[Filburt]

Quote:

Originally Posted by ATAT The 2107 is the opamp of choice for filburt. he's been raving about it, and since the 2107 is a low output current, high precision, low noise, its basically nearly ideal for the PPAS-type topology (compared to high current, low precision stuff..). Of course, this is all untested and therefore just speculation. but as soon as I get my boards over in japan, I'll test out the follow'in Opamps - Signals - AD8620 OPA2107 OPA2227 OPA2134 AD8066 LM6171 (dual) Grounds - THS4621 (or something.. forgot the exact #..) LM6171 (yes, its an "unstable" opamp..) AD8610 LM7171 Buffers - BUF634 OPA551 LM6321 Any other suggestions?

The dual LM6171 is the 6172. I do not recommend the OPA551 unless you absolutely must use it as it's too slow for most of the op-amps we're looking to couple with it.

Hopefully the LMH6321 will sound more like the LM6171/2 sonically than the BUF634 as, IMHO, the BUF634's colouration of the sound isn't particularly suited to some of these op-amps. I don't personally like the 634 on practically any amp I've ever heard with it, and the ones I didn't dislike it with I still felt were lacking in some manner, so I'm probably going to stick with the LMH6321 or something else if possible (and provided they sound better).

Another op-amp you can try, if you can restrain yourself from using 2x9v (12v supply max) is the LMH6622.

 

[ozshadow]

When is Die returning home and any eta on when the boards will be finished up at the shop ?

 

[ozshadow]

Are teh Intersil HA3-5002 buffers used in the original PPA possible for this ? I will have to lean on your observations soundwise. I have yet to hear anything with a buf634 buffer, but comments about a veiled sound do not sound great - especially for $8 each.

 

[ATAT]

Oz - I dont find the BUFs particularly "veiled".. filburt hates the BUFs, I find em just fine.

The intersils can be used via adaptor. rsabo made a pretty good intersil -> SOIC adaptor which I'll make a few of..

ETA on boards is 8 days and counting + 3 days for shipping to Die's place.

Filb -

The OPA551 is basically for compatibility testing, as the OPA seems more abundant and some may want to use it.

and if I was limited to 9v only, there'd be a BUNCH more opamps id like to test, but i just dont have the time / boards to do that.


NeilR-

There is a specific set of DIP headers that are high-density and have the same spacing as the SOIC pads. You bend out the leads on the pads and you basically convert SOIC to DIP (not DIP spacing though..)

 

[Filburt]

Okay so I finally got time to actually troubleshoot daniel's PPAS that I received where the right channel wasn't working. Wow, I am lucky I didn't kill my super-secret Technics earbuds with this thing. Offset on the right was 5,8v (yes, that would be 5800mV). Left was 0,03mV. Although the BUF634 current limits, so that's probably why nothing bad happened to them...they still sound really sweet as far as earbuds go ^_^

Anyhow, got them both down to 0,02ish mV, so I'm probably good to go there.

The sound? Pretty impressive. Definitely has that BUF634 sound going on, but I guess I can tolerate it. Sounds worlds better to me than the MINT w/ OPA2132s and BUF634s. Has high levels of detail and stereo/instrument separation and imaging. It's quick as well, and has a lot of power on tap from what I can tell.

Configured as follows (by Daniel): OPA2132 on L/R, BUF634s, THS4631 on ground. 2x9v. I'm definitely glad I ordered several boards. This thing will be a whole lot of fun. I'm starting to wish I'd ordered more.

What I'm going to try eventually, probably:

OPA2107 on the L/R on this amp, and then OPA2107 w/ LM6171 or THS4631 on ground and LMH6321 as buffer. Maybe try discrete after that.

 

[ozshadow]

I got several 2107's in the mail right this minute. Let me know how that works out - I have two boards coming to me. One will be 8620, the other, I dunno - whatever gets praised enough !

 

[Filburt]

Quote:

Originally Posted by ozshadow I got several 2107's in the mail right this minute. Let me know how that works out - I have two boards coming to me. One will be 8620, the other, I dunno - whatever gets praised enough !

How many? Willing to share (sell)?

 

[ozshadow]

Well, by several, I meant 3. I want to play around with them first. If I do not like em, I'll pass them along.

 

[Filburt]

Quote:

Originally Posted by ozshadow Well, by several, I meant 3. I want to play around with them first. If I do not like em, I'll pass them along.

K. I just compared them to 627s...they sound fairly similar. The 627s are probably more neutral/accurate and a bit more detailed.

 

[ozshadow]

Who has the Buf634u's now ?

Digikey lists them currently at 06/19/2006 Hope they get a lot !

 

[ATAT]

DieInAFire intends to buy a batch of em I think..

I get my ICs from DiAF and Cire so I have no clue where .. you should PM them

 

[ozshadow]

Are there any jumpers in the path from the two R4's to the outputs ? If not, probably a little late now, but a jumper spot would have given the option of tieing in an optional bass boost circuit.

Something like this ?

http://ozpk.ginnypotter.com/bassboost.jpg

 

[ATAT]

Nop. No tie outs there..

Honestly, I'm not a big fan of bass-boosting circits (i think digital bass boost is better.. ) but if you really want, you could take the taps off of the SMD pads.. (i can make a writeup on how to do it.. but its really "no duh".. and its pretty easy with wire-wrap wire.


by the way, if you just want bass boost on all the time, put a cap on top of the resistor and solder both on in parallel =p

*edit* on second thought the ^ above wont work at all. NVM.

 

[wowie11]

Hey Dieinafire...how does the PPAS sound compared to your mini^3ified PINT?

 

[ozshadow]

Is this the week coming up that Die receives the boards back ?

I gotta get to planning parts buys !