1

LA502 Optical Compressor / Re: Absolutely no gain working.

« on: October 21, 2025, 05:15:15 PM »

Still following the signal:
How many volts do you get across R17, with the multimeter probes on either side of R17?

2

LA502 Optical Compressor / Re: Absolutely no gain working.

« on: October 21, 2025, 11:11:57 AM »

Try to follow the signal
Good on R2 and R5

How many volts on U1 pin7 ?
How many volts on TP1 ?

Cant check input transfo as my voltmeter isn't accurate enough for 2ohm
It is not 2 ohms but 2 kiloohms.

3

AB528 Microphone preamplifier / Re: The T1

« on: October 15, 2025, 05:30:45 PM »

I hope that is correct.?
Yes, correct.

4

AB528 Microphone preamplifier / Re: The T1

« on: October 13, 2025, 03:43:39 PM »

Looks like the same step for me
One is for the front and one for the back.

But it has to be on the "soundskulpture side" right?
Inserted from the "Not visible" side, soldered on the Sound Skulptor side.

it looks like the through-hole "silver-connecting-pads?" are so wide so it's touching the next pad?
On the front PCB, the pins are all independant, not connected between them.
On the back PCB, they are all connected together, this is normal.

How do I post pictures?
You can post a link to a picture with "Insert image" icon.

5

EQ573 Equaliser / Re: Hi Frequiency "Hiss" when it is at pre mode

« on: October 10, 2025, 05:03:43 PM »

It seems to be a gain staging problem.
Try increasing the gain at the preamp, via the gain switch and decreasing the level with the trim pot.
What is the sensitivity of your converters? If adjustable try reducing it. If not possible you could also add a Pad after the preamp.

6

EQP501 Passive Equalizer / Re: Son faible et pas d'EQ

« on: October 06, 2025, 09:23:29 AM »

Merci pour votre retour. À ce stade, c’est notre premier cas de défaillance sur ce modèle de switch parmi plusieurs milliers d’unités livrées, d’où notre étonnement.

Pour affiner le diagnostic, pouvez-vous confirmer s’il n’a pas pu être altéré lors du montage ou d’une manipulation ? En particulier :

• Contraintes mécaniques : Choc, effort sur l’axe/capot, torsion du levier, mauvais alignement avec la façade.

• Thermique/soudure : échauffement prolongé (> 3–4 s par patte), reprise multiple.

Selon ces éléments, on confirmera rapidement s’il s’agit d’un défaut pièce ou d’un incident de montage.

7

MU524 Vari-Mu Tube Compressor / Re: Stuck on step 7

« on: September 18, 2025, 05:48:33 PM »

Hello, your module is repaired.
There were two problems.
The first was the broken 2n7000 (be careful of static electricity, this component is very sensitive) and the second was the defective solder on the tube's PCB. I think the solder you're using isn't the best quality for proper soldering. I noticed some residue due to the solder. The connection to the tube wasn't perfect (there was noise in the tube and the tube's balance voltage was impossible to achieve).

The module has been calibrated and reassembled. It's ready to use!

8

MP566 Tube microphone preamplifier / Re: MP566 fault troubleshooting help needed.

« on: September 16, 2025, 05:50:42 PM »

The L272 has become difficult to find these days.
You can replace it with a TCA0372DP1.
Like any other integrated circuit, it can be killed by overvoltage on any pin, a short circuit on some pins and by overheating.

9

MP566 Tube microphone preamplifier / Re: MP566 fault troubleshooting help needed.

« on: September 14, 2025, 04:39:05 PM »

The problem is on U4 or U5 or U6 or U7 or several of these.
Remove U4 and create a small jumper with a little piece of wire, between pins 2 & 3.
Place the voltmeter between 0V and TP2 and power on. If the high voltage is present then U5 is OK.
Remove the jumper and place anotherone between pins 1 & 2.
Place the voltmeter between V- and TP8 and power on. If the 12V is present then U6 and U7 are OK.
If both tests are OK, you just need to replace U4.

Did the 2 pres broke down at the same time? Did they overheat?

10

Discussions about the products / Re: Christmas wish-list new modules suggestion!

« on: September 09, 2025, 11:39:45 AM »

Thank you for the clarification.

11

Discussions about the products / Re: Christmas wish-list new modules suggestion!

« on: September 08, 2025, 05:48:30 PM »

Thank you for these suggestions, they are much appreciated. We are constantly thinking about what the next module should be.

Stereo width module: already considered. What do you think would be the advantage of analog over plugin?
Stereo fet compressor: It is already available in the form of 2 CP5176. Same thing with the varimu.
Analog chorus: Really? This would also needs a stereo module. Would you use it on stage or in the studio?
Analog delay: I think the best delays are digital (like Eventide).

