BHK Preamp - setting warm-up time & resetting tube hours

I’m sure this is buried somewhere in one of the threads but can someone please explain the procedures for setting warm-up time & resetting tube hours for the BHK Signature preamp?
There is nothing in the manual and I can’t find this mentioned anywhere in the user interface so I’m guessing it’s a hardware adjustment or it’s a firmware upgrade issue???

thanks in advance, Mark


I believe the warm up time is fixed and cannot be changed but to reset the tube hours, press and hold the button to go into setup, click through until you see tube hours, press and hold the button, ‘clear tube hours’ will appear, keep holding for a moment longer and the hours will be zeroed.

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Thanks for that. I read a review that said it was possible to change the warmup time but I guess the reviewer was wrong. I’ll check the setting menu again when I get a chance.


Would be great to know if there’s a warmup time at all…tube life matters :wink:

I’ll try the pre, too in near future.

Worth the try ! ~Especially when you swap out the stock tubes for Tungsram PCC88 / 7DJ8 ones.

There is no way on the BHK to change “warm up time” because I don’t think there even is a warm up time if I am understanding correctly. The standby mode keeps all the solid state devices on and warmed up always - something we recommend doing. Out of standby mode the tubes light up and just work until placed in standby mode again.

I‘m no expert at all, but if tubes are supplied with full power from start instead of slowly powering them up and are immediately available for music playing, my state of knowledge was, that this is not good for tube life.

Maybe BHK has a different opinion on this…would be interesting to know.

Oh, you are referring to the ramp up voltage? Yes, this is done properly in the BHK though I don’t know the particulars.

Yes, this is what I mean, the time until the voltage is up and the unit is ready for playing…would be interesting to know how this works in the BHK.

In both the amp and preamp, the high voltage is always on when the back panel power switch is turned on. The tube filaments are turned on when the unit is taken out of standby. One advantage to this is the high voltage regulators are always on and warmed up.

While in standby, all of the high voltage and output stage regulators are on and the whole solid stage circuit is active, but with reduced current in all of the active devices. This way, the circuit will take less time to get up to full sonic quality when set into operate mode as opposed to starting from a total cold start and putting into operate mode right away.

Regarding the warmup - The time delay allows the tube heaters to come up fully and the plate voltages to stabilize. The tube heater voltage is applied full on. The delay also gives the coupling capacitors that feed the solid state output stages to fully charge up as their outputs are shorted to ground during the time delay. Then, the coupling capacitor outputs are unshorted. This is true of both the preamp and the power amps.

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I have a 90 second warmup on my unit, hence my desire to reduce it!

The warm-up time is not user configurable.

Mine is variable. From a cold start I see 90 secs but if I power off to unplug the power cord to move something and back on I believe its only 40 secs. I consider it meditative time to prepare myself for the magic about to come.

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I’ve owned a whole series of tube pre-amps. The Cary SLP-05 is my current (considered the BHK but need a unity gain out).

They have all worked the same way…a 1 to 2 minute warm up time. On a weekend morning, I get up, turn the pre-amp on, grind the coffee beans, then play sweet, sweet music.

The BHK has unity gain out in HT bypass mode. I understand the unit goes to unity allowing volume to be adjusted by another device upstream…I don’t have any experience with it simply trying to relay what I read in the manual.

It’s a unity gain input when in HT bypass. I need both unity input for HT and output for an integrated amp I use to drive outdoor speakers. Basically a tape loop. Always thought it was an oversight in the BHK design.

Couldn’t you simply find the volume level that meets the need? I’m not trying to convince you to get a BHK, just looking to learn and understand more.

Nope. I run both the inside and outside systems simultaneously when I have guests over. I set the inside system volume for an appropriate level with the SLP-05 and the outside with the integrated amp. I then adjust the whole thing, depending upon mood, with my phone using JRemote.

If I took a variable output (would have to Y the output BTW) into the integrated it would almost always be too low for enough volume and I’d have to play the inside system too loud. Just about every pre-amp made has at least one tape loop (not the BHK).

You’re not suffering with the SLP05. It’s a brilliant bit of kit.

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