Fender Super Champ Tube Swap: AX7 vs AT7
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- Опубликовано: 5 июл 2024
- Viewers asked for it, so in this video I swap the preamp tube in the Fender Super Champ amp. I switch between a AX7 and AT7 and focus on changes to touch sensitivity and overall gain/output.
I show the process of installing the tube, do some noodling and use a loop for direct A-B comparison.
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Gear Used (click links to check prices):
Fender Super Champ: amzn.to/2rgSEwH
Shure Sm57 Microphone amzn.to/2jqaZSv
Recorded in LogicX.
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Hi Everyone, hopefully these time stamp links are helpful to anyone wanting to jump around to specific moments.
• Intro to how this hybrid amp works: 0:00
• Recording process: 4:33
• How to do a tube swap: 6:28
• Testing Amp Dynamics: 8:47
• A/B loop pedal test: 11:25
• Final thoughts and summary: 13:12
I changed mine to a premium mullard ax7 and the power tubes to premium matched set of mullard. And replaced the speaker with a Warehouse speaker. All made a huge difference.
I like the tone of the AX7 over the AT7. I have a XD. I put a matched set of JJ’s and bias to 40ma. What a difference the JJ’s made it. Cheers.
Sorry - the video did not clearly explain why you would want to change to a lower value tube.The objective of changing to a lower value tube is to lessen the gain on the front end. Yes - the AT7 will sound quieter compared to the AX7, BUT this allows you to turn the amp up and get the power tubes more involved. In other words - you have to increase the volume control to get the same loudness with the AT7. Tube amps get into their sweet zone when the power tubes are pushed harder. Pushing the front end harder, as with the AX7, gives more gain but allows more harsh frequency spikes and the distortion is not as pleasant as that which you get from the power tubes. The AT7 lets the power tubes carry more of the load in achieving the same volume. It also gives you smoother control over the amp's breakup. It's pointless to compare the two tubes with the same amp settings. The comparison should have been done at equal volume levels - not equal amp settings.
I appreciate this feedback. This swap was definitely a learning experience for me and I would like to revisit it again checking both tubes at max volume.
@@JeffStarr You should find you also get a slightly lower top volume with the AT7. By the way thanks for the info about the placement of the modeling in front of the pre-amp tube and how the normal channel is also a part of the modeling circuitry. I was thinking about getting an XD mostly to use the normal channel but now I will reconsider. I have tried modeling amps and they are not for me.
@@timwhitlock2684 Not a modeler,,on the front of xd amp it clearly states in print " VINTAGE MODIFIED TUBE AMP " no modeling amp breaks up beautifully when cranked as this one does
@@ampcruz2540 what’s your favorite settings? Just got this have 6 days left to decided I want to keep it. Mostly play at home. Trying to get great tube break up
@@brucek8934 sorry bout delay ,,, favorite amp settings are 123 ,4 and 7
I tried that trick years ago with my Super Champ when US made new/old stock tubes were still available. With good AT tubes the sound was a little cleaner and crisper, but I still preferred the standard setup. I used a Princeton Reverb II for the clean crisp sound. Back then (late 1980s-early '90s) it was getting harder to find good tubes that weren't microphonic and "ringy," although Groove Tubes were okay. Pricey but tested and usually guaranteed.
The 12AX7 in Super Champ XD amps is only a "phase inverter" tube which sends the signal to the power tubes. It does not feed any preamp tone stack, which in these amps, is completely digital. For that reason, you will not affect gain or obtain more headroom by replacing the 12AX7 with a 12AT7. It only reduces volume output. Gain, and headroom remain unchanged at a lower volume.
That's incorrect. The first triode is preamp, second triode is phase inverter. The effects are injected into the preamp stage just like an effects loop. Pull up the schematics.
@@singletonepickups There is only one triode in the SCXD or SCX2, isn't that correct?
@@mickjagger8904 the 12ax7 tube has 2 triodes. The super champ SD uses both of them. The first triode is v1 preamp and the second triode is v2 phase inverter. I don't know about the super champ x2. I haven't looked at the schematic.
