[M3 EuroLTW]

On the back of my 3BST and 5BST, I have the usual small switch to go between balanced and unbalanced.  There is no indication that there is a 6 db boost for the XLR input vs the RCA.

On the back of the 9BST amplifiers, I see the switch that performs a similar function to be labeled +6db.

While building a Media Room, and adding on amplifiers all of which would be using XLR mean that the 9BST would be louder at a given input vs the 3BST and 5BST?

Or.... do the 3BST and 9BST do the same 6db boost, just not label it as such?

Thank you in advance.

[James Tanner]

On the back of my 3BST and 5BST, I have the usual small switch to go between balanced and unbalanced.  There is no indication that there is a 6 db boost for the XLR input vs the RCA.

On the back of the 9BST amplifiers, I see the switch that performs a similar function to be labeled +6db.

While building a Media Room, and adding on amplifiers all of which would be using XLR mean that the 9BST would be louder at a given input vs the 3BST and 5BST?

Or.... do the 3BST and 9BST do the same 6db boost, just not label it as such?

Thank you in advance.

Correct they are just labelled differently. 

james

[M3 EuroLTW]

Thank you for your continued support of the forum.

Prompt response on a weekend exceeds all expectations!

Alex

[Sir Yacho]

Hello,

Isn't the 6dB of gain specific to the "pro" versions only? 
As per this,

http://bryston.com/PDF/Other/STPRO_NOTES.pdf

it was my understanding that in the Regular versions, the inherent +6dB of an electronically balanced input stage was offset by design.  No?

[James Tanner]

Hello,

Isn't the 6dB of gain specific to the "pro" versions only? 
As per this,

http://bryston.com/PDF/Other/STPRO_NOTES.pdf

it was my understanding that in the Regular versions, the inherent +6dB of an electronically balanced input stage was offset by design.  No?

On the Pro versions you have a rotary gain control as well as the sensitivity gain switches.  The Balanced inputs do add the extra 6dB

james

[Sir Yacho]

Thanks for your reply, James!

I guess my confusion stems from this paragraph in the linked pdf:

"Some PRO models provide different inherent gain and/or different gain options
from REG models. This is due to the fact that a balanced input inherently
provides 6dB of gain if each of the two halves of the input (or if each input phase)
is operating at unity gain. This 6dB of gain is sometimes desired by professional
installers, but can be an annoyance in home installations where every successive
balanced in/out stage in every piece of equipment in the audio chain adds 6dB of
gain. This can quickly add up to an excessive level. In general, REG models do not usually add 6dB of gain at the balanced inputs, whereas PRO models do."

This is what I was originally reffering to, but I may be misunderstanding something.

[James Tanner]

Thanks for your reply, James!

I guess my confusion stems from this paragraph in the linked pdf:

"Some PRO models provide different inherent gain and/or different gain options
from REG models. This is due to the fact that a balanced input inherently
provides 6dB of gain if each of the two halves of the input (or if each input phase)
is operating at unity gain. This 6dB of gain is sometimes desired by professional
installers, but can be an annoyance in home installations where every successive
balanced in/out stage in every piece of equipment in the audio chain adds 6dB of
gain. This can quickly add up to an excessive level. In general, REG models do not usually add 6dB of gain at the balanced inputs, whereas PRO models do."

This is what I was originally reffering to, but I may be misunderstanding something.

No I think that may be incorrect but I will check with engineering.

james

[James Tanner]

Hi James,

Just to clarify, All of the CUBED amps, PRO or REG, have the same overall gain (23dB or 29dB, depending on position of gain switch), irrespective of input type (BAL or UNBAL).

As an example, a 1V UNBALANCED input signal (1V with respect to GND), will yield the same  output signal at the speaker terminals, as a 1V BALANCED input signal (.5V each leg with respect to GND).

However, many audio sources (All Bryston preamplifiers and most "consumer" equipment), will have a balanced output that is 6dB hotter (1V across each leg, with respect to GND) than its UNBALANCED output. Most BRYSTON amplifiers include a 23dB/29dB gain switch, to address this increased level.

Additionally, BRYSTONs PRO amplifiers employ a variable attenuator, providing up to 14dB further attenuation.

Hope this helps!

Regards,
David Nelson
CAD Engineer

[Sir Yacho]

Thank you James and David for the information!

However, I believe that the amplifiers in question were of the original ST line, not the new CUBED series. These amps do not have an input sensitivity switch of course, just the bal/unbal selector switch, which disables the input jack not in use.  And the schematic of the input section topology certianly shows some differences in the gain structure resistors between the REG and PRO versions, I'm just not certain what results those differences provide.

Thanks for the info dig!