BHK Amplifier Longevity

Audio Components Amplifiers
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I love my BHK 250. It is the most musical amplifier I’ve ever heard in my system. Like any exceptional relationship, you may wonder how long it will last. I’d love to know if the BHK 250 owners in this forum have had problems with their amps, particularly those who have had them for some time.

The BHK is great because it is a radical new design. With new designs you are on the bleeding edge and only time can tell about long-term health. Class A amps run hot. Even if they are well-designed to shut down on excessive heat, parts may have a shorter life if the amp is left on all the time, as I do and is recommended.

I live in the Palm Springs area. It probably has the largest concentration of luxury vehicles anywhere. After owning Jaguars and Land Rovers and talking to others I realized luxury takes frequent maintenance and/or repairs. Most owners I know lease and do not plan on keeping their cars past their warranty period.

The BHK250 is a luxury audio component. I want to know if I should plan to repair or replace it past its warranty period. Shoppers contemplating a purchase may want to know if they can afford to keep it up. The official PSA line is not to worry but, without actual experience and hearing from owners, we don’t really know.

It’s not unreasonable for customers to want to know. If we buy a tube amp we know tubes will have to be replaced, sometimes annually depending on use. I’m fine with having my beloved BHK 250 refurbished as needed. I’d love to have some idea what to expect when.

How is your BHK amplifier doing?

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BHK250 & 300’s are not Class A amps; they’re Class AB biased to Class A for only about 1 watt, so heat shouldn’t be an issue in longevity. My BHK300’s run for hours & the heat sinks get a little warm but never hot.

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Do we know why they are only biased in class A up to 1watt? Doesn’t that seem really low? I’m not doubting their sound quality - it’s just many of us have been trained to think class A is ‘it’ from a sound quality perspective.

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Do you all leave your amps on or just in standby when not in use. I’m wondering since the tubes last for thousands of hours and are cheap to replace if I should just leave it on all the time. Is there any sonic benefit to this? Or is it best to just leave it in standby when not in use.

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Many listeners use less than 1 watt for much of the time; in my case I estimate 95%, and the 5% in AB is very brief; never continuous. I’ve never heard a difference. This, of course, will vary based on loudspeaker efficiency, room size & characteristics & listening preferences.

Regardless of whether or not you’re in Class A or AB, significant contributors to the “magic” are the tube input stage with independent power supply & use of N Channel only MOSFETS in the output stage, which also has it’s own power supply.

Enjoy the music & don’t worry too much about the rest. Once an amp is burned in a thousand hours or so, and hasn’t shown any problems, it should be good for a very long time. If something is going to go wrong it usually happens early on.

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Yah. I agree. However - I thought most AB amps were biased higher than that. I was curious as to the reason.

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Good question for 'The Boss". If you’re reading this Paul, what’s the answwer?

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At about four minutes into this video Bascom and Arnie discuss the biasing of the BHK amp.

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What an awesome video.

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I loved that discussion. I’d be willing to bet a lot of @cardri’s money that with relatively efficient speakers, in a typical sized room, we’re listening at milliwatts.

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I have the M700 monoblocks and leave the amps on 24/7 (both back switch and front button), but they are 100% solid state.
But tubes??? I would keep the front button off and the back switch on. This way the solid state portions that take a long time to warm up stay on and warmed up all the time. The tube section supposedly takes around 15 minutes to fully warm up. (on my BHK Pre I keep the back switch on 24/7 and turn on the tube section when I listen to music)

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How old are you?

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Damn, I love the learning in these forums. I agree that once electronics in general run for awhile they are likely, like the Energizer bunny, keep on running.

I have no doubt the references to biasing, etc. are correct. My point, however, is that constant heat over time may reduce the life of components. Burson, an Australian company, recommends turning off their amp when not in use to prolong its life (not in the manual).

I do not know about Burson’s Class A biasing and I don’t expect any company to publicly recommend turning off their amps when not in use for fear of discouraging sales. Perhaps that is why we do not see anything in this regard officially from PSA.

I don’t know what the BHK 250’s internal temperature range is supposed to be and I don’t have to because I can’t measure it anyway. However, measured externally at the front center with an InfraRed Thermometer from 3 feet, it ranges from 90 to 95 degrees.

On the right side fin, again measured at the center (fin base) it ranges between 110 and 115 degrees. At that point it begins to get toasty.

My home is at 72 degrees all the time. I expect homes kept hotter may see higher amp external temperatures.

It may not matter what the outside temperatures are if they are dissipating internal heat and the internal temperature remains within a safe range to prevent a shutdown or long-term damage to components.

Of course, we won’t know until time passes by and maintenance or repairs are needed. That is why I was asking the customer base here in the forum about any past problems.

I am OK with parts wearing out. Everything in life does with use. The question is, in this case, at what temperature threshold and for how long should we let our BHK 250s run without some form of air cooling. An answer would require endurance testing, which I did not hear mentioned in the excellent video.

Anticipating maintenance requirements, a potential owner can make a better purchase decision. A current owner can pay attention to SQ and take corrective action.

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psalvet,
Just wanted to make sure you are aware that when the BHK is in standby it keeps the solid-state electronics active but only draws about half the power compared to when fully on.

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Right. I do that for about 6 hours a day when I sleep. I’m retired so I listen to music quite a bit, some might say excessively :slight_smile:

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I know that our fearless leader has always recommended leaving the solid state part of the gear on all the time, that the rushing of power to the capacitors will cause way more wear and tear on the internal components and that leaving the amps on 24/7 will actually prolong the life of the amps (have watched many of his videos). But I have not owned PS Audio gear long enough to be able to properly answer your question from the viewpoint you are asking. I did make sure that I have space in my setup that allows for good ventilation of the amplifier and regenerator components that are on 24/7.

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Thanks. No, most amps are biased at quite a bit less. Typically, when we bias a class AB amplifier, we turn up the bias enough to eliminate the crossover notch distortion. That’s seen on a scope as a a blip just above and below the zero crossing point. As you turn up the bias, the notch reduces to zero because the amp’s always on, but not more than a few milliwatts.

You’ll not that what Bascom’s saying is that for the first watt of music the amp’s 100% class A, which means there’s no change in output wattage when music plays for that region. That results in quite a lot of heat, though it surely doesn’t sound like it’s much. But, it is.

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I also understood from Bascom, that over the 1 Watt the BHK amp (seemed like a mixture of experience and luck) showed similar characteristics as are usually achieved by higher biasing.

Would you have allowed a design with higher biasing if meaningful to you? I mean they get hot and that’s not everyone’s favorite. And possibly you’d need more expensive parts to resist the heat? Or was your goal not to offer a higher biased A design but get a 1 Watt A design as good as it can get?

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Hi, adifferentpaul, love your user name here. Thanks for addressing my concern directly. What I’ve heard mirrors exactly what you said.

It seems that no information is available on the temperature range threshold that, if exceeded, would reduce parts longevity over the long term. The finger test is not sufficient because our sensitivities to heat can be different, and “don’t worry about it” does not cut it.

Absent a more customer-friendly answer to long-term heat concerns on reliability, I’ll do what many luxury car owners do, sell my beloved BHK 250 before the warranty is over. Although, given my age and the ongoing pandemic, the BHK may outlive me :slight_smile: I surely hope not. Stay safe!

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Sure, but we experimented and found no advantage, sonically, to more so left it at that. Had we found more we would have done so but at the expense of more heat sinks and a higher price.