Ground reference for relay circuit

[blue_cloud]

Hey all, long time lurker, occasional poster, can't access my old email so had to make a new account.

I'm working on an amp build which is essentially a JCM800 2204 with a Fender 2-tube reverb. The reverb circuit is lifted from the Twin Reverb and stuck between the treble knob and master volume of the 2204 (will probably require some tweaking as to not change the original JCM800 sound/gain levels). My question is not tone-related though.

I'm planning to use a 5V relay to switch the reverb, using the 6.3V filament winding to generate 5VDC. Something about having the reverb tube's grid connected to a 15 ft wire that goes outside the amp, just bugs me in a mid-high gain design, I dunno.

I found an appropriate 5V relay circuit somewhere on the internet (see attached). My question is: the power transformer I'm using has a center tap on the filament winding. The schematic I found shows an artificial center tap (2x100R's), I feel like if I ground the 5V circuit on my amp, it will burn out the diode bridge (shorted to ground through the transformer winding).

What to do? Disconnect the center tap and add 2x100R to ground? Put a resistor between the 5V "ground" and chassis ground? Let the 5V float and hope for no hum?

Advice is welcome. Thanks in advance and Happy new year!

[wpaulvogel]

You can’t have a center tap along with a full wave bridge rectifier. The center tap is going to cut each half wave to 3.15 volts and you won’t get 5 volts. You need a separate winding to run the relay ( separate transformer).

[ViperDoc]

Hoffman's supply and relay boards work well.

Using a relay does not require diverting your signal down your foot switch cable. Simply use your foot switch to change the 5V power supply ground on or off to operate your relay, as is actually shown in your drawing from Hoffman's website.

[10thTx]

There is alot of information about relay circuits on this link & also the answer to your question about ground reference.

https://el34world.com/Forum/index.php?topic=14348.0

With respect, 10thtx

[blue_cloud]

There is alot of information about relay circuits on this link & also the answer to your question about ground reference.

https://el34world.com/Forum/index.php?topic=14348.0

With respect, 10thtx

Thank you, super helpful! Sounds like the general consensus is there's no need to ground the 5V circuit, so I'll just float it. I was concerned about hum or noise but I guess only the coil is floating, not the switch contacts.

Hoffman's supply and relay boards work well.

Using a relay does not require diverting your signal down your foot switch cable. Simply use your foot switch to change the 5V power supply ground on or off to operate your relay, as is actually shown in your drawing from Hoffman's website.

That's exactly my plan, just wasn't sure what to do with the 5V's ground..