@@singletonepickups both the SCXD and SCX2 should be the same schematic in that regard. I have an SCX2 head, that I play through a 12" V30. I am not an electrical engineer and cannot really read schematics. All I know is that if you swap the 12AX7 out, and install a 5751, a 12AT7, or a 12AU7, you do not improve headroom, you only lose volume. The relative amount of gain to volume in the clean channel seems to remain the same throughout the volume pot sweep.
It seems like the preamp tube has little effect on the preamp tone stack as there is no change in relative gain, only a loss of volume, which I assume is the result of the phase inversion of these various tubes. This is generally not the case when swapping tubes in preamps having multiple preamp tubes, from my experience. As such, I recommend staying with the higher gain, 12AX7, in these amps.
As a side note, I have found that these amps are generally biased cold from the factory. A common result is unpleasant, "flabby," low end distortion. Fender recommends a bias of 40mA at the R20 test point. If you bias these amps between .045V and .050V, which should be within the 70% plate dissipation at idle rule, at the test point, with 375 plate voltage (I use .047V), it resolves the low end distortion problem, and these amps sound great.
@@mickjagger8904 the perceived lack of change from tube rolling is just that....loss of volume from lower gain. Tube rolling doesn't have a massive effect in these amps due to the fact that they always have an effect injected. It's like constantly having some sort of pedal run through the loop...the pedal colors more than a tube. They do however have a tube preamp gain stage though before the phase inverter.
I recommend caution when using the hard number of 40ma. I'd rather advise checking at each tube as each tube will draw different current....even when matched. Current draw also differs by manufacture. 40ma may or may not be the correct value for your tube. My xd is pulling 381v at the tube, so 40ma was actually still cold. I ended with apprx 22ma per tube to reach 70% bias point. It sounds really good. I did find that the noise floor is greatly improved with a spiral wound filament preamp tube, whatever style you choose. I personally run an nos raytheon 12ax7a in mine and it sounds much better than the Chinese tube in it when I purchased it. I am running eh 6v6 in mine as well.
I threw a 12AU7 (quieter than AT7) in my Micro Terror, for slightly lower gain... sounds great!
Just wanted the hamburger not restaurant. ..
I really prefer the Original Fender 12AX7 tube
Same, but I've also recently been experimenting with a stereo amp setup using with multiple delays and I've found that the AT7 might be a good option to help tame some of the high end spikes I get with the AX7.
Originals are crap and unreliable they are Chinese made with a Fender stamp. Plate current went all of sudden to high and put HIGH voltage to ground without a fuse back to the transformer. Result Burnt out chassis. Beware of budget tubes guys
The original smokes the phillips
@@Stereostupid I agree
On many forums, everyone writes that it is risky to put 5Y3, citing some data, blah blah.
Fender champ 5F1, and all other amplifiers made according to the same scheme, have 5Y3 in their assembly as a rectifier.
Since it has a larger voltage drop than 5AR 4, it is logical that this is reflected in the tone of the amplifier itself.
Especially if instead of 12AX 7, you insert 12AT 7
.Specifically, I inserted these lamps in my amplifier, which is a member of 1: 1-Champ 5F, - Joyo-Fame sweet baby JTA-05, and it works perfectly.
12AX7 -gives less gain, and doesn't make the tone dirty at higher volumes
there is a 5Y3GT at the power supply stage, but if you want
to get more output power, then you can change it to 5AR4. (this is recommended by the manufacturer-it says in the declaration)
The tone is more compressed - cleaner - at a lower volume of more out.
Joyo has the same component values as Champ 5F1, only it is not a real PTP.
I definitely set up a 10 "speaker as well - with a small 8" speaker, the amplifier can't give its right tone, I think that's clear to everyone.
For me, the most important thing is to get the cleanest possible - glassy tone from the amplifier.
And the pedals are always there to additionally color the tone - at the request of the one who plays. And these amplifiers work very well with all pedals.
Yeah..not gonna fiddle with mine but thanks for the video.
If you want to have a smoother sound, I suggest a NOS JAN GE 5751. 70% gain of a 12AX7 but same plate resistance. I have tried the 12AT7 in place of 12AX7s and they kind of made the sound thinner.
