filter caps and tone

[iknowjohnny]

i know it's a highly subjective subject, but let me explain my situation and tell me what you think. i built a amp similar to a marshall 2204, then a second one. the second one sounds quite a bit better and a lot more like a marshall while the first one sounds much darker and not as marshall like. I have measured voltages and component values looking for something way off. But everything is close and all components are the same including the trannys and choke. there is only 1 exception.....the new one has F&T caps for all 3 nodes (PI and V1/V2) while the old one has sprague atoms. They are almost the same as far as value so i can't imagine that mattering. (F&T=22uf, Atoms=20UF)

I have tried a number of things to try and make the old one sound like the new one but nothing changes at all. I know everyone says filters should no make any difference sonically, but is it possible somehow in this case?

[roberto]

Filters DO make difference. Let's try different ones and you'll hear. JJ are softer, FT are darker, TC are punchier, and so on. You could try different ones in different points of the amp. Going to TC usually the amp feels more powerful. Going to JJ the amp sounds a little more saggy. Just try to change the first stage filter.

[iknowjohnny]

Thanks. The amp with the F&T is actually a good bit brighter, so i guess spragues are very dark if it is indeed the caps that are causing it. Oh,and if by the first stage filter you mean the can, it's a 32/32uf JJ in both amps. Only the PI and preamp stages are different.

[roberto]

Why have you underfiltered all the amp? More sag? Try some JJ in the first stages (I like the mid tones they give to the amp) or try a 22n in parallel to the can of the first two gain stages.

[iknowjohnny]

i think you misunderstood me. what i was asking is whether the different filters could be the reason for the difference between two amps which otherwise share the same other components. I'm trying to find out why it sounds so different.

[roberto]

In the first post I said that filters change sound. In the second one I suggest you another brand of 22u filters to ear a more clear difference from others you have.
You can post the two layouts, maybe there are some more differences rather than just supply filtering.

[iknowjohnny]

But my point was that the 2 amps are exactly the same as far as component values and brand except for the 3 filter caps, and i'm just trying to understand if it's possible for those to make the kind of difference i described. I'm not trying to determine what caps are going to make it better, but whether it could be the caps that might account for the considerable difference in tone. The reason i ask is that if i know it's not possible for the spragues to cause the amp to sound that much different, then i can search for the real reason. If it IS possible, then i can tell him to buy the F&T's and let me install them for him. The entire point is that i need to know whether it is possible for the different brands to account for the tonal difference or not.

[iknowjohnny]

Sorry once again for the double post, but again the board shows me a "debug mode" error, whatever the heck that is. And when i try to repost it, it allows me to but it also allowed the 1st try to post. Is there an issue with the board?

[Andy Le Blanc]

the board does that....... and you can lose your posting....... if it pops up back up to your posting
and save it just in case you have to re-post.....then get back to the board to see
if the original made it thru.... before you re-post..... happens enough to be a pain
but not all the time......

with the amp...... tubes are 20% devices and when you add the % tolerance
of the rest of the components you can have two identical amps that sound very different....
with the power supply.... the different caps will yield supplies with greater or lesser
over all impeadance which will effect the tone of the amp....... try the cap that you
preferd the tone of in the other amp it wont hurt....

[iknowjohnny]

Thanks. I probably will try them, but it's my friend's amp now and i wanted to get a better idea as to whether this could be it or not because i have to tell him to spend $20 on something that may do nothing. Other than that i suppose i could clip my OT into his amp to see if there a big variation in that, but what a PITA that is.

[Andy Le Blanc]

its a tuff call.... there really are a lot of factors that can and will effect the tone....
Id try swap-in the tubes around...... if its not the tubes then look at the power side....
its the same basic repair steps..... one thing to look at is how well balanced
the phaseinverter is...... DC on the plates and AC output..... this could be the
culprit...... and has a real effect on bandwidth and tone... the ideal is two
equal but 180 degree out of phase signals for the best push-pull operation....
shoot for equal AC...... its a quick measure with a DMM..... as close to zero as you can get it...

[billyz]

Coupling caps also make a huge difference. Did you actually measure each one? I don't always measure each cap but when I do , I find quite a bit of variance. I recently measured one that was rated to be .0022 and found it to measure .005. several .02 measured .03+ and etc. Resistors and especially transformers vary quite a bit. It all adds up. I have never heard two amps sound the same.

[iknowjohnny]

its a tuff call.... there really are a lot of factors that can and will effect the tone....
Id try swap-in the tubes around...... if its not the tubes then look at the power side....
its the same basic repair steps..... one thing to look at is how well balanced
the phaseinverter is...... DC on the plates and AC output..... this could be the
culprit...... and has a real effect on bandwidth and tone... the ideal is two
equal but 180 degree out of phase signals for the best push-pull operation....
shoot for equal AC...... its a quick measure with a DMM..... as close to zero as you can get it...

It's not tubes, i already did that. But i'll look at the PI. When you talk of measuring AC do you mean at the PI plates at idle or what?

Coupling caps also make a huge difference. Did you actually measure each one? I don't always measure each cap but when I do , I find quite a bit of variance. I recently measured one that was rated to be .0022 and found it to measure .005. several .02 measured .03+ and etc. Resistors and especially transformers vary quite a bit. It all adds up. I have never heard two amps sound the same.

i did check them on his amp and the mallorys all spec'd out pretty much right on. I'll check mine tho and see. I really don't think thats it tho because i have swapped caps around a lot on both amps and i should have heard a difference. But i'll check mine and see if they differ from his to any notable degree.

[Jana]

I have done a lot of tinkering with the 2204 circuit. As others have mentioned, it could very well be the tolerance of components. One of the first parts I would check is the .001uf (1000 puff) bright cap on the gain pot. If one amp had a cap significantly on the plus side of tolerance and the other was on the minus side, this could make a big difference.

Are these amps you built? If so, could it be possible that, for example, the treble pot in one is linear taper and the other is audio taper? That would be a huge difference if both of them *appeared* to be set on 5 for example.

This could turn out to be a very lengthy process if you are determined to get to the bottom of it. It could also be very rewarding in the end. I once had an amp that I just threw together from all the parts I could scrounge out of my junk box. I wasn't all that concerned about making anything pretty or great, just bored and didn't want to spend a dime on it. Well, by sheer dumb luck the amp was one of the sweetest amps I had built to that point. What the heck happened, I wondered.

I wanted to know what it was that made the amp sound the way it did. So, I measured every part, recorded every voltage, applied signals and watched things on the scope, recorded all those voltages (clean, various levels of clipping, etc. Measured how much gain each stage had, everything I could think of. For tubes I used whatever was rolling around in the junk box.

That whole experience really taught me a lot about the finer points in the quest for tone.

I don't know how much time you have, but it seems as if the universe has handed you a gift, it's up to you how far you want to pursue it.

[Andy Le Blanc]

its equal AC measured from ground at the grids of the power tubes....
or as close to zero measured between the grids...... this is done with a signal
applied to the amp.......

DC balance is measured between the plates of the inverter tube with no signal......
theres some discussion of this on dumble forum..... to find the magic spot
but all textbook discussions of push-pull amps assume identical tubes on each
side of the inverter.....equal DC ..... and equal AC at the grids of the power tubes
this is not always reality..... but AC balance really improves performance