regulated valve buffer with lm317 and lm337

ebijma · 23rd August 2004, 12:00 PM

Regulated valve buffer with lm317 and lm337.

I want to regulated a valve buffer of a gainclone.
I know i can do this with the lm317 and lm337.
Have them laying around.
The transformer i want to use is 30 volts.
So that would be 40 volts DC on each rail.
Thats the max input voltage of these regulators.
And i want a output of 35 volts.
I don't want to run them that high.

My question is can i lift the adjust pin with a zener diode?
Lets say i put in a 10 volt zener, so that the input to adjust pin on
the lm3xx would be 30 volts.
Is this possible?

Nuuk · 23rd August 2004, 12:15 PM

But the power supply for a valve buffer is around 6 volts!

I presume that you want to regulate the PSU for the chip rather than the buffer. In which case, use the LM338s.

ebijma · 23rd August 2004, 12:24 PM

Thanks for the reply nuuk.
i ment the +- 35 volts rails.

So not the 6.3 volt villament.
i know the lm317 and the lm337 can handle the ampers.
So if i just lift them up with a zener.......

moamps · 23rd August 2004, 12:33 PM

Hi,
you don't need zeners for LM317/337 output voltage seting.
Just use two resistors...R1=ca 220ohms,
Vout=1,25*(1+R2/R1)
Regards
Milan

Franz G · 23rd August 2004, 01:21 PM

I would be interested in a comparison with and without regulator, for the tube buffer.

Do you have both solutions?

I think, because the tube buffer is running completely in class A, there is a constant current, wich make regulators in this case workless.

Maybe I am wrong?

Franz

ebijma · 23rd August 2004, 02:18 PM

Hallo Franz G,

Im not trying to regulate the current.
Im want to regulate the rail voltage of +- rails.

So............

Franz G · 23rd August 2004, 02:23 PM

I think I understood you right: you want to regulate the anode voltage of the tube.

And there is a constant current, imho.

Franz

ebijma · 23rd August 2004, 02:45 PM

I know there's a constant current.

I don't think i understand you Franz.

As i see it the voltage of the +- rails of about 35 volts can drop or rise when the mains is not stable.
So with regulation this will be stable.

So my question was how to let the lm317 and the lm 337 work with an input voltage of 40 volt.
I don't want to run them on there maximum input voltage.

moamps · 23rd August 2004, 02:47 PM

Quote:

Originally posted by Franz G
I think, because the tube buffer is running completely in class A, there is a constant current, wich make regulators in this case workless.

Hi,
Regulators are used to suppress ripple from bridge stage. Tube buffer has poor PSRR and needs very clean rails. But, regulators can insert HF noise in rails also, etc. CLC network is the best solution, IMO. Or maybe using Didden's regulators.

Quote:

Maybe I am wrong?

Yes, You are wrong. Regulators are normally used in constant current applications. Three pin regulators are usually poor performers in power amps applications.

Regards
Milan

Upupa Epops · 23rd August 2004, 08:24 PM

CLC network is not regulator ( stabiliser ). " ... constant current application.. " - realy ? " ... three pin... " - realy ? Why ? Summary : Franz, do all like in year '26, 'cos all past this year is wrong

.

23rd August 2004, 12:00 PM	#1
ebijma diyAudio Member Join Date: Mar 2004 Location: Huizen	regulated valve buffer with lm317 and lm337 Regulated valve buffer with lm317 and lm337. I want to regulated a valve buffer of a gainclone. I know i can do this with the lm317 and lm337. Have them laying around. The transformer i want to use is 30 volts. So that would be 40 volts DC on each rail. Thats the max input voltage of these regulators. And i want a output of 35 volts. I don't want to run them that high. My question is can i lift the adjust pin with a zener diode? Lets say i put in a 10 volt zener, so that the input to adjust pin on the lm3xx would be 30 volts. Is this possible?

23rd August 2004, 12:15 PM	#2
Nuuk diyAudio Member Join Date: Feb 2003 Location: Somerset, SW England	But the power supply for a valve buffer is around 6 volts! I presume that you want to regulate the PSU for the chip rather than the buffer. In which case, use the LM338s. __________________ The truth need not be veiled, for it veils itself from the eyes of the ignorant.

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23rd August 2004, 12:24 PM	#3
ebijma diyAudio Member Join Date: Mar 2004 Location: Huizen	Thanks for the reply nuuk. i ment the +- 35 volts rails. So not the 6.3 volt villament. i know the lm317 and the lm337 can handle the ampers. So if i just lift them up with a zener.......

23rd August 2004, 12:33 PM	#4
moamps diyAudio Member Join Date: Oct 2002 Location: Croatia	Hi, you don't need zeners for LM317/337 output voltage seting. Just use two resistors...R1=ca 220ohms, Vout=1,25*(1+R2/R1) Regards Milan

23rd August 2004, 01:21 PM	#5
Franz G diyAudio Member Join Date: Jun 2004 Location: Bern / Switzerland	I would be interested in a comparison with and without regulator, for the tube buffer. Do you have both solutions? I think, because the tube buffer is running completely in class A, there is a constant current, wich make regulators in this case workless. Maybe I am wrong? Franz

23rd August 2004, 02:18 PM	#6
ebijma diyAudio Member Join Date: Mar 2004 Location: Huizen	Hallo Franz G, Im not trying to regulate the current. Im want to regulate the rail voltage of +- rails. So............

23rd August 2004, 02:23 PM	#7
Franz G diyAudio Member Join Date: Jun 2004 Location: Bern / Switzerland	I think I understood you right: you want to regulate the anode voltage of the tube. And there is a constant current, imho. Franz

23rd August 2004, 02:45 PM	#8
ebijma diyAudio Member Join Date: Mar 2004 Location: Huizen	I know there's a constant current. I don't think i understand you Franz. As i see it the voltage of the +- rails of about 35 volts can drop or rise when the mains is not stable. So with regulation this will be stable. So my question was how to let the lm317 and the lm 337 work with an input voltage of 40 volt. I don't want to run them on there maximum input voltage.

23rd August 2004, 08:24 PM	#10
Upupa Epops diyAudio Member Join Date: Aug 2003 Location: Prague,Czech Republic	CLC network is not regulator ( stabiliser ). " ... constant current application.. " - realy ? " ... three pin... " - realy ? Why ? Summary : Franz, do all like in year '26, 'cos all past this year is wrong .