Project: REV A v1.15

Issue: Qbias calibration. Cannot get 1 dB drop. Can't get any drop.

Audio passes (and sounds great btw). If I turn the Attack on, I gradually get more distortion from 4:1-20:1 (greatest distortion). I have read a bunch of other posts and your responses, so I did some testing. The questions are from you Mike, albeit to other folk.

Try this:

Input/output: Mid Way

release/attack: full CW

Ratio: 20

Meter: GR

Feed and confirm a 0.775VAC 1K signal measuring between input XLR + and -.

No measure these TPs using chassis as your common.

TP22 - Measure for AC for all ratios and list them.

TP21 - Measure for DC for all ratios and list them.

Answer:

TP22- VAC TP21-VDC

[email protected] -5.91 @20

0.365 @12 -3.39 @12

0.294 @8 -2.61 @8

0.217 @4 -1.81 @4

What is your V AC at pad 15 under the same conditions?

Answer:

TP15 VAC

0.946 @20

1.116 @12

1.378 @8

1.827 @4

TP15 with GR off = 3.15 VAC

What is it at the output XLR pin 2?

Answer:

8.05 VAC

With the FET out, what is your DC at the GATE pad of Q1 as you rotate the qbias from end to end?

Answer:

Q1 = -0.828 (Full CCW) and -1.428 (Full CW)

What is your DC range at pad 18 rotating the pot?

Answer:

-1.0 VDC (Full CCW) and -1.744 VDC (Full CW)

Voltages:

Q2: D= 8.44V ; G= 2.88V ; S= 4.61V

Q3: C= 14.95V ; B= 8.46 ; E= 7.87

Q4: D= 14.69 ; G= 2.33 ; S= 4.42

Q5: C= 26.47 ; B= 3.41 ; E= 2.87

Q6; C= 28.28 ; B= 2.872 ; E= 2.334

Q7: C= 15.20 ; B= 4.71 ; E= 4.16

Q8: C= 31.02 ; B= 15.20 ; E= 14.58

Q9: C= 17.98 ; B= 3.533 ; E= 2.966

Q10 C= 31.03 ; B= 17.98 ; E= 17.41

Q11: D= 26.25 ; G= -0.938 ; S= -9.14

Q12: C= 26.23 ; B= -9.14 ; E= -1.59

Q13: C= 24.67 ; B= -0.809 ; E= -1.40