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Hi,
I'm going to purchase a pair of M60 MKIII cause I really liked the clarity an detail which the M60's brought to my system compared to my VAC PA60 which sounds kind of veiled in direct comparison.
I would like to know if someone finds the M60 too clear or even thin or lean as I could read between the lines in some reviews.
I'm a little curious that I might miss the warmth palpable sound of my VAC amps in the long run.
By the way I tested the M60 with the Speltz autoformers on 4Ohm, 91dB Cabasse iroise speakers.
best regards
Ron
Follow Ups:
Many people are aware that an OTL amp prefers speakers with a fairly high impedance. But the smoothness of the curve matters as well - in fact, all else being equal I'd prefer a smooth 6-ohm impedance over a roller-coaster "16-ohm" one.Note that with OTL amps the impedance curve will modulate the speaker's published frequency response curve (which was measured on a solid state amp no doubt). This is because a high output impedance amplifier will tend to put out more power into an impedance peak and less power into an impedance dip - which is the exact opposite of a solid state amp. Since most speakers are designed with low-output-impedance solid state amplification in mind, those with roller-coaster impedance curves are less likely to sound good on an OTL amp (though the Zero autoformer can help a great deal by pushing the impedance up high enough that it has less of a modulating effect on the frequency response, at the same time enabling the amp to deliver more output power).
Duke
Duke - very helpful info. Here is a measurement of a speaker whose manufacturer cites it at 93dB sensitivity, with an 8-Ohm nominal and 4-Ohm minimal impedance. Without knowing more, what would you say about driving this speaker with an OTL?
JTimothyA, that's an excellent real-world question. I'll do my best...
Okay the short answer is, this speaker will sound different on a low damping factor OTL amp than on a solid state amp. There's a chance that it would sound better on an OTL amp, but I think the odds are against us at least in the frequency response domain.
The long answer is, to really appreciate the magnitude of the difference we must first look at what a solid state amp would be doing into this impedance curve. Let us focus on four points of interest: The peak at 55 Hz, the dip at 100 Hz, the peak at 2.5 kHz, and the dip at 8 kHz.
Assuming an output level equivalent to 1 watt into 8 ohms, a typical (that is, voltage-source-approximating) solid state amp will be putting out .7 watts at 55 Hz; 1.6 watts at 100 Hz; .6 watts at 2.5 kHz; and 2.8 watts at 8 kHz. If the speaker is "voiced" for a solid state amp, this will already have been taken into account.
Now let's assume we drive this speaker with an Atma-Sphere S-30, which has a high output impedance (and does not behave like a voltage source). I happen to be somewhat familiar with the S-30. At an output level equivalent to 1 watt into 8 ohms, we'd get about 1.3 watts at 55 Hz; .7 watts at 100 Hz; 1.4 watts at 2.5 kHz; and .5 watts at 8 kHz.
At 55 Hz, 100 Hz, and 2.5 kHz the wattage difference are roughly two-to-one, resulting in a frequency response difference of about plus or minus 3 dB between the S-30 and a solid state amp. At 8 kHz, the wattage difference is over four-to-one, so there we'd expect to see a 6 dB difference between the two amplifiers.
Now if we used an MA-2, the magnitude of the frequency response differences compared to a solid state amp would be more like plus or minuse 1.5 dB (and a difference of 3 dB at 8 kHz). This is because the MA-2 has a lower output impedance than the S-30.
If we used the S-30 with an autoformer set to quadruple the impedance of the load the speaker sees, we'd end up with a frequency response curve similar to what we'd get with the MA-2.
Now there are some loudspeakers out there whose impedance curves "zig" where the frequency response curves "zag", resulting in a smoother frequency response when a high output impedance amplifier (OTL or SET) is used. Silverline Audio has several models that fit this description (nope, I'm not a Silverline dealer).
