Looking for nice OPA134 preamp to build

robmil · 12th September 2010, 07:51 PM

Hi

I would like to build a small preamp based around the OPA134 or AD797 with a 4 transistor follower discrete buffer. I've hunted around but can't find anything.
Can anyone point me in the right direction please. The voltage rails are +/- 15v but I can go higher on the output buffer as I have an extra winding on the transformer I have (+/- 24vac with a center tap).
I would like a Class-A discrete zero-feedback buffer as I have seen one somewhere.....but where?

thanks for the help

Rob

AndrewT · 12th September 2010, 08:29 PM

Walt Jung details combining opamp with buffer.

richie00boy · 12th September 2010, 08:33 PM

You probably haven't found anything because there is little point in adding a discrete buffer to an op-amp stage to driver power amps. The op-amp is more than capable enough on its own.

Maybe what you really want is just a simple discrete pre-amp. I've got a design ready if you want to try?

robmil · 13th September 2010, 08:42 AM

Hi

Thanks for the options and replies. I pretty convinced that I do not want to go the chip opamp way (by itself) as a friend played me the difference between chip with and without a buffer on his DIY preamp and yes although sound came out of the chip opamp and was able to drive the power amp, adding the buffer sounded so much better, fuller, better soundstage and more 'real'.

I've looked at the Millett diamond buffer but it's too much. Something like the Sijosae class-A but that will work at +/- 15v

R

Voegelchen · 13th September 2010, 09:02 AM

Walt Jung is worth looking for... and see here....
http://www.ac-vogel.de/TransBuffer_A...fer_APN_1.html

I've build a CLASS-A Buffer and measured THD/THD+N.......

Andreas

Albrerta · 14th September 2010, 01:22 AM

how about this one

Current boosted diamond buffer preamplifier stereo kit on eBay.ca (item 320538649111 end time 22-Sep-10 23:38:36 EDT)

robmil · 15th September 2010, 05:34 PM

Albrerta...how did you find that? That is just what I was looking for..infact that is pretty much it.
Thank you

regards

R

12th September 2010, 07:51 PM	#1
robmil diyAudio Member Join Date: Jun 2004 Location: London	Looking for nice OPA134 preamp to build Hi I would like to build a small preamp based around the OPA134 or AD797 with a 4 transistor follower discrete buffer. I've hunted around but can't find anything. Can anyone point me in the right direction please. The voltage rails are +/- 15v but I can go higher on the output buffer as I have an extra winding on the transformer I have (+/- 24vac with a center tap). I would like a Class-A discrete zero-feedback buffer as I have seen one somewhere.....but where? thanks for the help Rob

12th September 2010, 08:29 PM	#2
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	Walt Jung details combining opamp with buffer. __________________ regards Andrew T.

12th September 2010, 08:33 PM	#3
richie00boy Did it Himself diyAudio Member Join Date: Nov 2003 Location: Gloucestershire, England, UK	You probably haven't found anything because there is little point in adding a discrete buffer to an op-amp stage to driver power amps. The op-amp is more than capable enough on its own. Maybe what you really want is just a simple discrete pre-amp. I've got a design ready if you want to try? __________________ www.readresearch.co.uk my website for UK diy audio people - designs, PCBs, kits and more

13th September 2010, 09:02 AM	#5
Voegelchen diyAudio Member Join Date: Jun 2010 Location: Germany and www.aca-vogel.de	Walt Jung is worth looking for... and see here.... http://www.ac-vogel.de/TransBuffer_A...fer_APN_1.html I've build a CLASS-A Buffer and measured THD/THD+N....... Andreas __________________ Designing audio electronics isn't a job, it's a mission

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13th September 2010, 08:42 AM	#4
robmil diyAudio Member Join Date: Jun 2004 Location: London	Hi Thanks for the options and replies. I pretty convinced that I do not want to go the chip opamp way (by itself) as a friend played me the difference between chip with and without a buffer on his DIY preamp and yes although sound came out of the chip opamp and was able to drive the power amp, adding the buffer sounded so much better, fuller, better soundstage and more 'real'. I've looked at the Millett diamond buffer but it's too much. Something like the Sijosae class-A but that will work at +/- 15v R

14th September 2010, 01:22 AM	#6
Albrerta diyAudio Member Join Date: Jun 2007	how about this one Current boosted diamond buffer preamplifier stereo kit on eBay.ca (item 320538649111 end time 22-Sep-10 23:38:36 EDT)

15th September 2010, 05:34 PM	#7
robmil diyAudio Member Join Date: Jun 2004 Location: London	Albrerta...how did you find that? That is just what I was looking for..infact that is pretty much it. Thank you regards R

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