enjoy this amp regularly now.
Hi!
I reckon everybody who has really actually done the mods, will appreciate the effort you put in
The others opinions don't really matter very much, I feel..
The lengths people will go to, to defend a product they don't want to admit any inadequacies is laughable.
I don't get it, you are offering these people solutions openly, you'd think a little gratitude and appreciation would be there.🤦 If I'd brought this thing I'd be thankful for the fix.
Thank you for all your videos and lessons. Ignore all the jack ass people. We appreciate all you do.
So thankful for the work you've done on this! Don't give the gnats your time of day!
Thanks so much for all you show and teach. Changes and results.
I have been building audio tube gear for some time now. I have learned so much from you Thanks for that. Just remember one thing you can't tell a box of rocks or a tree stump anything so don't let small minded people get to you thanks again.can't wait for the next video
Haters will be hatter. I for one (an I don’t think I’m jut one) are very thankful for what you’re doing. I’m glad to hear the OP transformers ok. They last time I checked the A10 we’re going for $400. I seen one go on eBay for $275. I’m thinking about trying a separate transformer for the heaters, to take some of the load off the power supply. I’m in the camp of just leaving stuff turned on. That’s a debate for another day lol. Thanks for your videos, an have a great Holiday 🌹🌹🌹🌹🌹🌹🌹
Good morning.
Great job SKUNKIE !
I'm quite surprised that no one has noticed that the bleeder resistor (430K/2W) is missing on the modified diagram.
Some indications such as the wattage of the resistors could also have been reported to help even more in understanding the MOD.
Keep it up, you're on top !
The results speak volumes…. Pun intended! 😂 I champion your work whenever I can regarding this amp. You really have turned a turd into a diamond. I did love the turd before, but how the amp stands after your mod, I can see how much of a turd it was. I am very new to tube amps, I’ve always used solid state, and took a chance after seeing glowing reviews on RUclips. I can appreciate what those reviewers saw in the amp, but I’m sure they would agree that after your modification, it sounds so much better now. I wonder if the manufacturer would be willing to take on board your improvements…
Thanks again :)
And Merry Christmas!!!!!
Love your videos. I'm thinking of buying this amplifier, just on your knowledge. Keep up the good work. I would rather buy your thousand dollar kit. How long should it take on average to build your kit amplifier? I'll adjust a few hours up or down from your estimate, lol
Sorry, I don't sell kits
You mentioned a deep dive on the schematic. Did I miss it buried in one of the videos?
Piss on the negative people. Your videos rock and I always learn something. I trust what you say and do.
Just needed to give you another THANK YOU for this. Just finished your Mundorf EVO Aluminum Oil Capacitor upgrade and changed the Schade resistor to 620K to work with my Klipsch RP-600M speakers. Dialed in my Polk subwoofer and just sat back and enjoyed the tunes. Really made a difference from stock.
On an aside note, my cousin wants me to do one of these for him but is concerned with needing more inputs, tone and balance controls. Please note that I DON'T need them. I came up with adding a Schiit Loki+ (for tone and another input) and changing the volume control to a concentric pot to control each channel. Do you have any better ideas?
Nope, that should work!
Merry Christmas and a happy new year Skunkie. Your mods worked for me...
Thank you for your videos, I did your mods along with some nice NOS tubes and it transformed this little amp.
Stephe, We are thankful for your videos!
Don’t let them get to you Stephe. Your channel is growing because most enjoy your content. Still trying to decide which amp build to do next year.
Hello, I purchased a tung sol 5ar4, I'm new to tube amps.. is it just a direct swap? I have the a10.
Yes, you can exchange it for the Chinese rectifier. As a result your operating voltages go up. The power supply caps are 400V and should be ok. Do not use the JJ brand for 5AR4 rectifier as it has a reputation for open filaments within little use on these hifi amplifiers.
also very excited to see the results of the solid state rectifier!
I think I may incorporate that into my next 6P1 mods as well!
From what I’ve seen, it still gets quite hot, but takes longer to do so. I’ve not been able to take accurate temperatures, or how warm it gets over time… as soon as I figure out how to get that data, I’ll share it :)
Thanks ,have a nice day
Great work!! I am buying the amp and following your upgrades. Can’t wait to hear the results!
great series!
Super job. Thanks for your time and effort to help out the community. I enjoy your videos, and I don't think you talk too much haha. I have built several guitar tube amps, so you are speaking my language. I'm thinking of purchasing this amp and doing the mods as you suggested. Thanks again!!
I appreciate that!
You certainly know your stuff. The Reisong A12 update was very well thought out. Please continue your excellent RUclips videos!
