1

LA502 Optical Compressor / Re: Absolutely no gain working.

« Last post by justebruyat on Today at 01:02:24 PM »

Merci de votre réponse
Oups, sorry...

Input transfo
Pin 1-5 : 2.06 kOhms
Pin 10-6 : 1.8 Kohms

With input 1khz, 1vac:

R2 right pin: 0.6v
R5 right pin : 0.3v (non 0.5v)

Gain à 0 : TP0V - TP1 : 0.3Vac
Gain  à 100 : TP0V - TP1 : 9.2v

Gain à 0 : TP0V - Pin7 U1 : 0.3Vac / 0.4Vac
Gain  à 100 : TP0V - Pin7 U1 : 14.4Vac

Bypass ou In n'affecte pas ces données

2

LA502 Optical Compressor / Re: Absolutely no gain working.

« Last post by JPK on Today at 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

LA502 Optical Compressor / Absolutely no gain working.

« Last post by justebruyat on October 19, 2025, 12:23:43 PM »

HEllo,

Everything has been done as guide intended; comp. seems to be working.
Bypass let the sound go trough ....
When turned to IN, there in absolutely no VAC. out
Re soldered evrything that needed too, zero short, diodes, caps and ICs in right order.

Relay doesnt click when changing the main psu switch, then sick to this position
Only clicks when turning on / OFF the whole unit
Though seems to be working fine with an outside dc quickly applied to its coil.

I also did a mistake on desoldering C4 (i had put first wrong value of capacitor and had to change it)
Wich broke the connection of the component to the PCB on the up side. Seems perfectly ok on the down side.
I have continuity as described by the pictures.

I'm not so good at reading schematic but it seems to me this is not the issue, as i still have contuinuity to the components it's supposed to .
C4 goes to 6 and 7 (in and out b) of U1B puis 7 est lié à U1A (3) in+... etc etc...
Sauf si le potard est à zero, je ne constate aucun court circuit. j'imagine donc que ma petite erreur n'est pas trop grave. Et que le problème vient d'ailleurs.

Thank you anyone, by advance for any help.

D'ailleurs -

"Check you get no DC volts on TP1. Any DC above a few millivolts here shows that there is an issue." --- zero or .001 V, pas de problème de ce coté là

Good on R2 and R5

23omh outside beatween 2/3 pin out.
5 ohm Between 0v and TP1.

1-3  ? 10 ohms (5 ohms if in circuit)

6-8  ? 10 ohms (5 ohms if in circuit)
9-12 ? 12 ohms
13-16 ? 12 ohms

All that is checked well.
Cant check input transfo as my voltmeter isn't accurate enough for 2ohm

4

AB528 Microphone preamplifier / Re: The T1

« Last post by JPK on October 15, 2025, 05:30:45 PM »

I hope that is correct.?
Yes, correct.

5

AB528 Microphone preamplifier / Re: The T1

« Last post by Consigliere on October 13, 2025, 05:03:17 PM »

Thanks JPK

1. ok. I admit, I misread the text about the sides.
2. But why is there a step 17 that says the same thing twice? Only difference is that the headline is Back intstead of Front? (and the addon to adjust the pins) Would be less confusing if you removed that step. 
3. Ah, I'm not at home and check the pins atm. So testing on the ((solderside) (soundskuptor side) (front side)) I should have connection if I test with a DMM. But if I test on the pins on the ((connector side) (not visible side) (back side)) I would have a problem if I get a sound from the DMM testing any pin to another?

I think I got it but. The extra step and all different names for the same thing is a bit confusing. -  Back side = not visible side AND Front side = SoundSkulptor side?

The picture on step 16 Named "front side" is on the back side.
The picutre on (not needed) step 17 named "back side" is on... also the back side.

EDIT:
Haha facepalm! I thought it was the same PCB on both step 16 and 17. I didn't see the difference on the pictures.  
Home again with DMM. Have contact between every second (ie pin 1,3,5,7 etc) on both sides. I hope that is correct.?

6

AB528 Microphone preamplifier / Re: The T1

« Last post by JPK 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.

7

AB528 Microphone preamplifier / The T1

« Last post by Consigliere on October 13, 2025, 03:08:30 PM »

I'm on stem 16 and 17 (seems to be some errors in this manual. Looks like the same step for me) and also it says:
       Insert the 90°, 13 pins headers, long tails first, into the holes, from the bottom side, marked “Not visible”.

But it has to be on the "soundskulpture side" right?

Anyway. Soldering the pins on the backside it looks like the through-hole "silver-connecting-pads?" are so wide so it's touching the next pad?
I measured and many pins seem to have connection to each other. What should I do?

How do I post pictures?

8

AB528 Microphone preamplifier / Re: AB528

« Last post by Consigliere on October 12, 2025, 12:11:54 PM »

You must skip the holes without a pad. These pins are unused. Leaving them unsoldered will make it easier if you ever need to replace the relay in the future.

Thx. Also had questions about those.

9

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

« Last post by JPK 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.

10

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

« Last post by ktziavos on October 08, 2025, 09:08:02 PM »

Hello there! Perfect sounding Eq! Have a small problem with the eq that i want to solve cause i want to use the pre mode. Yen i am in xlr mode everything sounds good. When i turn it to the Pre mode, sound is the same like in xlr but it adds a hisss (hi frequency noise) and it is unusable. Any idea?