SE vs Balanced volume

@ steakster

Still waiting, what is the name and model of this amp so we can put this to bed.

Cheers  George

What is meant by "summing stages for single-ended output" Thanks.

This is usually, a proper fully balanced circuit, and then an opamp/circuit is needed to sum both +- make it SE, in this case the xrl/balanced should sound better as the SE has the extra opamp/circuit in the signal path.

But in the OP’s case it seems to be the other way around, to which he still hasn’t given any model or manufacturer name so we can put this to bed.

Cheers George

@steakster

What is this amp??? That you got rid of Artemis 6c33c monoblocks for, I am intrigued.

http://img.usaudiomart.com/uploads/large/1369416-cr-developments-artemis-mono-blocks.jpg

http://img.usaudiomart.com/uploads/large/1369418-cr-developments-artemis-mono-blocks.jpg

Cheers George

because the signal coming in on the RCA connector together with the inverse of that signal provided at the output of the INA134 enables the input board to be provided with a balanced pair of signals.

That means one phase only going to the "balanced" input board is going through the INA134, as it’s clearly just a single ended output, pin 6 on the data sheet. If that's the way it’s no wonder some think the balanced sound better. This should be called fake single ended. Why sacrifice sound quality of the rca for the sake of the same gain.
http://circuits.datasheetdir.com/164/INA134-pinout.jpg

I can see it using the AD8476.
http://www.mouser.in/images/microsites/low-power-diff-con-fig01.jpg

Cheers George

So what your saying then is the RCA input uses the IN134 to provide an extra 6db of gain to keep both inputs the same level, but there’s no feedback network to set the gain, and as the data sheet says it’s fixed gain at unity. Also then wouldn’t the switch have to have to be more than just a simple two pole switch?
If not then and I’m wrong the rca is at a disadvantage having to go through the opamp.

Burr Brown INA134
FEATURES ● SINGLE ● FIXED GAIN = 0dB (1V/V) AUDIO DIFFERENTIAL LINE RECEIVER ● SUMMING AMPLIFIER ● UNITY-GAIN INVERTING AMPLIFIER ●

Cheers George

Ok then it's now solid state, can the OP still post the make and model of it.? So we can put this to bed.

Cheers George

And also Al while were waiting for the OP's answer, I use two s/s amps with fully balance discrete input stage. This amp has rca inputs and xlr inputs with a switch between the two, no opamps involved. When switched to rca it just put’s pin 3 of the xlr to ground.

Cheers George

As I have explained in precise detail multiple times

Sorry Al, but you assume the amp itself is fully balanced, where and who said this. Can the OP state what amp make and model it is? So we can stop the assumptions.

PS: I just looked at the OP's posts on his amps they use a  (12ax7 as a phase splitter) still saying they're fully balanced?  

Because what I see is the IN134 used to make a balanced input single ended, just as I’ve seen with a certain Classe models, which is fake balanced.

Cheers George

Read PS: above.

Cheers George

That’s could be right also Al, didn’t look at it from that angle, just saw the shielded cable going to that point. In any case I wouldn’t like to have that single ended INA134 in the signal path on my amp/s.
And as I said before if the amp was full balanced they would have used the INA2134 to get balanced output from the opamp even then, yuck!.

Cheers George

How can they feed a balanced signal from 1 x INA134 to the amp input board, when it (IN134) only has a single ended output? They would either need two IN134's per channel or 1 x  IN2134.

Cheers George 

If you guys look at the shielded cable soldered connection you'll see it's one live and two connections to the ground plane making it single ended.

https://onedrive.live.com/?authkey=%21AGcHA6Bqk4TpTLo&cid=31799128EF335049&id=31799128EF335049%2127368&parId=31799128EF335049%21117&o=OneUp

Cheers George 

but it is also possible that it is a two-conductor shielded cable, conducting a balanced pair of signals.

It maybe Al but not used as such when the fake balancing opamp only has a single ended output. Only if the opamp was the  INA2134 not a INA134
Cheers George

Like I said the only time balanced is an advantage is for noise rejection, but is only an advantage over rca with very long interconnects, and there is no sound advantage, if anything it’s a worse sound in this fake balanced connection case above with an opamp in the signal path, the $2 INA134 was never designed for high-end audio use, more like PA audio.

Cheers George

INA134 is a differential amp (instrumentation amp), designed for audio, that provides very high (90dB) Common Mode Noise Rejection.

It’s still a faked balanced into what is obviously not balanced amp, and it’s also an unwanted opamp in the signal path, of what must be a single end input amp. In the end it’s which is going to sound better, I’ll lay money on the single ended input.
Like the saying goes the best opamp is no opamp.

Cheers George

steakster
Here’s a photo of the innards behind the RCA & XLR inputs of the SS amp. XLR is on the left, RCA on the right, the yellow wires go to the external toggle switch. Why the different results? Thx.

Without the circuit, that to me looks like fake balanced with that opamp (INA134?) sitting there, if so then the single ended should sound better, unless your running 10mt interconnects, then the balanced "maybe" a touch quieter for noise but not better in sound.
As you got red green and white for opamp power, and the single whitish one to the right looks like it’s the single ended shielded signal carrier to the input board.

Just looked yes it is a fake balanced, that opamp is a balanced to single ended converter.
http://www.ti.com/lit/ds/sbos071/sbos071.pdf
Best opamp is no opamp, go the single ended input, which bypasses the opamp.


Cheers George

steakster

Seeing this amp is fake balanced, I would just use the rca out of the preamp (just incase it's also fake output) into the rca in of the amp, for the best sound if your interconnects are <5mt.
No advantage in using balanced out of the preamp to rca in of the amp.

Cheers George