Note that I have only focused on the frequency response domain here; OTL amplifiers imho have benefits that are not related to frequency response but given my dealer status spouting off about them would cross the line into "advertising". So back to my short answer: There is a chance that this speaker would sound better on an OTL amp, but unfortunately I think the odds are against us.
Duke
Duke, thanks much for taking the time to do a thoughtful analysis and most helpful reply. I've got MA-1s, so those 'other OTL benefits' are already friends to my ears.
I've started my search for new speakers, and impedance and sensitivity are some of the first things I look at - most manufacturers at least publish those numbers. There being more to matching amps with speakers than nominal impedance and sensitivty numbers is good to keep in mind, and thank you for your clarity in describing that. Now I know to look at the frequency response vs the impdeance curve for mirrored zigs and zags. I wish every maker published the plots in addition to the base line numbers.
Tim
Thanks for all the interesting posts...My pair of the M60 will hopefully arrive in 1-2 weeks...I can't wait any longer :)
Has anyone experiences with M60's on ZU Druid's speakers? I find these speakers very interesting. I asked the guys of ZU about experiences with the M60 and they responded that this combination works well but is kind of lean below 80Hz because of the impedance mismatch...the Druids are rated 12Ohm but I guess they dip below that in the lower bass---
Ron
Ooh la la
How can a sound that's "kind of lean below 80Hz" be considered a match that works well, as the Zu Audio guys state?
Makes no sense to me.
Lean below 80Hz would be a non starter in my view.
The M60s deliver superb tonal nuance that is neither lean, cool, nor dry. Their clarity can be startling in direct comparison to amps possessing a bit more of that second order harmonic distortion perceived as warmth or fullness. To my ears this is most noticeable in the mid-bass where there the M60 has ever so faintly less weight, though no lack of the fundamental, and plenty of tonal depth. The amps reveal upstream sources and reward them appropriately. Enjoy them with balanced ICs. I concur with rfogel8's assessment (below) about the mate with the MP-1.
Atma-Sphere amps are happily susceptible to tube rolling. Its worth exploring the differences in weight and texture between the stock Chinese 6SN7s and, say, RCAs, Raytheons, or Ken-Rads.
I found the autoformers work as advertised. While they do not entirely escape having a sonic signature (what does?), using them when needed typically tips the tradeoff in their favor.
My opinion, YMMV.
Tim
"I found the autoformers work as advertised. While they do not entirely escape having a sonic signature (what does?), using them when needed typically tips the tradeoff in their favor."
This is precisely my own assessment of the Zero Autoformers - not without any artifact, but (when required) the benefits drastically outweigh the costs. Good to hear this kind of corroborating feedback.
FWIW, I run relatively (91-93dB) efficient 8ohm speakers with my own M-60s - yet I still have a pair of early Zeros running on the 1.5x setting. In theory, this makes my 8ohm speakers look like 12ohms to the M-60, increasing the power output to almost 80W. I note improvements in deep bass texture and authority, and general transient response.
Rfolgel's opinions on the MA-1/MP-1( both mkIII) combo are right on the money.
I bought a used pair of M60 MK2.3 amps to try with my Silverline Sonata III. Preamp is an Atma MP-1 MK III.
It was not a good match, IMO. Incredible clarity, but a lack of midrange and bass resulted in a sound that was tipped up and too aggressive for my taste.
I just think they were a poor match for the speakers.
Sounds like a simple matter of impedance matching, and I agree that the Speltz Autoformers might help a lot to improve midrange and bass response. Can you get hold of some impedance vs frequency data for your speakers, to verify that the Zeros would help?
I sold them, so it's a moot point.
Interesting Grant...I had been using the MA1 MkII.3 amps with Ridgestreet Audio Sason speakers and a BAT VK51SE preamp. Sound was excellent; however, when I recently inserted an MP1 MkIII preamp in for the BAT, it was dramatically better in every conceivable way. It gave the impression of doubling the size of the power amps in an underpowered system while adding greater transparency, detail, micro and macro dynamics, and tonal density.
