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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: Choosing a BJT?
PostPosted: 22 Dec 2019, 19:03 
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Joined: 31 Jan 2019, 03:46
Posts: 1
Hi, first post here.

IM trying to optimise an emitter follower to drive my high impedance headphones.

I have researched and tried a fair amount of different amp topologies
e.g op amps, discrete, semi discrete
In the end the best sounding design was Class A emitter follower, no gain, as simple as can be.

I am using BD139 currently and was wondering about replacing it with something else
Thanks to low current requirement of high impedance headphones there is a much broader choice of BJTs, and suspected some of the lower current devices may offer better performance is that the case?

What should I look for in a BJT for emitter follower for lowest noise and distortion? High hFE?

im current running 100ma quiescent current on 12V supply. I may increase supply voltage to 20V at the max but I dont listen very loud and it keeps transistors cooler.


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 Post subject: Re: Choosing a BJT?
PostPosted: 29 Dec 2019, 17:45 
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Joined: 23 Feb 2017, 02:02
Posts: 618
You should look for the circuit design for best sound quality.

Changing transitors don't get you far.
Hint for transitors and personall exprience is that any Japanese ones sound very hard and should not be considered, 2SA,2SC,2SD,2SA.

BD139 140 is very nice for audio being honest.


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 Post subject: Re: Choosing a BJT?
PostPosted: 30 Dec 2019, 17:47 
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Joined: 23 Feb 2017, 02:02
Posts: 618
For what your doing you changing the output capacitors to HIFI ones will give you more sound quality gains than transitor swaps.


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