I just bought one of these a12 hoping in the miracle... No miracle happened. :(
Very high distortions all over the spectrum. For sure the problem is amplified by the monitor floor standing speakers I'm using,, but old mengyue push pull ampli was alot better. Ill try your mods for sure (video 1 and 2 from november 2021 i suppose). I hope it will be achieve a better sound and limit distortions. Thank you for all you di (sorry for my eng, cheers from italy!)
Merry 🎄 Christmas. Love your channel!
Thank you! You too!
I finished watching this series and while I'm not anywhere close to a tube expert I did somewhat understand what you're trying to get across. When I can afford it I plan on buying the Nobsound 6P1 Tube Amplifier and doing the mods on it. I'll be getting the one with the headphone jack on the front as I need that setup. Funny to see how some people can't understand graphs as they are presented as I did. Keep up the good work!
We'd be hard pressed to find a better EL34 amp once it's Skunkie modified. To the trolls, take your Adderall and watch the whole video!
This channel is quite technical for newbies. If a person think that himself is so technically advance, please look somewhere else.
And if a person wants a technical
answer make short, please see a
sales oriented salesman. That is as simple as a way forward, no need to have negative complians.
Hi, I'm just ordering all the bits to tackle the mods on my A12. Are there any potential implications of being in the UK where our power supply is ~240v? Thinking maybe rectifier choice?
Nope, after the transformer, the voltages are all the same. It's just the primary windings of the transformers are different.
@@SkunkieDesignsElectronics brilliant, thanks for all your work on this, looking forward to trying the mods!
@@SkunkieDesignsElectronics
Well that was exciting! Just did the mods (+ coupling caps) on my A12. First time wielding a soldering iron or doing any kind of electronics. Felt very accomplished, turned everything on... Tubes light up, then there's a lovely puff of smoke and a hmmmmmmwupwupwupwup noise from the right speaker.
Turn everything off. Open her up again. Realised the output tube capacitor on that side wasn't properly soldered to ground. Disassembled and tested the cap and all the resistors on that side - all seem fine, but spotted the voltage drain resistor on the filter cap was scorched and shorted so removed that.
Removed and checked both filter caps for good measure, seem OK. Reassembled everything, hid around the corner and switched everything back on.
All good! I have music and it sounds great. More bass, more detail and my Denton 80ths feel more responsive at low volumes. Have some NOS Svetlana Winged C EL34, Sovtek 12AX7lps and Sovtek GZ34 tubes turning up on Monday to celebrate.
A fun introduction to electronics, thanks very much for all your work!
I just completed mine. It sounds fantastic. Thank you so much.
It seems that your A50 mod, which uses a cascade first stage, significantly lowered the distortion at lower power levels.
Why not use a cascade 12AX7 stage on the A12 mod instead of using just 1/2 of each 12AX7! Wouldn’t this lower distortion?
I meant “cascode” instead of “cascade”. The spelling corrector struck again.
The reason this worked on the A50 was that original cascade front end provided too much gain at lower levels and then got distorted when it was really tasked with creating the large voltage swing, at fairly high current, a 300B need to make power. This mod not only lowers distortion, it allows the amp to make a LOT more power before it starts clipping.
On the A12, because the bias point of the EL34 is so much lower and is an easy to drive tube, there is no large voltage swing needed (or high current), so 1 side of a 12AX7 provides plenty of gain and doesn't distort much either.
The issue I found with running both sides parallel was: while doing this lowers the plate resistance (which wasn't a problem) it also doubles the miller capacitance, which is a problem.
I know it seems wrong to have a triode just sitting there unused and if I was designing this amp, I would only use one 12AX7 to drive both tubes. But this amp is already made with two driver tubes, so the easiest mod was just to use 1/2 of the tube. I do feel that the simple solution to a problem is likely the best solution :)
@@SkunkieDesignsElectronics Thank for your incredibly detailed response. I understand and agree with everything you said. I am surprised that you don’t lose more high frequency response with a single 12AX7 driving an EL34 due to the high output impedance of the 12AX7 stage and the grid capacitance of the EL34. In pentode mode an EL34 has very low grid capacitance, but in ultra linear mode and especially triode mode it can be quite high.
Your frequency response results certainly look good enough, but one option would be to use 1/2 of each 12AX7 as a cathode-follower to lower the output impedance.
