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Old 12th March 2010, 08:55 AM   #141
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Originally Posted by atmasphere View Post
That 75V AC rating on the secondaries of the B+ supply for the output tubes seems a bit low to me. Typo?

Stancor used to make a 20-amp filament transformer that did the job nicely, but it didn't have a 235V capability. The Hammond 266V6B is rated at 20Amps also.
atmasphere,

The 75VAC@5.3A per secondary winding is correct; that was the "best-fit" combination of voltage/current that I was able to locate to power the output stage "floating" power-supplies.

In your post #60 in this thread, you stated that it was OK to run with somewhat lower voltage (down to 100VDC). The currently designated transformer would give about 106VDC; will this be problematic?
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Old 12th March 2010, 09:25 AM   #142
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Originally Posted by markusG View Post
Stancor TGC175-12 (28A@6.3V) and TGC130-12 (20.60V@6.3V) looks to be in the right area.
Yes, both Stancor and Hammond offer filament transformers with high-current capacities, so that approach is certainly an option. However, those transformers are all of E-I core construction, which I have always found to be prone to emitting mechanical hum; that's why I tend to focus on the use toroid power-transformers (combined with a good DC-trap circuit). A custom-wound toroid could be specified that would allow us to have just one filament power-transformer; the cost would likely be comparable to the five inexpensive 50VA-rated transformers currently specified in the schematic. Depending upon the response from "atmasphere" regarding the voltage output of the currently specified output-stage power-transformer, we may need to consider a custom-wound unit for that device as well...

Quote:
But wasn't the T2 supposed to be two separate transformers? Not just separate secondaries?
We only need independent/floating power-supplies for the output stage, so using a single power-transformer with dual secondaries meets the requirement. However, it would be simple enough to add a second output-stage power-transformer to the power-supply design if you want to minimize any potential for cross-talk between the secondaries. It's a DIY project, which gives us the lattitute to do whatever we feel is needed to optimize the audio characteristics...
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Old 12th March 2010, 11:49 AM   #143
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Originally Posted by atmasphere View Post
That 75V AC rating on the secondaries of the B+ supply for the output tubes seems a bit low to me. Typo?[...snip]
atmasphere,

Perhaps more to the point; would running with 75VAC secondaries for the output stage power-supplies be sub-optimal from a music reproduction standpoint? Those of on the thread are, of course, interested in maximizing the music reproduction capabilities of our DIY M-60's...

I see that we can get off-the-shelf 600VA-rated toroids with dual 50VAC@6A secondaries (Antek - AN-6450); if we were to use one of these transformers per "phase" of the Circlotronic output stage in a "stacked" secondary configuration, that would give us 140VDC@6A for each of the "floating" output stage power-supplies. It would double the number of power-transformers needed to provision the output stage, but the important question is, "Would this approach be better from a sound-quality viewpoint?". If so, I'm more than happy to revise our proposed power-supply design.

I've also submitted a price quote request to Toroid Corporation (I've used these folks for customer transformers) for a dual-secondary 99VAC@6A power-transformer (equipped with 117/230VAC reconfigurable, dual-primaries), just to see where the price range would fall. It's possible the price for a single custom-wound toroid might be less expensive than two of the off-the-shelf transformers that I just described.
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Old 12th March 2010, 01:57 PM   #144
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Default M-60 OTL Power-Supply Schematic (v1.1)

OK, apparently I experienced a Homer-Simpson-esque "Doh!" moment when originally searching for appropriate off-the-shelf power-transformers for the M-60 mono-block project. At the heart of the matter, I failed to consider the use of stacked secondaries in order to more closely approximate the design center provided by the custom power-transformers used in the commercial M-60 project. Mea culpa...

So, attached is the revised M-60 power-supply schematic (again, in both JPEG and PDF formats) that uses a pair of Antek AN-6450 (Antek - AN-6450) to power the M-60 "floating" output stage power-supplies. Each of these power-transformers provide a combined 100VAC (50+50VAC) output, resulting in a 140VDC@6A output. Obviously, I'll need to cook-up an updated parts-list, but I'll get that posted soon.

