noisy relays

look at something like a 4066 chip or equivalent. just bridge them together via a latter network.

--
Real Programmers Do things like this.
http://webpages.charter.net/jamie_5

I doubt the relay contacts are the problem, but are probably just reacting to the problem. I would be looking for a DC bias that is being switched, with the audio riding on it. You might have a leaky coupling capacitor. I think each contact should have a high value grounding resistor on each side of the contact to precharge the coupling capacitors to 0 volts DC long before any of them open or close.

I'll check the ins and outs of the fx pedals for DC. The odd thing is that it doesn't really matter which combination of fx I switch in or out, I still get the pop, although I didn't do a comprehensive test of each available combination. I'll check for DC first though before trying the resistor trick.

Thanks

the

Lately,

contacts

through 6

worried

here?

These work well for lots of things, but have a large typical R(on) of

250 ohms at room temperatures with Vdd=5V. For higher voltages, the R(on) is smaller, getting down to 80 ohms for a 15V Vdd. If he is stringing 5 of them together, he may have an issue with attenuation of the signal.

(This is from the MC4066B datasheet from ON semi)

--- Regards, Bob Monsen

The question of the ultimate foundations and the ultimate meaning of mathematics remains open; we do not know in what direction it will find its final solution or even whether a final objective answer can be expected at all. "Mathematizing" may well be a creative activity of man, like language or music, of primary originality, whose historical decisions defy complete objective rationalization.

- Hermann Weyl in 1944

Yes, that was kind of my concern about using the SS switches (although they sure are cool). Unless there are some super R(on) models out there. I'd still like to stay with the relays, as implementing the switches will take a fair amount of altering the existing circuit.

Thanks

its

Signal switching may require gold-flashed relay contacts. Are yours gold-flashed?

Cheers, John

no, don't think so. Are these much quieter than normal ones?

Thanks

through

As I understand it, some other contact alloys will oxidize unless there is sufficient voltage and current to get through the oxidizing layer that forms. Cadmium is a metal I remember, but I don't remember if it is particularly troublesome. Maybe it is the "wiping action" on an oxidized contact surface you are hearing. Maybe not.

The point is, they make gold-flashed relay contacts for a purpose. I was told it was for very low signal levels. I have successfully used these contacts in applications where the signal was in the millivolts/microamperes.

Look at the detailed specs for your relay. You should see a voltage/current

*minimum* specified. If not, contact (no pun) the manufacturer and find out.

Good luck.

John

Hi John;

I checked the inputs and outputs of each effect, and had varying results. Some gave a dead 0VDC, while others started at around 1 mV and dropped to 0, or dropeed to a few 10ths of a mV. Still others just read in the 10ths of mV. I had one that peaked at 24mV but then died down to 0.2 mV.

Are these readings close enough to 0V, or does it sound like a leaky cap in there somewhere?

BTW, I tested each effect individually, with no signal applied.

Thanks

the

Lately,

contacts

through 6

worried

here?

Did the pop sound the same as each contact opened and closed, or were some of them louder?

I checked the DC levels of the relays themselves, and did indeed find a few millivolts (sometimes more) on each one (this is from the signal contacts of the relays). Where would this be coming from? There are no caps (except in the effects pedals themselves), so could it be from the control voltage part of the relay? Also, in this case, should I still drop a hi value resistor to ground (from the signal contacts)? Thanks

the

Lately,

contacts

through 6

worried

here?

Hi John

I didnt actually listen while I was testing, (I had removed each effect from the chain to test) so I don't know. I know that some sound louder than others in normal use, but the switching system may be turning off more than one relay at a time, which would account for the louder pops.

Thanks again.

results.

to 0,

of

in

Hi John;

I tried putting in the resistors as you suggested, but it made little or no difference. I no longer measure any DC on the relays, but the pops are still there. I connected the resistors about 18" from the relays (on the input and output jacks going to each of the effects) because it was a little easier to get to. I don't see how this would be any different than connecting them right at the relays, but I thought I'd mention it just in case.

Thanks

results.

to 0,

of

in

That pretty well rules out my guess.

Well, actually, maybe not. I did some testing again today, and there is a noticeable improvement. Sometimes the switching was dead quiet, and overall there were fewer pops, but some switching was pretty loud still.

Perhaps the contacts are an issue, but I think this was definitely contributing to the overall noise.

Thanks again for your help.

no

still

and

easier to