Amp biasing question

@whart  , yes, I agree that is separate from biasing.  And I may have misunderstood the postings I have been referring to.  I just was getting the impression that before turning the amp on, the pre should always be on.  If I had that right, one would have to have his or her preamp on while adjusting the bias.

The point of sequencing is in case your preamp causes a thump when turned on.
This way I f the amp is off, the thump does not go through to the speakers. If your equipment doesn’t do it, then not something to worry about.

My preamp or up stream equipment does not produce any noise, so it doesn’t mater. I don’t think I owned a piece of electronics that thumped for decades.

All of my equipment is tube and has a delayed soft on. So, no racket regardless of the sequence. 

@ghdprentice  , do you bias your ARC with the preamp turned off or on?

ghdprentice

The point of sequencing is in case your preamp causes a thump when turned on.
This way I f the amp is off, the thump does not go through to the speakers.

Yes, agreed.

If your equipment doesn’t do it, then not something to worry about.

Here I disagree, because preamps can fail on startup, and especially tube preamps can send nasty noises in such an event that will reach your speakers if the amplifier is powered first.

In an unusual sloppy mood last year, I failed this best practice that I'd followed for years. That's when tubes in my ARC REF5SE blew and it shook the house. (Fortunately, no collateral damage.)

@immatthewj

Depends on what your intentions are.

Are you planing on only checking the tube bias and then shutting the amp off and not listening to music, Then there is not any need to turn on the preamp.

If you want to check the bias and then listen to music then turn on the preamp and then turn on the power amp. Preamp not playing music. I leave my preamp on mute. Allow the manufacturer’s recommended time for the power amp to stabilize before checking the bias for each channel. My ARC amp says allow at least 15 minutes of uninterrupted stabilization time. I have have found to allow 30 minutes or so of uninterrupted stabilization time works best.

If you want to listen to music first, and then check the bias, first stop playing music then mute the preamp. Wait at least the recommended manufacture’s time for the amplifier to stabilize before checking the bias. In my case I allow the amp to stabilize for at least 30 minutes.

Also,... YMMV But but my two ARC amps are getting old. I have found I need to reset the bias on each channel, when I reset the bias on one channel and then reset the bias on the other channel. I usually have to fine tune the bias on the first channel again. I then recheck the bias on the second channel and sometimes I have to fine tune bias again on the second channel. Older ARC amps are a pita to bias the power tubes.

Also worth noting when it’s time to buy new power tubes buy pre burned in power tubes. It saves a lot of time checking the bias of new tubes without any hours on them at all... At least 48 to 72 hours pre burn in times on the tubes works well...

Also before installing new power tubes adjust the bias pots down a little first. Especially if the old tubes were biased regularly and were near their end of life... You can damage new power tubes if you don’t.

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