BHK300 Clicks during warm up & cool down

Has anyone noticed intermittent (about 5 to 10 minutes apart at start, farther apart after about an hour) single clicks directly from the BHK 300 amps (not through loudspeakers) starting about 20 minutes after turn on (front panel only), lasting about 1 1/2 hours, then again about 20 minutes after turn off (front panel only) for about an hour? Caused, I suspect, by metal parts (perhaps heat sinks) expanding & contracting due to heat buildup at turn on, and cool down at shut off. Rear panel on/off is always “on”. Left channel amp does this more frequently than the right. Are there other possibilities or anything to be concerned about? Will this decrease or stop entirely as amps break in: amps in use about 222 hours,. Thanks.

This has been discussed recently. I think others have mentioned the same thing.

This is why one of my amps has gone for repair - although I’m not sure if our cases are identical because in my case the sounds (pops and clicks) were coming out of the audio signal (ie. the speaker).

They did initially seem to coincide with warm up and cool down and only started early this year (after about 6 months of having the amps).

They started out mild and intermittent so that at first I thought I was hearing sounds from the road outside and not the hifi system.

Over time they got worse until there were loud pops and bangs coming out of the speakers almost all the time and by connecting and disconnecting components it became clear it was one of the BHK 300 amps. The sounds were even there if I turned the volume of the preamp to zero (indeed volume did not change their intensity) - I’d say the volume was at time louder than most of the music I play. Even disconnecting the input to the amp (but still having the speakers connected) did not stop them.

Interestingly the other amp from the pair made no such sounds at all (not even mildly).

Eventually it would start as soon as the amp was turned on and it became impossible to listen to any music, so despite the massive hassle I returned it for repair.

As of tomorrow my BHK 300 (which sounded amazing until this began) will have been away for almost five weeks.

Hopefully I will get some kind of idea what the problem is this week and maybe an ETA for when I can I have my proper hifi functional again. As others have mentioned one of the problems here (UK) is that if you have any problem it takes an age to get it sorted out due to the distance from PS Audio.

I envy those of you in the USA since you can get things sorted out fast.

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It’s temp expansion/contraction, most likely. All my Pass Labs amps have always done this. So does my 911.

I suspect distance has nothing to do with it. When I send a busted power plant to our Australian distributor it has been repaired and back out the door again within 2 or 3 days. I’ve got a hunch the distance between Adelaide and Boulder is even further than London is to Boulder.

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My situation sounds are coming directly from the amps, not through the loudspeakers. Amps are dead quiet (absolutely no hiss or hum even turned up & ear right up to Focal Sopra No. 2 loudspeakers) and always sound great during playback. In system with Audio Research LS28 preamp. Marvelous, synergistic combination.

I have a large tub amp with EL34 power tubes which make wonderful tinkling noises as they cool. I would miss these sounds.


Thanks for your post. My 300’s do the same and I thought (as did PSA service) that I was the
only one hearing things. The persistent “ ping” seems to be mechanical in nature and is every 5-10 minutes or so after warm up and lasts till in standby mode. My uneducated guess is thermal expansion between an output device and heat sink. In any case, the units sound fine but the sound is annoying and I have no romantic reference to soften the blow.

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I’d have been surprised if I was the only one, especially since it’s both amps, which I doubted was a coincidence.

If the cause is as you suggest, and assuming not all output devises are involved, can the one(s) that are be replaced to eliminate the noises? Is this a case of a loose or bad connection of the offending devise to the heat sink, or a problem with the devise itself? If it was “normal” I’d expect all output devises to do the same thing, which I don’t think is happening.

I don’t necessarily expect you have the answers, but I wanted to post these questions in case someone who’s following this thread does.

Thanks for the feedback.

Yes, it happens with both amps. Guess we have to make a collective case to PSA.

So, as the amps, (their metal enclosures), heat up and expand during warm-up and contract during cool-down when they’re turned off, make expanding/contracting ticks, you see this as a design or performance flaw?
Class D amps are probably what you’re looking for. Try auditioning M700’s. I’ll bet you’d be pleased. They’re great amps. And you could get a great trade deal, no doubt, come away with money.

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He said he finds the “ping” sound of the amps annoying, I don’t think the cause has been determined yet. And he’s not alone. The sound might be normal, or it might not. As a helicopter pilot it’s just ingrained in me if something is making an odd noise you stop using it until the cause is determined. Hence, if my amps were making an annoying or odd noise I’d want them thoroughly checked out. Which, by the sound of it, PS Audio is attending to.

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First, whether this a thermal heating/cooling issue is supposition.

Second, 22 plus years in system never heard this from my Adcom GFA-5802 power amp. This is not necessarily to be expected from a powerful Class AB, biased to Class A, amplifier.

Third, and most important, the reason for question is an interest to find out if this is to be expected with the BHK 300’s, or if it’s an anomaly which should be checked out.


I’m with you. Proceed as planned.

Agreed. I have not had the need to service any component of a complete PSA rig and like the sound quality. I might live with the noise, but just want some company research which I hope will be forthcoming. I am more curious than an unhappy camper.

Based on the response from PS Audio Head Engineer, which I very much appreciated (see below), I’m also taking a wait & see (listen) position. Amps too good to send on a road trip for no reason. Here’s the response:

"There are several relays in the BHK amps that turn the circuitry on and off in specific sequences, but once the unit is up and running there shouldn’t be any changes. I’m sure it’s nothing to worry about and I hate to bring a unit back that is otherwise working great, but it doesn’t sound normal.”

The only reason I posted here is, since no definitive cause was identified or suggested, I was interested if others were having a similar experience & what they thought about possible causes.

Good luck & let us know how things are, going forward. I’ll do the same.

Thanks! You and Brodric have convinced me. Press on until you get an answer that you’re comfortable with.
And that Adcom was a great amp! I still have one.

I still have the GFA-5802, definitely a great amp. BHK 300’s on another level, though.

Found this response from Emotiva regarding a similar question about one of their amps. I pass it along for what it’s worth:

The clicking sound you are hearing is coming from the heat sinks inside the amplifiers and will have no bearing on the performance or longevity of the unit. What is happening all comes down to thermal expansion (when the amps are running) and thermal compression (as the amps cool down). This is just a byproduct of all high bias amplifiers (the XPA-1 is currently the only high bias unit we manufacture). You see the root cause of a clicking sound is the aluminum heat sink expanding and contracting at a different rate from the steel chassis that it is mounted too. With any high bias amplifier design you will need larger heat sinks to dissipate the thermal energy that comes from the output devices. So large aluminum heat sinks are required for long term reliability. When rigidly mounted to a steel sub-structure (also needed to support the weight of the heat sinks) there will be expansion and contraction differences due to different thermal properties of steel vs. aluminum. In most cases the clicking sound is very soft and usually masked by the music being played. Since the metallurgic properties of both aluminum and steel alloys vary slightly during the foundry process, it is not unusual for one amp to be a little more prominent from the other.

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I have a pair of Pass class A monoblocks and they do something similar. In my case its definitely from the thermal cycling of the heat sinks. They emit one or two “pings” as the amps come up to temperature. Same thing on cool-down.

About once a year I re-torque the bolts that hold the heat sinks to the chassis and that stops the pinging. It seems that the thermal cycling loosens them enough to allow movement between the aluminum heat sinks and steel chassis.