i'm on a roll... the kgsshv

[Lil' Knight]

What would be the negative effects when just using SE source? Would the voltage swing be the same?

[spritzer]

The voltage swing would naturally only be half of the XLR inputs. In practice this shouldn't make any difference.

[Lil' Knight]

In practice this shouldn't make any difference.

Could you elaborate this?

[luvdunhill]

Could you elaborate this?

You won't be able to tell a difference.

[justin]

What would be the negative effects when just using SE source? Would the voltage swing be the same?

i would not be the final authority on this however

using a SE source would only be equal to using a balanced source if the amplifier is a perfect SE->Diff converter. for a low feedback design like Gilmore's this will require great parts matching and thermal control

also, the typical source adds extra op-amps to convert balanced to single ended. so you are adding an extra op-amp stage that is not needed

but still, what luvdunhill said

[Lil' Knight]

i would not be the final authority on this however

using a SE source would only be equal to using a balanced source if the amplifier is a perfect SE->Diff converter. for a low feedback design like Gilmore's this will require great parts matching and thermal control

also, the typical source adds extra op-amps to convert balanced to single ended. so you are adding an extra op-amp stage that is not needed

but still, what luvdunhill said

Makes sense, thanks.

The reason I asked this is I'm thinking of adding one more channel to 'upgrade' my 3-channel B22 to balanced, but my main source is only SE. Asked amb about this and was told doing that way would only make the amp pseudo-balanced. I'm not 100% sure if this would apply to Dr Gilmore's designs so I just asked to make sure.

[justin]

i dont think it applies. but you could probably build a balanced bridged version of the b22, and then you'd have something similar to the way the e-stat amps are setup.

[spritzer]

Marc and Justin pretty much covered this but yeah, even with minimal matching and thermal drift you shouldn't be able to hear the difference between SE and XLR, assuming the outputs of the source are of equal quality which they almost never are.

Also to add to what Justin said, there are quite a few sources out there which only have SE output stages but then generate a balanced output from that. There are also plenty of Euro and Japanese gear which simply isn't balanced even though they shipped with balanced outputs.

[wink]

Is the BOM for this amp pretty much set in concrete, or are there envisaged changes to parts in the works?

[nikongod]

i dont think it applies. but you could probably build a balanced bridged version of the b22, and then you'd have something similar to the way the e-stat amps are setup.

Thats the b24

Nobody looks at it twice because "its a speaker amp", then they put binding posts on the back of the b22. clusterfuck.

[justin]

is the b24 more powerful? (besides the balanced bridge output)

[spritzer]

Isn't it about equal in Class A?

[Nebby]

Yes according to amb's site, the b24 is 170W into 8ohm while the b22 does 50W into 8ohm balanced bridged.

Amb has also listed the parts changes required for changing the beta24 for pure class A, with a target output power of 30W into 8ohm.

Not sure what the max output is for either the b24 or b22 while staying in class A, I think they're hidden in the long headwize threads.

[kevin gilmore]

Pretty sure the B24 also uses higher voltage power supply rails. At least +/-40 volts.

The SE/balanced thing works out great on all the electrostatic amps because the closed

loop gain is so high, 54 to 60 db. So if you measure the output voltages both ways, the

difference is a small fraction of a db.

Low loop gain things are much more trouble. This is why the kgitsojc circuit is specifically

designed to match the gains in SE to balanced as well as balanced to balanced. Something

the original never did because it was unbalanced input only.

It is true that a lot of stuff out there has very poorly designed balanced outputs.

krell,levinson and ayre do it right. The worst offender it seems were all of the

balanced singlepower disasters. Ray did not do it right on the B52 either, although

the A10 is supposed to be correct.

Then there are the transformer based things that are labeled as balanced when in

fact they have hugely different rise and fall slew rates.

Fully differential fully complementary symmetry amps are the best. Unfortunately not

possible in electrostatic amps unless you want to do serious transistor stacking.

[wink]

Fully differential fully complementary symmetry amps are the best. Unfortunately not

possible in electrostatic amps unless you want to do serious transistor stacking.

.

Something for the future....??

[kevin gilmore]

i posted this a while back.

http://gilmore.chem.northwestern.edu/vhvtest2.pdf

someone build it and let me know how well it works.

[jgazal]

Is this correct?

Fully complementary = signal path is balanced, so every noise that enters both paths with the same phase will be canceled each other.

Fully differential = a bipolar power supply is used, so the power supply rails are balanced and every noise coming from the mains with same phase in both power rails (the positive one and the negative one) will be canceled each other.

Symmetry = it is all about symmetric topology, then loops are better controlled in terms of delay (if any, considering the velocity of the electrons in such circuit) and phase reversions (the signal coming from the loop enters the first stage with the wrong phase).

I was wondering if point to point circuits with circular traces and input and output very close each other would be someway beneficial.

What do you think about phase splitters in the input? I think Woo Audio WES has something like that.

[kevin gilmore]

Not exactly.

Fully complementary: a transistor in the top half of a circuit is matched by a transistor of opposite polarity on the bottom half of the circuit.

Slew rates are identical or close to identical in every section of the amplifier.

Fully differential: input signals with common mode noise with respect to ground are ignored.

Special care for electrostatic amps, for which the outputs both go up and down with respect to ground for

common mode noise, but the bias would therefore change for signicant amounts of dc at both inputs.

Symmetry: Everything is active in both directions. The result of fully complementary.

Tubes can be fully differential, lots of circuits exist. Tubes can never be complementary as there is no such

thing as a p-channel tube. The output circuit of a circlotron can be considered as fully symmetric, but the

drive circuit is anything but.

Dynalo, dynahi,dynafet,b22 and B24 are all fully complementary, fully differential and fully symmetric.

Lots of power amps over the years are the same. Very very few dynamic headphone amps do this.

Mainly due to cost issues.

The electrostatic circuit above is all of the right things. But the required super-symmetry

causes the input impedance to be way low. Plus a huge amount of parts, lots and lots of heatsinks

and board area.

kgss, kgsshv, kgbh, T2 and every other stax amp are balanced and have differential inputs, but

are not symmetric and definitely not complementary either. One of the results is that power supply

noise and drift are now a significant issue.

[wink]

someone build it and let me know how well it works.

.

You know you want to build one...................

Perhaps nattonrice might fall for it..!!

[spritzer]

No phase splitter is needed with these amps since the gain is so high. The WES is basically a GES with the front end removed so to run it SE they had to add the front end to the circuit again. The

ESX also has gain issues when running in SE mode which are due to the amp not using ECC81's like it should.

[nattonrice]

Haha I think I've maximized the amount of shit I can fit in the floor space I have.

I need to start finishing things... doh!

[wink]

How about Quasi Complementary Symmetry?

All the same topology, N-channel or P-channel.

[wink]

I need to start finishing things... doh!

.

Tom,

You're way ahead of most headphone buffs - they're finished before they're started when it comes to building their gear....

[luvdunhill]

How about Quasi Complementary Symmetry?

All the same topology, N-channel or P-channel.

how about not posting

[Craig Sawyers]

how about not posting

Oof.