[AnthonyH]

Hi all

I've recently bought a used (+- 10 year old) Bryston 4B-ST amp and BP-25 pre. While I'm absolutely blown away by the sound etc... I've noticed that the amp gets quite hot. This happens even if no music is playing and the Pre is muted. Is this normal?

I have no way of measuring the temperature but I can keep my hand on it for a minute without getting too uncomfortable. Factor in that the temperature in the room where the amp is kept is quite high (Yes, summer has finally started here in the UK) around 26 degrees Celsius.

Thanks

[James Tanner]

Hi Anthony,

It sounds like it may be a little over biased. Contact PMC.

james

[AnthonyH]

Hi James

Thanks for the response, I'll contact PMC UK to find out what to do. From what I've read getting the amp re-biased isn't a major job and it will be nice to get a service done and have peace of mind. Unfortunately my hifi aspirations and my wallet don't match up so second hand gear is all I can do.

I'll be sad to be without it for a while as I've enjoyed rediscovering my music collection What a great amp!

Anthony

[predrag]

It is summer here and temeratures are about 25 - 30°C.
My 4B SST has been on for the past 72 hours or so and it has on cover plate 45 - 50°C what seems OK with me.
Just as you describe the hand can be kept on it for a minute.
Have in mind that this is serious amp with serious power and it is normal that it dissipates a lot of heat.
A class amps with only 30W get much hotter!

[AnthonyH]

Hi

I have wondered if I'm just being paranoid!  How did you measure the temperature? By holding a thermometer on the top plate? I ran the amp for a few hours last night (playing music) with a small fan blowing air over the top of the amp and it didn't run too hot.

I have no real reference as my last amp, an AVI integrated, didn't run hot at all.

A

[predrag]

I did not measure the temperature but if you consider that body temperature is around 37°C to my estimation the cover plate was 10°C more. If it was 60°C or more it would be too hot to hold the hand on the amp for long.
Finally the big heat dissipation is why our amps have such a large cooloing surfaces aside.

[richidoo]

Is the 4B SST or any of the quad complimentary designs biased into classA at all? If so, how many watts into class A on 4BSST? AB amps don't necessarily make much heat at idle. 
Thanks
Rich

[James Tanner]

Is the 4B SST or any of the quad complimentary designs biased into classA at all? If so, how many watts into class A on 4BSST? AB amps don't necessarily make much heat at idle. 
Thanks
Rich

Hi,

Yes our amplifiers are bias for Class A for about 10% of their range.  The amp should run warm at idle and hot at full out (depending on the speaker load) but not so hot that you can not leave your hand on it.

james

[vegasdave]

Thanks for the info, James.

[niels]

Predrag gave a great description of temperature, 60 degrees will indeed be very hot. Hot water in normal houses is 55 degrees and this will be pretty hot, you want to pull your hand away.
My B100 gets comfortably hot, its faceplate and volumeknop will also heat up but I have no problem keeping my hand on it.

[b5pt9]

My 4BST always ran very warm, borderline hot to the touch even at idle.  Maybe the ST series amps ran alot of bias current?  My 4BSST runs much cooler by comparison.

[brucek]

My 4BST has been on all day playing music, and I just went and put a temperature probe on the top panel, and another in the middle of one heat sink.

The top is 34 C degrees and the heat sink is at 40 C degrees. Not much worse than a very warm day. I can easily put my cheek on the heatsinks..

My 3BST and my 5BST are all about the same.

If its hot at idle, it likely needs to be rebiased.

brucek

[AnthonyH]

Hi

Thank you all for responses. My 4BST doesn’t get so hot that I can’t keep my hand on it but it does run quite hot at idle. This makes me think that it needs to be re-biased at some stage.

I don’t think that it is in any danger yet and a small fan trained on it from a few meters keeps things cool enough. I’ll send it off in the next few months for a health check, just can’t part with it at the moment as I’m enjoying the music too much

[b5pt9]

Maybe James could confirm if Bryston checks the bias every time an amp comes in for service?  My 4BST was in about a year ago for a problem with the softstart circuit, and in light of this thread it would be nice to know if the bias was checked or not.  Thanks!

[James Tanner]

Maybe James could confirm if Bryston checks the bias every time an amp comes in for service?  My 4BST was in about a year ago for a problem with the softstart circuit, and in light of this thread it would be nice to know if the bias was checked or not.  Thanks!

Hi,

Yes anything that comes in for service is completely checked over before it goes back to the customer. Try not to worry to much about slight differences in heat - the bias is set independently on each channel (to optimize performance) so slight differences in temperature from amp to amp or channel to channel is not uncommon.

It still should not be too hot to touch though.

james

[danman]

Just got my 4B-ST and have noticed it gets quite hot even at idle as well! I don't know if I should be concerned or not but thought I would bring this up again since I am new to Bryston. I can say that this is the best amp I have owned and the sound is wonderful.

How would I know if there is a problem?

[b5pt9]

Hi Danman,

My personal opinion is don't be too concerned.  My 4BST idle temperature is considerably higher than my 4BSST, 5BST, or 1989 model 3B.  My old 1982 4B runs nearly as hot as the 4BST but not quite.

The only recommendation I would make is make sure the amp gets ample space on top and sides so the heat sinks can dissipate heat properly by natural convection.
   

[danman]

I am not really concerned as it sounds great with no problems. The question just stems from the fact that I don't know the brand very well yet. I have it placed totally in the open on top of my rack so it has no blocks at all.

What a great amp! I can hardly imagine how good the 4B-SST would sound!!? Eventually I will upgrade to that level but one step at a time!

[MOZ]

I've got a 4 channels 8B-ST (rear channels) on top of my 5B-ST (front channels) and there isn't a lot of place for the air to evacuate so when i watch long "action" movies (more than 3-4 hours, especially the kind of "boum-boum ones")... the 8B puts itself on protection, cuts off the EX channels... and wait till the heat comes down.
Eventually cuts off all rear channels for some time.

Then it starts again.
Never had a problem with it !!!

But my speakers are 4 ohms and i use to put it "really loud at home" !

So don't be afraid if it's a "bit hot"... mines could cook some eggs