12

MP573 Microphone preamplifier / Re: Loud Pop When Changing dB Rotary Switch

« on: August 30, 2025, 09:12:22 AM »

10% tolerance is enough for these DC removing tantalum caps.
Electrolytic aluminum caps are generally 20%.
Ceramic and film are 5%, 10% or 20% depending on their role.

13

MP573 Microphone preamplifier / Re: MP573 LED not behaving correctly

« on: August 30, 2025, 09:04:49 AM »

It does make sense!
What we do is remove the cover of the XLR plug to access the pins and connect the meter to them.

14

MP573 Microphone preamplifier / Re: MP573 weird behavior (no volume after 20)

« on: August 28, 2025, 08:38:56 AM »

15

MP573 Microphone preamplifier / Re: Loud Pop When Changing dB Rotary Switch

« on: August 28, 2025, 08:37:17 AM »

KEMET, KYOCERA, Vishay.

16

MP573 Microphone preamplifier / Re: MP573 LED not behaving correctly

« on: August 28, 2025, 08:35:12 AM »

You must not go through a mic but instead connect a balanced cable between an output of your converter and the preamp mic input.
Then send a sine signal to this output and measure the amplitude with the DMM on AC Volts connected between pins 2&3 of the XLR. The measurement must be done while the output is connected to the pre input.

17

MU524 Vari-Mu Tube Compressor / Re: Stuck on step 7

« on: August 27, 2025, 09:52:54 AM »

Contact me here: https://www.soundskulptor.com/en/content/6-contact

18

MP573 Microphone preamplifier / Re: MP573 weird behavior (no volume after 20)

« on: August 27, 2025, 09:50:24 AM »

Here are the voltages for the REV 1.3
The voltages are measured against TP3.

Pins 3 and 12 are both with -9v and i dont think this is right.
I think this is not measured against TP3?

19

MP573 Microphone preamplifier / Re: Loud Pop When Changing dB Rotary Switch

« on: August 27, 2025, 09:34:38 AM »

I don't know this particular brand but the specs are the right ones: 22uF - 16V.

20

MP573 Microphone preamplifier / Re: MP573 LED not behaving correctly

« on: August 27, 2025, 09:28:58 AM »

With an input signal of 1kHz, Gain=10dB, Trim=-10, Z=1200.
What AC input voltage do you need to light up the green LED?
- Normally about 140mVAC (measured with the preamp connected)

With an input signal of 1kHz, Gain=10dB, Trim=+10, Z=1200.
What AC input voltage do you need to light up the red LED?
- Normally about 1.4VAC (measured with the preamp connected)


It is normal that Q6 gets warm. It dissipates around 1.25W.

21

MP573 Microphone preamplifier / Re: Loud Pop When Changing dB Rotary Switch

« on: August 26, 2025, 03:29:39 PM »

is that "pop" going from 20 dB to 30 dB "normal"?
Some pop at this position is normal because the 30 position adds a preamplifier stage to the audio path.
If it is feels too loud it could be that the reversed tantalum as suffered from the reversed polarity (not unlikely).

22

MU524 Vari-Mu Tube Compressor / Re: Stuck on step 7

« on: August 26, 2025, 03:22:56 PM »

All OK.
Check again the tube heater (step 4 of the setup guide).
I am sorry, I am short of ideas. Do you want to sent it to us for a check at the lab?

23

MU524 Vari-Mu Tube Compressor / Re: Stuck on step 7

« on: August 25, 2025, 03:32:52 PM »

Check that the input transformer is in the correct orientation.
Check that TR1 and TR2 have the correct value.
Check that R3 to R10 have the correct value.
Check that the voltage on B+ is stable.
Check the input transformer coils resistance (in circuit, input pot on max): 

• 2-4 : 37 ohms
• 3-5 : 37 ohms
• 7-9 : 100 ohms
• 8-10 : 100 ohms

Check the input resistance (between XLR pins 2&3, input pot on max): 4.6k

24

MP573 Microphone preamplifier / Re: Loud Pop When Changing dB Rotary Switch

« on: August 25, 2025, 03:16:16 PM »

Pops are often caused by a reversed electrolytic or tantalum capacitor.
So the first thing to check is the direction of these caps: The + sign on the layout must match the + side of the capacitor. 

25

MU524 Vari-Mu Tube Compressor / Re: Stuck on step 7

« on: August 24, 2025, 09:18:48 AM »

Can you change the tube with the one from the other unit and check if it stabilizes better?