And I think the 12AX7 won in this video.
skunkproductionsMLA very good recommendation. Interesting!
good to know
Sup bro, is it normal for the power tubes to be blackened? I thought mine were gone cause I was getting no sound from my Schamp, could it be the preamp tube? tnx.
I’m not an expert on this but if the tubes are not glowing when you turn the amp on then you might need some new tubes. I would check with an amp tech in your area.
Hey my amp after while of playing, it stops giving sound but it seems to be on do you know what might be wrong with it please help nice video
Hummm... sorry I wish I could help but I’m not sure what the problem could be. Are you using any pedals?
@@JeffStarr loose dsp chip.
Loose dsp chip.
The fender tube is definitely better I have the same amp and have experimented with lots of tubes try using unbranded Russian tubes you can get some great sounds.
It's very subtle
Great video.
I love the X2, and will be changing AX7 to an AT7. Your are right describing how the AX7 functions in this amp. The first half is a fixed gain preamp and the second half a phase inverter for the grids on the push/Pull output valves. You are correct about output volume. If you look at the 12AX7 data sheet it's gain is 100 whereas the 12AT7 has a gain of 60. So with the AT7 installed the signal from the DSP to the power tubes will be around lower. This will be a noticeable reduction in output sound level compared to the AX7, but no where near a 40% change in SPL. The preamp tube does not 'colour the sound, this is upstream via the DSP. But because the power tube grid signal is lower the output is pulled back a bit from breaking up and the valve tone is slightly changed due plate voltage, current curve characteristic. What we should get is a better, more subtle change in how the volume and gain pots work. It would be nice to measure the SPL readings for the 2 valves on channel 1 with the volume at 3. I'm guessing the SPL for volume 3 for the AX7 will be nearer to 5 for the AT7. So in summary the AT7 will have a slightly different tone, the power tube breakup will start at a slightly higher volume and the amp will be better and more controllable at lower volume (bedroom practice). Plus tube amps always sound different as the volume pot increases.
Well said and very detailed! :) for anyone looking for mod this amp I think a speaker swap is going to give more bang for the buck compared to a tube swap. Thanks for watching.
@@JeffStarr Agreed the AX7 change is subtle but changing the stock speaker to Ragin Cajun transforms the Amp.
both halves of the 12ax7 are used as phase invertor. www.thetubestore.com/lib/thetubestore/schematics/Fender/Fender-Super-Champ-XD-Schematic.pdf
@@JeffStarr absolutely, I had one for a few years with a greenback Celestion in it. It was awesome.
The AX7 cut through better. The AT7 was quite polite, but did have a roundness. Was tbh a bit too weak and unforgiving.
Interesting experiment. The AT7 has potential, but better sounds on the day with the AX7
Ch.1 on my X2 is shite but I actualy love the models all but 2.Killer amp I just wish I got the combo.If it was stolen I would get a new one but the combo..
Hi Jeff. Are you still tuned in? The difference between these tubes is in their gain. The AX7 has a higher gain -- 100 vs the AT7 gain of 60. What this means is that you can push the AT7 harder before it generates those higher frequency harmonics. Usually this means that the AT7 will give you a "rounder" and "warmer" tone at similar volume levels.
Yes, this was a big learning experience for me and I’d love to try it again to explore it more.
@@JeffStarrThen I'll share a story of what I did, years ago. I have a Leslie simulator for a 20 year-old electronic Hammond organ with good organ tones, but lousy Leslie simulation. My Leslie box is meant to sit on top of an amp with a 12 or 15 inch speaker. and is from a now defunct outfit called Motion Sound. It has a real rotating set of 2" horns with two set speeds, just like a real Leslie cabinet and an electronic connection to the amp to simulate the rotating low end, which sound realistic. Now, it also has a distorting high gain loop that takes the high frequency signals through a 12AX7. I have never liked the high frequency harmonics generated in this tube -- even for guitar, and it sounds worse with the clean sound of Hammond tones. In my humble opinion, of course. So, I opened the box of my Motion Sound and swapped out AX7 for yet another triode of the family -- 12AU7. This tube has a lower gain than even the AT7. By the way, this is the value labeled Mu on a vacuum tube specification sheet, which is used by the engineer who designs the circuit. Remember the mu values? AX7 =100, AT7 = 60, and AU7 = 25 (I'm trusting memory, which gets less reliable each year.) I do recall pouring over the old spec sheets from my student days, and picking this tube for its gain. I wanted some of the even harmonics at 90 - 100% power, but not a lot. The AU7 worked great for my purposes with the Hammond sounds, and the Motion Sound model I own allows one to control the tube bias with a dial.
