Tube amp forethought


Hello, im researching my retirement two ch audio system and tube amps are in the forefront of my “wants” my plan will be a pair of QUAD ESL’s not sure which just yet

What do i need to know about maintaining a tube amp, like a AudioResearch 120 for starters or other tube amps. Biasing is totally new to me. Tube life and modes (triode, Pentode, UltraLinear) all foreign to me.

im a 40 year hobbiest so im pretty versed, this is just an unknown territory for me, thanx guys !

kgveteran
If you don't mind the lack of a mono amp behind each speaker (thereby requiring only very short speaker cables---I used one-footers---though long inter-connects, one reason why it's great the M-60 is balanced, as long as your pre is as well), an S-30 (a stereo amp) is sufficient for a single pair of 57's. The speaker was made to be powered by the original QUAD tube amplifier, a 15w/ch design.
Roger Modjeski used the QUAD as his load when designing that amp.

We still use a Quad 57 in the shop today when we test amps we build or repair. If the 57s in question have the Zener clamp boards (an upgrade as they were not supplied at the factory with them) this prevents any over voltage condition within the panels and stops stator-to-stator arcing. So you will have more amplifier options at your disposal.

He has offered in in two versions: as a 35/35w Class-A/B, and as a 25/25w Class-A.
What might be one of the best kept secrets is the original RM-10s ran up to 15 watts in Class A and if you light load them you pretty nearly had a Class A amplifier.

I run my 57s with either the RM-10 or Atma-Sphere M-60s, but just picked up a Harvard H3 (Futterman) that Roger Modjeski and I will restore so it will be interesting to here this amp on the 57s when we are done.
Uh, is it just me? I don't see anything in particular about the ESL57 in the OP- just Quads.


So ESL63s or any later model like the 989 could be in the mix.


My experience with the Quads has been that you really have to watch it with the ESL57 because it really can't take much power. I've also seen updates that include protection circuits.


The ESL63 could take more power. We found that right about the point that our MA-1s were going to overload was also the point that the original protection circuit would energize. We also found that due to the way the amp interacted with the impedance curve, it could drive the ESL63s with greater volume than any other amp we tried.


The later Quads have been used with both our M-60s and MA-1s. Only the ESL57 has the low power limit issue.

Now if you are worried about the speaker no longer being made or that sort of thing, the ESL57 and 63 have a lot of support in the aftermarket- new diaphragms, power supplies and the like are available through various rebuilders. But you also have other alternatives like Sound Lab who arguably makes the state of the art in ESLs.
Ralph darn it. Don't complicate things. I'm trying to get him to buy your amps and you are spending all his money on Sound Lab's speakers.
kg, just in case you are interested the Quad equivalent Sound Lab would be the 545:)
I've said it before but don't mind saying it again: Tubes are more fun. These days I use an original version Schiit Freya into a Dennis Had Inspire "Firebottle HO" (12wpc more or less depending on tubes) with 99db efficient speakers. The detail this rig digs out of recordings, the physical beauty of the tubes themselves (no user biasing with these components, but my previous amp, a great sounding Jolida 502p, had user biasing and I liked doing that), tube rolling (unlike transistor rolling which isn't a thing for most people) to change things a little sometimes...all fun...with a couple hundred watts of (2) REL subs to assist. There are no tube subs (or ARE there?), but RELs do use the tube amp signal so there's that. Having said all this I am planning to get either a Pass XA25 or a much less pricey Schiit Aegir to see if I'm imagining all of this so called "fun." The Aegir got a great review in Stereophile recently so that got my attention.
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