Thanks for that. Did you have to open the amps to do this, or are the bolts on the outside of the chassis?
Pass amps (old and new) are a “dreadnaught” type design with the heat sinks attached to the outside:
The machine screws have heads that accept hex (allen) wrenches and are located between the heat sink fins.
For amp designs with internal heat sinks, or external heat sinks fastened from inside the chassis, it will be necessary to pop the top or bottom off to locate the fasteners. (unplug the amp and make sure the power supply caps have fully
drained first, though, to prevent unpleasant surprises.
Mail](https://go.microsoft.com/fwlink/?LinkId=550986) for Windows 10
l
Thanks again. Unless someone from PS Audio sees this & responds I’ll call them Monday & ask if BHK 300 heatsinks can be tightened from the outside.
I think they can using an Allen Key as there are bolts on the outside.
I suspect you can’t go tightening these things willy-nilly. There will be a specified torque value, and the bolts should be tightened during manufacture to the correct torque.
Interesting, what people are willing to accept from their expensive equipment. I could never live with what is discussed here. And I consider it a design flaw. Luckily, in more than 40 years, I didn’t experience anything like that, neither from “cheap” nor from expensive units. On the other hand, most expensive in my case means flagship Accuphase in the early '90s. Probably not “high end” enough 
1 Like
My Sansui power amp from the '70’s did the same thing. No problemo.
My Corvette Z06 makes the same noises from the exhaust system heating up and cooling off but I have no intention of sending it back to the dealer for repairs to something that is not a performance issue. It is just simple natural forces at work and easily acceptable trade off for the performance gained.
1 Like
Great answer and it’s exactly what happens with BHK amps.
The BHK amps will always make the light ticking noise as they warm up and cool down. The heat sinks are quite tight but it’s the expansion and contraction of the differing materials. The main chassis is steel, the heat sinks aluminum, the side corners cast
zinc. I don’t know that there’s any means of quieting this down. Mine do it as well but it’s nothing that I am bothered by nor get concerned over. Your mileage may vary.
1 Like
Thanks for coming in on this discussion. My concern was that if something was loose that, over time, it would get worse and cause damage. Sort of like driveway and road cracks widen as water freezes and melts through the winter. Your answer places this in the “not a problem or concern” column. As I get older I find I’m placing more and more things into that column, and happy to add this one.
Great amps. At 70 this is my last audio rodeo. Mille grazie.
Engineers call this CTE (Coefficient of Thermal Expansion)… every material has this property. When two materials of differing CTE are connected they expand and contract at different rates, based on CTE. A very large CTE difference can create havoc in mechanical systems and the CTE differences and large temp swing is responsible for @Baldy (Vern’s & mine) Z06 exhaust noises…
1 Like
My power amp AND my 911 click away when cooling down. As Elk said, I’d actually miss it. It’s the object cooling after a job well done.
3 Likes
It’s just a few screws on a stereo power amplifier. It doesn’t take a military procedure to see if they are tight and it is not rocket science. Certainly not worth the shipping damage that could occur on an unneeded trip back to the manufacturer to investigate. A set of 300’s is on my short upgrade list and when they arrive it will be added music to hear them heat up and cool down.
If my Corvette exhaust is quiet when I turn the engine off it means that it was not a fun trip. 
2 Likes
Thanks. Agree. Performance off the charts, get them in your system ASAP. Warning: you’ll be changing tubes more frequently than you might anticipate. Once they’re on you won’t want to turn them off.
With my amps generally 3 or 4 soft clicks per amp over a period of an hour and a half. After that, no noises regardless of how long the amp is on (often 8 to 10 hours). A couple of clicks after turn off is totally meaningless.
Accuphase always made first class products & still do… Hi end in my book.
Thanks for the warning. It will most likely be next year before I can make the swap for my M700’s which already sound pretty damn nice.
Not really. Materials expand and contract at different rates whether connected or not. Lucky that, by some fluke of nature, steel and concrete contract and expand at the same rate with change in temperature otherwise most of our modern built world - made of reinforced concrete - could not exist.
Yes; however, the manifestation of the physical reality is measured, felt, smelled, heard… when two materials are tied together. You missed your calling… LAW… for the ADD, the take away is every material has CTE and you need to be careful when you tie materials together… that is the CTE brief I just filed. Opposing arguments will be heard in judges chambers tomorrow…
I have measured the temperature of the heat sinks on my BHK 300s with an infrared thermometer.
The highest I ever measured was 123 degrees F.
I have never heard the click noise on my amps.
I have heard the click noise on my P20 when i was using tube amps. None since I switched to the BHKs.
So I wonder what your BHK heat sink temperature is?
@st50maint - YES on the P20 and NO on the BHK300s. In addition, I’ve never measured above 115F for the P20, and BHK300s worse was 110F using a laser thermometer… that is after 16hrs at 300-400 watts as seen on P20 display.