Visit to Henk van der Hoeven -- Apogee Acoustics Re-builder/Restorer

[Ron Resnick]

. . .
With the foil only ribbon, the original passive Xover could not be used, so the speaker was active bi-amp with a pair of Sonic Frontiers Power 3 (220W, 8 ohm) for the bass, and a Sonic Frontiers Power 2 (110W, 8 ohm) for the mid/treble ribbon.

My Fullrange was restored by Rich in the US. It is being active bi-amp driven with the above Sonic Frontiers combo, or 2 pairs of CJ Premier 8.

. . .

Which active cross-overs are you using?

 

[bonzo75]

Which active cross-overs are you using?

Pass Labs. c1ferrari uses it for his Dalis as well

 

[Ron Resnick]

. . .
High powered SET is likely to lead to high powered distortion as SETs typically have increasing distortion with power. To me, SET isn't as much about sweetness or liquidity, but rather the first watt simplicity and open/vividness/holography the amplifier provides. It therefore is ideal at a couple of watts, period. Rather than an effect, its a design philosophy. And those designs typically require higher efficiency speakers than Apogees. SETs also are not happy with low impedance and impedance changes. When impedance nosedives, SETs produce much less power unlike other topologies - so its a double whammy. A question for NAT is how much distortion at 100 watts? If anything like the Wavac, its a lot. 150 watt SET in that case is over 10% distortion.

Tetrode tubes and SS would be much better wagers for these speakers and negative feedback controls might prove useful like on the latest Siegfrieds. But the Apogee guy himself designed with Krell, so re-inventing the wheel may not be necessary.

. . .

Keith, so to what use do you surmise people are putting high power SET amps?

 

[KeithR]

I don't know, Ron. But Wavac's 550lb, 150 watt SET has this distortion/wattage:

So, what about the SH-833's output capability power? Those 550 lbs and that humongous transmitter tube promise a lot of power, not to mention the specified "effective" output of 150W. As you can see from figs.5 and 6, which plot the percentage of distortion and noise in the Wavac's output against power from the 8 and 4 ohm taps, respectively, that promise is not kept. At our usual definition of clipping—1% THD+noise—the Wavac gives out just 2W or less into loads ranging from twice the nominal tap impedance to one quarter that nominal value. The highest power is obtained when the load is half the nominal tap—ie, from the 8 ohm tap into 4 ohms—but even then, the definition of clipping has to be relaxed from 1% to 10% for the amplifier to approach its specified power. Looking at the waveform on an oscilloscope during these tests, the point in these graphs when the waveform clips is actually the sharp notch in the traces. At 10% THD, the amplifier is putting out a pretty good squarewave!

image: http://cdn.stereophile.com/images/archivesart/WAVacFIG05.jpg



Fig.5 Wavac SH-833, 8 ohm tap, distortion (%) vs 1kHz continuous output power into (from bottom to top at 10W): 16 ohms, 8 ohms, 4 ohms, 2 ohms.

image: http://cdn.stereophile.com/images/archivesart/WAVacFIG06.jpg



Fig.6 Wavac SH-833, 4 ohm tap, distortion (%) vs 1kHz continuous output power into (from bottom to top at 10W): 16 ohms, 8 ohms, 4 ohms, 2 ohms.


Read more at http://www.stereophile.com/content/...er-amplifier-measurements#Z08IYRcxmgZ5W2ey.99

 

[KeithR]

Ironically, many SET fans think 845 SET isn't real SET. And that is 22-25 watts.

as Ralph Karsten says, you usually don't want to use more than 20-25% of power with SET - so 5-6 watts is optimum "range" on the 845 amp. This keeps it in low distortion, "first watt" mode.

