Hey everyone! Sorry for the necro-thread revival, but after a decade+ I've finally got my PPAv2 working! When I started the project I was broke af so I used a lot of parts that I already had, even though they didn't fit perfect. I apparently ran out of 10ohm resistors and janked in a SMT...

I feel like the Pimeta and PPA are really excellent designs. Hats off to Tangent for offering PCB source files! Has anyone tried to organize a group order?

Hey Everyone! It took me nearly a decade, but I finally got my PIMETA v2 working. I think the core issue from the past were no-so-great jacks that we're making weird connections. I replaced all the buffers and blew up a few opamps in the process of troubleshooting. Using a TREAD for a nice...

WAT?  looks at datasheet.  :palmface:   Ok.  I do realize I'm one of the knuckleheads often referred to in the instructions.  :)  Popped in an OPA27GP.  Because I have some.   @tangent nice.

Heh. I put the opa37 (not 637) in backwards. Perfect now.

Got it working, and it sounds really good. So happy. The OPA37 opamp for the ground channel is crazy hot though so I'll need to tinker with that. Running about 0.60 mA for the class A bias. I really like having the option to do SMT or through hole. Photos: (my soldering is not super)

I've had a board laying around too and I'm just waiting on four resistor values to show up.  Accidentally ordered 0402 package sized resistors.  Ha!  So small.   But yeah, hoping to brown dog some OPA637 as well.

I finally broke down and bought a Zhalou 2.5c DAC.  No mods other than some opamp rolling.  I put in a pair of browndogged OPA602's on the analog board and OPA2107's on the headphone amp since my other headphone amps (PPA2) are in for repairs.  The Zhalou headphone amp seems to do better now...

I didn't find any shorts, so I figure I'll put a 1k sine in and test the signal path with an oscilloscope.

Quote: Absolutely.  I don't care for bass boost.

I have a 10k resistor for R4.  My guess is gain would be 10k/1k = 10?  Or is my math wrong?  Left channel is a happy camper.  I could drop in OPA27's for testing.   A few parts are barely warm.  Nothing hot.  The capacitors all check out so nothing weird there.  The silicon parts are...

So I've had some issues with one of my channels with an OPA637 getting cranky. If you look at post #748 you'll see that I used cheap electrolytics and ceramic caps for power smoothing near the opamps.  So I reclaimed four Elna Certifines and some 4uf film capacitors and replaced the cheap stuff...

You're right. I didn't measure the input. Resistance is below 1ohm from the input ground to output. That would be a problem as you suggest.

Just measured the SMPS. All the outputs read in the kiliohms. Seems isolated to me. I'm tempted to swipe some nice Elna Certifines and film caps from other projects to see if that will stablize the OPA637's at higher voltages. Stay tuned...

I've not tried to open the case on the SMPS to determine if it is isolated. In any case it appears to cause the amp to go crazy so it goes back to where it came from. My bad. Wasn't thinking. Ohms law.