JFET preamp recommendation?

[leadbelly]

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]

Read,

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

at the Borbely Audio web site.

Regards,
Jam

 

[claudio]

Hi,
A very simple pre with 4 transistors:

http://www.diyaudio.com/forums/showthread.php?threadid=2269&perpage=15&pagenumber=1


Claudio

 

[Pedja]

This is it I'd say.

http://users.verat.net/~pedjarogic/audio/gainclone/gainclone.htm#buffer

 

[leadbelly]

This is it I'd say.

http://users.verat.net/~pedjarogic/audio/gainclone/gainclone.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]

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]

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

 

[leadbelly]

Which circuit from Borbely are you building?

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

 

[fab]

symetric j-fet input pre-amp

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]

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?

 

[fab]

Re: symetric j-fet input pre-amp

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...

I redrawn by hand written circuit with microcap and made a mistake, sorry. See the C1 to C4 caps connection.