Hello I’m new here.
I’m sure this topic has been kicked around a lot but......any advice on keeping hum on a SE amp to a minimum?
I know my way around a valve amp but I’m just getting started really. Please treat me as a novice. All the information I have found so far goes in to loads of Maths and technical jargon. I need simple info please. Thanks. G
SE amp hum.
Moderators: pompeiisneaks, Colossal
SE amp hum.
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Re: SE amp hum.
SE amps do not benefit from the hum canceling that push-pull amps do, so to combat the hum, you need stiff filtering, a choke, and careful attention to grounding scheme.
If you want help with your grounding, you need to show a schematic for your amp, and then on a photo, mark the location of every ground point.
If you want help with your grounding, you need to show a schematic for your amp, and then on a photo, mark the location of every ground point.
I build and repair tube amps. http://amps.monkeymatic.com
Re: SE amp hum.
Thank you. I have a rough schematic. I will do a better one during the week and mark the grounding points.
The amps are 70 years old so I’m not expecting to cancel all him but would like to at least cut it down a little.G
The amps are 70 years old so I’m not expecting to cancel all him but would like to at least cut it down a little.G
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Stevem
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Re: SE amp hum.
The first thing you need to do with any amp with a hum issue or even to try to improve on a ok amps hum level is to determine if your dealing 120 HZ with takes place on the D.C. Voltage side of the amp, or if it's 60 HZ ac hum from the heater string or coulpling inductive wise from the power transformer.
I have 2 Univox Push pull amps from 1966 and the power a output transformers are mounted within 3/8" of each other and as soon as you turn on the amp even without the tubes being warmed up, out from the speaker you hear a nice 60 HZ hum due to magnetic coupling.
I have 2 Univox Push pull amps from 1966 and the power a output transformers are mounted within 3/8" of each other and as soon as you turn on the amp even without the tubes being warmed up, out from the speaker you hear a nice 60 HZ hum due to magnetic coupling.
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Not screaming like the passengers in his car!
Cutting out a man's tongue does not mean he’s a liar, but it does show that you fear the truth he might speak about you!
Re: SE amp hum.
Okay thanks. How do I determine the source of the hum? Is it true that you can remove all the valves and if it still hums the ot transformer is the culprit?
Thanks again. G
Thanks again. G
Re: SE amp hum.
If you remove all tubes and you can hear hum thru the speaker, it's likely the PT radiating 60Hz EM into the OT. Normally you can orient your PT and OT so that this magnetic coupling is minimized.
I build and repair tube amps. http://amps.monkeymatic.com
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sluckey
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Re: SE amp hum.
The schematic you posted only shows two B+ filter caps and they are in parallel. If you built the amp IAW that schematic it's doomed to be a loud hummer. You need more R/C filter stages.