Very noisy Deluxe Electric Mistress V1

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saintgillis
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Post by saintgillis »

Hello I have a very noisy Deluxe Electric Mistress V1
This circuit : http://www.metzgerralf.de/elekt/stomp/m ... ematic.gif
I've modded it to this circuit (Deluxe V2) : http://www.metzgerralf.de/elekt/stomp/m ... ematic.gif
I thought it would help but it didn't.

I did a recap, a good calibration.
I've read a lot of things in this forum and I tried a lot of things. But there is still a lot of noise at the output. I even had a spare SAD1024 hanging around, I've swapped it and it didn't change a thing. I've also replaced the balance 1K trimmer.

Thank you for reading and for helping if you have any idea !

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karul
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Post by karul »

What kind of a noise?
Last edited by karul on 28 Mar 2022, 14:32, edited 2 times in total.

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saintgillis
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Post by saintgillis »

White noise.
When the Range is full CW there is more noise
It is an original EHX

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karul
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Post by karul »

Is it original EXH pedal or diy? Show some pictures of it. Did you change the tantalum cap, or just electrolytics? Do you have a audioprobe ? Try to find where the noise appears or became significant, at which stage.

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saintgillis
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Post by saintgillis »

Original EHX. I've change the 1µ tantalum. Yes I have an audio probe. Noise seems correct at the output of the 741, and seems excessive at pin 1 of 4558 (even with the feedback network disconnected)

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Post by karul »

Noise level is constant or wobbly? No clock ticking? I'm not closely familiar with this circuit, but firstly you must be sure that 4558 is working properly and not contributing to the noise problem. You should check the bias and gain 10k trimmers too, and that everything is ok with them. If 4558 is on socket, get it out and test it. Or you can try something else. There are no pictures so I can't tell if SAD is soldered of socketed. You've mentioned that you've try changing it, so I guess there is a socket. If that's the case, get it out, and see what's going on pin 1 and pin 7. You should have only dry signal. See if there is noise. If noise level is normal, the modulation part of the circuit is generating it. That's the idea. Also check all the trimmers, wire connections etc. etc..

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saintgillis
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Post by saintgillis »

Noise level is constant.
4858 has been changed (and socketed)
The sad1024 is socketed, when I remove it there's no signal on 4558 pin 7, but pin 1 seems too noisy

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Post by karul »

Remove 100n after the pin 1 (4558) so the two opamp stages are disconnected, and check the noise on the 4558 pin 1. You didn't reply about trimmers? Have you change them too?

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saintgillis
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Post by saintgillis »

Now I've removed the feedback loop, biased pin 3 of the 741, cut the trace going to the input of the sad1024, and noise seems too high on pin 1 of the 4558.
I've replaced almost all the components around IC1b, for now I don't understand

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saintgillis
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Post by saintgillis »

Yes I've replaced the bias trimmer (not the gain one yet)
And I also tried to remove 100n after pin 1 of 4558

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saintgillis
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Post by saintgillis »

Maybe it's just normal to get this amount of noise when it is set on "filter matrix" and "Range" to max ... but is seems huge...

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Post by uncleboko »

Range to max?? of course it'll be noisy. Have you set the BBD bias and trim correctly by ear?

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saintgillis
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Post by saintgillis »

Yes, I've trimmed it with the oscilloscope to get the minimum clock noise

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Post by uncleboko »

You can eliminate any power supply problems by running off 2 PP9 batteries.

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saintgillis
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Post by saintgillis »

Here's the waveform at one side of the balance trim :
IMG_0379.JPG
Here's the waveform at the otherside of the balance trim :
IMG_0380.JPG
And here's the wavefrom on the wiper of the balance trim with optimum calibration :
IMG_0381.JPG

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saintgillis
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Post by saintgillis »

Can anyone confirm if the big amount of noise when the "Range" is full CW is normal ?

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Post by txjeff »

I know this is an old thread. I was looking for white noise with Electric Mistress, and I have the non-Deluxe version 1. And I too have a ton of white noise. I don't believe it always had it. I didn't mod it but I did insert it into a box that has a bunch of stomp box circuits in it, moving the footswitch and powering it by a central power supply. I watched a youtube on it and it was really quiet vs my noisy one, so something has gone sour. The only thing I haven't tried is hooking up two 9V batteries vs the power source to see if that is the problem.
""For in the same way you judge others, you will be judged, and with the measure you use, it will be measured to you."

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