Sound Skulptor forums

Build help and troubleshooting => MP573 Microphone preamplifier => Topic started by: b.riesel on August 22, 2022, 07:01:44 PM

Title: Strange behavior when internal connected to EQ573
Post by: b.riesel on August 22, 2022, 07:01:44 PM

Hi Jean-Pierre
I now have both of my MP573 connected to the EQ573II via the internal conexin-cable. So far, everything works fine. But when I switch of my whole setup and switch it on again, I have some pulsing high level on the outputs, when the EQe is set to pre.
When I switch to XLR or off, it disappears, as long, as I switch back to pre. After a while this behavior is gone. As if a condensator is discharging.
Do you have an idea, what could be wrong, or what I could check for?
Best regards
Stefan

Title: Re: Strange behavior when internal connected to EQ573
Post by: JPK on August 23, 2022, 09:46:19 AM

This happens in some setups. It is caused by the slow start on the MP573 which creates a pulse in the EQ which is reinjected in the pre and makes a loop.
The best solution in this situation is to remove the slow start on the pre (if your lunchbox can stand some inrush current):
On the MP573, remove U1 (LM317T) by heating the 3 pins together with a blob of solder, it will fall off.
Now link the 3 pads together with a blob of solder.

Title: Re: Strange behavior when internal connected to EQ573
Post by: b.riesel on August 25, 2022, 11:43:09 AM

How can I check, if the Lunchbox can stand some inrush? I use a Fredenstein Bento 8.
I have 2 MP+EQ Combis in my Box.

Title: Re: Strange behavior when internal connected to EQ573
Post by: JPK on August 25, 2022, 08:42:30 PM

Try it. If it fails, the lunchbox will not be able to start. It will switch to a protection mode, believing there is a short circuit.

Title: Re: Strange behavior when internal connected to EQ573
Post by: b.riesel on August 25, 2022, 11:34:43 PM

ok, i will try...thank you for your help and your patience!
best regards
stefan