91

MP573 Microphone preamplifier / Re: Loud Pop When Changing dB Rotary Switch

« Last post by JPK on August 28, 2025, 08:37:17 AM »

KEMET, KYOCERA, Vishay.

92

MP573 Microphone preamplifier / Re: MP573 LED not behaving correctly

« Last post by JPK on August 28, 2025, 08:35:12 AM »

You must not go through a mic but instead connect a balanced cable between an output of your converter and the preamp mic input.
Then send a sine signal to this output and measure the amplitude with the DMM on AC Volts connected between pins 2&3 of the XLR. The measurement must be done while the output is connected to the pre input.

93

MP573 Microphone preamplifier / Re: MP573 weird behavior (no volume after 20)

« Last post by camarada78 on August 27, 2025, 06:05:20 PM »

FIXED - it was a bridge solder from a previous fix i've made. 

Thanks a lot for the help. 

have a good day.

94

MP573 Microphone preamplifier / Re: MP573 weird behavior (no volume after 20)

« Last post by camarada78 on August 27, 2025, 02:47:45 PM »

My voltages, in reference to TP3, are as follows:

95

MP573 Microphone preamplifier / Re: Loud Pop When Changing dB Rotary Switch

« Last post by musicarr on August 27, 2025, 02:29:21 PM »

Thanks for the confirmation. Are there brands that you are familiar with that you recommend?

96

MP573 Microphone preamplifier / Re: MP573 LED not behaving correctly

« Last post by davidfloegel on August 27, 2025, 11:23:36 AM »

Hmm I'm not sure how to best measure this.

With an input signal of 1kHz, Gain=10dB, Trim=-10, Z=1200.
What AC input voltage do you need to light up the green LED?
- Normally about 140mVAC (measured with the preamp connected)

I can't actually get the signal loud enough through my speakers to trigger the LED at all.

With an input signal of 1kHz, Gain=10dB, Trim=+10, Z=1200.
What AC input voltage do you need to light up the red LED?
- Normally about 1.4VAC (measured with the preamp connected)

I can get it to go green, but I can't get the signal loud enough through my speakers for it to go red.


Are there other ways I can feed in a signal?

97

MU524 Vari-Mu Tube Compressor / Re: Stuck on step 7

« Last post by JPK on August 27, 2025, 09:52:54 AM »

Contact me here: https://www.soundskulptor.com/en/content/6-contact

98

MP573 Microphone preamplifier / Re: MP573 weird behavior (no volume after 20)

« Last post by JPK on August 27, 2025, 09:50:24 AM »

Here are the voltages for the REV 1.3
The voltages are measured against TP3.

Pins 3 and 12 are both with -9v and i dont think this is right.
I think this is not measured against TP3?

99

MP573 Microphone preamplifier / Re: Loud Pop When Changing dB Rotary Switch

« Last post by JPK on August 27, 2025, 09:34:38 AM »

I don't know this particular brand but the specs are the right ones: 22uF - 16V.

100

MP573 Microphone preamplifier / Re: MP573 LED not behaving correctly

« Last post by JPK on August 27, 2025, 09:28:58 AM »

With an input signal of 1kHz, Gain=10dB, Trim=-10, Z=1200.
What AC input voltage do you need to light up the green LED?
- Normally about 140mVAC (measured with the preamp connected)

With an input signal of 1kHz, Gain=10dB, Trim=+10, Z=1200.
What AC input voltage do you need to light up the red LED?
- Normally about 1.4VAC (measured with the preamp connected)


It is normal that Q6 gets warm. It dissipates around 1.25W.