I had also found the amps worked exceedingly well with my previous Magnepan MG3.6r speakers, much better than the Parasound JC1's in my 18x21x8 room.
Sounds like in your case the speaker-amp interface just wasn't a good match...have you tried the Atma's with the Speltz autoformer?
I tried the Speltz in my System when I was auditioning the M60`s at home. Without the Speltz the sound was to lean in the mids and bass for my taste. The impedance match of the amps with my 4 ohm Cabasse speakers might not be perfect. The Speltz helped to improve a lot. With them the missed substance in the sound was there. I could also not detect any negative influence when using the 2x conversion. With the Speltz in 4x configuration the sound was too mechanical and not as fluid as before.
i ordered a pair of Speltz in cherry boxes together with a pair of M60`s incl. custom teflons and power supply boost.
I also tried the MP3 at home but after a few minutes I was convinced that the MP3 could not be a substitute for my beloved Paragon 12A which had more nuance and inner detail, if not the very wide sound stage of the MP3. The MP3 might have gained more impression on me while being longer in my system but from the first contact I was not convinced to hear something fundamentaly better than my 40 year old Paragon preamp...but theres also a lot of personal taste and preference to such a opinion.
Interesting! I was considering going with the MP3 due to the very large price difference, but worried that it would not better my BAT VK51SE (and I'd lose volume control). I went with the MP1 and the sound was so dramatically better than the BAT in every conceivable way...and obvious from the first few notes. I just want to kick myself for not doing this sooner! LOL
With the MP1 in the system, inner detail and tiny microdynamics (instrumental shadings, voicing, artistic expression, etc) are so unforcefully obvious and transparent. This is for me the most important improvement in that it gets me so much closer to the music. If the Paragon has "it" in your system and the MP3 does not, I'd do the same as you and keep the Paragon. If you have a chance, try an MP1...I'd be curious if the MP1 and Paragon are similar in your system?
I don`t want to say that the MP3 is worse than the Paragon but I liked the sound of the Paragon more. At least it appeals more to my feeling of how music should sound. Someone else might have different expectations on the sound of a preamp. One big plus point of the Paragon and a reason to keep the unit even if I might experience better sounding units (MP1?) in the future is the possibility to connect 3 tonearms.
Well, you're talking about completely different amps...140wpc versus 60wpc, Not really a fair comparison, IMO.
Yes, the amp/speaker interface was not good in my case.
I'm certain the MA1 amps would perform significantly better in my system than did the MA-60.
True...I was primarily commenting on the synergy between the MP1 and Atma amps...adding the MP1 just made my system sound so much more powerful and yet what you had described sounds like a leaning out of the sound?
As you said, it's really an apples to oranges comparison on two levels (M-60's v. MA1...more power, but essentially similar sound quality I presume and the key I think...M-60 & Silverline speaker interface).
Thanks for the response!
I purchased the MA-1 Mk3 monos a while back after owning VTL Sig 250's for several years and while the M60's have less power than the MA-1's, I gotta believe they sound very similar.
Yes, they are extremely transparent; more than any amp I've heard previously yet they still retain enough warmth to know you're listening to tubes. The VTL's were warmer but these sound more believable. They also sound way more refined with a purity to the sound that is hard to describe but is easily heard. Resolution is another area where these amps excel. On good recordings, little nuances come through much more clearly than with previous amps I've owned.
One more thing, I originally mated the MA-1's with a single-ended Cat Ultimate Mk2 which made for some beautiful listening. After a while I decided to take the advice of those recommending going fully balanced with an A-S preamp. I figured the MA-1's were so good that they deserved to be mated with an MP-1 so I went with the new Mk3 with phono stage. In a nut shell, it was the best decision I've made when it comes to audio.
