Unity gain NFB speaker-buffer

[Skorpio]

I want to try with a special buffer between my poweramp and the speaker, to isolate the feedback loop from the speaker load.

I have a trafo 18-0-18V/800VA and 2x47.000uF, + heavy heatsinking...

Now I need a circuit to use...do some of you have some experiences?

🙂

 

[PMA]

Yes.

 

[darkfenriz]

these circuit are called "power followers"
You'll find one in PMA'a webside, nice one.
I guess he meant this saying "yes".

 

[PMA]

Darkfenriz,

you are right. I prefer a little bit of self-confidence and creativity, for example to perform a search. I belive that it leads to better results than just following recommendations.

 

[djk]

This looks interesting, two versions, 'hot' and 'cool'.

http://www.audiodesignguide.com/my/Hot_Follower1.GIF

Full text:

http://www.audiodesignguide.com/my/index.html#MY_A

 

[Skorpio]

Nice design PMA 😉

But I don't like the output configuration, I prefer a standard darlington type.

Do you have any remarks to the termal stability this type in your circuit?

 

[UniQ]

Hi,

I guess you have 2 ch stereo amplifier... take the output of one channel and feed the other channels input through a resistor divider corresponding to the gain of your amplifier, done!

Cheers Michael

 

[richie00boy]

I assume that you are wishing to use a non-global feedback power follower and some favourite main amp then? Or the exercise is pointless as the follower will be affected by the back EMF etc even worse (due to massive feedback) so the problem remains. In fact, instead of such a power follower, why don't you just make the main amp non-global feedback? This would be cheaper, easier, smaller, use less parts, less heat...

 

[AndrewT]

Hi,
try http://www.altmann.haan.de/splif_page/ just up your street.
Global feedback to get the best out of your classAB power amp and a follower stage to drive the speakers. Even a guide on multiple followers if you want to have separate outputs for individual speakers. A cheap way to bi-amp your speakers, but not suitable for active speakers

 

[mtlin12]

Hi,

Try this NFB Power Diamond Buffer ,

and some pictures are in http://www.diyaudio.com/forums/showthread.php?s=&threadid=59952&perpage=10&highlight=&pagenumber=2.
It has been tested with tube-pre & speakers and worked quite good for several months.

 

[djk]

That's a bit complex to be simply called a 'diamond buffer', OTOH, the 'hot follower ' linked to above is a 'diamond buffer'.

 

[mtlin12]

That's a bit complex to be simply called a 'diamond buffer', OTOH, the 'hot follower ' linked to above is a 'diamond buffer'.

Though I admit it is too complex for a normal DB, but if the supply
voltage is not too high say 18-0-18, it can be much easier to take
off the STAND-BY & Voltage Reference circuit and about 8 trannies.
Because the 2SK246BL can sustain only 50V.

Q8 through Q11 are for JFET source follower and bias provider,
no gain, but the DC output level can be adjusted by tunning the SVR1.
The circuit's thermal control is very easy.