Any thoughts on S.E. to balanced signal conversion?

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#1
Have a client over there in the States who's asked me to fab up another batch of cables for him. He initially ordered some RCA to XLR cables and I gave him pre-warning that a signal path from S.E. to XLR via a cable isn't going to offer any benefits and won't magically become a 'balanced' signal. Beneficial of course if you're restricted on I/O options where you have to use such a cable. I bridge pins 1 and 3 at the XLR connector, 2 is hot of course.

In any case he's come back asking for more RCA-RCA and XLR-XLR cables to use with an S.E. to XLR converter box which will sit in the midlle of his signal path.

Not having had any experiences with such devices I'd be interested to know what your thoughts are on this box of tricks from avahifi?

The customer's looking to achieve lower distortion figures of his amp by setting it to mid-gain instead of high-gain in concert with the box of tricks.
Seems a bit of an exuberent and expensive experiment if you ask me, but you know what they say; 'the customer is always right!' :D
 

Gepetto

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#2
Doubtful that he will achieve his goal by putting another distortion producing element in the signal path.

This comment is interesting, "to achieve lower distortion figures of his amp by setting it to mid-gain instead of high-gain"
 

Gepetto

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Many confuse the function of the power amp volume pots with that of gain control in power amplifiers.

Those volume pots are not controlling the gain of the amplifier circuit, the power amp circuit gain remains constant regardless of where the volume pot is set. The volume pot is just controlling how much attenuation is applied to the input signal prior to going into the power amp circuits.

So to take the preamp output, multiply it by 2x (the converter box), to then attenuate the signal by 2x (the power amp volume pots) is only adding distortion to the signal. All of that function should be relegated only to the preamp.
 
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Doubtful that he will achieve his goal by putting another distortion producing element in the signal path.

This comment is interesting, "to achieve lower distortion figures of his amp by setting it to mid-gain instead of high-gain"
One of my first thoughts was that it may just actually introduce noise into the signal path due to it having its' own power supply.
Telling that there are no THD/Noise figures given in the specs.
 

Gepetto

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One of my first thoughts was that it may just actually introduce noise into the signal path due to it having its' own power supply.
Telling that there are no THD/Noise figures given in the specs.
Correct Chris, plus all the commercially available SE to XLR conversion ICs cite their specifications and surprisingly, they are not zero. No doubt that this box just uses one of these ICs mounted on a circuit board to do the conversion. The majority of the build cost in that box is in the enclosure and connectors, not the circuit.
 
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Correct Chris, plus all the commercially available SE to XLR conversion ICs cite their specifications and surprisingly, they are not zero. No doubt that this box just uses one of these ICs mounted on a circuit board to do the conversion. The majority of the build cost in that box is in the enclosure and connectors, not the circuit.
Well, I shared my opinions on it as well as relaying your own comments to him.
Of course I may lose a sale from giving him advice against buying it, but I also advocate experimentation. So he could go either way and my conscience as a *kof* ethical seller remains intact. lol

Thanks for comments and input all.
;)
 

Gepetto

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Well, I shared my opinions on it as well as relaying your own comments to him.
Of course I may lose a sale from giving him advice against buying it, but I also advocate experimentation. So he could go either way and my conscience as a *kof* ethical seller remains intact. lol

Thanks for comments and input all.
;)
It's his money to burn...

You have not reached the point of diminishing returns, you've just run out of money
 

J!m

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#9
I discussed this topic at length with Wyn Palmer because a phono cartridge is intrinsically balanced. It also is a very low level signal that could benefit from all the noise rejection it can get due to the upcoming gain stage…

But adding the SE to balanced conversion within the main board caused an increase in noise that was unacceptable.

I still think a fully balanced design using four op amps (2 each parallel for hot and cold) may be worthwhile. But I can’t design it and Wyn wasn’t interested.

I would at least like to get my line amp done someday.
 

Gepetto

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I discussed this topic at length with Wyn Palmer because a phono cartridge is intrinsically balanced. It also is a very low level signal that could benefit from all the noise rejection it can get due to the upcoming gain stage…

But adding the SE to balanced conversion within the main board caused an increase in noise that was unacceptable.

I still think a fully balanced design using four op amps (2 each parallel for hot and cold) may be worthwhile. But I can’t design it and Wyn wasn’t interested.

I would at least like to get my line amp done someday.
Life is single ended...
 
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