Sjöström Audio DIY forum

Your reply above posted just before I posted the response above it (I was working on it for quite a while).

No, the transformers output different voltage (see above), and neither is 12V.

I don't recall seeing any instructions about insulation. What does that mean in this case? The data sheets for the National Semiconductor LM.... regulators (purchased from Newark) don't mention insulation.

Which parts are DA44/45? I don't see this designation in the BOM or on the board.

The Pulse 030-7330-0 that palchiu suggests is exactly what I ended up buying (from Mouser). I had the same professional PCB assembly firm remove the 230V transformers and mount the new Pulse units. But they don't do voltage tests.

Back home, a technically adept friend who owns a good multimeter applied 120V power and tested the transformers. 120V in, exactly right on both. But TR1 produces 6.65V and TR2 = 18.09V. () TR1 gets hot, while TR2 remains fairly cool.

This makes no sense to us. Is a transformer defective, or is there a short downstream? Or other???

Putting the probes on various points on the regulators and on the outputs yielded even more puzzling readings. Exactly which points are the test points on regulators and the output?

I should add that I ended up substituting two OPA1641AIDs for the AD8610s on the recommendation of a local headphone and amp expert who likes the OPA better than the 8610.  I assume this will not alter the essential functioning of the amplifier?

SUPER! Thanks for checking.

The BOM calls for two. I just sent you an email.

For the QRV07 parts I've spent $127.43 from Digikey and Newark in the USA, including shipping.

It's taken an awful lot of time to find everything, trying to match parts with specs. I hope there's been no mistake in part selection. If I did this again I would order everything possible from Elfa, despite paying more for shipping and maybe customs duty, since most of the part numbers are already on the BOM.

There's one last little part I can't find that no distributor in the US has in stock (and some want to sell me over 1000 pieces to back-order it). It's the two Kemet/Evox Rifa foil capacitors (Elfa part 65-557-59) for C1 and C8.  Would anybody have a couple of these lying around? I can pay via Paypal or wire transfer in EUR, or US$$.

Alternatively, how closely do the specs have to match that particular capacitor? Newark has a similar one in stock, Kemet part #LDEEC3100KA5N00, but it's rated at higher voltage and tolerance: 0.1 microfarad, 100V, +/-10%, 2220, polyethylene naphthalate. Another is rated 1.0uF, 10%, 50V. Would those ruin the QRV07 board or its performance? Mouser has a closer one in stock in a smaller size -- 0.1uF, 10%, 50V, 0.8 DF, but size 1210 (3225 metric), only half as big. Mouser has another at 0.1uF, 10%, 63V. 0.8DF, size 1812 (4532 metric).

I'm no electronics expert at all so all this is confusing.
Doug