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QRV-08 Build #3

Started by BMF, December 27, 2016, 12:59:02 AM

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I received my 3rd QRV-08 PCB on Dec 24. I built the power supply and tested it; all measurements are within spec.

I next built the regulators and almost all specs are correct.

Today, I built the DC Servos but not the amps. The specs are not correct from the opamps:

IC  Pin 2   Pin 3  Pin 4  Pin 6  Pin 7
1   13       13     14      14     14
3 250mv   2.4    13      13     14
Note: I have not built the amp sections.

Other measurements:

BR3 20     E33  24.7
BR4 20     E32 -24.7
BR1 19.8  R33  24.1
BR2 19.7  R32 -24.1

H3  1.74    V34 -2.5
H4 -1.74    V33  2.5
H1  1.74    T34 -2.5
H2 -1.74    T33  2.5
All 4 LEDs remain lit.

IC     Pin 2  Pin 3  Pin 4  Pin 6
IC11  6.9    6.9    0        6.9
IC15 -6.9   -6.9  -13.6  -6.95
IC2    7       7       0        2.5
IC6   -7     -7     -13.6   -6.9

IC12  6.9
IC16 -6.9
IC4    6.9
IC8   -6.9

E45  13.9
E44 -13.9
R45  13.9
R44 -13.9

C/G  14 -13.8
C/G  15  13.8

Comparing Left to Right, the regulator components: C39, T34, T32, T30 and DZ2 measure significantly lower than their G and V counterparts.

1) Is IC2 Pin 6 = 2.5v a problem?
2) What is the linear range for IC 2, 6, 11, and 15? I couldn't find this information from a Google search.
3) Is it possible that the servos will come into spec once the amp sections are built?


You can't have the DC servos alone since they have their feedback via the amplifier.
/Per-Anders Sjöström, owner of this forum

Homepage with my DIY hifi stuff



I finished QRV-08 last night, cleaned the PCB, and re-tested, today. All previous normal measurements remained normal and unchanged.

The problem measurements at IC1 and IC3 are now correct:

IC    Pin 2     Pin 3    Pin 4    Pin 6    Pin 7
1     0.0v      0.0v     14v     -5.9v    14v
3     0.0v      0.0v     14v    -250mv  14v

2     6.9v      6.9v     0.0v    6.9v

I did not need to jumper on the solder side of the PCB.
Left and Right offsets = 0.0v.

The sound quality is excellent from top to bottom. Very nice details. Balanced FR. I'm listening with HD-650 at the moment.


I finished my amp, today. I really like the sound quality, P-A. Thanks!


/Per-Anders Sjöström, owner of this forum

Homepage with my DIY hifi stuff


To illuminate the blue LED for the power switch, I added a 1k resistor as shown. This dropped the voltage by 0.9v but I don't hear any SPL attenuation on that channel compared to the other channel. Is this an acceptable hack to illuminate the blue LED?


The sound quality is impressive... Wide soundstage, punchy and controlled bass, clear and balanced mids, very good treble resolution, excellent micro-details, and fast. I'm really liking what I'm hearing.