A tube (or transistor) is designed to work within a specified range of voltage-current pairs called its operating range. Essentially, this is the purpose of tube bias, to hold the tube within its distortion-free operating range. When you push a tube beyond that operating range, you get clipping on the high end, or under saturation on the low end. When you push a tube into clipoing, you get distortion. A tube will naturally deliver certain even harmonics at attenuated levels -- this is why we guitarists like the sound of tubes. Clipping is another animal. You can see clipping if you look at the amplified signal with an oscilloscope. A normal signal resembles a sin wave. In a clipped signal the tops of the waves become flattened, and the further one goes into clipping, the flatter and smaller they get. If you study the same signal in the frequency domain, you'll see the harmonics increase in number and size. So, the trick with tube bias is to distort, but only at higher input signal levels. Some amps allow a technician to change the bias level with a potentiometer. The Fender Super Champ does not.
By the way, the digital sound generator chip does no amplification in this amp, which is why it sounds so good! I haven't seen a block diagram for this amp, but I imagine that the sounds and some effects must be supplied before the tubes. I could be wrong.
You may have guessed. I own one of these, too, although I haven't owned it for long -- the X2. I have yet to try the software. I don't know if its compatible with Windows 10, and of course, Fender no longer supports FACE.
Correction -- the AU7 mu = 20. (I looked it up because I'm OCD like all good engineers.)
Nice video. These amps are really appealing. I think I prefer the sound of the stock Fender tube. Sounded like it had a bit more top end sparkle however I might be wrong.
I would agree that the stock tube has a bit more sparkle. A 12AX7 tube has more gain output than a 12AT7 so those highs and the dynamic squashy feel is more apparent. With a dirty tone the lower gain AT7 might be a bit more pleasing as it softens those highs. But it's all subjective. :) Thank you for watching and leaving a comment!
12AX7 was more "musical sounding". Fender product engineers could of used either with no price difference so in testing I'm sure it was the best choice not to mention more readily available.
I have similar thoughts. I would be curious to check this out when doing overdriven tones to see how it changes the response.
Cool video.... I think I prefer the 12ax7 but it's really close
Yeah I agree
Try the AY7 tube, that gives a better Fender Tweed sound
As others have mentioned, the 12AT7 is lower gain, so to leave the volume controls at the same level is not really a fair comparison... While the AT7 will always sound more controlled, and less full than the 12AX7, when ya give it some juice and get it to start breaking up, that's where you find the value of a 12AT7's sonic characteristics...Not better or worse than a 12AX7, just different...Then with any tube, it's a matter of which brand produces the basic tone you're looking to achieve , which is a much larger convo...FYI, no such thing as a Fender tube, vintage ones will be rebranded American made like Sylvania, RCA, GE, current production amps will pretty much have Chinese Shuguangs like you have there...Nothin' like NOS tubes though...
12AT7 Have 30 percent less gain than a 12AX7 But i prefer the cleaner sounding AT7
AT7 has a much warmer cleaner full body tone even though the gain is lower
I can tell a difference in volume but little in the way of tone. These aren't like tube amps with multiple ax7 tubes. I would stick with a stock number tube and maybe get a better-quality US made one (if you have money to burn), but I wouldn't use a different one. I follow the don't mess with things you know nothing about.
The AX7 sounds right. The AT7 sounds weak.
These are made in Mexico now.
I dont think you will hear much difference between a 12AX and a 12AT playing clean.
The 12AT is a lower gain tube and thats the primary difference between them.
