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I am continually amazed, by such sheer beauty, the openness, effortless ease
and transparency of my Atma Sphere MA1 amps. They're so organic,
especially driving (8 ohm) Silverline SR17 Supremes
or on occasions Quads ESL57, as shown.
I stayed up until 4am listening last night listening to vinyl.
Another sleepless night lie ahead, amps are warming
up right now... a night of blues is in store.
Follow Ups:
Has anyone heard Tim Mellow's 6C33 OTL? It looks to be one of the simplest OTL circuits to try to build, so I am thinking about trying it out. This will be my first OTL...
"Has anyone heard Tim Mellow's 6C33 OTL? It looks to be one of the simplest OTL circuits to try to build, so I am thinking about trying it out. This will be my first OTL..."
Yes, I have built one, and it has been my main amplifier for daily use for a couple of years now. It has never given me any trouble, and the performance is very good.
Chris
Have you compared its sound to any other OTL amps? I know Transcendent Sound and Atma-Sphere have their followers, and some of their circuits are reasonable to build. Maybe the sound would be cleaner using several parallel tubes instead of just one pair of 6C33C?
"Have you compared its sound to any other OTL amps?"
I've built another totem-pole OTL using two 6C33Cs, designed by Hans Beijner, and a circlotron using four EL509s, by Alan Kimmel. Also, a totem-pole based on an old design by Dickie and Macovski, using four 6082s.
I'm not very good at hearing differences between amplifiers; I seriously doubt that I could reliably distinguish them apart under double-blind conditions. (Or indeed, any amplifier that is not suffering from some gross defect!) Of course when one knows what one is listening to, hearing differences is easy.
Anyway, I can certainly say that the sound is excellent, and stands up well against anything else I have heard. I suppose in general tube OTLs could be expected to sound more like solid-state amplifiers than tube amplifiers with transformers, simply because they lack the colourations that could be introduced by the output transformers.
Chris
Here's mine:
And a perspective of my 14 X 13 music room:
It sure gets hot, but I'm going solar and will be cranking the AC when the need arises!
That's a nice looking setup, bet it sounds as good as it looks....
Rock on!
Thank you Rhino!
OTLs rule? Now that depends on what amp you are comparing them to and what speaker you are driving, doesn't it? Black and white situations are pretty rare.....
Coming form a guy with several OTLs who has been through at least a dozen.
Otl definetly rules, even better when OTL/OCL which larger amount of power to work even with difficult speakers.
I am using a GRAAF GM200 with 32 Pl504 (27gb5a) on Magnepan 20.1 and they can handle it with ease, alltough I also have a additional room heater.
"Otl definetly rules, even better when OTL/OCL which larger amount of power to work even with difficult speakers."
I certainly agree with the general sentiment. But I'm never quite sure about the OCL aspect. Presumably this refers to not having a big output capacitor that is directly in series with the loudspeaker. (All my OTLs are OCL, in fact.) But the capacitors in the power supply are just as much in the audio path as an added output capacitor would be, so I've never really seen why OCL or not is a big issue. All OTL amps have capacitors in the signal path.
Chris
Is that a cap in Series or parallel with the output? An what size cap is in your OTLs output? thanks
"Is that a cap in Series or parallel with the output? An what size cap is in your OTLs output? thanks"
In both cases (output capacitor or power-supply capacitors), the capacitor would effectively be in series with the output. I don't use an explicit output capacitor in my OTL amplifiers, but the power-supply capacitors in mine are something of order 4000 uF.
Chris
So are you saying all amps OTL are SS have a cap in Series at the output?
What an I missing?I see no cap at the output?
thanks
"So are you saying all amps OTL are SS have a cap in Series at the output?
What an I missing?I see no cap at the output?"
You need to look also at the other schematic in that Tim Mellow article, showing the power supply. The audio signal current passing through the output tubes also passes through the smoothing capacitors of the power supply.
Chris
Not with the Graaf gm200!
Here a small section:
"Not with the Graaf gm200!"
I'm not sure if you are suggesting it has no capacitors in the signal path in its output stage, but in any case it does. Just like any OTL, whether totem-pole or circlotron, the power supply capacitors form part of the signal path. I'm not saying that's a bad thing (and, in any case it is unavoidable); I'm just saying it is a fact of life.
Chris
But to most people,some OTLs output PS caps look like there in parallel not in Series
Now some OTLs have a big 4-6mf cap in series with the speaker right?
Is this Like, is there a real class A OTL amp?
thanks
"But to most people,some OTLs output PS caps look like there in parallel not in Series"I'm never entirely sure what people mean when they say that the power supply capacitors are "in parallel with the output." But if they find those words more satisfying than "in series with the output," then I suppose that is fine, although it seems to me to be a misleading way of saying what is happening.
