Beast Boost

tca · April 20, 2012, 12:16:55 PM

I've started to play with this circuit which uses a TL431 has a super transistor, it is a beast in fact. Does anyone played with the tl431 to make a booster. It doesn't seem to be very common in guitar stompboxes.

The first part is just a buffer to drive the tl431.

Any comments/sugestions? Similar projects?

Cheers.

Refs.: http://www.techlib.com/electronics/audioamps.html

rutabaga bob · April 20, 2012, 12:58:54 PM

1) As always...any sound clips?
2) Any controls involved?

tca · April 20, 2012, 01:02:17 PM

It is just a VERY BIG clean boost. No controls.

Bill Mountain · April 20, 2012, 01:38:40 PM

Quote from: tca on April 20, 2012, 01:02:17 PM
It is just a VERY BIG clean boost. No controls.

Like...how big?

tca · April 20, 2012, 04:09:07 PM

Well... bigger than: a SHO at full gain, a MPF102 minibooster, ...

PRR · April 20, 2012, 07:39:07 PM

With R5=180, current consumption is a beast. If you ever run battery, it should work nearly the same with R5=5K or so.

> first part is just a buffer to drive the tl431.

Actually to drive R3 coming back from a gain of -300, acting like ~~1.5K. The JFET is straining to wiggle against that. This is probably a Good Thing. If not straining it would probably sound a lot like an opamp.

Interesting use of a part specified for other work.

tca · April 20, 2012, 07:47:10 PM

Hi PRR, nice to ear from you again.
I've tried with diferent values of R3; R3=5K will work but frequency response changes and a different value of C2 is needed to compensate the change.

allesz · April 21, 2012, 06:47:00 PM

Hey tca, I made something similar (the idea came from the same site you linked by the way...) but without the input buffer and with a diode as a clipper on the output (I wanted to make an overdrive). I posted a schem on the other site.
The real funny thing is that it can drive a speaker too.

tca · January 24, 2013, 07:00:16 PM

Quote from: allesz on April 21, 2012, 06:47:00 PM
Hey tca, I made something similar (the idea came from the same site you linked by the way...) but without the input buffer and with a diode as a clipper on the output (I wanted to make an overdrive). I posted a schem on the other site.
The real funny thing is that it can drive a speaker too.

Just found your entry on the other side... and forgot to post my headphone amp with the TL431.

It partially solves your problems of extra gain, and indeed it can drive a 8Ohm speaker.

Cheers.

PRR · January 25, 2013, 09:17:31 PM

Volume pot is wired unusually.... is that how you want it?

tca · January 26, 2013, 06:36:27 PM

Quote from: PRR on January 25, 2013, 09:17:31 PM
Volume pot is wired unusually.... is that how you want it?

Yes I know, it makes the tone control working much better than the usual setup for a volume pot.

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Beast Boost