Check out Steve H.'s new WAVAC amps!

Wow. Now THAT'S an amplifier!

Check this out:

http://www.enjoythemusic.com/news/

 

Got a spare $47,000?

 

Wow. That's a lot of money. Not per channel?

I bet they sound fantastic though. 100 watts of SINGLE ENDED power? No phase splitter? Direct coupled? I bet those amps can light up a dark room!

Never saw a tube like THAT before! An RCA 833 tube. Made for Broadcast transmitters and now---Steve's stereo!

Well, if they help his do his work, they've gone to the right place!

 

$47,000 a pair, list price. I don't have any idea what kind of discounts are available, but it'd have to be about a 95% discount to be in the realm of possibility for most people : )

 

Well, I've got a pair of Laurel IIx Ultimate Upgrade monoblocks from Ron Welborne running KR Enterprise 300B output valves and these put out 8 watts. They cost close to $3000. The WAVACs put out 12 times the power and cost about 12 times as much. Seems OK to me.

Of course, power should not be compared using a linear scale as I just did, so the above is stupid.

I have coveted the WAVAC EC-300B for some time. Here it is:



Regards,
Metralla

 

WOW... They look "WA" impressive!

I hope they sound as good as they look... Especially for that kind of cash!

My speakers will NEVER have the pleasure of pumping WAVAC watts.

Enjoy Steve!!

 

Yes that Wavac stuff is really beautiful, and I'm sure you get what you pay for. Of course it isn't cheap, but I bet the sound is like liquid music. At least that's what the reviewers say.

The Japanese rediscovered single ended triodes (mainly the USA Western Electric circuits) all on their own a while back, and we owe them bigtime. When you consider that the "single ended" design predates even the "Push/Pull" designs of the middle 1930's, it's a humbling thought.

1920's electronic technology, (with just ONE output tube doing all the pushing and the pulling), still sounding amazing in the year 2002. Wow.

 

World's dumbest question ever asked here:

What does "Single Ended" mean?

 

Single ended: a circuit topology in which an output device or parallel output devices (tubes or transistors) operate by regulating the flow of current in a single loop within the circuit. (Think of one person sawing a log with only a "pull" stroke, with a spring pulling the saw back into position after each stroke.)

A Single Ended amplifier is always biased in Class A (which means there is always current flowing through the output devices.)

The counterpart to Single Ended is Push-Pull which contains two output devices regulating the current flow in two complimentary loops - one side "pushes" while the other side "pulls." (Think of a two-man lumberjack's saw, one guy pulls, then the other guy pulls.) This circuit requires a phase inversion circuit because the two sets need to be fed signals which are the inverse of each other. (The "push" devices will see a negative-going signal at the same time the "pull" devices see a positive-going signal.)

A push-pull amplifier can be biased in Class A, Class AB, Class B etc. Class AB means the current flows for more than half the negative-zero-positive-zero-negative input cycle, but not the whole cycle. Class B means the current flows for approximately half the input cycle.

Typically audiophile Single Ended amplifiers use triodes (SET= Single Ended Triode) - particularly Directly Heated Triodes (or DHT's) and have little or no loop feedback. A "purist" (some might say "primitive") approach.

As a general rule push-pull operation largely cancels second harmonic distortion and reduces even harmonics above the second. As a general rule single ended operation yields the most distortion at the second harmonic and each successive distortion product is smaller and smaller in proportion to the signal.

-j

 

Single ended means there is only one amplification element, in this case a triode vacuum tube, as opposed to two working in tandem (push-pull), in a amplifier stage. In a push-pull tube amp stage, one tube drives the positve direction and the other the negative, which means a larger operation range but its cross-over distortion causes lesser linearity than the single ended configuration. Most single ended triode (SET) amp has less power, but not this monster. Just look at the output tube!

One caveat for SET amps: due to the asymmetrical design, the output signal of the output stage has a non-zero DC bias, which can permanently magnetize the coils/cores in the output transformer.

 

Steve,

Thanks for the history and technical lesson. We are fortunate that you enjoy sharing your knowledge and teaching! On peaks, will your new amplifier dim your room lights?

Bob

 

Steve,

Are you selling this amp? I'll give $75 for it w/tubes included...

Todd

 

Trades...anyone?

I'll tell ya, I'm a bit cautious on buying any piece of equipment until it gets a “thumbs up” from Tom first.

I might take to chance and trade in my Technics receiver towards this one....it's a tough decision

 

vinylrec,

Just make sure they give you some store credit on the price difference. Remember, that Technics is solid state and should bring you a good dollar compared to those old tube things...

