new GAN amplifier

This, what you wrote below, I cannot just accept on the face as factual. The drive requirements, biasing, temperature compensation, bandwidth vs. drive, etc. are so significantly different between a BJT pair and MOSFET pair, that unless you essentially modified the whole amplifier, you could not do this and at which point you essentially have two different amplifiers and at that point, any comparison has lost all meaning.

georgehifi6,173 posts11-16-2019 2:38pm

How can you know "what to listen for"

There’s a post a member put up a couple of weeks ago (go find it), who does mods for his customers, where he takes a Mosfet amp removes the complimentary N/P channel Mosfet output stage and replaces it with complimentary NPN/PNP Bi-Polar (BJT), and he and his customers say it all in their description of the sound change.

what you wrote below, I cannot just accept on the face as factual.

That's your opinion, it is, and if your are a tech you'll know that it's very possible to do this to the driver/output stage.
Cheers George

No that is not an opinion that is a experience. The drive requirements for a set of bipolar transistors and a set of mosfets is much much different. Add in different biasing requirements, different thermal compensation, different bandwidths for a given drive circuit, etc. If you change the two you don’t have the same amplifier anymore. Do you design amplifiers or are you just repeating others?

Of course there are different drive conditions and they are all addressable in changing over mosfets to bjt, you just choose not to believe it. 🤦‍♂️ 

And I'll post once again the pro's for going bi-polar

"BJTs tend to have better, more linear gain characteristics…and can give you a lot higher voltage gain than MOSFETs.…They're also able to handle higher output currents…and have a lower output impedance.…That gives BJTs a huge advantage over MOSFETs…for building amplifier circuits…that need to provide a significant amount of output power…and or drive loads that have low input impedance.…MOSFETs are going to have a harder time…driving a low impedance load…because they have a higher output impedance.…"

 

You can't just swap out the output FETs for the BJTs. There are a lot of other things that need to be addressed. It is not the same amplifier any more.


Again, do you know how to design amplifiers? I get the impression no or your replies would be more technical. Hence what you are posting is mainly heresay.