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New Mint build

post #1 of 9
4/1/05 at 11:06pm
Thread Starter 
Well, I finally finished my Mint...

I'd originally planned on some sort of wall wart, but in the end decided to go with battery power. I also added a ground channel, with the implementation pulled directly from the Pimeta design. I guess this makes the design more Pimeta than Mint...sort of a hybrid.

Component choices:
OPA627 for all three channels
BUF634 for all three channels, double-stacked on left/right channels
1000uf 25V Black Gates in the power supply
1uf Wima input caps
Alps Blue
Neutrik locking 1/4" jack
Cardas RCA's
Silver wire (0.80mm) with teflon tubing in the signal path
CRD's for biasing
Vishay-Dale resistors
Decided on a red LED...it just looked better with my enclosure.

Wiring was a chore, I must say...next time I'll buy PCB's. That said, I lucked out & wired it all up right the first time. The amp worked on the first power-up, but I encountered some ground buzz/hum. This ended up being a combination of poor interconnects & my failure to properly tighten the nuts on the backs of the RCA's. Once this was corrected, the amp ran fine.

Pics:







I'll be interested to see what kind of battery life this thing gets...I'm kinda worried! I may yet end up adding some sort of AC supply, but we'll see.

Lastly, I wanted say thanks to the folks who helped with my questions in other threads.

Peace,

Graz
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post #2 of 9
4/1/05 at 11:26pm
very neat and nice houseing
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post #3 of 9
4/1/05 at 11:30pm
WOW! That is one good looking amp. You picked a beutiful enclosure. Great job!
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post #4 of 9
4/1/05 at 11:44pm
Very nicely done and rather artful. My version - mostly intended as a test bed - doesn't look nearly as neat.

I would think it more logical to double the BUF-634 count on the ground channel, rather than signal. I didn't do that in mine (single in all 3, using Senn HD600s), but wasn't looking at it as achieving the most critical sonics.

I did do the wall-wart (24VAC), along with an LM317 regulated PS (conventional National Semi manual-based configuration) to provide 16V bipolar (split via a virtual ground), on same Vector board as the amp circuitry. Mine doesn't use the OPA627s, compromising with OPA2134s (well, right now) instead. I'm saving the 627s for a M3 assembly.

Congrats on the initial startup - I had to spend 2 nights eliminating DC offset issues, ultimately found to be caused by a single wiring error.
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post #5 of 9
4/2/05 at 5:32am
Thread Starter 
Quote:
Originally Posted by KarlDL
I would think it more logical to double the BUF-634 count on the ground channel, rather than signal. I didn't do that in mine (single in all 3, using Senn HD600s), but wasn't looking at it as achieving the most critical sonics.
Hmmm...I found this quote while digging around at tangentsoft in the pimeta tweaks section (specifically, this link here: http://www.tangentsoft.net/audio/pimeta/tweaks.html):

"You might think stacking power supply buffers would help. After all, the benefits mentioned above should help the virtual ground as well, since this is where the amp's output currents return. For reasons I don't yet understand, though, stacked ground buffers don't seem to help much, if at all."

I might give it a try though & see if I can hear any difference. But I'm gonna let this thing burn in a while first...

Peace,

Graz
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post #6 of 9
6/10/05 at 3:30am
Nice work Graz. A hybrid, eh? Very invetive!
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post #7 of 9
6/10/05 at 5:51am
Looks very nice!
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post #8 of 9
6/10/05 at 11:40am
A MINT wired point to point?

*claps*

Looks nice!
I can't imagnie the rat's nest I would've ended up with with out the pcb.
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post #9 of 9
8/6/05 at 6:01am
Very well done, excellent-looking and creative. *applauds*

Now for the report on its sound, time for an update Graz
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