Hi Ozzy, I certainly acknowledge and give credit for a well thought out long term upgrade/updating pathway.
Charles
Amps Atma-Sphere M-60 Mono blocks OTL design
I just purchased a used OTL Atma-Sphere M-60 mono blocks that I have sent to Atma-Sphere to be upgraded to the current model 3.3 and I also added the option of a higher quality power supply and V caps.
I have sold my old trusted Eggleston Andra 2’s speakers and have built some monitors using Aurum Cantus ribbons (102db) and Aurum Cantus midwoofers (90db) that are both rated as 8 ohm nominal. I have a DEQX Premate and will be crossing over to (2) JL Audio F-113 subs at 80hz.
Currently I am using a solid state high power stereo amp (Pass Labs) that I used with the Andra 2’s.
The Atma-Sphere M-60 is rated at 60 watts class A and is said to work better with higher impedance loads.
It will probably be a few weeks until I get the M-60 and was hoping someone could provide opinions of what to expect.
I listen to late 60 early 70’s classic rock music mostly. Sometimes loud.
ozzy
245 responses Add your response
Doesn’t using zero transformers defeat the whole point of an OTL amp? It’s putting a transformer in and makes it similar to a non OTL push pull tube amp.That’s a logical question, which has been stated here in a number of other threads in the past, but basically the answer is "no." From a technical standpoint the following statements quoted from the FAQ at the zeroimpedance.com site are good ones IMO: 12) What is the difference between the ZEROs autoformer and a typical tube amplifier’s transformer?As I said, from a technical standpoint that all makes sense to me. Basically, all transformers and autoformers are not created equal :-) Regards, -- Al |
Doesn't using zero transformers defeat the whole point of an OTL amp? It's putting a transformer in and makes it similar to a non OTL push pull tube amp.'Defeat' as used in the question above suggests that an OTL is trying to do something that is somehow in opposition to a normal amp with a transformer? It isn't. What we are trying to do is get as close to the music as we can. The fact is that the ZERO has a very low turns ratio. Because of this it has very wide bandwidth- wider than almost any amplifier made, tube or solid state. You can't do that with a regular tube amp with an output transformer. You need to start with an amp that already has a fairly low output impedance, and a circuit that is not putting DC through the transformer winding. The ZERO is really a problem solver- for example, here in Minnesota a lot of people want to use the M-60 with Magnaplanars. Usually they have smaller Maggies, but the M-60 is usually challenged when presented with a 4-ohm load. The ZEROs fix that and you don't loose the transparency of the amp. My rule of thumb is that when using the ZEROs you don't encounter any serious sonic tradeoffs. If the amp sounds better without the ZEROs then you just don't need them. I think its better if the amp doesn't need the ZEROs. That usually means the speaker load is 8 ohms or more as in the case of ozzy's speakers. |
Too bad more Maggie lovers who want to drive them with M-60's aren't aware of the Eminent Technology LFT-8b loudspeaker. It like Maggies is an inefficient planar-magnetic design, but the LFT-8's impedance is nominally 8 ohms, and if bi-amped the m/t panel (frequencies below 180Hz are handled by a sealed-enclosure dynamic woofer) has an impedance of 12 ohms, much better for a tube amp than the 4 ohm Maggies. |
Not to be a pain, but I wonder if you should leave the transformers set at a connection for a period of time. I only say this because, when I adjusted my Vandy M5-HP crossovers, Johnny Rutan said they need to settle in for a few days before they exhibit their true character. This situation may be different, but I thought I would post my thoughts with the hope of having you make the best informed decision. (BTW- I recall reading that Steve McCormack felt that the Zero Transformers made a significant difference even with his SS amps). Bob |
gdnrbob, Thank you for your post. Did you find the higher multiples better? What did you finally end up preferring? I am pretty sure that the 2X is better with my amps and speakers. To me it was quickly apparent. The 3X setting increased the sense of more dynamics but the soundstage was not as open sounding. So, for now I will leave the 2X setting attached for maybe about a week .The only question is whether the system will sound better without it. ozzy |
Ozzy, I've been considering a Pass xa30.5 vs Atma-Sphere S-30, which I assume is pretty similar to your amp comparison....just lower power. How would you describe the sonic differences? I prefer a full-bodied, dense tonality, but with bottom end slam....not looking for a lean, highly detailed presentation. Thanks, Phil |
Ozzy, I don't have the Zero's. I only mentioned it because when I changed the crossover settings of the M5-HP, things sounded grainy/shrill. John Rutan said it was that the circuit needed to settle in for about 60 hours or so. Hence, I was wondering that if you changed the Zero settings, it, too, might need to 'burn in' in order for you to gauge the differences in sound quality. As I said, it may not be the same thing, but I thought I would mention it. Glad to hear the Atma's living up to your wishes. Bob |
Well, I just removed the Zero’s from the M-60’s after about 10 days connected and once again used the amps solo. After listening to a few tracks I then replaced the Zero’s with the 2X connection. In the end, I’ve got to admit the Zero’s are a needed complement to my DIY speakers. There is a wider soundstage along with much better dynamics. So Ralph and others the Zero’s are keepers with my Atmasphere M-60's and my DIY speakers. I also found that the Full Music 6SN7 tubes are the same as the Sophia tubes and at much lower price! ozzy. |
Why not try 4 M60 Amps, Wiring the Mid and Tweeter with 1 amp. Wiring your lower Woofer with another M60. I was just thininking of doing this to my classic audio loudspeakers. I have the New Atma-Sphere Nirvana Amps and 2 Pairs of M60. The Nirvana are being used for the large speakers. The M60 is paired with a 2 way Studio Monitor. |
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Glad that the Full Music 6SN7s worked out well for you, Ozzy. Your findings regarding their excellent sonics are consistent with many others I’ve seen reported for their Sophia counterpart. Including feedback Ralph mentioned earlier in this thread that he has received from a number of customers. However, I’ll note for the record and for the information of those reading this thread that at various times in the past I and at least two other members here experienced totally unacceptable hum problems with the Sophia version of the tube. See my posts dated 4-2-2017 in this thread, and the link provided therein, and also the post in that thread dated 4-3-2017 by Tubegroover. It can be expected that sensitivity of preamp and power amp designs to what I determined was apparently the cause of the problem (measurably excessive heater-to-cathode leakage, resulting from either a design defect in the tube or a quality control problem in its production) will vary widely among different designs. I would suspect that some designs will be totally insensitive to it. And FWIW, apart from the hum issue the Sophias did sound great in my amp. Best regards, -- Al |
almarg, I have noticed a very low level hum when I place my ear up to the speakers with no music playing. But, it is minimal and I overall prefer the sound quality over that minor annoyance. Perhaps if they are installed in a preamp it may cause more problems downstream. charles1dad, How does Sophia get there brand on the tubes if they select the best ones? I think they just purchase a lot of the tubes from TJ and have them branded "Sophia" then they grade them A-C. I think the grade A ones are used in the USA market and sold direct from within the USA. ozzy |
