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Balanced vs Single Ended

Since you are asking, here are two:

"The power supply is more complicated too because you have to have a positive supply rail and a negative supply rail. "

You don't. You can build single-supply balanced gear.

In fact balanced operation reduces the load on the power supply, since the signal current is no longer passing through it.

"Also you find lots of feedback is normally applied to keep the crossover distortion low."

This has nothing to do with the subject.


It is trivially easy to make a balanced-in moving coil phonostage with something like an SSM2016, 2017, INA217, or whatever today's equivalents are named. You'll find it free of hum even in the most carelessly assembled systems.

The price is noise: as the two legs' input devices appear electrically in series their noises sum and so there is a 3dB penalty, give or take. With today's loud low-output MCs that is not really a problem, though.
 
Werner said:
Since you are asking, here are two:

"The power supply is more complicated too because you have to have a positive supply rail and a negative supply rail. "

You don't. You can build single-supply balanced gear.

In fact balanced operation reduces the load on the power supply, since the signal current is no longer passing through it.

"Also you find lots of feedback is normally applied to keep the crossover distortion low."

This has nothing to do with the subject.



It is trivially easy to make a balanced-in moving coil phonostage with something like an SSM2016, 2017, INA217, or whatever today's equivalents are named. You'll find it free of hum even in the most carelessly assembled systems.

The price is noise: as the two legs' input devices appear electrically in series their noises sum and so there is a 3dB penalty, give or take. With today's loud low-output MCs that is not really a problem, though.
Click to expand...

+1 ;) Those are the real howlers yes!
 
...or even 'the signal having to go through twice as many components'. No- each leg of the signal goes through the same number of components there are just + and - legs to each channel as well as gnd.

Come on Graham you're a designer, be a little more exacting in your posts and make sure they say what you mean.
 
Werner said:
Since you are asking, here are two:

"The power supply is more complicated too because you have to have a positive supply rail and a negative supply rail. "

You don't. You can build single-supply balanced gear.

In fact balanced operation reduces the load on the power supply, since the signal current is no longer passing through it.

"Also you find lots of feedback is normally applied to keep the crossover distortion low."

This has nothing to do with the subject.


It is trivially easy to make a balanced-in moving coil phonostage with something like an SSM2016, 2017, INA217, or whatever today's equivalents are named. You'll find it free of hum even in the most carelessly assembled systems.

The price is noise: as the two legs' input devices appear electrically in series their noises sum and so there is a 3dB penalty, give or take. With today's loud low-output MCs that is not really a problem, though.
Click to expand...

I had assumed we were talking about a discreet design (tube or transistor) not some sub £500 op amp design!!!

Check out some commercial designs from ARC, Mark Levinson et al and you will see that balanced designs have double the devices, double the components and dual rail power supplies (solid state designs anyway) as I stated on my original post. I have two 4 draw filing cabinets full of manufacturers schematic diagrams showing this.
 
sq225917 said:
...or even 'the signal having to go through twice as many components'. No- each leg of the signal goes through the same number of components there are just + and - legs to each channel as well as gnd.
Click to expand...

Yes, in a cheap op amp design. I was rather hoping people on here would be using something a little better than that.
 
Werner said:
"Also you find lots of feedback is normally applied to keep the crossover distortion low."

This has nothing to do with the subject.
Click to expand...

It has everything to do with the subject!!!

You can design a single ended circuit without feedback. Feedback has a massive effect on the audio performance and ultimately the sound quality of the amplifier.
 
Heed the China Syndrome!

OK then. I can design and build balanced equipment, with a single-ended supply, without loop feedback, and without 'cheap' opamps.
 
Werner said:
Heed the China Syndrome!

OK then. I can design and build balanced equipment, with a single-ended supply, without loop feedback, and without 'cheap' opamps.
Click to expand...

And you are not the only one..... not that it would be my personal choice to do so! Certainly do-able though yes.
 
No one doubts that truly balanced gear requires twice the number of amplification circuits if done correctly Graham, one for each additional negative leg . But that isn't the same thing as passing through twice as many components, each leg of the signal does not pass through one stage followed by another stage. They each only pas through their own single stage.

I get what you mean, you just aren't actually saying that.
 
sq225917 said:
No one doubts that truly balanced gear requires twice the number of amplification circuits if done correctly Graham, one for each additional negative leg . But that isn't the same thing as passing through twice as many components, each leg of the signal does not pass through one stage followed by another stage. They each only pas through their own single stage.

I get what you mean, you just aren't actually saying that.
Click to expand...

Apparently they are Simon!

Here is a simple balanced input circuit for a microphone which is not that different to an input circuit for a phono cartridge, not taking into account the RIAA equalisation which would normally be done after the first stage.

http://www.circuitdiagramlinks.com/wp-content/uploads/2011/07/Balanced-microphone-preamp-.gif

Note: what ever component in the "+" input section is also in the "-" input section too. Two coupling caps (C2&C3). Same for the resistors and any other component in each + or - signal leg. The signal is effected by all of these parts. Note also the more complex +12v & -12v power supplies needed which most balanced designs adopt. Normally circuits for the + and - are mirror images of each other. This circuit actually goes from balanced to single ended for its output.

Here is a simple single-ended microphono circuit.

http://www.tradeofic.com/Circuit/3024-SINGLE_ENDED_MICROPHONE_PREAMP.html

As you can see the input is is much more complicated in the balanced circuit than in the single-ended circuit.
Note approximately half the components used in the first stage plus a much simpler power supply is needed as only one rail is used. As we all know, the more parts the signal has to travel through the more the signal is degraded. Everything shown here is as described in my original post. These circuits are very typical of those used in todays budget phono stages using op-amps. Better more expensive designs will use discreet devices, like those used in Naim Audio equipment for example.

I am not saying balanced equipment cannot be done differently (e.g. without open loop feedback etc etc) but it is very rarely the case. This makes it more costly to implement and to a certain extend "cost to make" is what manufacturers are driven by these days for commercial designs. I'll leave there so you can draw your own conclusions...
 
harrisonfraud said:
I'm no engineer, but I believe plenty of designers produce balanced, zero-feedback circuits, like Charles Hansen of Ayre:
http://www.ayre.com/technology.htm

I have an Ayre P-5xe phono preamp that I run balanced in and out and it sounds noticeably cleaner, clearer and more dynamic in balanced mode than single-ended.
Click to expand...

You have to be very careful here. Manufacturers of solid state electronics often quote "zero feedback" in their designs but what they don't tell you is they apply liberal amounts of localised feedback around each stage(s). It is well known that global feedback is the greater of the two evils...
 
Arkless Repairs said:
Knowledge of electronics obviously not a requirement eh Graham?
Click to expand...

It depends on what knowledge of electronics you are referring too, and seeing that you have mentioned the soft smelly stuff on here a few times, plus farting in a lift I'm assuming you are from the Peter Sellers School of Electronics...
 
Note approximately half the components used in the first stage...
Click to expand...
You've not really chosen good examples. For example the first circuit implements phantom power, which mandates a balanced input.

Paul
 
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