Designing a versatile pre with balanced and unbalanced in/out

[ThorstenL]

Hi,

Originally Posted by TheShaman

Btw, The Wire is this.

You may be better off with one of Walt Jung's compound Op-Amps.

I see little to even recommend the above project, the circuitry shows nothing past 1980's levels. Much better options exist for the balanced input with improved CMRR. I can also one or two possible stability nightmares lurking there.

In your application I think you can dispense with the input followers, as I expect your preamp's balanced outputs will have low output impedance, so they are redundant.

Better power supplies are available and will improve this "not much of a wire" circuit as well.

Ciao T

[Nikon1975]

I think that the choice of a specific circuit or device at this stage is premature. Personally I use "The Wire" as I have it, and I bought it mostly to get wet with SMD work. So I am not married to that.

Anyway, there is a good point in the discussion: granted that the "Black Box" will have both balanced and unbalanced, inputs and outputs, all the "processing" like input switching, volume control etc., should be done in SE or with Balanced signals ?

For sure I see the complication of keeping everything balanced internally, but I also see the "beauty" of having the balanced signals reaching the balanced amp without a conversion back and forward to SE, just for volume control.

I wouldn't like to sound too philosophical, but I would be tempted to keep the BAL signals as intact as possible. Like mixing the liquids, increase entropy and some informative content get lost. (Here maybe I am mixing things. Sorry I try to fill my electronic knowledge gaps with what I know better, so I could be very wrong)

Actually modifying the sources to have both type of outputs, and build two pre-amps, one serving SE amps and the other one BAL amps, could ease the task a lot. Beside the fact that I already have a SE pre-amp.

Thorsten, no worries about the suggestions. I think people can recognize genuine advice from commercial and I think your follow in the first categories. It is obvious that you like what you designed, otherwise you would have done it differently :-)
We all know you like transformers :-). I don't have much experience with them, except few OPT for tube I use, but I like their apparent simplicity.

D.

[yangbaibing]

what is SE?

[Nikon1975]

SE means single ended. Mainly all the normal signals with two pins.

Was your question sarcastic? :-)

D.

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[EUVL]

Whether you want to do things SE or balanced depends on whether you like some second harmonics to "sweeten" things,
or you go for minimum distortion (then mainly odds remaining).

Matter of taste I guess.


Patrick

[SGregory]

Look at the topology in Nelson Pass's Bride of Son of Zen. Should be able to find the write up on PassDIY. It does exactly as you want. Not bad sounding either. WHile my gear is all valve today, I use that preamp to drive my Aleph5, Zen4, and 100W AlephX mono blocks in my other systems. Have SE and Balanced inputs into it.

[Nikon1975]

SGregory,

Do you refer to this: http://www.passdiy.com/pdf/balzenpre.pdf

I cannot see any BAL to SE conversion here.

Thanks,

D.

[enregistree]

Originally Posted by Nikon1975

Anyway, there is a good point in the discussion: granted that the "Black Box" will have both balanced and unbalanced, inputs and outputs, all the "processing" like input switching, volume control etc., should be done in SE or with Balanced signals ?

For BAL/SE -> BAL/SE versatility you want, make it balanced internally. Conversion is needed only for SE -> BAL, it could be done with LTP – differential amplifier – as input stage and shorting BAL– input to GND when source is SE.

[SGregory]

Nikon1975.

Yes that is the circuit, and yes it does the conversion quite well. Read through the text and it explains how and why. Not only does it sound good, it does a nice job as a converter. SE - > Bal Bal -> SS.

[Nikon1975]

I see where it says about the conversion, but I do not understand how it works. If I have an SE signal in, where do I get the antiphase?
Additionally, why not doing the supplies using linear regulators? Is there any mosfet that can be used, with lower voltage?

Thanks,
D.

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