1

MP573 Microphone preamplifier / Loud Pop When Changing dB Rotary Switch

« on: August 25, 2025, 03:11:47 AM »

Hi,

I've just finished building my second MP573. Both of them seem to be working well, from the tests I've done according to the Setup Guide. All tests were good. But on the first one, when changing the dB level on the rotary switch, there are little pops, not terrible, but present. On the second one, the pops are quite pronounced, especially when going from 20 to 30 dB. So much so that it puts the meters into the red within Pro Tools.

So main question: Is this normal, or should there be no pop at all when change dB positions on the rotary switch?

I searched for "pop" in the support forums and found the following two threads:

• Low output and distortion at lower gain levels (https://www.soundskulptor.com/forum/index.php?topic=232.0)
• MP573 Having issues after plugging in (https://www.soundskulptor.com/forum/index.php?topic=260.0)

As I'm quite new to DIY, I didn't fully understand all that was said in the above threads, hence this new thread. Sounds like the pops should not be happing. What would be my starting point to test for what might be wrong?

Thanks

2

MP573 Microphone preamplifier / R47 and R20 Differences

« on: August 03, 2025, 04:09:31 PM »

Hi,

Finished my first unit build, and it worked great. Love the sound. I've started working on the 2nd one. I've just run into a little confusion that I don't remember having on the first unit. I'm thinking I just got lucky, with the first unit, as I seems to be working great.

I noticed that R47 and R20 have the same color rings and order: yellow, violet, black, gold, brown. But the R47 is 1/2 watt, where as R20 is 1/4 watt. The R47 is horizontal on the board, and the R20 is vertical. The R47 is a larger resistor, whereas the R20 is smaller like the majority of the other resistors. On the PCB, R47 has a larger "outline" than the other resistors, minus R26, which is also larger and 1/2 watt. Seems like the R47 is indeed 1/2 watt, and not 1/4 watt, simply because of it's physical size, and the "hint" of a larger outline on the PCB. Pretty sure that is correct. Is it?

Secondarily, as very much a beginner, it's not perfectly clear to me that the larger resistor is the 1/2 watt and the smaller resistor is the 1/4 watt, as they both have the same colored rings and order. Is that normal that two resistors would have the same colored rings and order, but different wattages? If so, how would I tell the difference between the two, visually, other than with a multimeter?

Thanks

3

MP573 Microphone preamplifier / Short Circuit Test

« on: July 07, 2025, 03:10:31 AM »

Hi,

I've finished doing the build, and have started testing. Step #1 is to do a short circuit test. As I am very new to this, I'm uncertain as to how to specifically go about getting the correct readings. Here's what I've done so far and the readings I've gotten.


Multimeter set at 200k ohms
Black test lead is on common input
Red test lead is on ohms input

Check #1
-------------------------
V- has black test lead
OV has red test lead
Result: 80.xx - continues to slowly increment

Check #2
-------------------------
V+ has red test lead
OV has black lead
Result: 75.xx - continues to slowly increment

Any other combination of leads on V-, OV, and V+, gives me a reading of ‘OL’ which according to my multimeter, is ‘over limit’, but that’s also what it says when the leads aren’t touching anything.

What I don’t know is if these readings are what they should be. I’m very knew to this, so any input is helpful, as I continue to learn.


One thing I was also a little confused about the JMP3. Should it have the jumper in place or not when doing the Short Circuit test? The build guide directs say to put it on, so by the time you get to the setup guide, I'm assuming it's supposed to still be on, as I didn't see anywhere saying to take it off. But -- in step #2 of the setup guid, it says to the put the jumper on, which is odd, as it's already on. Did I miss something saying to take it off before doing test #1, or should is still be on?

Thanks

4

MP573 Microphone preamplifier / C34 Film Capacitor Placement

« on: June 22, 2025, 11:53:15 PM »

Hi,

The C34 Film Capacitor has two pins, but the PCB has three holes. Which holes should the capacitor go in?

Also, just want to confirm that the "WIMA 0,47 100-" is indeed the C34 capacitor. Is that correct?

Thanks.

5

MP573 Microphone preamplifier / Missing Capacitors

« on: June 02, 2025, 04:48:15 PM »

Hi,

I'm in the middle of the build, and it looks like I'm short three (3) 330u-25v capacitors. There should have been 9, but there were only 6. I purchased two of the pre's and checked the second one, and there are 9 there, so that's good. But I'm short three (3) on the one I'm currently building. What's my best option here? Do you send me the 3 missing capacitors, or shall I just get them another source like amazon:

Replacement for 6 pcs Panasonic FM Series Capacitors 25V 330uf Low Impedance
https://www.amazon.com/pcs-Panasonic-FM-Capacitors-330uf/dp/B073YR6GCY/ref=sr_1_1_sspa?crid=2FZSVGKV9AHY6&dib=eyJ2IjoiMSJ9.lYGszSaGmIKqSmxQ-NYYR3toB8oaNxkK1x6ow_9wMxRNUkzN02RcFEcB3edtqYU9UtljTMxS0N6U717AmUy53o8btpqtdoBJVeTYAm_l0R3h-6-EotxYrAY9uudKCvvi8K02SvPwAy9CEQ-2dn7UUFWkgOnpxVdACeHKNRSpjB0XZWaVvJdwpTo5GnCYXifRGbXCMuf5gjOP7P07xCfgDqmMKBiYHhYITMEqpUO3dig.ODc-pEs8bNJvWepUptD3d3cL4qy-FmY6WLl7NM9Gcik&dib_tag=se&keywords=330uf+25v+capacitor&qid=1748875453&sprefix=capacitor+330uf%2Caps%2C181&sr=8-1-spons&sp_csd=d2lkZ2V0TmFtZT1zcF9hdGY&psc=1

If the latter, I just want to make sure I get the correct ones.

Thanks

6

MP573 Microphone preamplifier / Laster Version of the Assembly Docs, Docs-24

« on: May 04, 2025, 01:52:49 AM »

Hi,

Was about ready to start my build. On the outside of the box, is says, "DOCS-24". I'm presuming that's the current exact docs version I need for this version of the kit I have. But on the product page, it only goes up to "DOCS-20". Where can I find "DOCS-24"?

Thanks.

7

XT500 Lunchbox connector extender / Ribbon Cable Direction

« on: April 27, 2025, 11:10:47 PM »

Hi,

Getting ready to build my first Sound Skulptor units (MP573). In prep for that, I'm building the XT500. It looks like the ribbon cable has one "wire" at the top that is red. On the each of the two PCB's, there is a white dot. From what I can glean from the two images on the product page, the top, red "wire" on the cable should be oriented to the white dot's on the two PCB's. Is that correct? If so, and because the ribbon cable connectors can only go fit in one direction in the ribbon connector sockets, it looks like the cable that connects to the PCB that connects to the inside of the 500 series chassis is 180 degrees different than what's in the product images. See images. It'll be a little cumbersome to get it into the 500 chassis because of the cable direction/orientation of the ribbon connector, but if the "red line to white dot" orientation is the important part, then I guess that's the way it is. Granted, I can flip the ribbon cable, but then the ribbon will be kind of going over the test pins. Or... is the cable that was sent, manufactured 180 degrees the wrong way on one end? Just want to be sure before I use it for testing.







Thanks