Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: phsyconoodler on April 05, 2014, 11:00:08 pm
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I want to add an op-amp reverb circuit to an existing amp that has no room for tube sockets .Is it best to add a transformer for the op-amp power supply or is it ok to use a rectified ac power source?I want to utilize a blues jr design that requires a 5v power supply for the op-amp.Having not done this before,I kinda would like to not stress the PT if it can't take it.I can't see an op-amp drawing very much current but I may be wrong.
Anyone done this successfully?
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... I want to utilize a blues jr design that requires a 5v power supply for the op-amp. ...
Are you planning on using the same opamps that the Blues Junior (http://el34world.com/charts/Schematics/files/fender/Fender_BLUES_JUNIOR_REV_D.pdf) used? If so, a +/-15v supply was used, derived from a ~20vac winding.
Looking at that schematic, it appears there is ~16mA is drawn from each leg of the +/-15v supply, based on the voltage drop across R50 & R53. If you have the needed winding, I bet you know if you can spare 16mA.
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A tube power transformer will not even know an op-amp is there. The current draw is tiny.