Which PSU caps?

[daz]

i tried some 47uf caps in parallel to some of the PSU caps in the amp. first i stuck two 47's in parallel to my 32/32uf can which itself is wired in parallel. So i had two 33uf and two 47uf caps all in parallel which according to my elec. calculator is 160uf. I have no idea why, but i heard/felt no difference. at least nothing i was sure of. Then i stuck 47uf's in parallel with each of my 3 node caps so that each node in the PI/preamp was now 69uf. This DID make a big difference and i liked it. The lows got tighter which the amp needs.

That said, my questions would be why did the first dual 33uf can not make much or any tonal/feel change when it went from 66uf with both sides in parallel to 160uf with the two 47's added in parallel? Second, i figured i'd get F&T 80uf caps for the nodes, but do you think 100's would be better? It could still be slightly tighter, but i don't want things to get too stiff.

Anyways, i'm definately going higher on the nodes, but unless someone can tell me why i should go with a bigger dual can for the PA, i'll just leave that as is.

EDIT: after more A/B listening i do notice the difference in the first can with more UF added. Guess i'll go with the traditional 50/50uf there.

Never mind. I wanted to order them today to have them by the weekend so i just ordered them. All F&T. 3 80uf for the nodes and a 50/50 can. The amp's bass for the first time ever sounds tight. Could go a bit tighter maybe, but the caps i got are a tad bigger that what i'm using so that should help a bit.

[mooreamps]

Then i stuck 47uf's in parallel with each of my 3 node caps so that each node in the PI/preamp was now 69uf. This DID make a big difference and i liked it. The lows got tighter which the amp needs.

That said, my questions would be why did the first dual 33uf can not make much or any tonal/feel change when it went from 66uf with both sides in parallel to 160uf with the two 47's added in parallel?

Because, you are on the right track. You are "tuning" the circuit. More is not always "better". For power supply filtering, there is an optimal range of filter capacitance for the job at hand. You just keep on doing what you are doing, and your builds will become a cut above the rest. "trust me"





-g

[daz]

More is not always "better". For power supply filtering, there is an optimal range of filter capacitance for the job at hand

Well, i worried about using 80uf for the nodes for exactly that reason, and i never see other amps using that high a value. But then i tried 47uf's in parallel with the current 22uf's to total 69uf per node and it sounded damn good and not stiff at all. so i figured 80uf is close and shouldn't be so much bigger as to ruin things in that way. I sure hope not or i'm out $30.

[mooreamps]

Well, i worried about using 80uf for the nodes for exactly that reason, and i never see other amps using that high a value. But then i tried 47uf's in parallel with the current 22uf's to total 69uf per node and it sounded damn good and not stiff at all. so i figured 80uf is close and shouldn't be so much bigger as to ruin things in that way. I sure hope not or i'm out $30.

only $30 bucks ? you should see my parts bills.


BTW : sounds pretty close to the values I use. I don't think you have anything to worry about. Just enjoy what you have. Sounds like you're doing just fine to me.



-g

[daz]

Thanks, i think i'm getting there. Funny thing is i had the amp sounding great to the point i didn't touch it for months. Then one day i started messing with one little idea that i had and before i knew it i was back into it and had made numerous changes and took it a good ways from where i had it ! This is some addictive stuff.

But the nice thing is after all the time i spent tweaking this thing, it was just now that i came to realize that maybe the most important thing in getting great tone is the PSU. Once you have that right i believe the rest becomes 10 times easier. A little change i made to it several days ago was so beneficial i decided to experiment more with it and hence the purchase of bigger caps. In fact, if anyone has any PSU tricks and tips they don't mind sharing i'm all ears.

[Chuck H]

There are some tricks for the PSU but none I've found that did my builds any justice. One trick is to bridge your filters with a 1uf film cap. It's supposed to improve the ESR figure which is often poor with electrolytic caps. I don't know about all that. but I'm sure it improves the ESR for any AC that will pass the 1uf cap. You can experiment with smaller values like 8 or 10uf on the last node (for V1). This can give a more squeezed and midrange feel to that stage that, for some designs, sets up well for over driving following stages. Usually not much ripple and noise left by the time you get to that node so smaller caps are fine. Larger caps give a broader more spanky feel. If your amp has fewer gain stages than the modern multi cascade type distortion circuits, big caps can work fine for a tighter feel. But in the multi cascade type amps it can have the opposite effect because you have stronger bottom end from the early stages and can cause a mushy feel by the time all that bass gets to the end of the chain.

One trick thats been kicked around here is bypassing the screen resistors with different size caps. I haven't tried it.

If your worried about the caps being too large from a 'but now my amp is a wierdo with unusual circuits' perspective, get over it. Lots of guitar amps have employed differences that are uncommon. I used to have a Dean Markley DM something or other that used filters of several hundred uf on the preamp nodes. It had excellent clean tone and I wish I still had it so I could learn more about it. Consider that top shelf tube mono block amps for home stereo sometimes use filters of many hundreds or even a thousand uf. Your well below those numbers.

You have other elements to your circuit that contribute to a softer feel. So these bigger caps are tightening things back up a little. But probably in a different way. So it's all experimenting and finding what works for each circuit and what works for you.

Chuck

[daz]

Chuck, i hate to sound noob, but then you already know me well enough to know i am. But what is ESR, and when you suggest bridging the filters how do you mean that wiring wise? I like that idea about caps on the screens...i will certainly give that a shot. The amp is really sounding great and improved in some ways i've been wanting to improve it. But i still feel theres one more thing i need to improve, and that screen cap trick may help there. I feel the amp is a bit too warm because while i like it like that, when i add high end to give it articulation thru that warmth it gets too high endy. Don't get me wrong....it's nothing bad. But i'm nit picking here and shooting for near perfection to my ear, which i know i can achieve because i'm darn near there. But i need to find a way to add a tad of clarity w/o thinning out the tone, so that may be a possible way that i haven't tried.

I received the caps tonite and i also ordered enough mallory 150's to replace all the original 150's in my amp because i felt they have been soldered and re-soldered so many times they may not be in top shape. Sure enough when i got all the caps in the amp definatly sounded fuller and i began to think thats how it used to sound and wondered is they had deteriorated gradually over the months from so many re-solders. Or maybe it was the filters. in any case i can't wait till tomorrow to REALLy hear it because I couldn't crank it up due to neighbors tonight.