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1000uf cap in apheared/cmoy.

post #1 of 9
Thread Starter 
Aloha,
I just changed the power supply electrolytic capacitors in my apheared/cmoy amp from the 220uf to 1000uf. JMT was my inspiration in doing this mod, my first. I was surprised how much it changed the sound, the low end in particular. The 1000uf cap gave the low end a noticable boost, a little to much for my taste. Actually, it's kinda boomy now. Also I noticed a decrease in the extreme highs. By the way, I am running a Sony D-EJ915 (line out of course) into this amp (powered by 16 AAs) and out through SR60s. I'm not really happy with the results. But I can see if the headphones you are using could use more bottom and less highs then this is the mod for you. It's 4:15am and I'm kind of tired so tomorrow I'm going to try a 470uf instead of the 1000uf to find my nirvana. Though the results weren't what I was looking for, I'm glad that I did it because I learned something new about audio circuit design.
post #2 of 9
in order to balance out the High's with large Electrolytics you need to bypass them with larger film types those Wima box type of about 0.47uf aare small and good. Also if using resistors for the Virtual groung replace that with a buffer. REMEMBER the power supply is in series with your Headphones so if it is not up to par then you are wasting whatever qualities are available in your gain stage.
post #3 of 9
But aren't we talking about filter caps here? As far as I know their only purpose is to filter out any AC ripple that might be present on the DC line to ground. Are you using a walmart on your amp? If on the other hand your just powering it from batteries I don't see how this would improve the bass response of the amp? Anyone care to explain?
post #4 of 9
It doesn't make a lot of sense at first, because it's just the power supply, right? But he's correct. The treble is really about the brand and type of cap, but the low end... just supersize it.

Impedance... The cap's resistance graph looks like a "U" and the catch is the upper freqs... as freq increases so does the inductance.

So we use bigger caps and/or parallel them for the low end... with a given cap, then 3 of them parallel is 1/3rd the impedance at low freqs. ESR is important! And bypass the electrolytics with film(s) to take care of the high end inductance.

You can also use a regulator or a virtual ground driver to lower the power supply impedance... or a combination of both methods (which is what you see for normal AC powered gear usually)
post #5 of 9
Thread Starter 
Wow, looks like I opened up whole can of worms here. I was happy just to discover that bigger caps increased the bass and decreased the highs. All this other stuff like bypassing with larger Wima boxes and resistors for the virtual ground and buffers is way over my head right now. I think when Headwize starts up again, all of these theories in amp design should be put in the archives along with diagrams for visual peaple like me. Anyway, right now I changed the 1000uf caps to 470uf and I LIKE IT! This balance of highs, mids, and lows works for me. Going from 220uf to 1000uf and settling on 470uf kinda make me feel like Goldie Locks and the Three Bears except that I'm a dude and and my hairs black.

Please keep the discussion going on this type of mod because I think it's a good way to personalize your pocket amp to your taste and I also want to learn about Wima boxes and buffers. Thanks.
post #6 of 9
it's not a "mod" per se, that's just the behavioural trait of the caps. Some caps have better high frequency handling than others, and the bypassing with a film isn't as necessary.

Which is what art's doing, he's tryin to "tune" with the cap size swaps. But now to ruin his fun... hey art, if you try it with different 470uF caps you'll get the same kinds of change that you got from 220 to 1000. Try some low ESR, try some photoflash, try some generic and some esoteric... hehe now he's mad.

Just know that this is a tonal change. If I see you in another thread talking that purist crap: "I never use tone controls! Equalizers are bad!" I'll remind you of this type of tone controls.

(which is why I laugh heartily at the purist party.. as if all amps are the same, right?)
post #7 of 9
Thread Starter 



Apheared,
You know what, I'm gonna listen to these Panasonics for a while just because it's a lot of trouble getting the board out of it's case. I works good and it sounds great. I'm happy....for now. By the way, I'm not in the purist party, I'm in the K.I.S.S. party.
post #8 of 9
OH! Sorry art... that wasn't directed at you but it sounded like it was... my bad.

I'm upset at people that probably don't post here, but you know how it is when you get dragged into an arguement where all 6 sides think they are right..

Alot of people take this Purist stance, no tone control adjustment, shortest signal path possible, etc... and arguing with them, when they have no idea what's inside their gear... it's just a collection of black boxes. It can be frustrating. I let that leak into this post, that's all.

I wish HW forums were up, there's a historic post about the comparative sound of certain 'lytics as power supply caps... ah well, sooon very sooooon.
post #9 of 9
Thread Starter 
Hey Apheared no worries. You guys are good people along with being good teachers. I'm dying to show you what I did with your and cmoy's amp design. A friend of mine has a digital camera and will soon shoot my portable rig!

Keep up the good work with these forums.
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