[Marius]

HI James,

I've been auditioning and changing speakers recently, and doing so finally tried to work out why there is a soft but persistent hiss i should have done a lot earlier.
So please let me ask you here and now.

On my Quad ESL's  the hiss is very soft, on my Kef 102's it's much louder.
I use a BP26, 28b's and 10bsub. All seems in order, switching connections, cable's etc didn't make a difference.

The hiss is only there when the 10bsub is powered, even with the volume control on the BP26 completely turned down.

Why would this be, and, more importantly, what can i do to take it out. It is really annoying, once you start to hear it, and concentrate on it...

Cheers,
Marius

[James Tanner]

HI James,

I've been auditioning and changing speakers recently, and doing so finally tried to work out why there is a soft but persistent hiss i should have done a lot earlier.
So please let me ask you here and now.

On my Quad ESL's  the hiss is very soft, on my Kef 102's it's much louder.
I use a BP26, 28b's and 10bsub. All seems in order, switching connections, cable's etc didn't make a difference.

The hiss is only there when the 10bsub is powered, even with the volume control on the BP26 completely turned down.

Why would this be, and, more importantly, what can i do to take it out. It is really annoying, once you start to hear it, and concentrate on it...

Cheers,
Marius

Sounds like transistor noise coming from the 10B sub and depending on the efficiency of your speakers and the overall gain in your system becomes more ore less noticeable.   Try reducing the overall gain by using the 2 volt sensitivity setting on the 28B's

james

[Marius]

James, thank you, ill try when i get back.
Would it be worth the trouble to take the 10bsub for testing purposes ?

If it is the 10bsub, transistor-noise, could you change/modify it so that is filtered out?

or is it possible to modify the speaker cables to attenuate somehow? (My Sub cable was changed so that it allowed me to dial in the controls better, maybe the L/R speakers need that too)?
Right now, the Kefs won't allow me to dial the volume much further than 0800 .. Quads are a bit more needy, but never past 11 o'clock.

Marius

[James Tanner]

James, thank you, ill try when i get back.
Would it be worth the trouble to take the 10bsub for testing purposes ?

If it is the 10bsub, transistor-noise, could you change/modify it so that is filtered out?

or is it possible to modify the speaker cables to attenuate somehow? (My Sub cable was changed so that it allowed me to dial in the controls better, maybe the L/R speakers need that too)?
Right now, the Kefs won't allow me to dial the volume much further than 0800 .. Quads are a bit more needy, but never past 11 o'clock.

Marius

We can check out the 10B for you but my guess is you just have too much gain in the system.

james

[Marius]

And besides setting to 2v (which i believe i have done before) are there any other options?

We can check out the 10B for you but my guess is you just have too much gain in the system.

james

[James Tanner]

And besides setting to 2v (which i believe i have done before) are there any other options?

Not that I am aware of other than there are ways to reduce the gain in the 10B - ask Mike on that one.

james

[Marius]

HI James,

MY 28b's are on the 2v setting.
Strange thing is that where i had to turn the volume of the BHA up to 14 o'clock, i noticed i had to turn it down lately to even below 10 for it not to become too loud... 

maybe its not the (pre) amps but the BDA1-out that's too strong? Could this have changed over time?

Marius

[James Tanner]

HI James,

MY 28b's are on the 2v setting.
Strange thing is that where i had to turn the volume of the BHA up to 14 o'clock, i noticed i had to turn it down lately to even below 10 for it not to become too loud... 

maybe its not the (pre) amps but the BDA1-out that's too strong? Could this have changed over time?

Marius

I can not see how the BDA-1 would change - did you ask Mike about reducing the gain in the 10B?

james

[Marius]

Yes i did, but did not receive an answer yet, you were in cc..Please give Mike a wink.

My remarks about the BDA and BHA were only concerning the earlier tendency of the BHA to be not loud enough to being easily too loud now. Excluding the BP26 in the chain. The output signal of the BDA has already been turned down with the code in the BR2 remote. nothing there to brake or blow that needs to be checked?

Marius

I can not see how the BDA-1 would change - did you ask Mike about reducing the gain in the 10B?

james

[James Tanner]

Yes i did, but did not receive an answer yet, you were in cc..Please give Mike a wink.

My remarks about the BDA and BHA were only concerning the earlier tendency of the BHA to be not loud enough to being easily too loud now. Excluding the BP26 in the chain. The output signal of the BDA has already been turned down with the code in the BR2 remote. nothing there to brake or blow that needs to be checked?

Marius

I am pretty sure you can reduce the gain in the 10B by 6dB just by changing a pin connectors position.

james

[Marius]

I never found this before http://bryston.com/PDF/Other/10B_GAIN_ATTENUATOR_NOTES.pdf is this what you mean?

Not sure what to change though.... so many options.
definitely need some guidance here.
to be sure: this is also for the 10bSUB?