You're a real pro. I enjoy watching your videos. I'm a TV repairman and still in business even after 35 years I'm 58 now and can't retire yet LOL I have to put up with these Chinese made newer ones and sometimes I get to repair something exciting. A customer brought in a TEAC reel to reel and a McIntosh 275 Tube amp I love McIntosh old tube amps. He told me he plugged it in and it made a loud pop and a lot of smoke LOL. I took it apart and saw a bunch of black tar blown out of one of the electrolytic capacitors. I had fun cleaning up all that burnt tar out. I have a can of Zenith spray lube de moisturizer with ZDDP that stuff must be 30 years old but it did a good job dissolving burned tar. It kinda smells like a can of bust loose. It was all original so I ordered all new capacitors and measured the resistors and only two were out of spec. All the transformers had continuity. One of the 6550 had no emissions and the rest were marginal. One of the 12BH7 had a little short. I ordered one of those. He wanted it to be functional for now so I didn't spend a bunch of money on matched tubes just made it reliable so it won't pop when it's plugged in. I found one Svetlana 6550 on eBay for twenty bucks but it was aired when it came in. Found a 6550 GT for $30.00 and it came in good. The 12bh7 that came in had a little short when the heater voltage was turned up on the tube tester but not as bad as the original I was a little disappointed but went with it anyway. After all that time and effort and also cleaning the tube sockets and controls with contact cleaner I tested it with a dim bulb tester and it proved reliable for full power and it sounded great of course I don't have trained hearing for detail but it sounded good to me. I told him for best performance order all new matched tubes preamp, driver, phase inverter outputs all of them gotta go with decent brand matched sets I think groove tubes are good. It will be very expensive but it will enhance it.
Thank you, thank you! I have followed your series and will be finishing up these mods today, plus Miflex 600V coupling caps. Looking forward to your final video with impressions of the modified A12’s performance.
Excellent work and tutoring. I will see if my 2× five thumbs eventually will be able to handle the task :-D Thanks a lot for your effort and happy new year-greetings from Scandinavia
Great work. I appreciate what you did there and I think I will buy one and do the modification. Very cool. Have a great Christmas and Happy New Year Skunkie!!!!!
Thanks for your work. Lots and lots of revelations big and small about amp building. Happy New Year
Excellent tube amp upgrade process video. Thanks for sharing the science.
Thank you, my friend and I have been looking for a project to distract us from the stock markets. Forget the haters and keep up the hard work.
Thank you very much for your excellent content. Merry Christmas and a Happy New Year! Stay safe.
Since I found this channel, it brings me back all those good memories when I began a long long journey in this wonderful electronic world. You are doing a "Great, Fantastic and Astounding work". My respects from this side. And a Big Thank You.
Great evaluation and upgrade of this amp
It really worth to upgrade Thnx 👍
The more people that subscribe to your channel the more of these people you'll run across. The best thing you can do is just let their BS roll off you like water off a duck's back.
ADD … I love it.
Don't let the haters and negative comments get you down. Great job on making this amplifier sound better. Amazing how rolling good matched tubes changed things.
Thanks, will do! I honestly was just shocked at how dumb some of those comments were. I have to just lol at "She is scared to show us.."
Just done remodeling my Reisong A10 according to your mod suggestion.
I didnt think it was a so bad amplifier before the mod. with just matched EL34s from a god brand, but... Oh MY! Now it sound so great ! Thanks! I kept the 6n9 from Vostock-rocket and rolled in a pair of Svetlana EL34s , Now there is an incredible base and really clear 3D feeling in the mids and higher areas. Definitely keeping the 820K feedback as is.
I am stunned by the quality of this little simple amp now! .
My next step is to try to find out WHY it sound so great now :-) Now am diving back into the world of electronics again... after 40 years. LOL
Thank you for giving me this joy ! 🌞
Amazing how good tubes sound when they are setup right :)
merry christmas and a happy new year to you and yours , from sweden.
I'M APPRECIATIVE!! I was going to sell this piece of junk! I heard the distortion IMMEDITELY and I'm going deaf so I have no idea what the reviewers heard. I have watched these videos to determine if this is even worth salvaging or if I have the skills to do it and yeah... I think I will. So thank you. If they don't want to listen or think you're full of it then they can enjoy their stock A12's. Bless their hearts.
The mods for this amp are pretty easy and it REALLY transforms it.
Massive thanks for doing these mods. I own a BRZHIFI A20. It is very similair to the A10. BRZHIFI already did lower the cathode resistor on the EL34. I have done most of the mods to the PCB of the BRZHIFI A20 and am very pleased with the results. Massive thanks! I have shared my story on diyaudio forums. Search for BRZHIFI A20.
Thanks for sharing
your mods worked great and i love your videos! Thank you for all your efforts!
Thanks you so much Stephe !!!
Thanks you for all your videos and for what I have learned from you. You are doing a great job !!
