Bryston BHA1 Headphone Amp

[Pars]

Doesn't appear to have enough relays to be doing a relay-based stepped attenuator. Digital volume control?

I'm sure they wouldn't be using a shunted differential pot such as this

[n_maher]

The volume could be a shunted pot, right? No clue what they'd do for balance.

[luvdunhill]

I vote balanced to single ended conversion and then back to balanced. Explains the gain and the pot.

[spritzer]

That would be plausible but idiots over on HF will not like it...

[Pars]

I'm not sure they are even discussing it there yet. I'll be waiting for the usual "Yeah, Spritzer, we know if it isn't Gilmore, its shit" response when you finally do get a crack in

[grawk]

I just got an email from ttvj, they're selling it now too, $1295

[Hopstretch]

Think that's an input selector (balanced/unbalanced) not a balance control.

If this is implausible or clumsily expressed, please consider the mitigating circumstances. Which are that I'm drunk.

[spritzer]

The input selector is a toggle switch to the extreme left of the amp. The small knob is a balance control.

I'm not sure they are even discussing it there yet. I'll be waiting for the usual "Yeah, Spritzer, we know if it isn't Gilmore, its shit" response when you finally do get a crack in

So fucking true... Still it's a Bryston so it's certainly better than most of the crap out there.

Edited February 29, 2012 by spritzer

[Hopstretch]

This is why drinking is bad kids.

[spritzer]

But... but... it's so much fun!!??!!

[swt61]

RVFTMFW!

[cutestory]

Not to necro, but my BHA-1 finally came in (black, with female XLR connections). The sound so far doesn't suck.

I have the manual here; would anyone care for me to upload the included schematic?

[spritzer]

Sure, why not. Interesting to see if they claim the amp is truly balanced.

[cutestory]

Here it is.

Begin analysis! Here are links to my Dropbox in PDF and PNG formats.

https://www.dropbox....jxhfoq/bha1.pdf

https://www.dropbox....u9vovq/bha1.png

Enjoy!

Thanks for looking, spritzer, and anyone else who's interested...would be interested in some feedback.

Edited September 26, 2012 by cutestory

[spritzer]

Is it just me or what's the point of this amp? Why on earth would anybody build something like this? So a fully balanced amp except it isn't since the input section is single ended and with only a two gang volume control which then feeds to two amp sections per channel. It's get better though as they capacitor couple the output so one gets to enjoy the sound of a quad of 4700uf/35V electrolytic caps. I truly don't understand this amp or the logic behind it.

[Dreadhead]

Preface with that I may be entirely off base/misunderstanding (on the balanced part): They are using the balanced signal in its original use which is to cancel noise. Then invert the SE signal out and do fully balanced amplification?

[spritzer]

There is special stage to do inverting after the volume control. My gripe is that they could just have married a balanced input buffer with a quad pot and had a fully balanced amp.

[Dreadhead]

But then they would not have gotten the noise cancellation right? Or does it just happen at the transducer?

[cutestory]

Is it just me or what's the point of this amp? Why on earth would anybody build something like this? So a fully balanced amp except it isn't since the input section is single ended and with only a two gang volume control which then feeds to two amp sections per channel. It's get better though as they capacitor couple the output so one gets to enjoy the sound of a quad of 4700uf/35V electrolytic caps. I truly don't understand this amp or the logic behind it.

Would you mind explaining to a layman why this is bad?

I'm not a circuit guy, but I understand the bit about the input section being single ended (which does seem silly). It's the "two gang volume control" and "they capacitor couple the output" parts that I'm not groking.

Thanks in advance...

[nikongod]

But then they would not have gotten the noise cancellation right? Or does it just happen at the transducer?

Noise cancellation of COMMON MODE noise happens wherever the phases of the signal are compared. If the phases are compared at the inputs, noise cancellation happens there. If the phases are compared across the drivers that is where the noise cancellation happens.

The cool thing with amps like this is you get noise cancellation regardless of whether you use the SE or balanced outputs. With 4-boards in one box amps (icky) you only get noise cancelation when running balanced. 4boards-1box amps also amplify the noise through the whole amp, gobbling up overhead - if you get rid of the noise early (in either SE or 2ch balanced amps) you can improve performance greatly.

A 2-channel balanced buffer would be infinitely better than 4-boards in one box. Separate is not equal.

Edited September 26, 2012 by nikongod

[spritzer]

Would you mind explaining to a layman why this is bad?

I'm not a circuit guy, but I understand the bit about the input section being single ended (which does seem silly). It's the "two gang volume control" and "they capacitor couple the output" parts that I'm not groking.

Thanks in advance...

Two gang volume control means it's only stereo. Why they took what is essentially a balanced input stage and then fed it through a stereo volume control and then onto a quad output stage is just odd. Why not go all the way and go balanced through out?

As for the capacitor output, this is used to block the natural DC offset of the output stage. This is a common feature in Bryston designs so I'm not surprised but it only takes a few parts to make a servo which is completely transparent (certainly more so than a PSU capacitor) and means the output can be DC coupled. Amps like the GS-X do it like this so more transparent.

I do agree with Ari that RCA inputs are often badly catered for but I've all but given up on them anyway. Why bother with them when one can go fully balanced...

[luvdunhill]

I like it. Nothing wrong here.

[cutestory]

The cool thing with amps like this is you get noise cancellation regardless of whether you use the SE or balanced outputs. With 4-boards in one box amps (icky) you only get noise cancelation when running balanced. 4boards-1box amps also amplify the noise through the whole amp, gobbling up overhead - if you get rid of the noise early (in either SE or 2ch balanced amps) you can improve performance greatly.

A 2-channel balanced buffer would be infinitely better than 4-boards in one box. Separate is not equal.

Does this mean only the balanced output is worth listening to on this piece? Or that the whole thing is junk (relatively speaking, of course)?

It also sounds like spritzer says I should be ordering an amp from Justin, which I should think about doing anyway.

[nikongod]

Does this mean only the balanced output is worth listening to on this piece? Or that the whole thing is junk (relatively speaking, of course)?

No, it means that there should hardly be any difference at all. Which is very cool.

Ooh, unless the output impedance is different running SE and BAL.

People put WAY too much importance on Balanced amps, especially in high feedback circuits.

[cutestory]

Ooh, unless the output impedance is different running SE and BAL.

How would one be able to tell this? Volume comparison with SE and balanced cables with the same headphones and an SPL meter? Assuming one doesn't take the beast apart, of course...