Simplistic balanced preamp/buffer

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C

cypher

Member
Joined 2007
Hi Guys,
I'm looking for schematic/inspiration for balanced preamp/buffer. What is my goal / requiremts

Very low output impedance let sey 10-50R max
one balanced and one unbalanced input
One balanced output
Capability to drive 1,8kR balanced input of my amp
Amp needs only 0.7v rms for full output
No DC at output (amp has DC protection circuit and shuts down at very low DC at input)

This buffer/pre does not have to have volume potentiometer since I'm using software for volume regulation in my computer which is the main source of my music ..

My amp is Burmester 911 so we are talking rather about high expectation in terms of sound quality ;-)

Regards,
Artur
 
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xrk971

xrk971

Founder of XSA-Labs
Joined 2012
etsy.com/shop/XRKAudio
Paid Member
cypher said:
Hi,

Are you talking about this implementation ?

THAT Driver: Differential line driver / preamp

Regards,
Artur
Click to expand...

That could work, and Tomchr's implementations are excellent. But I was actually thinking of this one - it has very low impedance and can drive headphones even. One important distinction is that the outputs are discrete and operate in Class A. I think 750mW into 30ohm load is possible so it can drive any amp.

Dual Class-A Line and Headphone Output Board Documents - Pro Audio Design Forum

This is actually an updated design using the THAT DRV134 chip:
DCAO_173_DRV134_Schematic_Small.JPG


Implementation looks like this:
DCAO_173_DRV134_stuff_small.JPG


You can buy a dual (stereo) balanced board pre-built for $200 here:
Dual Class-A II Reference Headphone Line Amp PC Board

I am in no way related or benefit from this recommendation - I just think it is very good based on the THAT1646 HPA from Wayne Kirkwood that I made myself. Perhaps one of the lowest distortion amps I have ever tested:

643819d1509784405-esp-hpa-that1646-hpa-1vrms-50ohms-fft-jpg
 
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C

cypher

Member
Joined 2007
Unfortunately this amp has only XLR input and my DAC has only RCA output ;-( I could go for simple conversion XLR > RCA (shorting pin 1 and 3) but this seems to be bad idea.

Further more, for sure my DAC is not designed to drive such low impedance ..

BTW. If my amp using XLR connection has 1.8 kR input impednance how much i will get shorting pin 1 and 3 ? Will it be the same as XLR ?
 
A

AndrewT

R.I.P.
Joined 2004
xrk971 said:
Can you point to a link for the schematic that is easier to find? The links in Post 1 are all broken. I hate threads that hide the schematic.
Click to expand...
Not all.
Others found the link. It's right at the end of post1.

I do agree that we Members should be attaching all our information.
I have been championing that for years. The Forum did promise that the new software, two or three generations ago, would only allow attached info and block remote servers. But that never happened.
 
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