Channel Switching Relay

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cbevans
Junior tube assistant
Posts: 5
(4/19/04 7:22 pm)
 Channel Switching Relay
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 Has anyone worked with channel switching relays in their preamps? I need A-B footswitching between two independent preamp circuits. I have come up with this design: SPDT switch before the circuits and DPDT after the circuits including a shunt on the unused circuit. Does anyone know of a preferred manufacturer and model of relay? I plan to tap off the filaments for power (rectified of course).
 
jc
I only work on Fender's
Posts: 701
(4/19/04 8:01 pm)
 Re: Channel Switching Relay
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 PHATamps may have what you need. I think Paul has done something similiar. Check out the top left picture on the link.

www.phatamps.com
 
DIYWulf
Junior tube assistant
Posts: 89
(4/20/04 3:52 am)
 Re: Channel Switching Relay
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 I have used channel switching in my amps. I have an spdt relay at the output and also an spst shunt after the first stage of the overdrive channel which is engaged when the clean channel is selected. This prevents crosstalk from the OD channel. Otherwise I always hear a slight buzz in the background when playing clean. I don't need a shunt on the clean channel. The levels are lower and with a distorted signal that is so much louder the crosstalk simply is not perceptible.
I wouldn't put a relay directly at the input. Relays always produce a little "pop" when switching. Especially on overdrive channels, through all the gain stages that follow, this is usually translated into a big "POP". That's why I put the relay after the first gain stage and only shunt the input to ground. Small caps (like 100n, 1uF also worked) across the coils of the relay help reduce the "pop". For me, the caps seemed to have the greatest effect when

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have the greatest effect when put directly next to the relay. Makes sense.

Hope that helps
DIYWulf
 
Funkalicousgroove
Junior tube assistant
Posts: 71
(4/20/04 10:09 am)
 Re: Channel Switching Relay
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 I have and do use DPDT relays in my amps, I prefer the NTE brand, but there are alot of good brands out there. I tend to lean toward the 5v 200ma size because I rectify my fillament current to power them. In some designs I footswitch the power to the relays individually, some designs I use 1 relay to switch the power going to the other relays.
 
EL34  
I got your parts right here.
Posts: 2272
(4/20/04 3:49 pm)

  Re: Channel Switching Relay
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 There are many things to work out in channel switching.

If you look at designs like boogie, etc, they are not only switching a signal, they are attenuating signals, mixing signals to have the same approx volume levels, etc.

I don't mess with it. I have an old fashioned channel switcher on my guitar. (volume control)
 
Funkalicousgroove
Junior tube assistant
Posts: 75
(4/20/04 5:53 pm)
 Re: Channel Switching Relay
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 A 1n4007 works quite well to make the "Pop" go away.
 
j allen shaw
Junior tube assistant
Posts: 42
(4/20/04 7:11 pm)
 Re: 1N4007 diode w/Channel Switching Relay
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 Funk,
Could you explain where in the circuit the diode is placed? In series w/ the signal?
I am thinking of using this same approach (Relay) to switch the Tremolo pot in/out on my AB763 for a foot-switchable boost.
I have it rotary switchable at the pot now, but it would be great to be able to do it "on-the-fly".
What do you think? Would that work?
Jeff
 
Strat1965
Junior tube assistant

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Strat1965
Junior tube assistant
Posts: 5
(4/21/04 12:12 am)
 re:
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 Could you explain exactly what relay you are using? It seems that most relays are for PCB use. What would be a good choice for a PTP amp? Do they mount to the chassis?

Thanks!
 
Voxbox
Junior tube assistant
Posts: 70
(4/21/04 9:11 am)
 Channel switching relay
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 Doug,

why do you say not to mess with it?

Strat,

"Continental" style relays have a built in fixing screw on the underside that can be used to mount to a chassis or onto a little aluminium frame (which can hold a number of relays) that you can buy. I used to get these from RS Components, dont know if they still do them.

Cheers, Voxbox
 
Funkalicousgroove
Junior tube assistant
Posts: 76
(4/21/04 4:48 pm)
 Re: Channel switching relay
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 I've been using the PCB type relays. Radio shack makes a little printed bread board that works perfectly, otherwise I etch my own small pcb boards, it's ALOT easier than it sounds. The 1N4007 goes across the coil of the relay in the direction of the current to ground, you can also go 1 step further and put a .01 disc across the diode to reduce the diode switching noise. I've also used the larger mechanical relays with solder lugs ala Silver chassis Dumble amps-Nothing will make them Not "pop" But with a band behind you no one will notice.....I can't say the same for your livingroom couch
 
cbevans
Junior tube assistant
Posts: 6
(4/24/04 4:39 pm)
 Re: Channel switching relay
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 Thanks to all for your responses. It has been very helpful. It also shows that there are many different ways to accomplish the same results when building amps. If anyone else has ot

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cbevans
Junior tube assistant
Posts: 6
(4/24/04 4:39 pm)
 Re: Channel switching relay
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 Thanks to all for your responses. It has been very helpful. It also shows that there are many different ways to accomplish the same results when building amps. If anyone else has other channel switching suggestions, please post them so all can see and learn.

Berry