QRV-08 Build #3

[BMF]

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.

Questions:
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?

[peranders]

You can't have the DC servos alone since they have their feedback via the amplifier.

[BMF]

OK, thanks, P-A.

[BMF]

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.

[BMF]

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

[peranders]

Looks good!

[BMF]

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?

[BMF]

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.