In Reply to: Amplifier for AA Uno Nano ? posted by aaron1608 on March 17, 2016 at 17:25:50:
So after I got my la scalas, it was basically like hooking my stereo up to a signal tracer and cranking the gain all the way... Hum, hiss, thermal noise, ticking sounds, insanity... The amp was fine with normal speakers but this is a true torture test. I found the following helps:
1. Try grounding the amp chassis directly to an earth ground
2. Try substituting all the small signal tubes, a mild heater to cathode short can be a huge problem
3. A marginal solid state rectifier diode can make a spike which makes intolerable
Buzz... Way worse than just him... Try to scope the output and make sure the hum is not actually buzz
4. Crappy DC filament supplies for output tubes can create lots of problems... If it's just a rectifier and a capacitor it is almost worse than running AC
5. Tube shields need to be intact and functional
6. On one system I put a 10k reaistor across the high impedance input and a 100k reaistor in series with preamp output... This served the dual function of vastly reducing preamp noise and also reduced hum pickup for the first stage of the amplifier
7. Grounding and layout are critical... Even a tiny amount of power supply ripple current in signal ground can create major hum problems.
Guitar amps are high gain and have high efficiency speakers... Lots of info online for reducing hum in guitar amps applies here too
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Follow Ups
- Fighting hum - maxhifi 22:28:35 03/18/16 (0)