Thoughts on horizontal sweep tubes?

[pchw]

Dave,

I happen to own a ML-22 line level preamp and a PP-150 amp from McAlister. Both are no longer in the product page, and they don't look as nice, too. I purchased my McAlister from my friend who never got a chance to really play them (long story ....). Peter McAlister is nice chap, very talkable, and supportive . Even though I didn't purchased from him, he answered my questions when I was repairing my set. Mine came with the 6LB6, not PL509's. Peter doesn't believe tube matching, my tubes are in different brands :-) The amp does sound very good and powerful. It can drive my 86dB Carver ribbon speakers to the level that I never need. However, I don't have scope or any equipment to measure the real specs of the amp.

[Miles Prower]

Originally posted by DaveCan
Been looking at the McAlister audio stuff and wondered what people thought or think of his approach?

He does a lot of things right. He favours fixed bias, as do I. He likes horizontal deflection VTs as audio finals, as do I. I've found that 6BQ6GTBs are every bit as good as 6V6s, and are a good deal more robust, can take abuse (would work just swell for a gee-tah amp as we all know how axemen abuse finals) and have a listener-friendly harmonic distortion distribution. The spec sheets make no mention of possible audio useage, and that's a good thing: it keeps some of the finest sounding VTs well below audiophool expensive

My passion for high-end audio design always remained and my years in television repair introduced me to horizontal sweep tubes, which became my output tube of choice in single ended, push pull and OTL amplifiers. This type of tube in many respects is superior to the standard array of audio output tubes currently used (some of the best vacuum tubes ever designed and made were for the television industry).

Couldn't agree more, except that a great many of these horizontal deflection finals don't work so swell in SE since you can't really hit the best part of the plate characteristic without going into red plate destruction. You need a PP loadline for that.

However, he ruins his presentation with nonsense like this:

Transistors are current amplifiers with odd order distortion products as opposed to vacuum tubes which are voltage amplifiers with even order distortion products. Well designed vacuum tube products are very musical without listener fatigue, are reliable and will quickly become "your partner for life".

Vacuum tubes are not "voltage amplifiers". If they were, then what would happen if you disconnected your speeks with the amp cranked to 11? The output voltage would rise but a little as the copper losses and leakage inductance losses disappeared. The plate current of the final(s) would drop to near zero milliamps. That doesn't happen. Disconnect your speeks, and the voltage shoots way up. Possibly high enough to flash over xfmr insulation. The plate current doesn't fall at all. Instead, it tries to pump the same current through that infinite impedance.

I X INF= INF

Of course, it never gets there since something's sure to poof.

So far as "even order distortion" goes, that's a function of loadlines and Q-Points. Choose wrong, and you can get ESSSSSS-Loads of odd order harmonics from VTs, and a sound that's almost as bad as the worst of SS. Furthermore, balanced topologies suppress even order harmonics, but not odd order. Lastly, high order even harmonics are just as nasty and dissonant as high order odd harmonics. You don't want these in your output.

And this:

The fundamental difference between solid state and tube based technologies: solid state products are current amplifiers with odd order harmonics and tube products are voltage amplifiers with even order harmonics. Well designed tube products will sound much more musical due to even order harmonics and with proper design dispel any myths that exist due to vintage circuit design performance.

No, the fundamental difference between solid state and hollow state are linearity (HS beats SS on this by a wide margin) and clipping behaviour. VTs clip softly, but transistors clip hard and fast. The end result is VT clipping produces mainly low order harmonics that drop fast with rising frequency since there aren't the sharp discontinuities in the waveform. Transistors produce lots of high order harmonics which roll off slowly with rising frequency since the clipped waveform has sharp discontinuities. Throw in gNFB and the clip behaviour becomes that much worse. That's why it's so essential to keep SS amps out of clipping, and why they have such huge power ratings.

Again, you don't have even order harmonics with balanced topologies.

May be he's grossly oversimplifying for atechnological audiophoolz, but still, it makes him look foolish to those of us who do know better. Big mistake, AFAIC.

[spock]

I've heard his M130's a few times with different associated gear. They sound quite good IMO. Sweet, well extended highs, nice palpable mid and good solid bass with lots of oompf.
Although they're not very pretty, they do sound good IMO.

[Tom Bavis]

Originally posted by pchw
Dave,

...Mine came with the 6LB6, not PL509's. Peter doesn't believe tube matching, my tubes are in different brands :-)

The brand is only what's printed on the tube. They could be the same manufacturer and lot, but different brands (LOTS of tube rebranding was done). And they may be electrically matched, even if they were different manufacturers.

[Milen]

I think that the horizontal deflection tubes are one of the best for audio in triode connection. But most of them are ugly with cap on the top... One of my favorite tubes is russian 6Pi45C (6Ï45Ñ). Last month I found in sale "EL509-MK2" - inside construction is like on mine favourite tube, only the name is different Here is it - http://www.tubebuilder.com/EL509MK1N2.html

Is indeed 6Pi45C construction in other baloon and other base ?