LM317 for output stage

regiregi22 · 27th September 2011, 01:13 PM

I have been thinking that a linear adjustable regulator, like the LM317, allows you to vary the output voltage by varying the adjustment pin current.

So in theory, if you manage to vary this current depending of the voltage amplitude of a musical signal, you should be able to modulate the output voltage of the regulator in concordance.
In the same way that when you trim a pot, the output voltage varies, but in function of a musical signal.

It may sound a little funny, but with a decent slew response rate maybe the sound can be decent.

Has anybody ever tried something like that? What are your ideas for varying the input current of the adj. pin byt following a signal?

Regards,
Regi

wintermute · 27th September 2011, 01:15 PM

The answer is yes

see here for an example SE class A regulator-chip-amp madness

Tony.

regiregi22 · 27th September 2011, 01:54 PM

Well, now I feel like comin' late to the party

Thanks!

AndrewT · 27th September 2011, 01:59 PM

and there have been a few designs from years ago posted on the Forum.

janneman · 27th September 2011, 02:22 PM

It becomes more logical if you consider the 317 as a high-gain medium power transistor with a negative Vbe of 1.25V

NPN of course; the 337 would be the PNP equivalent.

jan didden

Elvee · 27th September 2011, 05:01 PM

Quote:

Originally Posted by regiregi22

Well, now I feel like comin' late to the party

Thanks!

Have a look here (non-exhaustive):
Class A buffer using LM317 3 terminal reg's
Quasi-complementary Hexfet monstrosity.
4-part Harmony, a 9 watt class A amp using a voltage regulator IC.
New kind of compound emitter follower?? or - another weird circuit ;-)
Just for fun: The Regulator-Chip amplifier
And now, the Regulator-Chip JLH Amp.
The Voltage-Regulator-Chip Amp family welcomes a new member:
Class A Chip Amp: and now, the complementary version
What happens when you cross a Tringlotron with a Regulator-Chip Amplifier?
SE class A regulator-chip-amp madness

wrenchone · 27th September 2011, 05:21 PM

A former colleague of mine actually came up with an amplifier circuirt using LM317 and LM337 while working for synth maker Sequential circuits. This was back in the the late 70's/early 80's. The curcuit escapes me right now, but no doubt one of you busy folks out there will rough something out.

27th September 2011, 01:13 PM	#1
regiregi22 diyAudio Member Join Date: May 2009 Location: Madrid (Spain)	LM317 for output stage I have been thinking that a linear adjustable regulator, like the LM317, allows you to vary the output voltage by varying the adjustment pin current. So in theory, if you manage to vary this current depending of the voltage amplitude of a musical signal, you should be able to modulate the output voltage of the regulator in concordance. In the same way that when you trim a pot, the output voltage varies, but in function of a musical signal. It may sound a little funny, but with a decent slew response rate maybe the sound can be decent. Has anybody ever tried something like that? What are your ideas for varying the input current of the adj. pin byt following a signal? Regards, Regi __________________ diyAudio, doing it as big as you can, JUST BECAUSE WE CAN!

27th September 2011, 01:15 PM	#2
wintermute just another diyAudio Moderator Join Date: Aug 2003 Location: Sydney Blog Entries: 22	The answer is yes see here for an example SE class A regulator-chip-amp madness Tony. __________________ Any intelligence I may appear to have is purely artificial! Some of my photos

27th September 2011, 01:54 PM	#3
regiregi22 diyAudio Member Join Date: May 2009 Location: Madrid (Spain)	Well, now I feel like comin' late to the party Thanks! __________________ diyAudio, doing it as big as you can, JUST BECAUSE WE CAN!

27th September 2011, 01:59 PM	#4
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	and there have been a few designs from years ago posted on the Forum. __________________ regards Andrew T.

27th September 2011, 02:22 PM	#5
janneman diyAudio Member Join Date: May 2002 Location: Where Germany, The Netherlands and Belgium meet Blog Entries: 6	It becomes more logical if you consider the 317 as a high-gain medium power transistor with a negative Vbe of 1.25V NPN of course; the 337 would be the PNP equivalent. jan didden __________________ /Another new issue: Linear Audio Volume 3!


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27th September 2011, 05:21 PM	#7
wrenchone diyAudio Member Join Date: Feb 2004 Location: Silicon Valley	A former colleague of mine actually came up with an amplifier circuirt using LM317 and LM337 while working for synth maker Sequential circuits. This was back in the the late 70's/early 80's. The curcuit escapes me right now, but no doubt one of you busy folks out there will rough something out.

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