I have just finished the upgrade of my A12. I choose a TAD GZ34, 2 EL34 from JJ, and 2 ECC83-STR from Harma (this last choice was oriented with advices from my local electronic reseller). My reseller gave me also new coupling capacitor.
The sound is Amazing, pure and clear. I am very happy with my new A12, and what a surprise at this level of price.
THANKS AGAIN !!! Best regards from France. Frederic
Hello Stephe , thanks for your response !!.
I am still working on my amp. I have changed the EL34 from JJ to EL34 Harma-Retro, after the advices of my electronic resseller.
The result is really interesting , compare to the JJ !! Much more precise basses with clarity of all frequences. I am really happy.
Best regards
Skunkie I bought the amp and I'm getting ready to do the modifications. I find it odd that they parallel driver stage in a 12ax7. I've never seen a 6SN7 parallel too much.
A couple questions. Can you or would you cascode the 12ax7? Can you or would you direct couple it? Or really not necessary? Also, I was looking at schematic from original to yours. I noticed B+ did not change but I'm thinking you improved headroom with the 5AR4 dropping less voltage and a few other things to reduce current, correct? Finally, I can't wait to play with Schade feedback, etc to fine tune. I'm pretty excited. Out of the box, the amp drives my Klipsch RP-8000s with plenty of volume and drive. Now for the better sound
No need to cascode or direct couple it. A single triode provides all the drive an EL34 needs.
Inpiered by your chanel I want to play around with the a12 to learn more about tube amps to to prepare for a own amp build. . I like to run the A12 in triode mode to see effects. Is that possible? I think it is more to take in account than cutting g2 at pin 4 to open connection to the center tab of the output transformer.
Can you give me some advice. In the net I find different confusing ideas.Thanks a lot
Hans
You have to disconnect the wire from the transformer and connect the screen to the plate with a 100ohm resistor. It's going to have about 1/2 the power.
@@SkunkieDesignsElectronics thanks for quick replay, does the 820 k Shade feedback resistor make sense for Triode mode?
@@SkunkieDesignsElectronics thanks, made a small donation to support your Channel
@@hansdoeing no, triode mode shouldn't need any feedback.
Hi. I really enjoy your videos. They are informative and have a good pace in order to take the information in. I would like to know if I can use the 5AR4/GZ34 rectifier tube if I don’t open up the A12 and make the modification? Thanks again.
You should be able to.
Once again, I would like to thank you for these videos. I implemented the mods and they really made this little amp sing. Please keep us in the loop for any tube rolling suggestions. Happy new year and THANKS AGAIN!!!
Awesome! I've tested a lot of EL34 and 6CA7, KT77 etc and my fav is the JJ EL34L.
Thank you times 1000! I have the parts on order and am very excited to try the mods. I have an A-10 and it looks like I can simply follow the new mods and the pre-side will now be wired for the 12ax7s (Connecting pins 4,5 and 9 to the heater also) correct? Have a great new year and thanks again for the great videos!
Glad I could help
thank you
The mods you recommend are great, i have done them to-one of my a10 amps and there is a huge difference, i did install different coupling caps in the circuit (.22 uf) and that also helped, would you recommend adding a pot on each of the el34 tubes and adjusting the bias do you see any value there.
No reason to do that, they should bias up close enough.
I did your mod on my A10 a few weeks back and am really enjoying the results. I was curious, did you get a chance to try the solid state rectifier and if so what did you think?
Not yet! Got sidetracked into another project lol.
Like what you do!
Thank you for everything you do! You helped change the sound quality of my Reisong A12. I noticed that the manufacturer made a power transformer with a voltage of 275v and not 290v in my amplifier, tell me, could this affect the power of the amplifier, which decreased, or is it GNFB? Can you tell me how I can change GNFB? Thanks!
Lower voltage will have lower power. You might be able to make some back with a lower value cathode resistor to raise the current some to offset the lower voltage. This amp stock, nor with my mods have GNFB, it uses local plate to plate feedback.
@@SkunkieDesignsElectronics Thanks!
Merry Christmas
Made the upgrades an the amp sounds much better. Thank you for the good job. After modification the B2 voltage is still to low at 291 Volts. Do you have any idea why it is so differnet to your measurements. I use Sovtek 5AR4 Tubes.
I have good audio grade Capacitors with 0.1 uF can I use it instead of the 0.22 uF orange coupling cap between input and output tube? I have a small humm in the system can other capacitors solve this.
Can we expect more from you in terms of the A12?
0.1uf is pretty low to use with a 270ohm grid leak resistor. You might lose some low end response. On the voltage, they seemed to use a wide variety of power transformers in these as I get people reporting a wide range of voltages. I would adjust what you can to get them close to what I ended up with is all I can say, if you have to use a SS rectifier, so be it.
