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Re: location for relay transformer? (help)...

2/26/2005 12:09 PM
Re: location for relay transformer? (help)...
It's probably best to put it over by the main PT, along with its rectifier and main filter caps.  
Then run the DC supply lines over to the relay or relay board, where you have an additional cap for further filtering and anti-pop service.  
That way you can have fairly long unshielded relay power leads and run them just about anywhere, and any stray signals picked up by the relay power lines will have that interference quenched by the caps at either end.  
Otherwise with just a cap at the rectifier end, the wire leading away from there can act as an antenna and you get signal reception which can be audibly really bad if the coil inside the relay transmits this *insignificant* isolated power line interference to an open high-gain input terminal a few millimeters away.  
If a relay board is designed to run on an AC source, then I would suggest twisting the supply wires from the relay transformer over to the relay board rectifiers. Like other AC supply lines inside the chassis you need to be careful not to run them too close to hum-sensitive areas.  
2/26/2005 2:07 PM
Ian Anderson

Thanks for the replies everyone, just thought I'd mention what I'll be switching since most people assume it's a clean/dirty thing.  
I'm just having one (very) dirty channel but with an additional louder 'channel' whereby an extra gain and master volume pot are switched into circuit.  
... Ian
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2/26/2005 2:14 PM
Ian Anderson

Also, I've got a small transformer with two seperate 12v taps to run the relays off since most of the threads I've read here seem to end up suggesting that this is the best way to go.  
... Ian :)
2/26/2005 4:50 PM
Ian Anderson
question for Gary (aka Glasman)...
Gary, what purpose does the 5.1v zener serve on that switching schematic you posted?  
... Ian :)
2/26/2005 8:24 PM
Gary (aka Glasman)

When i first build the amp, I didn't give a lot of consideration to driving the relays. The DC supply I ended up with put out about 18 volts so in lieu of using a voltage regulator, I dropped the excess voltage with a zener on the ground side of the relay. Those components are actually located in the footswitch.  
My latest amps use a voltage regulator (12v) to drive the relays. A little cleaner.  
2/27/2005 2:16 PM
Ian Anderson

Cheers Gary, I won't need the zener in that case since I have the 12v supply that the relays require.  
... Ian
2/28/2005 3:03 AM
Dave H

Hi Ian, are they DC relays? If you rectify and filter the 12V AC from the transformer it’s going to generate more than 12V DC so you may need to use some zeners.  
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