But what is not in doubt is that the audio signal is passing through the capacitors. If we consider a circlotron, for example, then there are two "signal current loops" in the output stage. One loop comprises the upper tube (or bank of tubes), the corresponding power supply capacitor(s), and the loudspeaker, daisy-chained in series. The other loop comprises the lower tube(s), the capacitor(s) of their associated power supply, and the loudspeaker, again daisy-chained in series. Any signal current that passes through a given bank of tubes necessarily also passes through the capacitor(s) of the associated power supply in that daisy-chained loop.
So provided one accepts that the audio signal "passes through the output tubes" (which seems like an uncontroversial enough statement!), then one necessarily must accept that the audio signal also passes through the power supply capacitors.
As far as class A OTLs are concerned, there do exist rather low power single-ended OTLs, which are necessarily class A. (They are also super-inefficient, even by OTL standards.) Such an amplifier would almost certainly have to have an "explicit" output capacitor, to keep DC current from flowing through the loudspeaker.
For push-pull types of OTL, whether totem-pole or circlotron, they are essentially what one would normally call class AB. Of course, for sufficiently low output levels they are "operating in class A," in the sense that if the signal is low enough that the tube (or bank of tubes) that is being driven towards non-conduction in a particular half cycle is not being driven fully into non-conduction, then for such a signal level both banks of tube are conducting all the time. But once the signal becomes large enough to take the current in the conducting tube(s) to about double the quiescent current, or higher, the current in the other bank of tubes will have gone essentially to zero, and so the amplifier is then operating in genuine class AB. In practice, the OTL will only be operating in class A for rather low power levels compared with the power it is capable of delivering in its class AB mode.
Chris
Edits: 12/07/14
As we know, theses things you are saying have been said befor,
You have clear way of saying it.
As I have always said,if you know how thing relly work,you can explaine it to anyone.
thanks
Hi Mike, I got a chance to listen the set of OTL3's I purchased from you and rebuilt on a set of new B&W 800 Diamonds last month, wow that was nice.
number 2
That looks like Audio Dimensions' setup in north OKC...
I have enjoyed the 800D/802D there many times.
Your correct that is audio dimensions in okc. " Russell' s place."
Nice pic of your amp! The MA-1s are sweet I'm sure. Given the heat any moderate or larger OTL generates though, I think a more apt description is that OTL amps are (both metaphorically and physically) hot! :-) :-)
I'm working on (bringing back into service) a older pair of Joule-Electra VZN-220s (Rite of Passage 220W OTL) right now for a customer. Jeez, just got one of the amps going so far and boy do they pump out some heat (last thing my listening room probably needs in the middle of summer) when it is running, but boy do they sound good.
Happy Listening,
Rich Brkich
Retailer & Audio Asylum Industry Liaison
I converted my old Atma-sphere MA240s to run four 7241s per monoblock, instead of six 6C33Cs per monoblock. Since the 7241 can handle even more current than a 6C33C, there is no loss of power, but I expected the amps to run no less hot, because the 7241s also suck up filament current. Yet, surprisingly, the modified output stage runs notably cooler.
That Joule monoblock would be intolerable in most rooms during a hot month in the DC area, where I live. I can only imagine the heat of 24 6C33Cs in any normal size room, assuming the amp in your photo is one of a stereo pair.
HOT is correct...I'm running sixteen 6C33's ;-)
Vbr,
Sam
NO THANKS!! I listened the 80 watt Joule for a month in February in Central Florida and the heat generated was just unbelievable with 8 of those 6c33s I can't even imagine 24! The price to pay for such a glorious musical presentation I suppose.
They had 4 x 6C33C per monoblock and they made the room swelter after only a couple of hours playing! Finally couldn't deal with that anymore.
Funny enough, the Class A SETs I have now run notably cooler than those Class AB OTLs. That 6C33C is one hell of a current hog.
My NYAL OTL3's use 6 6LF6's per side to generate 80 to 100 watts or so. They have a fan, to prolong the life of the tubes, but don't generate much heat overall. So I'm not convinced that brute force and massive heat are necessary for a successful OTL design.
A lot of the heat comes from the class of operation.
In the case of the 6C33s a lot also comes from the filaments.
I guess your new Novacron is a real cooker as well?
Yes, the heat is an unavoidable fact of 6C33s. That is why the Novacron has a reflective panel behind the tubes- people think its there for looks, which is fine, but it also serves to keep the temperature down in the power supply.