 

[spiritofmusic]

KeithR, every so often a post is written that is so blindingly obvious, you wonder what was wrong with your own thought processes before
And so it is with your skeptical words on SETs with Apogees
Having started my love affair with SETs upon finding the Audion Black Shadows some three years ago, and taking things on last year with the truly exemplary NATs, I completely get your idea that what I/we find entrancing about the sound is what happens in those first few Watts
If the magic is not captured there thru a particular speaker synergy, it won't be found anywhere else and certainly not toward maximum output of said SETs
This means I'm turning away from any notion of thinking about trying to run any potential Apogees with NATs, even the humongous 190W Magmas, or indeed any other SETs
If/when I get a chance to hear Duettas and Divas with Jon in the UK and Henk in the NL, if they truly bowl me over and make as big or bigger impression on me than other choices, and I really feel I have to go down their path, then I'll swallow my preference bias and investigate ideal choices of mega Watts tube amps like Ron's VTL's, hybrids like Ypsilon Aelius, and, God forbid, steroid enhanced SS like Bill's Analog Domain (which I've heard recently, and was quite in awe of)

 

[FrantzM]

I don't know, Ron. But Wavac's 550lb, 150 watt SET has this distortion/wattage:

So, what about the SH-833's output capability power? Those 550 lbs and that humongous transmitter tube promise a lot of power, not to mention the specified "effective" output of 150W. As you can see from figs.5 and 6, which plot the percentage of distortion and noise in the Wavac's output against power from the 8 and 4 ohm taps, respectively, that promise is not kept. At our usual definition of clipping—1% THD+noise—the Wavac gives out just 2W or less into loads ranging from twice the nominal tap impedance to one quarter that nominal value. The highest power is obtained when the load is half the nominal tap—ie, from the 8 ohm tap into 4 ohms—but even then, the definition of clipping has to be relaxed from 1% to 10% for the amplifier to approach its specified power. Looking at the waveform on an oscilloscope during these tests, the point in these graphs when the waveform clips is actually the sharp notch in the traces. At 10% THD, the amplifier is putting out a pretty good squarewave!

image: http://cdn.stereophile.com/images/archivesart/WAVacFIG05.jpg



Fig.5 Wavac SH-833, 8 ohm tap, distortion (%) vs 1kHz continuous output power into (from bottom to top at 10W): 16 ohms, 8 ohms, 4 ohms, 2 ohms.

image: http://cdn.stereophile.com/images/archivesart/WAVacFIG06.jpg



Fig.6 Wavac SH-833, 4 ohm tap, distortion (%) vs 1kHz continuous output power into (from bottom to top at 10W): 16 ohms, 8 ohms, 4 ohms, 2 ohms.


Read more at http://www.stereophile.com/content/...er-amplifier-measurements#Z08IYRcxmgZ5W2ey.99

Wow... This will make some people really unhappy but that is not what one should get from a High Fidelity amplifier...

To each his own but SET with Apogee from the experience I had with Apogees do not seem to me like a match made in heaven ... IMHO, IME, YMMV , FWIW, etc

 

[Ron Resnick]

Thank you, Keith. That was very illuminating!

 

[spiritofmusic]

Frantz, with KeithR's invaluable insight, I'm off any consideration of running SETs with Apogees
So my aim is to hear Jon's, Henk's and Rich's Duettas and Divas. If the experience is life changing, go down this route with amps that have Watts to spare.
Maybe get my fix of tubes with a valve preamp (NAT Magnetostat)

 

[bonzo75]

Frantz, with KeithR's invaluable insight, I'm off any consideration of running SETs with Apogees
So my aim is to hear Jon's, Henk's and Rich's Duettas and Divas. If the experience is life changing, go down this route with amps that have Watts to spare.
Maybe get my fix of tubes with a valve preamp (NAT Magnetostat)

Nat was never known to be a normal SET to apply general rules to. The transmitter did not get rated as 1 over twice priced Agostino for nothing. And AJ Conti did not buy it as the best amp for nothing. Florian uses it with his Grands, swears it can work on divas and duettas, and a guy in the US uses it in FRs. So don't give up that easily, just don't base your strategy around it which is also equally silly.

 

[thekong]

Amazing stuff. You are the King, Kong.

