1

EQ531T Tube Equalizer / Re: EQ531T build

« on: July 10, 2025, 09:14:56 AM »

2

EQ531T Tube Equalizer / Re: EQ531T build

« on: July 09, 2025, 03:49:11 PM »

The problem must be between U1, C8, C9, R5, R6, P1, J1a, J1b. There are no other components involved.
Check the values, the solder joints, the min/max value of P1, swap U1 with another OPA2134.

3

EQ531T Tube Equalizer / Re: EQ531T build

« on: July 08, 2025, 10:56:10 AM »

What is the attenuation of a 1kHz sine signal when the HPF is turned fully clockwise. It should not be more than 0.5dB.

4

EQ531T Tube Equalizer / Re: EQ531T build

« on: July 08, 2025, 09:34:52 AM »

Check that there is continuity between pin 1 of U1 and the center pin of pot P1 furthest from the front panel.
Check that there is continuity between 0V test pin and the center pin of pot P1 closest from the front panel.

5

MP573 Microphone preamplifier / Re: Short Circuit Test

« on: July 07, 2025, 03:46:43 PM »

0L on the DMM means resistor is too high to be measured. In this test check there is no short circuit or very low resistance.

6

EQ531T Tube Equalizer / Re: EQ531T build

« on: July 07, 2025, 03:43:46 PM »

Maybe one of them? Check that they are not shorted.

7

MP573 Microphone preamplifier / Re: Short Circuit Test

« on: July 07, 2025, 09:15:37 AM »

Any other combination of leads on V-, OV, and V+, gives me a reading of ‘OL’
This show you are OK. The resistance is too high to be measured.

Should it have the jumper in place or not when doing the Short Circuit test?
It doesn't matter.

8

LA502 Optical Compressor / Re: C5 or not c5

« on: July 07, 2025, 09:09:26 AM »

This is not normal.
Are you driving it from a low impedance?
The attenuation at 20Hz should not be more than 0.3 dB.
Check the value of C1, C2, C3, C4.

9

MU524 Vari-Mu Tube Compressor / Re: Light Hiss/Noise

« on: July 07, 2025, 08:57:29 AM »

No need to reinstall replaced components if the replacement did not make any changes.

10

EQ531T Tube Equalizer / Re: EQ531T build

« on: July 07, 2025, 08:52:40 AM »

Check the solder joints and value of pot P1, capacitors C8, C9 and resisstors R5, R6.

11

EQ531T Tube Equalizer / Re: EQ531T build

« on: July 03, 2025, 05:22:20 PM »

Check the output transformer connections: You should read around 35ohms between the output XLR pins 2 & 3, Power on, EQ on, no input signal.

12

EQ531T Tube Equalizer / Re: EQ531T build

« on: July 02, 2025, 05:17:32 PM »

I added a Try to follow the signal section in this thread: https://www.soundskulptor.com/forum/index.php?topic=7346.0
Try it!

13

EQ531T Tube Equalizer / In case your EQ531T doesn't work as expected

« on: July 02, 2025, 05:14:40 PM »

Check the usual suspects:

• Forgotten solder joint,
• Bad solder joint (reflow suspicious joints),
• Reversed components (electrolytics, diodes, transistors, IC's). In case of IC's, probably destroyed, better replace,
• Flipped IC's or transistors,
• Trim all the component leads and test pins as short as possible. Nothing must touch the chassis plate.

Try to follow the signal
Send a good constant sine signal on input, like 100Hz - 1VAC measured between pins 2&3 of the input XLR.
All controls on OFF, EQ is IN.
Connect the voltmeter black probe to the 0V pin and trace the signal on (values +/-10%):
TP1: 0.57VAC
TP2: 0.54VAC  /  89VDC
TP3: 0.53VAC
TP4: 0.5VAC  /  89VDC
TP5: 0.5VAC
TP6: 0.5VAC

14

Discussions about the products / MOVED: EQ531T build

« on: June 30, 2025, 03:18:00 PM »

This topic has been moved to EQ531T Tube Equalizer.

https://www.soundskulptor.com/forum/index.php?topic=7344.0

15

EQ531T Tube Equalizer / Re: EQ531T build

« on: June 30, 2025, 03:06:04 PM »

No issue there.
We have supplied all the 47pF in 250V to avoid mistakes.

16

MP573 Microphone preamplifier / Re: MP573 - No low end

« on: June 30, 2025, 03:02:24 PM »

Sure!
Contact me here.

17

MU524 Vari-Mu Tube Compressor / Re: Light Hiss/Noise

« on: June 24, 2025, 04:38:39 PM »

If the issue is caused by a defective component, no charge, you only pay for the shipping.
In the other cases, our rate is 59 € per hour (+VAT if applicable).

18

MU524 Vari-Mu Tube Compressor / Re: MU 524 Stuck on Step 7

« on: June 24, 2025, 09:04:56 AM »

Great news !
For the meter you can increase its sensitivity by decreasing the resistor R34. Try 3k3 or 2k2.

19

MP573 Microphone preamplifier / Re: C34 Film Capacitor Placement

« on: June 23, 2025, 05:05:45 PM »

It fits into the 2 holes on the left that best match the cap size. The PCB can accept a larger capacitor.

WIMA 0,47 100 is the right cap.

20

MU524 Vari-Mu Tube Compressor / Re: Light Hiss/Noise

« on: June 23, 2025, 05:01:56 PM »

Does the noise in the left unit depend on the presence of the right unit next to it?

21

MU524 Vari-Mu Tube Compressor / Re: MU 524 Stuck on Step 7

« on: June 23, 2025, 04:57:21 PM »

Reversed input transformer ? The label must face towards the back.
What voltages do you get in the Voltage checks here.

22

MU524 Vari-Mu Tube Compressor / Re: MU524 Low Tube PCB Voltage

« on: June 16, 2025, 10:02:20 AM »

23

CP4500 Stereo Bus Compressor / Re: CP4500 - No output and incorrect voltages

« on: June 11, 2025, 09:33:43 AM »

24

MU524 Vari-Mu Tube Compressor / Re: MU524 Low Tube PCB Voltage

« on: June 08, 2025, 09:26:03 AM »

You could have a noisy regulator. It could be intersting to replace it.
The noise that can be measured with or without the cover plate is very high frequency induced and shouldn't affect the audio.

25

MP573 Microphone preamplifier / Re: Tension identique entre CN2 branché ou débranché

« on: June 06, 2025, 05:39:52 PM »

Je pense que c'est finalement OK.
Je le pense aussi.

Concernant la LED, elle passe au rouge très rarement
Il faut vraiment beaucoup de niveau pour passer au rouge, environ +24dBu, soient 3dB sous l'écrêtage.

il manque la sérigraphie «MUTE»
L'inscription MUTE a été supprimée pour rester cohérent avec nos autres préamplis, et aussi pour allèger le design.