KT-88 single end ..audiopax question.

I own a pair of Audiopax 88 monoblocks. It is either the best amp overall I've ever heard or at least in the top 3. Certainly it is on objective music fidelity the best power amp solution I've owned. The designer has several highly distinctive innovations in his circuit but part of the beauty of the Audiopax is that it models SET behavior using a commodity tetrode/pentode tube. These amps take some break-in to sound convincing as "best" amps, and you must take your time to find the right TimbreLock setting to dial them in to their sweet spot. They also respond to tube rolling, so top-grade tubes are well worthwhile. I wasn't won over out-of-the-box, but six weeks later I couldn't bear to part with them.

Prior to this I owned other single-ended KT88 amps, the Acoustic Masterpiece M101, which when it has been reviewed has been very highly regarded, and the Audion Sterling ETSE KT88. The Audiopax takes the SEP approach with KT88s further than anyone so far, with fabulous results within their 30w capability.

The common thread trait shared by all the single-ended KT88 amps I've owned (and heard elsewhere) has been transient speed, objective clarity, meaty tone, excellent bass discipline and spacious soundstaging. Big-T TONE, as guitar players think of tone, has been excellent in the way a very high quality 300B can do it.

The Audiopax TimbreLock circuit is elemental to those amps' ability to surpass other similar SEP designs. It is unusual. In the 88s, each monoblock has 2 single-ended KT88 amps, one output tube each. These twin amps are paralleled at the input and are internally wired in series at the outputs, if I recall correctly. The dual output transformers differ in their winding in a small but undisclosed way. The TimbreLock controls are bias controls for each of the twin amps in the monoblock. Any setting in the range keeps the respective KT88 within its operating range. You use trial and error listening to find the best differential in the two control settings on each monoblock, first, and then refine your setting by finding the best absolute settings on each dial while maintaining the gap or differential between the two. The setting is influenced by your speaker load so you must dial them in for your specific system. When the TimbreLock sweet spot is found, there's sensational focus, transparency and realism.

Now, I also have a pair of unusual 300B amps that have a similar cost to the Audiopax 88s. They are on another system but I've compared the two on same systems. On balance the cost-peer 300B is fully competitive with the Audiopax but they are different. The 300B has extremely rich midrange density that exceeds what the Apax 88s can deliver. The two designs are comparable on what they can reveal. The 300B amps, which are Audion Golden Dreams Level 6, have very fine bass but not as quick and objective as the 88s, and the 88s do not contribute the last bit of high-frequency "spray" common to 300B designs, most of which has been wrung out of the Audion GDs, but not quite all.

It takes an exceedingly clean amp to work well with Avantgarde horns. It has to be dynamic and emotional too. The Audiopax has the right balance and emphasis on accuracy with tone. A commensurate 300B amp, like the Audion GDs will dial in a little warmth and body over the 88s. The 88s will tip a bit lean in body but give you very uniform transient character up and down its frequency range.

One caveat on the Audiopax 88s: gain is low, only 18 db. There is only a single 12AT7 ahead of the power tube in each of the twin amps within each monoblock. These amps are relatively input insensitive, so you need robust output from sources or some extra gain in your preamp for average material to drive full power from the amps. Choose your source/input combination to mate with the reality of an 18db gain design.

There have been many excellent KT88 amps over the past few decades. Google Acoustic Masterpiece M101 and you'll find an audio musing / positive feedback review that gives you a sense of what a simple SEP design can do with outstanding Tamura transformers.

Phil

So you still did'nt say which amp you think is
better on your avantgardes, if you could only
have one, which one would it be, audiopax? or
mastpiece? or the audions? I have avantgarde
trios and I'm now going to shoot it out between
to heavy weights, Yamamoto 08s & Art Audio PX25,
" I'm a wild and grazy guy " Please Reply. M.G.

I have Zu Definitions and Zu Druids in separate systems. 101db/w/m and the Definitions are 16Hz - 22kHz; Druids 38Hz - 22kHz. I have heard the Audiopaxes on Avantgardes though, and they work perfectly with each other. Between the Audiopax 88s and the Audion Golden Dream Level 6s, it's a tie, honestly. They're equally appealing but somewhat different. The Audiopax has advantage in bass definition. Audion Golden Dreams have advantage in midrange density. The two are even on top. I've heard the Art Audio PX25 on multiple systems including AGs, and Audion's PX25 amps. They're good -- very revealing and more objective than run-of-the-mill 300Bs, but sound is relatively cold, lean. Not in the same league as the Audiopax Stereo 88 let alone the 88 monoblocks. The Yamamoto 08s.....very nice by any standard but less dynamic, less lively than the amps I chose instead.

I'll be your Huckelberry, lets shoot it out! the
ultimate prize? can only come in my estimation
from 106DB speakers matched to the purest of
single ended mastery. The weapon of choice, well
"The Man Him self!" Joe Fratus, This Time we
let Em go scary crazy! One of a kind, Mono Block
PX25s, over sized custom output transformers, &
Newly implemented V-Caps though out, The REAL, I
mean "REAL GOOD STUFF" Joe admitted, we've never
Built a PX25 Like this Last One! You Know What
They Say? Its Not Over, Till Its Over. And By The
Way, I'm not ruling out the Yamamoto, having D.C.
regulation Mod. makes it the quitest Amp on the
planet, in conjuntion with the Best and Only Tube
to use, EML45s! it is said to have more presence
than any NOS Globe 45, by A wide margin, All Said
Dude, You better check your pistol, make sure you
have Bullits in it, Ha, Ha, Ha. I'll have report
in Apox. 3 weeks, Joes very slow, and 08s is now
5-6 wk. wait, direct from Japan, Its almost Sun
Down for the Show Down! M.G.

Well, the problem with the PX25 amp is the PX25 itself. It makes an excellent but relatively soulless amp, no matter what you throw at it in iron and caps. It's singular persistent sonic superiority is bass performance. In even mediocre designs the PX25 yields the cleanest bass heard from any power triode.

The Audiopax 88s, expecially if you spring for some EAT or NOS Gold Lion KT88s, has all the revelation, clarity and definition of the PX25, but communications more emotion. These differences are small, but quite discernible, compared to more ordinary hamfisted amps. The Yamamoto projects more emotion than the PX25 but has less aliveness than the Audiopax, IMO.

No doubt Art Audio can build a one-off to get the most out of the PX25. There's not a clunker in the AA line.

Audion isn't as well known here un the US but even their least expensive 300B amps have a charcteristic fast and penetrating quality. The Golden Dream is genuinely special in what it accomplishes. You don't have to put up with the 45's anemia but you get its emotion and incisiveness. And you get an electrolytic-less power supply with magnetic reserve. Fast!

Those Avantgardes are pretty frigid sounding and each one of those drivers kinda likes to go its own way. It takes a charming amp to corral them into a single voice. A PX25 ain't charming. And a 45 can't corral them.

But we're splitting hairs. Whether you abandon your nominated amps or check out mine, you're going to end up with something worth listening to. Avantagardes.....now that's another discussion entirely.

Phil