26

MP573 Microphone preamplifier / Question about Gain Staging

« on: February 12, 2023, 05:57:28 PM »

Hi everyone,

I am testing my new preamp and I have some questions, maybe you can help me.

In order to test the preamp behavior, I send a sine signal of 1 khz at -18 dB to the preamp. If I want to preserve in the DAW the same level od -18dB I must set the preamp like this:



obtaining this signal:




So, at this point, trying to test it without clipping, I put the preamp in Line mode in order to obtain the cleanest signal, con this configuration:



and this signal (very clean).



But, If I want to obtain more colour, boosting the output transformer, I get this:





It's almost the same signal, without any harmonics.

Is this normal? Maybe I'm doing something wrong?

Thank you so much for your advices!

Paco

27

MP573 Microphone preamplifier / Re: No Input

« on: February 03, 2023, 06:57:38 PM »

You were right! Transistor in B position 

Now tested and working!

Thank you so mucho for your big support, Jean Pierre!

28

MP573 Microphone preamplifier / Re: No Input

« on: February 03, 2023, 06:45:51 AM »

Great! I replace the resistor and now works fine!

Now, I have issues with DI

There's no sound. The relay works, I hear the clic connecting it. No sound when I move the jumper.

29

MP573 Microphone preamplifier / Re: No Input

« on: February 02, 2023, 09:37:58 PM »

I put 4K7

30

MP573 Microphone preamplifier / Re: No Input

« on: February 02, 2023, 10:24:18 AM »

Jean Pierre, I have detected i have solded wrong R28. It could be the cause? Should I have to desinstall the input transformer?

31

MP573 Microphone preamplifier / Re: No Input

« on: February 02, 2023, 07:34:39 AM »

Did you try to follow the signal as described here?

32

MP573 Microphone preamplifier / Re: No Input

« on: February 01, 2023, 08:34:23 PM »

Hi,

Yes, I renamed the I/O. The routing is: The preamp is in Slot 1 of my MIDAS L10. So, OUT 1 of the MIDAS goes to IN 1 of the Interface, and OUT 1 of the Interface goes to INPUT 1 of the MIDAS. That's the same routing of my other modules.

In Reaper, I create a track and insert a Reainsert Plugin. As I show in the pic, there's no return signal. Is like doesn't detect the module.

I am trying to do the test Jean Pierre asks in the post before, but I'm not sure how to so it. Sorry about that!

Cheers!

33

MP573 Microphone preamplifier / Re: No Input

« on: January 31, 2023, 07:35:43 PM »

Jean Pierre,

I am trying to test in the next way, but probably wrong:

I use Reaper and I insert the preamp in a track with "Reainsert". The problem is there is no return signal. (with other modules everything is OK). By the way, DI doesn't work either.

I put some pics:

With a MIDAS Compressor:
 
 

With the MP573

34

MP573 Microphone preamplifier / Re: No Input

« on: January 31, 2023, 12:55:27 PM »

In that case, I have all correct. Jumper in CN1 in place and in JMP3 installed because the DI board is out at this moment.

Any other thing I could check?

35

MP573 Microphone preamplifier / Re: No Input

« on: January 31, 2023, 11:36:07 AM »

Thanks Jean Pierre, 

Should I put off the 2 jumpers?

36

MP573 Microphone preamplifier / Re: No Input

« on: January 30, 2023, 07:26:28 PM »

Hi again Jea Pierre,

My check figures for today are very normals, I guess..

A. 2.6V
B. 4.1
C. 22.6
D. 13.6
E. 2
F. 13
G. 0.9
H. 4
I. 0.34
J. 3.4
K. ? 22.8
L. 3


But the results are the same. No input in the preamp.

37

MP573 Microphone preamplifier / No Input

« on: January 29, 2023, 04:34:36 PM »

Hi!

I just finished the assembly and I'm with the tests.

at point 3 I get 24.67V and 24.58 connecting the output of the transformer.

At point 4, I get 3.0V with the trim.

The problem is that I don't have output.

I have checked and got the following results:

A.2.6V
B.4.1
c. 22.6
d.13.6
e.2
f.13
G.0.9
h.4
I.0.34
J.3.4

I don't know how to measure point K, but I realize that at point L I get 0 Volts.

Can you help me?
Thank you!

38

MP573 Microphone preamplifier / 1N4004 Diode

« on: January 27, 2023, 05:45:01 PM »

Hi,

I can´t find 1 of the 5 1N4004 diodes in the kit. I have here a 1N4007 diode. Can I replace it safety?

Many thanks!