I am looking at a next round of minor mods, just got a lot of projects going on at once!
@@SkunkieDesignsElectronics FYI Added a solid state rectifier. Now I have 318 V at B2. Need to check if SS has a negative impact on sound. what do you think?
Hi Stephe,
Used to SET amplifiers I bought the *A10* out of curiosity what a pentode might bring to the table. It was no succes and I thought the SE penthode as a principle was to blame, so the amp ended up in the attic until I saw your video.
Modification of the operating points brought out the sun. Now it gives a clear soundstage while before it was foggy. Bass response has bettered
a lot and the midrange is quite decent (in comparison to expensive SET amps). The highs are a little strident but I haven't incorporated the plate-to-plate feedback yet as I was curious about its effect. Will report back.
My B1 voltage with GZ34 (5AR4) is a little low at 326V, you got 340V I noticed. EL34 cathodes are at 18,5V each and the ECC83 at 1,2V so on target.
Thank you very much for your effort because is brings quite a difference to this little amp. Love your videos!
Detmar
😃 whoa, this p-t-p feedback did clean up the highs a lot. I used 799K, might take it to 900K for comparison. Mind you, still with the stock ps-vane EL34 and JJ ECC83 (12AX7). Midrange is velvet, not too sweet. Bass could go somewhat deeper as I'm with 100nF still. Running a pair of 10 watt B&W DM1 speakers the volume is good for normal listening levels.
I settled on 861K p-t-p FB. It diminishes distortion at average listening levels to an acceptable level so highs do not sound strident any more.
Decoupling the EL34 cathode with two times 220uF brings better dynamics on the table, the amp now sounds as if it has more power than its humble 2x 6W. Although this mod improves the dynamics, the amp is still not on par with a good SET w.r.t. speed of delivery. Perhaps a solid state CCS fed from the rectifier PS may better this. So, now it is time to loose that heat producing rectifier but doing so brings the need for higher rated PS capacitors as their 400V working voltage will be exceeded at startup.
Must still double up on the coupling capacitors.
Glad you are enjoying the mods and you see why I am a fan of this p-t-p feedback, it's a great tuning tool!
Is it feasible or practical to think of moding this amp to run in triode mod/
You could: Disconnect the UL wire from the transformer to the output tube screen, tie the screen to the plate with a 100 ohm resistor, and live with 1/2 the power output.
@@SkunkieDesignsElectronics Thanks for such a prompt reply! I hear your caution about 1/2 the power output but that doesn't concern me too much. My speakers are nominally rated at 97dB efficiency, my listening room is comparatively small at approx 16ft x 20ft and my musical tastes don't include loud/hard rock types (these days).
What type and W rating would you recommend for the resistor?
BTW I found your series on the A12 to be the most helpful, direct and explanatory that I have seen for DIY mods. Thank you :)
@@SkunkieDesignsElectronics I found this info posted on diyAudio by Tubelab with respect to converting an EL34 from pentode to triode mode:
" I can tell you from experience that the 1/2 watt metal film resistors sold by Mouser or DigiKey will fry if the amp is overdriven. I have toasted 3. I now use 1 or 2 watt carbon film or carbon composition resistors and have not killed any even when using my SimpleSE as a guitar amp."
I would use a 2W vishay metal film, like I recommend for everything working with tubes. It's really not worth screwing around with 1/2W resistors etc. for anything in a tube amp to save a few pennies.
@@KenDangerfield Did you wind up doing this mod, and if so what are your impressions of the impact?
If they don't want to hear you talk this long, they sure don't want talk with me. I tend to explain things at their base level. Likely the difference in the PSvane tubes comes from the grids not having consistent spacing on the grid wires. Either the distance not being centered between the cathode and plate, or even spacing of each turn on the grid assembly.
That makes sense on the tubes. What is odd is I have used PSvane tubes that were fine/good, I wonder if these are seconds they sell cheap to the OEM guys?
Very likely they sell the ones they can't easily match in bulk.
I got the best result without feedback resistor. Then the amplifier has great dynamics, but also distorts the sound at the maximum volume level. I listen at a maximum of 50-70% so it's not a problem for me. However, in order not to be too bright, I set eq in my dac.
Did you play with different values? Depending on the speakers and your taste, anything from 300K to 1M will work. The lower values can sound too dampened with some setups, while the higher values (or no feedback) might be too bright depending on your situation.
@@SkunkieDesignsElectronics I tried several resistors from 470K to 680K and as 680K sounds good I love more the dynamic of no feedback.
@@wojciechkleszczynski7041 Ah OK, just making sure you understood the value of this resistor is not set in stone :)