Atmas M-60 with ZU Druid VI

Atmasphere

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Olivier, great to hear, from this long time (2008 onwards) Zu afficionado. I have been tempted on occasion by OTLs on my Definitions IV, but the lack of 16Ohms taps has deterred me. And I would like to find a tube amps solution that is more noise free than my current Nat Audio 6DJ8 based preamp/211 SETs amps chain.
If the new Definitions are 16 ohms that is a very nice match for the M-60s. The ZU Audio speakers (and 16 ohms in general) have always worked really well with our amps.
 
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213Cobra

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If the new Definitions are 16 ohms that is a very nice match for the M-60s. The ZU Audio speakers (and 16 ohms in general) have always worked really well with our amps.
Sean's current plan if to configure the Definition 6 as switchable for either 4 ohms or 16 ohms amplifier load. -Phil
 

spiritofmusic

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Phil, do you have much experience hearing Atmasphere or other OTL amps on Zu?
 

213Cobra

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Yes. Futterman OTLs (original), Transcendendent, and Atmasphere. Listened at length many times. I also owned Futterman OTLs for about 15 years much earlier, using them on double Rogers LS3/5a @ 30 ohms in one of my systems at the time and on ProAc EBS 30+ years ago. The OTLs are quite effective driving the 16 ohms Druids and Souls. If Sean follows through on delivering Def6 with the 4/16 ohms switchable option, I expect a rise in interest in OTLs by owners of that speaker.

Phil
 

spiritofmusic

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And your opinion, overall impressions?
Is it a case of OTL and SET bring different strengths to Zu, preference totally personal? Or does OTL have the edge on a spkr like Zu?
 

Atmasphere

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And your opinion, overall impressions?
Is it a case of OTL and SET bring different strengths to Zu, preference totally personal? Or does OTL have the edge on a spkr like Zu?
We had Druids here for a number of years; IMO/IME they were not efficient enough to take advantage of what the best SETs have to offer. Any by 'best' I mean SETs that have full bandwidth, which for the most part means SETs of less than about 8 watts or so. You really do need efficiency when working with SETs because if you run them past about 20% of full power, they take on a 'dynamic' characteristic caused by how the higher ordered harmonics (that they start to make at about that power level) interacts with the ear/brain system (the ear is keenly sensitive to the higher ordered harmonics since it uses them to sense sound pressure). The Druids certainly seemed to benefit from having some power behind them.
 

spiritofmusic

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I know Ralph. 27W Audion Black Shadow 845 monos in my room had a tendency to become grainy on my Zus when pushed past low to moderate levels in my 800 sq ft/10000 cub ft room. I hear since they are more like 7W than 27W.

My Nat 211 monos, paralleled pairs, dual transformers seem way better suited and energise my current room (same floor area, but half the volume) at lower volumes, and don't lose the plot at higher wicks.
 

213Cobra

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And your opinion, overall impressions?
Is it a case of OTL and SET bring different strengths to Zu, preference totally personal? Or does OTL have the edge on a spkr like Zu?
There isn't an intrinsic OTL sound just as there isn't an intrinsic SET sound. Well-executed OTLs have a quick, agile, transparent sound, but so do some OPT amps and so do some SET. However, there is a vast difference between, for example, a Cary SET amp and one from Audion (and not in favor of Cary), and OPT tube amp sounds are all over the sound traits spectrum. There are far fewer OTL makers with amps in the market so the sample size allowing evaluation of designer-to-designer variances is tiny. There are more reasons people like Atma-Sphere amps than the fact that they use an OTL design.

Druid and other 16 ohms speakers take advantage of the higher power available from an OTL amp at that impedance compared to a conventional load. You may hear this as delivering more shove and snap than another amp topology delivering the same, say, 80w from the Atma-Sphere M-60 in 16 ohms. A few decades ago I regularly ran Julius Futterman monoblocks into series-stacked LS3/5a in a small imitation of the old Double Advent System. The Futterman power peaked into 32 ohms and the series LS3/5a presented 30 ohms to the amp. That was an impressive combination at the time, in the 80s context of a quasi-point-source / line array experiment.