Todd

 

One quibble with Steve's description: Two amplifier stages can either be direct coupled or transformer-coupled, but not both. The WAVAC is transformer-coupled, and Steve is correct in stating that there is no series coupling cap in the audio circuit.

Direct coupling involves matching the DC levels from one stage to the next so that neither a transformer nor a capacitor is needed for DC isolation between the stages. This is not how the WAVAC works, I'm pretty sure.

With the IITC Shishido design I think the transformer is used for more than simply blocking the DC offset, which it does as a bonus. It steps down the drive signal so the driver stage has an extremely low source impedance to the 833's grid, and so the 833 can be run in class A2 (grid current) mode which is what a transmitting triode like the 833 is designed for.

IITC= Inverted Interstage Transformer Connection, and I think the "Inverted" refers to both the step down and also the way the transformer is connected so as to perform a cancellation of the DC flux in its core for wider bandwidth. I could look it up, I think, because I seem to remember that there was an article on it in Sound Practices.

Steve will not need a space heater for his listening room next winter. These are serious beasts, something like an amp of filament current and >1000V power supply voltage. The glass is to keep your fingers out of the Danger Zone!



-j

 

PS: Now you gotta hook this thing up to your cutterhead, Steve!

As a bonus you'll preheat the vinyl . . . .

-j

 

What are you using for speakers with them? I suppose they'd drive Quad ESLs no sweat?

 

Nice discussion on SET amps and the WAVAC Audio SET HE-833 in particular. Thanks to Steve for the enlightening discussion and well written - I certainly enjoyed reading it.

There were a couple of points I wanted to comment. First, the WAVAC HE-833 is a pure Class-A SET amplifier using zero feedback. Yes, that big 'ol 833 tube can shine a bit of light, but the amp actually runs cooler than most OTL amps with a gazillion tubes. An owner of Sound Lab U1 esl speakers replaced his OTL's with the HE-833 and can now enjoy muisc in the summer. Fortunately, they do not run hot enough to melt vinyl...only your music-lovin' heart.

Specifically, the WAVAC HE-833 (and all Wavac SET amps) has the input (WE437A) direct coupled to the driver (triode-wired KT-88) with the output tube is driven by the Wavac-Tango IT. All Wavacs have eliminated all coupling capacitors from the signal path.

I cannot comment on other SET designs, but Paul's comment that all SET's can permanently magnitize the coils in the output transformer is puzzling. The Wavac circuit specifically cancels any DC magnetization. The Wavacs are quite unique in design and implementation and we are indeed honored M.G. has added this to his stable of other fine products including his WAVAC MD-300B.

Finally, I want to say what a wonderful forum this is - filled with lots 'o music information and even a few hardware discussions from time to time.

 

So - to clarify my clarification above - Steve's WAVAC amp has three stages, and the first two are direct-coupled, the second two are transformer-coupled. Hope I didn't confuse anybody other than myself!

-j

 

In defense of Master Hoffman, he was right in stating direct-coupled circuitry was used. But you were right about IITC too. How could it be? There are three stages in HE-833 - the input stage, the driver stage and the output stage. I think the input and driver stages are direct-coupled and IITC is used between the driver and output stage.

I have never owned any SET amps. My questions for those who have:
Can you hear the effect of output transformers getting permanently magnetized? How does it sound like (humming)? Did you ever replace the output transformers?

I don't know if Shishido's IITC is immuned from permanent magnitization.

 

Paul, what's the source of your information about the permanent magnetization? I don't think that is true.

As I understand it, the AC signal through the core will degauss it as the music plays.

As far as I know, that's a non-issue.

Certainly I have never noiticed ill effects from it in my own SET amps.

-j

 

Forgot my source. It could be an interview of a tube amp designer (Audio Research's William Johnson?) in some audio mag. But I still remember how to make a temporary magnet out of an iron rod with a coil and a battery. I wonder what's gonna happen with the coil and the rod if the power stays on for a long time.

You are right about the AC current degaussing the cores in the transformers. The thing is that the output of an SET stage is not a PURE AC signal. There is a DC component in it so the average of the music signal won't be zero.

 

I'm drawing on some dimly-understood stuff here, so I apologize if my explanation is off.

As I understand it, the magnetic field's polarity depends on the rate of change of the signal, dv/dt, so while it is entirely correct that the AC + DC does not net out to be zero, the flux is constantly alternating through the core and this is the factor that would determine whether the core material would take a permanent magnetic "set." This is how I understand it, I may not have it right. Empirically, the "common wisdom" (if there is such a thing amongst SET-freaks?) is that output transformers break in and sound better and better OVER A PERIOD OF YEARS, not worse and worse.