[James Tanner]

From Engineering:

Hi James

RE: BP26 Volume control bleed through at min setting

All level controls  or potentiometers have some resistance between the wiping contact and the input and ground terminals. For attenuation we need only look at the wiper ground connection.
The Bryston BP26 preamp uses a dual 10K  Alps RK27  "Blue Velvet" volume control. The Alps spec sheet for the RK27 volume control indicates the residual resistance can be as high of 20 ohms.
Any we have tested are typically 1 to 2 ohms. The  attenuation spec for this control is a  min of 70dB. With a 10K control and a 1 ohm residual, the result is 80dB of attenuation, 2 ohms would be 75dB and 3 ohms 70dB of attenuation. For 70dB attenuation we need be below 3 ohms and we have never seen a reading above 2.5 ohms.
The bleed through can completely eliminated when the mute switch is engaged. Mute is the signal off condition.

Systems where bleed through is heard at min volume setting, generally we have high efficiency speakers, or the system gain may be too high or both.
Bryston Amplifiers have a gain switch for 23 and 29dB of gain. Selecting the 23dB setting would improve the bleed through by 6dB, and give better range for the volume control.
If your power amp inputs have level controls the power amp sensitivity also could be reduced using them.

[Anonamemouse]

With all due respect; bleeding is bleeding.
With a pre-amp at this level and with this price tag, this simply should not happen. No matter what gain is set or what sensitivity loudspeakers are used. 
The mute switch is called "power on/off" here.

[Laundrew]

This is a most interesting topic - I turned the volume down on my 26 and yes, you can hear the music playing very faintly from the JBLs. I went into the next room and turned on my Marantz SR 19 and with the volume completely turned off, you cannot hear anything out of my KEFs. Of course, I am not using balanced connections with the Marantz. If I get very ambitious, perhaps I will hook up my old Sony receiver and see what happens - or then again, maybe not. I am curious if other preamplifiers in the same class as the 26 also do this?

Be well...

[alexone]

...what about the SP3? would be interesting to know if there is a signal-bleeding, too...

al.

[PRELUDE]

Yes interesting topic and I just fund out how low noise is my active system.I have never tried such a test and I never owned any Bryston pre so I cannot talk about it.But just out of curiosity I turned my pre(SONIC FRONTIERS LINE2) all the way down and the room is dead quite now.Not only I do not hear anything coming out the speakers but I do not hear any noise also unless you put your ear right on tweeter then you hear a little noise which is 100% acceptable.

[Diamond Dog]

Yes interesting topic and I just fund out how low noise is my active system.I have never tried such a test and I never owned any Bryston pre so I cannot talk about it.But just out of curiosity I turned my pre(SONIC FRONTIERS LINE2) all the way down and the room is dead quite now.Not only I do not hear anything coming out the speakers but I do not hear any noise also unless you put your ear right on tweeter then you hear a little noise which is 100% acceptable.

Same story here, PRELUDE, but with a Manley NeoClassic 300B tube pre. With the source still sending signal to the pre, volume at zero is volume at zero - no sound. Nada.

D.D.

[Laundrew]

This is a most interesting topic - I turned the volume down on my 26 and yes, you can hear the music playing very faintly from the JBLs. I went into the next room and turned on my Marantz SR 19 and with the volume completely turned off, you cannot hear anything out of my KEFs. Of course, I am not using balanced connections with the Marantz. If I get very ambitious, perhaps I will hook up my old Sony receiver and see what happens - or then again, maybe not. I am curious if other preamplifiers in the same class as the 26 also do this?

Be well...

I should also add to be fair that my ear was inside of the horn and the room has to be absolutely dead quiet to hear this - a few inches away from the horn you can not hear anything at all. What is much more important to me is when I have my volume at full and no source, my JBLs are deathly quiet.

Be well...

[Laundrew]

Welcome back D.D. 

Be well...

[James Tanner]

...what about the SP3? would be interesting to know if there is a signal-bleeding, too...

al.

Hi al

No the SP3 uses a resistor ladder controlled by software volume control so the output is totally off with no resistance at zero - same with the new B135 Integrated and BP17 preamp.

james

[PRELUDE]

Same story here, PRELUDE, but with a Manley NeoClassic 300B tube pre. With the source still sending signal to the pre, volume at zero is volume at zero - no sound. Nada.

D.D.