There is no intrinsic OTL advantage on 6 ohms Zu Definitions and there are a lot of options for driving Defs with ~52w in the case of the M-60. Which is not to say OTL amps can't or don't sound good on that speaker. The basic speed and transparency qualities that make Audion SET synergistic with Zu make Atma-Sphere or Transcendent interesting too. Not strictly because they are OTLs but because they are in the relatively small coterie of musically-convincing amplifiers. There aren't many.

Phil
 

the sound of Tao

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Phil I tried many Audion amps out with quite a few different Zu speakers about 6 years ago and always found the Audion more in the Audio Note school of rather lovely sounding and nuanced but (relatively) not completely transparent nor immediate in nature in comparison with the OTL amps and preamps that I’ve heard and even relative to some other SET amps. Has Audion changed their approach to sound or is it just maybe subjectively we are not hearing these amps the same way?
 

213Cobra

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Phil I tried many Audion amps out with quite a few different Zu speakers about 6 years ago and always found the Audion more in the Audio Note school of rather lovely sounding but not particularly transparent nor immediate in nature in comparison with the OTL amps and preamps and even some other SET amps. Has Audion changed their approach to sound or is it just maybe subjectively we are not hearing these amps the same way?
Not my experience at all with Audion, so am not sure of any obvious explanation. They for me are uniquely fast and transparent sounding, but I didn't use stock tubes. I've gone head to head between Audion and Audio Note and I would not put them even in adjacent sounds; completely different. I first had a Golden Night integrated 300B SET about 20 years ago. Power tubes could be chosen for old school or new school sound. I ran the KR 300B -- big difference over the stock Shuguang cheapies or something like a Sophia/TJ mesh plate. Same was true for my Golden Dream monoblocks. The 845 Black Shadow is highly affected by its tube complement.

There's nothing in my over 20 years experience with Audion SET and push-pull triodes that aligns with your characterization as being Audio Note-like, or not being transparent or immediate. Speed, transparency and immediacy are the prime characteristics that have set Audion SET apart from the rest, for me. So I don't have an explanation for our differences, other than possibly the tubes. Zu speakers have those characteristics too, so maybe Audion SET character is more apparent and leveraged in a crossoverless speaker.

I did have my various Audion amps over time mildly modified, primarily recapping the power supply with electrolytics difference from stock, which further improved speed, immediacy and bass definition. But these were improvements furthering basic traits already present. Also, Audion has moved their sound further in this desired direction by updating models with better grounding, build quality, parts quality, and they have been winding their own transformers for the past decade or so.

There might be other variables. There are a lot of speaker cables that are not helpful to the sound of relatively low power SET. Many of the more complex cables smear and reduce immediacy. I view speaker cables as sort of fixed parametric equalizers. Few sound objective. I use Zu cabling because it is objective sounding and transmitting of the Audion qualities I cite. I'll put it another way: I auditioned SET amps for a dozen years, 1987-1999 and walked away every time until I happened upon Audion at the end of that period. Audion was the first SET I heard that delivered immediacy, transparency, agility and speed. If you try Audion SET, get KR power tubes. Forget Takatsuki, WE, Sophia, etc. BTW, same qualities are extant in their preamps, but again, upgrade from stock tubes.

Phil
 

the sound of Tao

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No worries Phil, like I said just subjectively different calls. It’s only that the way you describe Audion is exactly the way I favour amps to be... and I didn’t pursue Audions after auditioning with the Zu’s because they sounded differently to the way I had hoped and I did feel that I gave them plenty of goes... a mate had a Zu Audion pairing also. At the time I tried 3 or 4 auditions with Shadows, a Silver Knight 300B and a KT150 based single ended amp at the time.
 
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