JFET preamp recommendation?

leadbelly · 26th March 2004, 04:47 PM

I want to build a very simple JFET preamp for a GainClone amp which I am building. There are so many designs on this forum that look great, but most are overkill for what I need (unabalanced input to unbalanced output). I just need a very simple buffer stage with low gain that will be able to drive the low-ish 10k input impedance the amp will have. I like the idea of a JFET amp with CCS most from a "doing something new" point of view and would love it to sound better than a chip buffer, but have not been able to find something with a low parts count by searching the forum. Any help appreciated

jam · 26th March 2004, 05:00 PM

Read,

http://www.borbelyaudio.com/ae699bor.pdf

at the Borbely Audio web site.

Regards,
Jam

claudio · 26th March 2004, 06:40 PM

Hi,
A very simple pre with 4 transistors:

3 preamp to choose from

Claudio

Pedja · 26th March 2004, 09:31 PM

This is it I'd say.

http://users.verat.net/~pedjarogic/a...one.htm#buffer

leadbelly · 26th March 2004, 10:31 PM

Quote:

Originally posted by Pedja
This is it I'd say.

http://users.verat.net/~pedjarogic/a...one.htm#buffer

The Borbely circuit blew me away. I just ordered the parts.

But as I was ordering these Toshiba parts through Newark, I threw in a TDA1541 for the circuit board group buy...

fab · 27th March 2004, 02:33 AM

Which circuit from Borbely are you building?

For whom would be interested, I have designed and built about 10 years ago a simple (8 transistors) symetric j-fet (2n5457, 2n5460) input pre-amp that sounded very clean and detailed. It had a gain of 5.

Jonathan Bright · 27th March 2004, 08:23 AM

Dear FAB Yes, please, I'm sure many people would like to see your design. Jonathan Bright

leadbelly · 27th March 2004, 01:10 PM

Quote:

Originally posted by fab
Which circuit from Borbely are you building?

The full preamp shown in the link in the 2nd post in this thread.

fab · 27th March 2004, 02:35 PM

Here it is

Q4 and Q2 are medium power transistor since the DC output current is about 20 ma. Some peoples may critic the 470uf output cap but at that time I was very precautious so in case of output failure no DC voltage would apprear at the power amp input...

leadbelly · 29th March 2004, 04:55 AM

Now that I have decided to build the Borbely preamp, I am similarly overwhelmed by picking a PS design to use for it.

Zener noise, pass transistors, tracking preregulators, 3 terminal regulator noise...my head is swimming

Can someone recommend a nice elegant low parts count PS design to go with the nice elegant low parts count Borbely preamp?

26th March 2004, 04:47 PM	#1
leadbelly diyAudio Member Join Date: Dec 2002 Location: Calgary, Alberta	JFET preamp recommendation? I want to build a very simple JFET preamp for a GainClone amp which I am building. There are so many designs on this forum that look great, but most are overkill for what I need (unabalanced input to unbalanced output). I just need a very simple buffer stage with low gain that will be able to drive the low-ish 10k input impedance the amp will have. I like the idea of a JFET amp with CCS most from a "doing something new" point of view and would love it to sound better than a chip buffer, but have not been able to find something with a low parts count by searching the forum. Any help appreciated __________________ Aerodynamics are for people who can't build engines. Enzo Ferrari

27th March 2004, 08:23 AM	#7
Jonathan Bright diyAudio Member Join Date: Feb 2004 Location: Queensland	Dear FAB Yes, please, I'm sure many people would like to see your design. Jonathan Bright __________________ "It was the Spring time of the year when aunt calls to aunt like mastodons across the frozen waste." P.G. Wodehouse.

29th March 2004, 04:55 AM	#10
leadbelly diyAudio Member Join Date: Dec 2002 Location: Calgary, Alberta	OK, can someone now recommend a PS to match? Now that I have decided to build the Borbely preamp, I am similarly overwhelmed by picking a PS design to use for it. Zener noise, pass transistors, tracking preregulators, 3 terminal regulator noise...my head is swimming Can someone recommend a nice elegant low parts count PS design to go with the nice elegant low parts count Borbely preamp? __________________ Aerodynamics are for people who can't build engines. Enzo Ferrari

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26th March 2004, 05:00 PM	#2
jam diyAudio Member Join Date: May 2001 Location: Charlotte,NC,USA	Read, http://www.borbelyaudio.com/ae699bor.pdf at the Borbely Audio web site. Regards, Jam

26th March 2004, 06:40 PM	#3
claudio diyAudio Member Join Date: Feb 2002 Location: Italy	Hi, A very simple pre with 4 transistors: 3 preamp to choose from Claudio

26th March 2004, 09:31 PM	#4
Pedja diyAudio Member Join Date: Jun 2002 Location: Serbia	This is it I'd say. http://users.verat.net/~pedjarogic/a...one.htm#buffer

27th March 2004, 02:33 AM	#6
fab diyAudio Member Join Date: Mar 2004 Location: Canada	Which circuit from Borbely are you building? For whom would be interested, I have designed and built about 10 years ago a simple (8 transistors) symetric j-fet (2n5457, 2n5460) input pre-amp that sounded very clean and detailed. It had a gain of 5.

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