Welcome back D.D
I always wanted to try a good 300B designed pre with Bryston power.Even if I buy one I still keep the Sonic Frontiers.

[brucek]

Hi al

No the SP3 uses a resistor ladder controlled by software volume control so the output is totally off with no resistance at zero - same with the new B135 Integrated and BP17 preamp.

james

I suspect the question was in relation to the analog bypass of the SP3 (as it acts similar to an analog BP26).

In that regard, is not the resistive ladder used exclusively with digital inputs in the level control circuits? I believe the analog bypass passes through a similar motorized analog pot just like the BP26? or is the SP3 different from the SP2?

brucek

[redbook]

  Well there's an idea for a design tweak in the next generation of BPs ( if this is really an important issue of real concern). Thanks James for that comprehensive explanation .

.

[Marius]

Hi James,

Thanks, and what about the crosstalk on the source selector?

Marius

Hi al

No the SP3 uses a resistor ladder controlled by software volume control so the output is totally off with no resistance at zero - same with the new B135 Integrated and BP17 preamp.

james

[James Tanner]

I suspect the question was in relation to the analog bypass of the SP3 (as it acts similar to an analog BP26).

In that regard, is not the resistive ladder used exclusively with digital inputs in the level control circuits? I believe the analog bypass passes through a similar motorized analog pot just like the BP26? or is the SP3 different from the SP2?

brucek

Hi - Different - the new preamps use a totally different volume control circuit and all analog and digital signals go through the resistor ladder.

"The digitally controlled volume utilizes a resistance network on a chip. This technology, in reference to the signal path, is still implemented in the 'analog' mode.

It offers many advantages, for instance perfect channel balance, a simple integrated balance adjustment without additional parts, practically zero adjustment noises, first class behavior in reference to noise and distortion, as well as adjustment via software."

james

[James Tanner]

Hi James,

Thanks, and what about the crosstalk on the source selector?

Marius

Crosstalk is a function of where the signal traces are relative to each other on the circuit board.

james

[Diamond Dog]

Welcome back D.D
I always wanted to try a good 300B designed pre with Bryston power.Even if I buy one I still keep the Sonic Frontiers.

Hi : I don't think there are that many 300B-based pre's out there to choose from - idea for a thread in another Circle! That Sonic Frontiers pre of yours ( and the Manleys I've owned for that matter ) would probably surprise a lot of people who have prejudices against tube pre's in terms of "lack of sonic neutrality" - especially with the right tube selection. My Manley continues to raise my eyebrows every now and then - paired with Bryston power & conditioning and a good source it's always a fun way to hear some music...Fun is good! 

D.D.

[PRELUDE]

Hi : I don't think there are that many 300B-based pre's out there to choose from - idea for a thread in another Circle! That Sonic Frontiers pre of yours ( and the Manleys I've owned for that matter ) would probably surprise a lot of people who have prejudices against tube pre's in terms of "lack of sonic neutrality" - especially with the right tube selection. My Manley continues to raise my eyebrows every now and then - paired with Bryston power & conditioning and a good source it's always a fun way to hear some music...Fun is good! 

D.D.

You most likely right and even if you find one it won't be cheap.

[Marius]

Hi James,

Not sure I understand your answer correctly, but what I wanted to ask was if its normal bp26 behavior and why the difference between the various source selections.

Thanks
Marius

Crosstalk is a function of where the signal traces are relative to each other on the circuit board.

james

[James Tanner]

Hi James,

Not sure I understand your answer correctly, but what I wanted to ask was if its normal bp26 behavior and why the difference between the various source selections.

Thanks
Marius

The traces on the circuit board of the BP-26 are close to each other so if you have two sources hooked up and turned on and depending on the gain in the source and its proximity to the other trace will determine if you get any bleed through.

james

[Marius]

Hi James,

this what we're talking about: http://psec.uchicago.edu/library/anodes/Anodes_Crosstalk_Overview.ppt ?
"Crosstalk is the coupling of energy from one line to another via:
Mutual capacitance (electric field)
Mutual inductance (magnetic field)"


I believe to remember that my dealer once told me leaving the sources open at the back of the Amp made some difference, but can not remember the specifics. Empty sources caused the crosstalk to become more eminent, i think. Will have to ask about this theory when he's back. Rings a bell?

Marius

The traces on the circuit board of the BP-26 are close to each other so if you have two sources hooked up and turned on and depending on the gain in the source and its proximity to the other trace will determine if you get any bleed through.

james