Everyone good with this change? Any rational objections?
Attached Images
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Attached Files
File Type: pdf m60-power-supply-schematic-v1.1.pdf (191.7 KB, 131 views)
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Old 12th March 2010, 02:13 PM   #145
markusA is offline markusA  Sweden
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I guess a few more bucks won't make any huge difference. Looking good.
I'm running out of questions and things to comment on, in a way maybe that's a sign of the design reaching maturity?
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Old 12th March 2010, 05:21 PM   #146
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I guess a few more bucks won't make any huge difference. Looking good.
Agreed; we're in pursuit of a state-of-the-art topology, so there's really no point in cutting any corners during the implementation; in for a penny, in for pound...

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I'm running out of questions and things to comment on, in a way maybe that's a sign of the design reaching maturity?
There's undoubtedly more "lessons learned" that are still to be gleaned from the production implementation of the M-60; Atma-Sphere has been methodically refining their core balanced-differential topology for literally decades. And "atmasphere" (whom I suspect may well be Ralph Karsten, founder/master-technologist of Atma-Sphere Music Systems...) has certainly been amazingly generous and forthcoming in sharing information with the DIYaudio community. However, given the elegant simplicity that's "hidden in plain view" during this project, I agree that our current power-supply design is quickly coming into alignment with the overall design gestalt of Atma-Sphere Music Systems (but that may be overly presumptuous on my part...).
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Old 13th March 2010, 01:11 PM   #147
markusA is offline markusA  Sweden
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Actually there's one thing that keep bothering me. Please explain this to me.
Reading the data sheet for a Svetlana 6AS7 it reads plate dissipation 13W max.
I assume that's for one channel and we have two per tube i.e 26W per tube.
8 tubes makes that 208W.
140VDC @ P=UI -> I=1.5A

AN-4450 is rated 2x50V | 4.0A
Why not go with the smaller cheaper transformer? What am I missing?

Maybe it's even possible to run the AN-3245? But then we're loosing voltage, only 2x45VAC | 3.3A.

If possible to go with the smaller transformers we'd be cutting the cost in a big way.
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Old 13th March 2010, 03:52 PM   #148
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Originally Posted by mullardel34 View Post
OK, apparently I experienced a Homer-Simpson-esque "Doh!" moment when originally searching for appropriate off-the-shelf power-transformers for the M-60 mono-block project. At the heart of the matter, I failed to consider the use of stacked secondaries in order to more closely approximate the design center provided by the custom power-transformers used in the commercial M-60 project. Mea culpa...

So, attached is the revised M-60 power-supply schematic (again, in both JPEG and PDF formats) that uses a pair of Antek AN-6450 (Antek - AN-6450) to power the M-60 "floating" output stage power-supplies. Each of these power-transformers provide a combined 100VAC (50+50VAC) output, resulting in a 140VDC@6A output. Obviously, I'll need to cook-up an updated parts-list, but I'll get that posted soon.

Everyone good with this change? Any rational objections?
mullardel34:
First: Thank you for your extraordinary work and passion for all of us!!!
Second: Back to the class AB stuff for a moment. Will the previously posted power supply sch. and parts list work should one wish to go the AB route? If not, would you and atmashere be willing to give us the full panopoly of options in detail that one may build them?

Back to lurker mode..... and THANK YOU
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Last edited by tympani1d; 13th March 2010 at 03:53 PM. Reason: dumb thumbs>>>>>>
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Old 13th March 2010, 07:01 PM   #149
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I just joined today and havent read all the 140+ posts in this topic, but here in the UK, 4 x EL84 and a few ECC83 would be a popular choice in answer to the original question. Hope this is helpful, Steve.
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Old 13th March 2010, 10:56 PM   #150
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I just joined today and havent read all the 140+ posts in this topic, but here in the UK, 4 x EL84 and a few ECC83 would be a popular choice in answer to the original question. Hope this is helpful, Steve.
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