Hoffman Amplifiers Tube Amplifier Forum
Other Stuff => Solid State => Topic started by: 9volt1967 on January 29, 2010, 09:04:34 pm
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I am in the process of laying out a hi-gain channel switcher that operates with 3 separate relays. I want to use 2 relays to switch the 2 independent pre-amps in and out between the 1ST common triode and the effects loop and the second relay will ground a 250K (solo pot) that I will have mounted next to the master volume prior to the PI. I would like to mount LED at front panel to show switching. I have a few different power supply layouts that I am looking at and I wonder if anyone has any ideas on the subject?
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If you do like that, the jack shell can't be grounded or it will unbalance your careful heater balancing, maybe draw smoke.
Not sure why two 330 resistors per LED? Or if the 22u are needed?
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You could full wave rectify the heater voltage. That would work out better. Another way is to bridge rectify the heater voltage. Do not ground the other end of the bridge and use the negative side for your ground for the relays/diodes. Just be sure to use a stereo jack for that.
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Would I need to reference ground for tube heatersa before the switching circuit? Or would I have to float the ground from the bridge all the way to the footswitch plug? Thanks
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I have been studying the (-itty -awk) switching circuit and the power supply looks real similar to Dougs power supply on the hot switch mod. The couple of exceptions are the filter caps that follow the bridge rectifier are 4700uf 10V and they feed the heaters. After the heaters they have a series of 4.7uf 63V caps that feed each relay circuit. The TRS footswitch section feeds a signal back to the negative side of the 4.7uf to then switch relays and light diodes for the desired channel switch. Does this layout seem easy enough to implement into a proto-type pre-amp layout? Thanks in advance!