21

CP5176 FET compressor / Re: No sound CP5176

« Last post by Stam on January 20, 2026, 01:33:47 PM »

Hi!

Nr 3 on the checklist:

I have put a 1VAC sine 1 Khz signal to the input of the compressor and I don´t get any VAC reading on TP1, Tp2 and L1.

Nr 4:

I am not a skilled electrician and did not understand input sine 100hz at 100mVAC? Can’t even get that low signal from the software generator so did send a 100Hz at 1VAC instead. Maybe you can teach me there …

Ac level on TP3:
My multimeter read 0.04 VAC on every ratio.

DC level on PT4:
All value where correct on all ratio.

DC level on JMP1 pin 1:
Did not get any reading on any ratio

DC level on TP6:
Did get -2,7 VDC so it seems okey.

DC level on TP5 with jumpers JMP1 on 2-3 and 4-5:
 Was correct, I did get exactly 0.32 VDC

22

MU524 Vari-Mu Tube Compressor / Re: STEP 6 OUT 1Vac

« Last post by JPK on January 20, 2026, 08:56:11 AM »

D'après les photos envoyées, sur le 1er MU524, les trimmers ne sont pas à la bonne place:
TR1 5k au lieu de 2k
TR2 5k au lieu de 1k
TR3 1k au lieu de 5k
TR4 2k au lieu de 5k

23

MU524 Vari-Mu Tube Compressor / Re: STEP 6 OUT 1Vac

« Last post by FX on January 19, 2026, 06:00:22 PM »

IDEM SANS U4

R3=R4=2185 OHM
R5=2225
R6=R7=10K
R8=469

24

CP5176 FET compressor / Re: No sound CP5176

« Last post by JPK on January 19, 2026, 04:13:23 PM »

Every value was right except D: that should be - 0.2 V, and I did get - 0.133 V.
This is probably OK.

You must try to follow the signal as mentioned here.
It will tell you where the signal chain is broken.

25

MU524 Vari-Mu Tube Compressor / Re: STEP 6 OUT 1Vac

« Last post by JPK on January 19, 2026, 03:35:34 PM »

TP1=41,4 VDC
TP2= 40 VDC
Est-ce le même résultat en retirant U4 ?
Vérifier les valeurs et soudures de R3...R8.

26

CP5176 FET compressor / No sound CP5176

« Last post by Stam on January 19, 2026, 12:09:15 PM »

 I have built the main PCB and the front PCB on the CP5176. I connected them and did the setup test. I connected to my 500 box with XT500. Pushed the red button-the green led lighted up. I connected the multimeter black probe to OV and the red probe to the V+. Perhaps I did something wrong and made some connection with something because it came smoke from the area where the red probe sat. Unfortunately (it was late at night) I moved the red prob to the V- test pin and did get another smoke from the big transformer area. I saw that the R57 was burned. I replaced R56 and R57. Started the process again. The green led light up, but it turned off after a while. I measured direct on the replaced resistor R56 volt and it was +16.03v in, and +0.04 v out. On the R57 was -16.12 in and -0.54 v out. They were broken again. I replaced them again and also replaced the two TL074CN Quad Op-Amp. Started up the compressor again. Now I did get the right measurement on V+, V- and on TP7. Everything seems okey so far.
I build the SK25 and put it in place and send the 1khz sinewave to the compressor. Turned the in and out potentiometer up. No signal passed through the compressor. I measured the L1 with DC and did get 0,057 V, and the SK25 became warm after some minutes. Can’t find any misplaced components on the SK25 or obviously bad joints, but something is wrong I suppose. I also did the measurement on the resistors A to G without the SK25 described in the forum: https://www.soundskulptor.com/forum/index.php?topic=402.0  
Every value was right except D: that should be - 0.2 V, and I did get - 0.133 V.
I have also checked this: https://www.soundskulptor.com/forum/index.php?topic=9.0
Can’t find any problem so far. How Should I proceed?

27

MU524 Vari-Mu Tube Compressor / Re: MU524 is noisy

« Last post by JPK on January 19, 2026, 10:56:59 AM »

Check if any component is overheating, U2 in particular.

28

MU524 Vari-Mu Tube Compressor / STEP 6 OUT 1Vac

« Last post by FX on January 19, 2026, 10:54:40 AM »

Bonjour JP
Suite au premier test des deux MU524, j obtiens des résultats identiques sur les deux en terme de niveau de sortie aux pin 2/3 sur les deux entités.Autour de 1,...Vac
voici les relevés
 MU N°1
0/V+ =15,2 VDC
0/V- = -15,5 VDC
0/B+ =46,7VDC

TUBE 2->6V DC OK
TP1=41,4 VDC
TP2= 40 VDC

TP1= 0,37 VAC
TP2= 0,57 VAC
TP3=0,5 VAC

OUTPUT MIN= 1,34 VAC
OUTPUT MAX POT 10= 10,6 VAC


CHANGE COND

TP3=0,160 VAC
TP4=1,8 VAC
TP5= 1,8 VAC
TP6= -2,5 VDC
OUT= 3,7VAC
METER -6

T1 IMPEDANCE OK

---------------------------

MU N°2

0/V+ =15,2 VDC
0/V- = -15,5 VDC
0/B+ =46,7VDC

TUBE 2->6V DC OK
TP1=41,1 VDC
TP2= 41,1 VDC

TP1= 0,39 VAC
TP2= 0,37 VAC
TP3=0,521 VAC

OUTPUT MIN= 1,07 VAC
OUTPUT MAX POT 10= 11,6 VAC


CHANGE COND

TP3=0,06VAC
TP4=0,680 VAC
TP5= 0 VAC
TP6= -14 VDC
OUT= 1,5VAC
METER MAX -20 

T1 IMPEDANCE OK

les 2 T1 ont bien la face vers l arrière.

Si vous avez des pistes je suis preneur a 200%

je vous en remercie

29

MU524 Vari-Mu Tube Compressor / Re: MU524 is noisy

« Last post by OttoWei on January 18, 2026, 09:56:23 AM »

No, I have tested some more now and the tube does not affect the problem at all.

30

MU524 Vari-Mu Tube Compressor / Hiss when recording

« Last post by Pierro on January 15, 2026, 09:21:00 AM »

Hello JPK,

I built my 524 few month ago and it works perfectly when i send it line signal but adds a LOT of hiss when i try to record through it, so much that it's unusable this way. The is is just white noise.
Set up: microphone -> 1073 preamp -> MU524

Bringing up the input doesn't add noise but the output on 0 is already too much and bringing it up just adds more hiss.

Do you know what could be the issue?
Thanks a lot