Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: LooseChange on September 27, 2010, 12:35:25 pm
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I'm trying to install a Belton digital reverb unit in a small tube amp and I am having hum issues with the power supply. I setup a voltage doubler sourced from the heater supply and then regulated to 5 volts with a 7505 regulator chip. I used two 1000uf caps and adding uf does nothing. I have also tried many grounding schemes and nothing seems to help. Disconnecting the audio lines and keeping the power source connected still makes hum. I would call the hum a buzz at 120hz.
Any ideas?
Thanks!
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Why would you use a voltage doubler which is just asking for more noise? 6.3vac rectified will get you around 8.5 anyhow which is more than enough for a 7505.
That said, I just used a second transformer that I had laying around for the power supply. It's a nice reverb for sure but they can get really noisy at the higher output.
Which circuit are you using? I didn't like the one that is floating around the web at all-- to me it sounded better using an adaptation of the traditional Fender style circuit.
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> voltage doubler sourced from the heater supply
The devil is in the details.
Draw us a picture.
Or get a 4-pack of D-cells or a 6V lantern battery, power the Belton off that just to try.
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I found a small 5v transformer and hooked it up... Quiet as can be.
The reverb does not sound too bad.
The regulator is a 7805 (wrong above)