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Popping switch - Help!

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(first off, sorry for the redundancy of my posts, but I have beed advised that I could get more help in this forum)

I have a DIY guitar amp (a mesa/boogie 2:90 copy), and it has a problem.

One of the switches produces a rather large popping noise (from the speakers) when turned off.
Its not the main power switch, the switch increases or decreases the cathode voltage on a 12ax7.
I believe it's because of internal arcs inside the switch.

Installing a 10nf capacitor on the contacts did not remove the popping, and either way, the high end frequencies are compromised.
I have read here and a few other places that a contact suppressor and a vdr might help.

I invite you to read the discussion I had on the "Everything Else" forum, it contains schematics that could help you help me:


thanks in advance,


[Edited by lwi on 11-23-2001 at 12:52 PM]
Downhere, the switch is causing a popping sound from the speaker when opened. This is because the cathode jumps to its new operating voltage changing the cathode plate voltage instantly, hence the pop.
Iwi, after thinking about it over night, I think you should try the 0.1uF cap and listen out for any loss of top end.
If that dosen't do the job we may have to start trying soft swicthes, similar to those used in expensive mixers, (they are actually small simple circuits).

Meanwhile I'll try to get hold of a Messa circuit or manual, maybe someone on the forum could help?

Regards WALKER
oh, i have the original schematics, I can e-mail them to you if you like. Your e-mail address isn't available through your profile.. email me at lwi_b@hotmail.com, and I'll send them back to you.

for the time being i'll look into soft switches..

Iwi, I had difficulty posting the circuit. I have emailed it to you. As I can't measure some of the circuit parameters you my have too play with the values.
You could alter it and use any high voltage transistor or fet.
These circuits are very common in quality mixers, they allow you to switch in and out sources without hearing the switch click. They are also used to debounce switches.

Regards WALKER
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.