I must say a couple of things though - I understand that placing close to side walls can reiforce the bass even more. I prefer panels such the triangle is right, if they are too wide w.r.t the triangle it feels like there is a hole in the middle of the stage.

Normally, that would be the case, but not so with Room Coupling. Actually, the soundstage fills up the whole room, constantly extends further than the front and side walls. You just have to try it to believe it, and see whether you like it!

Regarding megapower SET, if you look carefully at the photo I posted, you would notice there was a pair of amps with 833 tubes on the left hand side, next to where I sat. That was a DIY project, including winding the output transformers, by one of my friends. I have actually used it on the mid/treble ribbon of the Duetta. While the midrange was very nice and smooth, I didn't get enough treble extension! Of course, I would be the first to admit that the output transformers were probably not first rate, and could be the cause of the problem.

But that brings out an issue with megapower SET. As far as I understand, there are great difficulties in making output transformer for high power SET. You can have one that excels in the treble, or you can have one that excels in the bass, but it is very difficult, if not impossible, to have it both ways! I have never auditioned the NAT, so not sure whether they have solved this problem.

As I have mentioned before, if I am going to use a single amp to drive the Duetta fullrange, I will not consider any tube amps (actually, any kind of amps) with less than 200W!

 

[spiritofmusic]

Ked, what is Florian's setup? What NATs does he use with his Grands?
And Gallant Diva? Uses two pairs of 120W Transmitters with his Graz Divas I believe?
Is there any suspicion their rigs are underpowered or deficient in any way?
What I mean by this is maybe the NATs with Apogees in these systems sound good in one respect, but inappropriate otherwise. Michael is alluding to having bass or treble, but not both, with SETs, esp thru the Apogees
Or are Apogee/NATs combinations with these guys in very tight spaces where the lack of megaWatts is less of an issue?

 

[thekong]

One more point on the Duetta, in the video I posted, you could see the front cover of the speaker was off, as I was in the process in repainting the cover. But to my surprise, the sound was much more transparent with the cover off, so it never went back up. My friends made jokes about it being like the Predator taken his mask off

If you can't stand that look (to be honest, who in his right mind could? ) , the next best thing is probably taking the protective grill off, but you have to be very careful not letting anything gets into it!

 

[microstrip]

Nat was never known to be a normal SET to apply general rules to. The transmitter did not get rated as 1 over twice priced Agostino for nothing. And AJ Conti did not buy it as the best amp for nothing. Florian uses it with his Grands, swears it can work on divas and duettas, and a guy in the US uses it in FRs. So don't give up that easily, just don't base your strategy around it which is also equally silly.

You are an experienced audiophile and a wise man. Unfortunately we were being guilty of one usual "technofile" sin - we were extrapolating data published 12 years ago by Stereophile on another amplifier and exposing our "official SET culture", with complete lack of knowledge of facts or reality.

Your PM about these amplifiers triggered my attention and I have now read the Hifi News Paul Miller measurements on the Nat Transmitter. Great news : it passed gloriously the dynamic power tests versus distortion using the SET standards up to 80 Watt, only failing at 1ohm! The shape of the distortion versus power curve is the opposite we were describing. BTW, the German Audio review is really enthusiastic - 140 points!

So IMHO the technical verdict must be - worth being considered for listening when used with some of the speakers being referred.

Thanks for pointing us such interesting amplifiers.

 

[cjfrbw]

I ran Apogee Stages for a couple of years with active crossover and a pair of Wavac 572b stereo amps nominally 50w/ch (which I still have lying around). The audiophiles who heard it all enjoyed it quite a bit, and some of them were pretty picky on sound. I transferred the SET over the the Analysis Epsilon with a more complex active crossover arrangement and a 45 tubed amp operating an additional pair of very efficient foiled tweeters.

Previous to the Wavacs, I ran the Stages with VTL 450 monoblocks through an upgraded passive crossover. I tried a 50 watt SET just to see if it would work, and was amazed at how much more open sounding and linear the SET sounded, so the the push pull pentode VTLs were sold.