Mr.Karsten
To solder conducting wires on that extra hot 6c33c-b sockets pins which type of solder wire yours company use ? , some standard 60/40 , 60/38/2 or some other type of solder wire ? , since that`s particular 6c33c tube socket solder points need to withstand good electrical contacts for years ( decades )ahead running under pretty hot environment ,
and did you ever consider to use cooling chimneys for 6c33c tubes in combination with some small & quiet cooling fan placed under(inside) the Novacron chassis ?
Best Regards !
__
Enlightened Evolution-Astral Projection
The area of heat that is the biggest problem are the filament connections.
We built a heatsink of sorts into the assembly to help out with the heat. So far it seems to be working fine.
Mr.KarstenThanks for you response !
BTW , I never understand why Russian manufacturer was build so powerful tube with so tiny tube pins ( except anode pin ) ! , with only 1,45 mm in diameter and only 10,5 mm long ,
maybe that was something intentionally with main design target to minimize temperature difference between joints of tube glass envelope ( bulb ) and metal pins just to avoid hard glass micro cracks( porosity ) and resulting vacuum loose , who knows ...
__
Enlightened Evolution-Astral Projection
Edits: 08/07/14
The reason it was done that way was because they were using an American tube socket design which was built for the 3C33, an American dual power triode. They doubled the plate area and made it into one tube instead a dual.
I have the Einsteins that use 4 of those 6c33 tubes each and it feels like having 2 little hibachi grills in that end of the listening room. I have visions of my electric meter spinning madly. But the sound!
Tom Collins
Nice....
Been wondering what you were up to, after the link you sent me of the big theatre speakers, Zeis Ikovox's, I was curious of what you were about to buy, those do look like they would bring the roof down, I also seen a pair of tannoy's on audiogon that the owner is in the same town you live in, they are still there, Tannoy Kingdom, built in 18" bass speakers you should check them out.
I picked up a pair of 57's last week, and a pair of Prodigy 150's, another version of the H3aa's.
Hope to get home soon and give them a try.
Kudo's to you Mike!!!
Rock on!!!
Gonna call you OTL man! Sounds are great, in the music making world.
In the (shop) realms of building; the unexpected HK and Hafler/Musical Concepts,
into Rowland & Atma-Sphere lineage is an amazing thing... the sound and
family progression suits and is a most worthy effort, worth the time.
I cannot wait to hear / experience your work - outside ;-)
- - SWEET - -
Those Novacrons are gorgeous!
that an intelligent matching of an OTL to speakers will always be rewarded. Don't make your OTL drive Apogee ribbons or some 4-ohm, 5-way behemoth conventional speaker, in other words.
If I were ever to get away from ESLs, the Silverline products would be high on my list, along with anything made by Duke LeJeune.
Lew, I have spoken with Duke and 'will own'
his speakers 'one day'... Not an easy choice
which exact one...Honestly I have yet to manage the emotion
of selling other gear in the main system where
I would use them. Things are kind of a jumble
at home, a good thing for an(y single) audiophile.**Having just experienced MA1/MA2s driving Sound Labs
at Brian Walsh's, I thoroughly understand the wonderful
marriage you are so fortunate to know of first hand.
Edits: 07/04/14
The first pair of Duke's Zephrin 46s in the midwest, introduced at the recent THE Show in Newport Beach, are due to arrive here next month, painted (at my request) in a copper metallic automotive finish (shown below) and with the optional grilles. The M-60s await. Saturday, August 23rd...be here for the cookout and listening party (RSVP).
Brian
So much music, so little time!
a '76 to '79 Turbo or a non-Turbo with options added?
Your Sound Labs presumably have the latest toroids, as opposed to the Australian (very non-factory) option, I would guess.
But yes, a late '70s 930, I believe. Shown here for the color, which will be used for the Zephrin 46s coming. It took quite a bit of digging around to find the color, the paint code, and sources of the paint. But I think the results will be worth it.
Yes, my U-1PXs have the Toroid IIs, a nice upgrade.
Brian
So much music, so little time!
Remarkably cool Brian, thank you for sharing in recent demo
and prospects of a listen to Dukes new masterpieces.
Based upon an update from Duke, it looks as though the unfinished cabinets will be ready by around Monday the 21st, maybe sooner, then go for painting and probably be ready for the goodies to go in a week later. If everything goes smoothly I could get them around the end of the second week in August. Not to worry, though, you'll be one of the first people to know :-)
I'm going to go out on a limb and speculate the automotive paint finish will be a popular option even though it'll add several hundred dollars to the cost. It will be interesting to see how many people order the optional grilles. I did a design for them and sent Duke samples of some stuff to attach them to the cabinets. Also will have some nifty feet to put under them...relatively inexpensive but ridiculously effective.
Brian
So much music, so little time!
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