I'm sure going balanced had much to do with the new sonic improvements but on it's own the MP-1 strikes me as a component in a class by itself. Take the comments I made regarding the MA-1 Mk3's and multiply times two. There is definitely that synergistic thing going on between the amps and preamp.
After approximately 25 years of playing at this hobby I can honestly say I'm done looking at amps and preamps; unless Ralph comes up with some super upgrades.
Xronx, if you go with the M60's consider the V-Caps and Caddocks then after you recover from the big hit to your wallet, think about the MP-3 to top things off. You won't be sorry.
To come back to the initial topic...does anyone compared the M60's or other Atma-Sphere amps directly to good 211 or 845 SET amps? What are the differences, how does the Atma-Spheres midrange sound in comparison since this is the area where SET seems not be beaten easily.
Dear Sir,
When I first aquired a set of M60's I was using a very high quality 4 ohm
speaker with about 86 db sensitivity. The sound was a complete mismatch. The M60's sounded lean and mechanical with no dynamics. I changed the speakers to a 8 ohm, 86 db sensitivity with flat response and the amps opened up and were warm, dynamic and very transparent. I then added a set of Zero's and used them at the 2X position and the amps were transformed again and became more dynamic with the same warmth and transparency. With OTL's it all about proper speaker matching. You will have better luck with a high impedance speaker and the higher the sensitivity the less power you will need to drive them. Also, the higher the impedance the better. I would say that with the M60's you need at least 8 ohms with a flat response and if you use a speaker with 11 to 16 ohms impedance they will really shine.
I can't comment directly on 211 or 845, but as far as large transmitting thoriated tungsten DHT's I like 805's, so...comparing the M-60's I have to the 805 in SET I have the Atma's are better in every way: power, smoothness in the midrange, palpability of presentation, non-fatiguing highs etc. I like the SET presentation for nearfield, fullrange presentation in small rooms with low or medium efficiency speakers; I have not met a high efficiency horn speaker system I really go nuts over yet. I'll not part with my M-60's, though I may upgrade them. You don't often see them for sale used, and if so, usually those moving up the power chain to MA-1's or 2's.
http://www.bezdz.com/images3/T10B.gif
I *like* the loudness button!
Mine are mkII.2 and silver wired. With the tubes they came with, RB5692 and sovtek they weren't warm enough for me. But with appropiate tubes in V1-V4 they warmed up just enough. Not as warm as the Fisher 800B that is the warmest I've got, though. But with that clarity that no transformer can ever let through. JMHO
I *like* the loudness button!
What tube are you useing, for V2 an V3 i find the Sovtek,GT work like the Sovtek 6AS7s tuff tube i have RCA red base on V1an V4,but the more output tubes you have V1 V2 an all sound diff. i have some old tung-sol ok.
just one man O-pine
There are plenty of good combos that will kick the sovtek 6N8S and RB5692 outta your amps, if you need some, just ask...
I *like* the loudness button!
Are thay OTLs,Circlotrons or what?
thanks
Those are fantastic looking amplifiers, but they do not appear to be OTLs. Looks like the two large tubes with top caps on the top level are transformer coupled to the output (with PS on bottom level). Did you build them or are they some old treasure you found?
They are circa 1950's Ballantyne SoundMaster MX-24 that have been worked up by William Hardy of Vintage Amplifier Restoration. They started out pretty much like these
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=260161015880&indexURL=7#ebayphotohosting
But all of mine were hurt to varying degrees. They are now all iron and tubes: 6SN7 differential input IT 6B4G PP IT 805 PP. I like them.
I *like* the loudness button!
Pretty sweet set of electronics there.. plus, they're their own stands!
Gotta love it.
Yes what speakers,i have had the M60s an all roads led to the MA1 an MA2 for me to get the warmth, it more about the amps them selfs the Circlotron,is a balanced differential,not eze to find in the wourld of tubes you can use 8 6AS7 or 20 6AS7s if you wont more warmth. But gets HOT!
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