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 NEW  Matt presents bias and operation data for the 6V6 tube in SE operation - 6V6 Single-Ended (SE) Ultra Linear (UL) Bias Optimization.

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 Post subject: stereo amplifier
PostPosted: 21 Mar 2019, 08:08 

Joined: 21 Mar 2019, 03:49
Posts: 1
Hello ! I am new here, I just wanted to know if I am at the right place to discuss my situation with a stereo amplifier that I made.
When I choose either, Left or right side, The output is good at a 4 Omhs speaker.
But when I choose both both side, I get this Hum and this Hum gets worse when I turn the volume'
I am not shure if this situation is a feed-back loop !
Please reply, to help me out with this !!!

here are the caracteristics.

I choose Tlo72 as a peamplifier, and then the medium power pramps (BD139-BD140) and then feed them in a push-pull transistors(2N3773; 2N6609) for power.


 Post subject: Re: stereo amplifier
PostPosted: 29 Mar 2019, 06:48 
User avatar

Joined: 05 Aug 2016, 14:35
Posts: 227
Hum loop, feedback loop, sagging power-supply, unshielded connections, could be so many things. Without schematics or pictures (preferably both) impossible to even suggest a direction or solution.

 Post subject: Re: stereo amplifier
PostPosted: 29 Mar 2019, 07:24 

Joined: 23 Feb 2017, 02:02
Posts: 677
Did you design the schematic your self, with op amps and such high open loop gain either it runs or it dosen't run if you get anything wrong.
High feedback means its unlikley to humm if you designed correctly since feedback helps ignore noise.

However if your using the op amp for finite gain and everything with finite gain then your will have to be awwear of noise in the design.

I got the grounding and layout wrong when I was a rookie getting noise.
Layout you want to keep input signals away from transfomers and other sources of magetic field radations.
Ground you want to get things sorted and is not a few sentances explained.

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