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location for relay transformer? (help)...

2/25/2005 4:31 PM
Ian Anderson
location for relay transformer? (help)...
I've got a small transformer with two 12v taps to run the relays in a Dual Recto homebrew I'm planning. Are there any layout issues I should be aware of with this transformer or can I mount it anywhere that is convenient?  
Cheers... Ian :)
2/25/2005 4:44 PM
Steve A.

    Keep the leads long and try moving it around to see if some locations and orientations are noisier than others.  
    IMO if you play guitar sitting down next to your amp you might get some noises that wouldn't get if you are standing up 10 feet away playing to a crowd of thousands of cheering fans... I think that in many cases the guitar is picking up RF hash from one of the transformers.  
Steve Ahola
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2/26/2005 6:47 AM
Ian Anderson

Cheers Steve, I don't know about a thousand fans though ;) :D  
Any ideas on cutting down the relay switch popping? (the best idea I've come up with is to use the mute circuit that the 5150 uses)  
... Ian
2/26/2005 9:20 AM
Gary (aka Glasman)

The one thing (and you may be doing this) is to make sure that each relay has a back biased diode located at the relay and across the coil and a .01uf (or so) cap across the diode. This should eliminate any noise caused by the relay coil field collapsing when the relay is disengaged.  
2/26/2005 9:59 AM
Gary (aka Glasman)

Here is a schematic of the diode and cap.  
3/4/2005 7:12 AM
I second the back biased diode. I also use the 10M resistor to ground on relays that have one side capacitively coupled (no dc path to ground). My amps are completely relay driven with no noise at all, and they are using little SPST reed relays from mouser at about $0.80 apiece (7 per amp, with 2 DPDTs for the activation circuit).  
2/26/2005 10:49 AM
Bob Ingram

Wanta save yourself a ton of headache, get the Weber 6V relay board. It runs from the heaters.  
It's $8 and includes all the components on a small PCB. I've used it 3 times in channel switching amp and it works great. Make sure that you use the Normally Open side for the distortion channel to minimize SS noise.
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