BHK preamp nearly caused a disaster tonight

I was listening to the system and adjusted the volume on the preamp. When the level went from 52 to 53 the sound level at first made the normal amount of adjustment and than suddenly went to an extremely loud level. It was screaming so loud that the BHK 250 shut down in protect mode. Thank God that happened so fast as it beat me to muting the volume. I was afraid it could have damaged the tweeters in my B&W 800 matrix. That would have been a disaster as there are no replacement drivers available for them. I am glad they have extreme power handling as they made it safely through the assualt. I am glad I am running balanced connections as I simply can connect the cable from the Directstream DAC with the cables that feed the amp and use the internal volume control and still have music. I will be calling for an RMA tomorrow And get the preamp in for repair. I hope no one else ever has this happen to their BHK preamp. It is a scary event! I am going to have them take care of the squeal with the Gold Lion tubes while it is there.

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Wow. I am happy there was no damage. Please let us know what you learn.

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I will once the tell me what the find. I never thought I had to worry about a runaway volume control when using this preamp. Since the incident the right channel is not outputting any volume and when turning the volume up with the level real low on the DAC when I hit 53 the left channel volume drops way down.

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What are you going to do without a Pre? Do you have something to use temporarily?

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Run the dac straight into the amp. It sounds good.

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Hope things turn out well…both for your speakers and the
recovery repair of your BHK pre

Best wishes

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I use mine for HT as well. I would have to borrow the Pre from my office. What a hassle.

I am glad you are up and running.

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There are reasons why I much prefer a power amp with input attenuators, this is one of them ( my max listening volume is much lower than maximum, YMMV).
Glad the precious speakers are ok - sourcing replacement drivers for my speakers would also be impossible so I feel your fear :slight_smile:

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Ps
I get why PSA want to remov potentiometers from the signal path, and it’s a noble quest, but considering the failure modes of complex systems used to be part of my job: a potentiometer is more likely to fail safe than a VCA type of circuit…

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Fortunately your speakers are working fine. My speakers too are a bit long in tooth, meaning replacement drivers are no longer available. As such, I do understand your concern. I had a similar experience, but with my PSA PST not a BHK preamp. It failed, took out my PSA DSD DAC with it and sent a horrendous noise throughout my system and speakers. I depressed the Preamp Mute, dialed down the volume and secured the PST. Hopefully PS Audio Tech Support can turn your preamp around quickly and provide a diagnosis as to what happened.

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Thank you all for your concern about my situation. My B&W 800 Matrix were built in 1996. They no longer carry any replacement drivers for them. It would be a difficult task to come up with drivers should they ever be taken out. They utilize a 1 inch metal dome ferrofluid cooled 4 ohm voice coil. The are quite efficient at 96 db per watt. They were designed for high power handling and use a resitor in line to take them down 3 db that assists further in power handling. No matter what I always try to protect them from abuse. I never anticipated what happened with the preamp yesterday and hope that once it is repaired never happens again. I hope no other BHK preamp users ever experience this issue. They might not be as blessed as I am to have their speakers survive.

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Dodged a bullet there. Has never happened to me with my BHK. But I very rarely if ever crack 52 anyway. I listen at moderate level nowadays. Will be very interested in hearing what the PSA service tech finds when it is investigated. Keep us posted on that. Everyone could benefit.

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I have been very happy with Fedex lately. When I shipped my P10 to the buyer it got to the destination two days earlier than the original projected date. This time the preamp was delivered 1 day early. I hope the technicians at PS Audio get to go over it soon to determine what caused the problem.

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I wonder if the remote itself or the remote signal receiver “stuck” on volume increase for lack of a better term? Just a random thought that came to mind.

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I do not think that was the issue as the display was still reading 53 even when the sound level jumped up. I think if it was remote related that number would have keep going up or have jumped to a much higher number. When I was testing the preamp after the problem occurred I was not using the remote.

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Okay. It was just a thought. Unintended motion or action is usually driven by some event in the command structure so I thought it was worth checking.
I have 10 or so CNC machines and when one of them does something unexpected it’s usually my job to figure out the cause.
Hopefully they can find the culprit in this case.

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You were fortunate that it didn’t cause any damage to your speakers, because you would’ve been on the hook for the repairs, which is not even possible because the tweeters are no longer in production. Don’t think homeowners insurance would cover it, and not sure any financial restitution would be possible from PSA.

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My preamp has been repaired and is packed up for shipment to me. They replaced the mainboard and are passing the one that failed to engineering to determine the exact cause of the failure. I will pass on that information when I get it from Caleb. I can’t wait to get it back to see how it is working. Of course I will have to go through break in to get it back to where it was.

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My preamp has returned safely home. It sounds like new and will take some time to get back to where it was as far as break in goes. So far all is well volume control is quiet and currently I am running the Genalex Gold Lion 12AU7’s without any noise from the regulators. I can’t report on what actually failed until the mainboard they removed is studied. I will though when I hear anything. Glad to have it back.

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