Im changing the 12AX in my tube head to a 12AT because the 12AX gets fizzy at higher distortion levels. So to remedy the fizz Im going to a 12AT. I only use maybe 65% of the gain thats available anyway....and theres always pedals.
Totally. For me the main difference was in the dynamics and the “pop” of the notes. The 12AT is smoother and more compressed in the way it feels. With higher levels of gain it would help tame some ear splitting high end as the transients are more mellow. Thanks for leaving a comment and talking gear with me. Cheers!
@@JeffStarr
Sure thing. I love talking gear!
That's right. I have that opinion too.
I think the most important thing is to achieve a good clean on the amp, and as you say the pedals are always there for extra distortion.
And as a rectifier lamp, only 5Y3
@@bluesman5049
Why the 5y3 recto? ...just curious.
Recently, Ive even been considering a 12AY in the gain stage instead of a "T"...because I just dont need much gain from the amp. As a matter of fact I feel like the less gain I get from the amp, the easier it will be to stack a pedal on the dirty channel.
I have a Big Muff Deluxe and there is no way to run that pedal on my dirty channel.... but I could handcuff it and stack it on a solid crunch from the amp. I think... That pedal is like unleashing a rabid dog. Hard to control...
drop this amp into marshall 2x12 1936 deep cab and grin!
Can’t really tell much of a difference
Didn't make a huge difference, but if I had to pick one, I would probably choose the AX7. The AX7 does seem a bit more ice picky, but that's helpful for cutting through a mix. In the end, this just seems like another example of tone being in the fingers. I look forward to seeing the tube swap with the orange micro terror amp.
Does orange terror have 3 tubes or more?
Does orange micro have at least 2 or 3 tubes in it ?
This is not really a pure hybrid amp. It is all tube on the left channel and hybrid on the right channel. It has two 6v6GTs (in mine, 6v6GCs in yours) and a 12ax7. The left channel is pretty awesome and the right channel sounds like a dirty butt hole. I have had one for about 10 years and use the left channel as a pedal platform, which is really awesome.
Ryan Hill yeah, I live on channel 1. It’s great!
Have you ever FUSED it and looked at the gain settings and presence, sag, and bias, for the preset voices? They are kinda all over the map and the gain settings they start at are all pretty high from the get go. I use FUSE once in a blue moon, usually to map a preset to some other position on the dial, and maybe tweak the pre amp effects in line for the preset, but otherwise its perfectly useable on channel 2 stock. It IS adjustable, though and I think a lot of people forget that, especially since Fender still sells them but dropped updating the software years ago. You can still get it. I think Shane over at "Intheblues" hosts the FUSE program on his website somewhere.
Good demo, but the tube swap is getting you nothing. That tube acts as a phase inverter, and by changing the tube for a 12at7 is only getting more current to the output tubes. Also, be objective, when playing in an a/b situation, play the same licks and the same vigor to those links. Cheers 😀
AX7.... the AT is for the tremolo, reverb
I like the marshall better
AT7 was warmer..almost bluesier....
AX7 tube has a brighter sound than AT7 . After hearing AX7 , AT7 seems like dull to me .
AX7 wins. Fuller sound.
Thanks for watching! This was a really interesting video to make. The biggest thing I noticed was the output volume and tube sag/compression between the tubes. Obviously there was a difference in gain, but that was relatively nominal compared to how much different each tube "felt" when playing.
I just picked up a used X2 for $250. Im amazed at how much low end it puts out with stock 10" speaker.
Agree. For home and studio use it's more than enough. It rattles the walls enough for me to get in trouble on a regular basis.
Do you not realize that a 12AT7 is a lower output tube than a 12AX7?
Yes, I should have clarified that in the video. Sorry for missing that key talking point. Thank you for taking the time to leave a comment.
The original is much warmer fatter warmer
No contact cleaner, not checking the tightness of the pins to base contact. Oh, well.
Terrible demonstration, you have to drive that amp crank it up get the tubes hot and not doodle 🤔
He already demoed the amp in other videos. So, 1 minute to change the tube. 5 minutes to hear it. Why is this 17 minutes long.
. Im not wasting my time on this