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MP512 Microphone preamplifier / Re: Clipping/distorting noise on High Z input

« Last post by JPK on Today at 11:04:36 AM »

Check that Q2 (2SK170) is in the correct position A.
Can you measure the DC voltage (against 0V) on both sides of R51: near connector (16V) and near C24 (15V) ?
Can you measure the DC voltage (against 0V) on both sides of R48: near C23 (8V) and near R41 (1V) ?

2

MP512 Microphone preamplifier / Clipping/distorting noise on High Z input

« Last post by hanssongt on August 17, 2026, 08:03:05 PM »

Hi!

Recently finished my latest build. Everything works except when connect the DI. I can hear the source (bass in this case), but it sounds like it's clipping/distorting even on low gain. Any idea what could cause this?

I should mention that when I first tried the DI I coulnd't hear anything, but that was because I had missed soldering a couple of the resistors on the DI board. After doing that I got sound but got the problem mentioned above. I hope I didn't mess anything up by testing it without all parts soldered first.

Thanks,
Tobias

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LA502 Optical Compressor / Re: Release time feels bit fast

« Last post by Slembones on August 11, 2026, 08:15:33 PM »

ok. played it in the 10ms mode and the release is better. so I going with it like it is. Thank you

4

LA502 Optical Compressor / Re: Release time feels bit fast

« Last post by Slembones on August 11, 2026, 04:49:08 PM »

My construction quality is world class. that being said what happens is with vocals its very good but with bass it swells to fast as the note dies. it feels like with a bit more release time it might compensate for the swell

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LA502 Optical Compressor / Re: Release time feels bit fast

« Last post by JPK on August 11, 2026, 09:27:39 AM »

Do you also find the release time too fast with the 10mS attack?
Check the value and solder joints of R32, C17, C18.
If still too fast try increasing R32 to 4.7M. You could also add an additional cap in parallel with R32. It will also slow down the attack time but you can compensate by decreasing R29.

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LA502 Optical Compressor / Release time feels bit fast

« Last post by Slembones on August 10, 2026, 08:03:50 PM »

Is there a way to slow the release time down a bit. it feels a little non linear. the unit sounds good and is set up per the manual so everything works and is in the right place.

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MP566-II Tube microphone preamplifier with HPF / Re: Green LED (LD2) does not light

« Last post by guenter1910 on August 07, 2026, 12:59:14 PM »

After reflowing the solder joints it seems to work now. This is a bit of a surprise to me because measuring the connections alway showed that everything is fine. Thank you for your help!

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MP566-II Tube microphone preamplifier with HPF / Re: Green LED (LD2) does not light

« Last post by JPK on August 06, 2026, 04:47:16 PM »

Check that R46-L is connected to the 0V. Check on the resistor leads, not the PCB pad.
Reflow the solder joints of R45, R46, R47, R48.

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MP566-II Tube microphone preamplifier with HPF / Re: Green LED (LD2) does not light

« Last post by guenter1910 on August 06, 2026, 07:08:42 AM »

what should I check next? 

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MP566-II Tube microphone preamplifier with HPF / Re: Green LED (LD2) does not light

« Last post by guenter1910 on August 03, 2026, 06:35:16 PM »

the connections are all ok