Apogees actually sound quite good with SET, presuming they are not the one ohm variety, but even then, as I recall, there were guys on the Apogee speaker site that managed to do it with special transformers. There was even one guy who ran Duettas (or maybe Divas) with 300b tubes and said it worked OK, which even I had trouble believing.

With the Epsilons, I am now using directly heated triode line drivers with ancient Sony and Yamaha VFET amps with the active crossover, and I like that even better, but sometimes do miss the warmth of the Wavacs.

 

[KeithR]

You are an experienced audiophile and a wise man. Unfortunately we were being guilty of one usual "technofile" sin - we were extrapolating data published 12 years ago by Stereophile on another amplifier and exposing our "official SET culture", with complete lack of knowledge of facts or reality.

Your PM about these amplifiers triggered my attention and I have now read the Hifi News Paul Miller measurements on the Nat Transmitter. Great news : it passed gloriously the dynamic power tests versus distortion using the SET standards up to 80 Watt, only failing at 1ohm! The shape of the distortion versus power curve is the opposite we were describing. BTW, the German Audio review is really enthusiastic - 140 points!

So IMHO the technical verdict must be - worth being considered for listening when used with some of the speakers being referred.

Thanks for pointing us such interesting amplifiers.

That amp has ultra linear and tetrode modes. Which measurement is it? Isn't a typical no negative feedback curve.

 

[Graz - APOGEE ACOUSTICS]

However I had no idea Duetta came with Pure Ribbon Foil as well, or is this a one-off Graz? Does this improve midrange, but I assume lower impedance will restrict the amps that can be used? Interestingly while the FR has wonderful mids with its pue foil the Grands also have a great midrange despit being Kapton backed.

Michael's Duetta was the first using a foil ribbon closely related to the Definitive. It has an unusual interface to make it very linear and amp friendly, and some unique characteristics...

Take care - Graz

btw - Carl - that is you! Still some early forum people out there

 

[FrantzM]

That amp has ultra linear and tetrode modes. Which measurement is it? Isn't a typical no negative feedback curve.

Thanks KeithR.

Was thinking the same here .. very different from what one would expect from a no feedback design ...Would like to know too.

 

[Zero000]

I've tried three cheap Pro amps on Duettas.

The Crown XLS1500 class D which lacks life and dynamics i.e. doesn't sound powerful even though it is. Sounds pleasant enough, and though a fraction vague there's traces of euphony in it.

Behringer A500 - cheap class A/B effort. Exciting and dynamic but a bit brash and harsh at times in the mids. Not bad for the money - not bad at all.

But this one is really good. Apart Champ One . This class G/H effort is so good I could live with it for weeks. I think it was around £700 new, but I picked one up for £200 2nd hand. It is no longer made.

Lively, dynamic, and lovely mids. Bags of power. I found it hard to take it out of the system, but when the Accuphase M-60s were plugged back in, it was obvious it is a little veiled and withdrawn soundstage wise.

Any Duetta owner, I think, should try quite a few amp combos. I reckon must be at around trying about 25 so far. Surprisingly few are what I would call good, but this Apart Champ One thing is definitely that, and is cheap as chips.

My faves are my 80 Watt 211 monoblocks, the Accuphase M-60s, the Parasound A21, and the Apart Champ. Oh BTW I have tried quite a few expensive amps too

Tube and solid state amps - you should own both and switch from time to time IMHO are you listening Marc OCD LOL?

 

[Zero000]

BTW the Champ has a tube and solid state mode of operation switch. It simply alters damping factor. The effect is subtle, as the manual states. So subtle there isn't much in it and both modes sound great, with the lower damping factor sounding freer and easier, the higher damping factor slightly tighter and fractionally more closed in.

A very interesting and well designed amp that delivers for very little money. It is a "musical" amp, as the manual claims.

Top stuff.

Interestingly, Apogees or planar magnetic speakers and headphones aren't actually that affected by damping factor, which I why I believe I hear so little difference between the modes.