Guest 02GF74

Ignoramous question about valve power amps

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ok, forgive my ignorance but want to confirm a few things about valve amps (googling this type of question usually ends up on guitar forums but I guess the same applies to hifi).

looking to try out valve monoblock power amps.

1. can I use my solid state pre-amp? (TBH I can't see why not but I imagine it depends on the input impedance of the vavle amp) (is audiolab 8000 Q)

2. is there restriction on speaker cable length than can be connected to valvle amp? (mine is 4 to 5 m max)

3. power on/off - does this cause speaker "pop" (my audiolab amps have a relay that swiches output about 5 sec after they are powered).

any other info for a vavle amp newbie appreciated.

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1. Yes

2. There shouldn't be.

3. There shouldn't be any pop.

You should make sure any amp sounds good with your speakers before dropping a big bunch of cash though.

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1. Almost certainly. Valve amps tend to have high input impedances which are actually easier to drive than solid state. A few vintage valve amps do need a lot of drive (1.4V rms for 15W out of the Quad II for example, and more if you want to push it beyond its nominal limit) and some modern pre's can't quite deliver that. But you'll be able to find the output of the 8000Q in the manual or on the interweb I guess, so it should be easy to check. Some vintage valve amps also need very little drive (e.g. the Leak Stereo20) and in that case you might need to turn the wick down. I read somewhere that the 8000Q has a pot to do this (is that right ?). Otherwise you could use an in-line attenuator.

2. Nope, again not in general. Very, very long leads may be capacitative enough to disturb the amp's stability. But well-designed valve amps are no more prone to trouble in this regard than well-designed solid state ones.

3. Power on tends to cause less popping in valve amps because nothing happens until the valves warm up, which they do gently. Likewise power off shouldn't cause trouble either. You're more likely to get clicks and pops from the pre-amp.

Valve amp basics include:

a) They run hot. Make sure ventilation will be OK and small children/pets/drunks aren't able to hurt themselves.

b) They tend to be heavy (big transformers) and the glassware is fragile. So try to make sure that the shelf they're on won't collapse.

c) Never disconnect the speaker while the music's playing. That really will make a pop ! Many people will say never disconnect it while the amp is powered at all.

d) If you're going for vintage then IMHO it's really worth getting them checked over by a competent professional. With the right equipment it's easy to spot small problems which can be pretty cheap to fix. If these are missed however they can quickly escalate into very expensive disasters. A good tech will also confirm that the kit is safe (properly fused and earthed and unlikely to ignite spontaneously). Once the amp is in good order it can work for years without a great deal of attention. A quick check over every few years wouldn't hurt though.

Edit: which is what Mark said. And I agree with his advice about listening before committing to buy.

VB

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Totally agree with the previous two posts,

Furthermore it's also often considered best practice to power up the power amp last & the pre amp source/components first to avoid pops through your speakers. This can also hold true for solid state amplification as well as valve amplification, particularly with amps not having relay switching at power up. Same sequence in reverse for powering down eqpmt. , so in this case power amp first. I can sometimes still get a pop if I power up/down my pre amp or dac out of sequence, but my previous Audiolab power amp was far more susceptible than my current XTZ

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Just a thought, and I wonder if my fellow wammers would agree. It would be intersting to know what power amp/s you are using, are they also Audiolab? If so these are good honest solid state amps. I would be more inclined to try a few decent valve based pre-amps 1st, this should bring immediate improvements to your system over the 8000Q, detail, soundstage, musicality etc.

There is many a good system that uses a valve pre with a solid state power amp/s.

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Funnily enough Alan I agree 100%. :^

FWIW & IME re Audiolab amps I feel the powers are the stars of the show with the pre's lagging quite some way behind. I'm saying this as a previous owner of 8000m's & also having tried an 8000q in my set up I still own an 8000av/8000x7 combo for my AV rig. Recently I had to revert to the 8000x7 for several weeks whilst waiting for a replacement power amp, & it was really no hardship although obviously not as good as the XTZ with my MF A1fbp pre. In fact for most of the last couple of years I was running Audiolab power amps I successfully ran them using a valve pre which simply destroyed the Audiolab pre's. In my experience I would say that the Audiolab powers don't really show their true mettle until paired with more capable pre's from other mfrs. whether valve or s/s. It does make me wonder if some may have thrown the baby out with the bathwater having never tried this when upgrading their Audiolab amplification. :?

The 8000q does have its good points but IMV they are mostly relating to features & flexibility i.e. adjustable gain settings which could undoubtedly be useful....however in this day & age I don't really see much need for 3 tape loops, although separate rec/source selectors is still something I do like to see. :^

Just a thought, and I wonder if my fellow wammers would agree. It would be intersting to know what power amp/s you are using, are they also Audiolab? If so these are good honest solid state amps. I would be more inclined to try a few decent valve based pre-amps 1st, this should bring immediate improvements to your system over the 8000Q, detail, soundstage, musicality etc.

There is many a good system that uses a valve pre with a solid state power amp/s.

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Just a thought, and I wonder if my fellow wammers would agree. It would be intersting to know what power amp/s you are using, are they also Audiolab? .

biamping with four 8000 Ms, WB Act speakers. (TAG CD transport with MF KW DAC)

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I'd be tempted to try a new pre.

The guy I recently sold me MF A1 FBP to was using an Audiolab pre and was impressed with the improvement.

I now use an Audionote M2 Sig pre and was impressed wit the improvement over the MF pre.

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biamping with four 8000 Ms, WB Act speakers. (TAG CD transport with MF KW DAC)

Whereabouts in the country are you?

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..... BTW I am using the MF DAC valve output stage; (I guess I'm just wanting to experiment)

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More important, 02G, what speakers are you using?

This will make potentially a big difference as to where valves might work the best in the system.

- - - Updated - - -

More important, 02G, what speakers are you using?

This will make potentially a big difference as to where valves might work the best in the system.

Ah, sorry, just seen the post above :oops:

I know them little, but my feeling (others may know better) is that generally WBs need a fair few volts and amps to really sing. In which case, I definitely would side with the 'valve pre' idea.

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^^^^ thanks for all the good advice..... got my beady eye on Audio Note valve pre on ebay :)

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^^^^ thanks for all the good advice..... got my beady eye on Audio Note valve pre on ebay :)

Which one and how much? Some are stunning, some are reasonable...

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