Making a BD139 voltage follower buffer

Posted on Feb 6, 2014

Schematic shows R4 at the emmiter of the transistor, as amb and majkel have suggested it should be between the opamp and transistor, this is also the correct configuration in the canamp. The amp i managed to get a look at has been modified and has had the input capacitors removed, with no measurable problems, as well as having a regulated

Making a BD139 voltage follower buffer
Click here to download the full size of the above Circuit.

PSU and upgraded caps and rectifer diodes. Yes. Better yet, do it M ³/Mini ³/PPA/Pimeta style. Use a TLE2426 as rail splitter for the nil-current signal ground, and use your 3rd channel to drive the output ground return from the headphone. The ground channel will source/sink the combined return current from the left and right channels, and if such signal is in-phase mono, then it would indeed be double. But the BD139 output stage has plenty of current capability so it doesn`t really matter. Now I`m not sure what this actually did and it does sound great, but the gain is too low and I wanted to raise it. When I "fixed" the amp by making it exactly by the schematic, I got a very nasty buzzing noise in the headphones. Still no offset, just this irritating buzzing noise. Not really a hum, a definite buzz. The thing that I`m curious about is that there was absolutely no noise when it was configured as a unity gain buffer and there is quite a bit of a buzz now. Any ideas how that happened There is a difference of almost 16dB between unity gain and gain of 6. Any amount of inherent noise, as well as interference (most likely from the transformer, but you could also have other sources of RFI and EMI) are amplified by the gain of the amp. 4 inches between the transformer and the amp is not a lot of distance especially if the transformer is sizable or if it`s an EI-core unit. You can try turning the transformer so that the mounting...

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