[Skyhawk]

I am curious about Class A Biasing in Class AB amps.  I am trying to learn a little more about how Bryston in particular is different from the rest of the Class ABers out there.

 I currently own a pair of 7B SSTs and I have read a review that states they make 25W of Class A before switching to class AB

I am wondering why the ratio of Class A to total wattage in the 7B is so much higher than all the other SST amps.  ie the 4B SST makes 3 watts of class A before switching to AB.

The other prong of this question is, which way are the amplifiers biased.  More towards class A or more towards Class B?

James Tanner is probably the only guy that knows, but I thought I would as here anyway.

[James Tanner]

HI Skyhawk,

Where did you read it was biased class A for 25 watts - that is not correct - it is a few watts as in the other amplifiers.

james

[Skyhawk]

Good evening James

I read it on the Bryston website several months ago.  It was in the form of a review either on the 14B or 7B cant remember.

I will look on the site again.  Beleive it was an inner ear report.

[Skyhawk]

http://bryston.ca/reviews/14bsst/pro14.html

Says that it will make 25 watts Class A.

[Levi]

I am interested to know.  What about the 9B SST amps?

[James Tanner]

http://bryston.ca/reviews/14bsst/pro14.html

Says that it will make 25 watts Class A.

I will have to contact the reviewer and get that changed.

james

[James Tanner]

I am interested to know.  What about the 9B SST amps?

All the Bryston amps run Class A for the first few watts.

james

[BeeBop]

So if you have a BP25DA, is the Class A output from that additive to the few watts of class A from an SST amp (3BSST in my case)? Assuming here that since the DAC has discrete Class A op amps, it would be outputting a certain amount of class A.

[James Tanner]

Correct - All our Preamps run full Class A all the time.

james

[Skyhawk]

Would that include the SP1.7?

And if so, only when it is in 2CH bypass or 6CH Bypass, or both?

All of things dont really make it sound better.  Its really cool to know though.  I always was interested in how electronics worked.

[James Tanner]

Yes the SP1.7 has the same discrete Class A gain stages as the BP26 ( instead of IC's)- thats why it sounds so great.

james

[nicolasb]

Semi-on-topic: is there any performance difference between the SP1.7 in 2-channel bypass mode and in 5.1 channel bypass mode? For example, if one is using a DVD-Audio-capable player to play both stereo CDs and DVD-A discs, is it worth using a separate pair of stereo interconnects into a stereo input to play CDs, or would the performance be exactly the same using two channels of the 5.1 bypass?

[James Tanner]

Hi nic,

I will check with Mike on that one - I believe the signal path is identical.

james

[Mike Pickett]

Hi nicolasb;

The 5.1 bypass mode is definitely cleaner and quieter than any DSP mode, but the 2 channel bypass mode will still be the best.  The 5.1 bypass mode still uses the level controllers on the DSP module, but the signal stays in the analog domain for the entire path.  The 2 channel bypass mode uses the actual volume pot for attenuation, and provides a much shorter, more direct signal path, avoiding the DSP altogether.

I recommend using either the 2-channel bypass mode or a digital input for CD listening, whichever sounds best.

Mike

[Skyhawk]

I was just thinking that the sp1.7 has been out for a while, so I am sure there is something up the sleeve of Shane and the boys at bryston.  

Wondering will the SP2.0 have balanced inputs?  Is there an upgrade planned to make 1.7 have balanced inputs?

[Levi]

Follow this link

I was just thinking that the sp1.7 has been out for a while, so I am sure there is something up the sleeve of Shane and the boys at bryston.  

Wondering will the SP2.0 have balanced inputs?  Is there an upgrade planned to make 1.7 have balanced inputs?

[Levi]

I found this post.  I hope this helps.

Hi;

   The Class-A output prior to Class AB for a 3B SST is about 1.5 Watts. On a 4B SST it's around 2.5 to 3 Watts.

   Btw, these amps don't ever switch to 'Class B', they always have some bias running. The distortion typically runs in the low thousandths of a percent at 20K at any power level below clipping.

   Hope this helps!

Chris Russell, writing for James Tanner

[James Tanner]

Thank you - I was looking for that.

james

[BeeBop]

So if I have a BP25DA and 3BSST, how much Class A in total would be going to my speakers before it starts to bias over (did I ask that right?)