Hi forum
I have a Bryston 4bSST2 that makes a hiss sound. Not trough speakers, but the amp itself. Regardless if input signal are connected, speakers, grounded or ungrounded circuit.
The hiss is in approx. 12 kHz region, and seems to be on the input PCB. I have to turn off the amp when its not in use as its very disturbing.
Any ideas are very welcome.
Thanks.
Schematics at official Bryston homepage:
http://old.bryston.com/PDF/Schematics/4BSST2_SCHEMATICS.pdf
I have a Bryston 4bSST2 that makes a hiss sound. Not trough speakers, but the amp itself. Regardless if input signal are connected, speakers, grounded or ungrounded circuit.
The hiss is in approx. 12 kHz region, and seems to be on the input PCB. I have to turn off the amp when its not in use as its very disturbing.
Any ideas are very welcome.
Thanks.
Schematics at official Bryston homepage:
http://old.bryston.com/PDF/Schematics/4BSST2_SCHEMATICS.pdf
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Does this amp have any kind of auxiliary power supply for things like remote power on detection and so on and if by chance it did, is that PSU a switching type.
Can't think of anything else on a conventional analogue amp and conventional PSU tbh.
Can't think of anything else on a conventional analogue amp and conventional PSU tbh.
Thanks for your reply Mooly
No, its a power amp with no additional PSUs. Only conventional linear rectification.
This is why I also are fumbling in blind. No obvious source.
And it disappears when power is turned off, so its not in my head either 🙄
No, its a power amp with no additional PSUs. Only conventional linear rectification.
This is why I also are fumbling in blind. No obvious source.
And it disappears when power is turned off, so its not in my head either 🙄
Could this be coming in on the mains? No mains filtering I note.
Also there's a microcontroller driving various relays - perhaps this is using PWM?
Also there's a microcontroller driving various relays - perhaps this is using PWM?
The only components that would usually make noise are transformers or ceramic (multlayer) capacitors. There are some unusual elements in this circuit such as the handoff relay, looks like it would need a PWM/switching signal from the micrcontroller to keep it active, unless I am missing something...
Thanks for adding the circuit diagram 🙂
I can't see anything obvious on the input PCB as it's called. 'Hissing' sounds like a wound component like a coil/transformer/relay etc. Putting fingers on and around such parts might give a clue... obviously be careful doing that though.
A scope probe with a small coil attached between probe tip and probe ground might just pick up the area of the noise if you hover it around various parts... but don't let the leads come into physical contact with anything electrically.
I can't see anything obvious on the input PCB as it's called. 'Hissing' sounds like a wound component like a coil/transformer/relay etc. Putting fingers on and around such parts might give a clue... obviously be careful doing that though.
A scope probe with a small coil attached between probe tip and probe ground might just pick up the area of the noise if you hover it around various parts... but don't let the leads come into physical contact with anything electrically.
Mark and ohdsp, thanks for your reply.
MC with PWM driving relays is a really plausible root for the hiss. Will look into it.
Mains noise is not the case. Same problem at two different locations kilometers apart.
MC with PWM driving relays is a really plausible root for the hiss. Will look into it.
Mains noise is not the case. Same problem at two different locations kilometers apart.
I had a similar strange sizzle sound in a DCG3 build. Turns out it was the output delay relay. It was fixed by adding a 100pf cap between the base and collector of the relay driver transistor, as suggested by Salas. In your case, so far I see only one similar circuit on the first page of your schematic (soft start board).
I found it using an old automotive trick. Take a length of shrink tubing, or some other type of non-conductive tube, long enough to hold to your ear while you pass the other end over each relay, or other places, to pinpoint where the sound is coming from. I wouldn't use anything conductive for obvious reasons.
TJ
I found it using an old automotive trick. Take a length of shrink tubing, or some other type of non-conductive tube, long enough to hold to your ear while you pass the other end over each relay, or other places, to pinpoint where the sound is coming from. I wouldn't use anything conductive for obvious reasons.
TJ