1

MP573 Microphone preamplifier / Re: MP573 Build - No Output with XLR Connector

« on: September 04, 2026, 10:17:23 AM »

Hi,

i swapped the relay which is working now, however, i fucked up the input trafo in the process .

I'll send you an email / pm because now i need spare parts, haha.

Cheers, 
Herbert

2

MP573 Microphone preamplifier / Re: MP573 Build - No Output with XLR Connector

« on: September 03, 2026, 10:23:54 AM »

Hi,

i figured it might be the relais, i'll try to (gently) replace them. 

I will replace C2 as well to be of the same type as C3.

Thanks & kind regards,
Herbert

3

MP573 Microphone preamplifier / MP573 Build - No Output with XLR Connector

« on: August 31, 2026, 01:35:06 PM »

Hi,

i finished my 2nd MP573 build and I'm having troubles getting it to work & would need some advice / guidance.


When the DI board is inserted, JMP3 removed, everything works fine. However, with no DI board, JMP3 on + Mic/Signal via XLR, there is no output.

Tests / measurements I did so far:

DC Values A-K all have the correct voltage.

AC Values with multimeter on 50hz Sine wave via XLR Input:
* In+ to In- : 0,6V
* C2 to C3: 0,6V
* TP2 to T1 Pin 7: 0V

Hints:
* The kit was missing C3, which i then substitutet with a ceramic cap "n47" 100V. (see attached pic).


* RLY1 edge got burnt (see attached pic2). I don't remember if it was from soldering iron (unlikely) or due to faulty connection...




Thanks for you support & cheers from Austria

4

MP573 Microphone preamplifier / Inline-attenuator after MP573 and before interface

« on: March 13, 2026, 02:30:03 PM »

Hi,

i just finished building my first of 2 MP573 - everything worked fine & sounds great. However, i only afterwards noticed, that the grey output level knob is placed before the output transformer (which is explained in a blogpost on soundskulptor website) and i can not fully drive the output stage and attenuate signal after (like i think it's possible on my MP512s) without overloading my RME line-ins.

Due to lack of space in my lunchbox i cannot use a PAD500 module - is it possible to just plug in a switchable inline attenuator like the Shure A15AS or the AT8082 which have around 1kOhm impedance according to specs, to get a similar attenuation without change in sound?

(My RME line-ins that come afterwards have 10kOhm input-impedance).

Thanks for you infos & cheers from Austria,
Herbert