Marius

I am pretty sure you can reduce the gain in the 10B by 6dB just by changing a pin connectors position.

james

[James Tanner]

I never found this before http://bryston.com/PDF/Other/10B_GAIN_ATTENUATOR_NOTES.pdf is this what you mean?

Not sure what to change though.... so many options.
definitely need some guidance here.
to be sure: this is also for the 10bSUB?

Marius

Yes there are 4 gain sections on each channel - I have forwarded your post to Mike.

james

[Marius]

ok thanks James,

Yes there are 4 gain sections on each channel - I have forwarded your post to Mike.

james

[Mike Pickett]

Hi Marius;

Most of the information in that '10B Attenuator' link is devoted to changing the individual gain of the high and low pass filters, and to the position of the gain control on the unit. However, if you look at the centre of the rear portion of the board, there are two jumpers for setting the input gain sensitivity of the 10B, and this is a much more effective way to reduce the noise floor of the system.

Depending on how the unit was configured at the factory, these jumpers may be installed across both pins, or uninstalled, in which case they would be on only one of the two pins.  To reduce sensitivity, and thus noise floor, ensure that both jumpers are shorted.

Regarding the unexpected change in gain of the system, please check the gain switch on the BHA1; it's possible that it was moved to the 'high' position, which would result in a significant increase in overall gain...

As an additional troubleshooting step, please check the noise level with the preamp turned off, and the 10B Sub turned on.  This can help determine whether the noise is originating with the 10B, or earlier in the chain.

Thanks,

Mike

[Marius]

Thanks Mike,


Great to see the 10bsub is such a versatile tool.


Please guide me to 'the centre of the rear portion of the board' on the pdf. i cant seem to find these jumpers on it. Would it be possible to highlight them on the map?


I do have the BHA1 gain setting set to high, have that since the beginning. I needed that to lift the volume up to the desired level. So no change there. Other than it suddenly seemed much louder...


The hiss is only there when the Bp26 is turned on. I can try to take the 10bsub out completely, to see if the hiss level is the same, and in doing so check whether the 10bsub amplifies this, or only passes it through?


Marius

Hi Marius;

Most of the information in that '10B Attenuator' link is devoted to changing the individual gain of the high and low pass filters, and to the position of the gain control on the unit. However, if you look at the centre of the rear portion of the board, there are two jumpers for setting the input gain sensitivity of the 10B, and this is a much more effective way to reduce the noise floor of the system.

Depending on how the unit was configured at the factory, these jumpers may be installed across both pins, or uninstalled, in which case they would be on only one of the two pins.  To reduce sensitivity, and thus noise floor, ensure that both jumpers are shorted.

Regarding the unexpected change in gain of the system, please check the gain switch on the BHA1; it's possible that it was moved to the 'high' position, which would result in a significant increase in overall gain...

As an additional troubleshooting step, please check the noise level with the preamp turned off, and the 10B Sub turned on.  This can help determine whether the noise is originating with the 10B, or earlier in the chain.

Thanks,

Mike

[G Georgopoulos]

what kind of source is in the system,usually analog sources like vinyl and cassette cause this

[Marius]

the only analog source right now is my phono-preamp. (no player connected for the time being)


there are several sources with switching power-adapters though. All connected to the BDA. don't think they cause this gain-hiss, but could be worth the try.

what kind of source is in the system,usually analog sources like vinyl and cassette cause this

[G Georgopoulos]

the only analog source right now is my phono-preamp. (no player connected for the time being)


there are several sources with switching power-adapters though. All connected to the BDA. don't think they cause this gain-hiss, but could be worth the try.

If you have a cdp connect it to preamp,then if you have no problem with hiss,suspect the phono preamp
I have never seen a problem with an amp or subamp using a digital source,no matter the gain!

[Marius]

HI Mike, James,


Could you please help me with the map? Before i open the 10bSub and dismantle my setup.... id like to be sure which jumpers to short 'on the rear portion of the board'.


Thanks,


Marius

Thanks Mike,


Great to see the 10bsub is such a versatile tool.


Please guide me to 'the centre of the rear portion of the board' on the pdf. i cant seem to find these jumpers on it. Would it be possible to highlight them on the map?


I do have the BHA1 gain setting set to high, have that since the beginning. I needed that to lift the volume up to the desired level. So no change there. Other than it suddenly seemed much louder...


The hiss is only there when the Bp26 is turned on. I can try to take the 10bsub out completely, to see if the hiss level is the same, and in doing so check whether the 10bsub amplifies this, or only passes it through?


Marius

[Mike Pickett]

Hi Marius;

I've sent you a picture via e-mail showing the locations of the jumpers in question.

That fact that the noise disappears with the BP26 turned off indicates that the 10B is likely not causing the issue, but reducing the gain may help nonetheless...

If the noise is present even with the volume turned all the way down on the BP26, reducing the gain at the 10B should reduce the level of the hiss.  If the hiss goes away with the volume down, and increases with increased volume, it's likely originating before the BP26, and reducing the gain at the 10B may not be useful.

Thanks,

Mike