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In Reply to: RE: schematic posted by tyu on August 19, 2011 at 09:29:14
The output transformer primary just hooks up where the speaker goes and the speaker hooks up to the secondary of the transformer.The same idea as Paul's Zero Autoformers only taken to an extreme.
http://www.zeroimpedance.com/Zero-New.html
Paul's autoformer is great, it just does not go far enough to load the tubes for real Class A operation. The 3 X hook up will make your 8 ohm speaker look like a 32 ohm load for the amplifier.
I hate to use the term extreme. It's not really. Loading 8 6as7g's in a Circlotron (Atma-Sphere M-60) circuit with 172 ohms is not extreme at all.
It's just proper loading for real Class A operation. It yields 42 Class A watts.If you remove 4 tubes per amp and load with 325 ohm you get 14 watts all Class A with very low distortion.
You will get less power, much less harmonic distortion and much better damping factor with a transformer.
I think a transformer winder like Heyboer could make any impedance you want.
Talk to Douglas (PakProtector) over in the Tube DIY forum about dealing with Heyboer.
The Freed transformer I'm using came from a Krohn-Hite amplifier with push pull parallel 6550's.
It has four identical primaries that I have wired in parallel and two identical secondaries that are wired in series. That's how I get to a 325 ohm primary with my 13 ohm speakers.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Edits: 08/19/11 08/19/11 08/19/11Follow Ups:
Interesting thing that Experience Electronics Germany 140W - A/AB Class , 6xEL34 Circlotron tube based Power Amp use the same 330 ohm Rkk primary OPT ( AP 634/2 ) impedance as yours rewired OPT transformer for yours 4x6as7g based OTL Circlotron Amp !
BTW , Circlotron cathode coupled OPT usually (and strictly ) need special ``split bobbin``coil configuration for EI typ of OPT to obtain the best Audio (electrical transfer) performance .
If you want to avoid your OTL Circlotron Amps to run in deep region of A2 class of operation but without to use impedance matching OPT , it is my personal opinion that it is better way to recone the single speaker with 330 ohm bobbin coil , or to use some line array loudspeakers configuration , with serial connected speakers of standard 8-16 Ohm impedance finally resulting in yours favorite non standard final high Z load impedance for yours OTL Cirlotron power Amps , running than only in A1 class of operation .
Best Regards
__
Enlightened Evolution-Astral Projection
Edits: 08/20/11
"Circlotron cathode coupled OPT usually (and strictly ) need special ``split bobbin``coil configuration for EI typ of OPT to obtain the best Audio (electrical transfer) performance ."I don't understand why a split bobbin would be needed.
I would think the best OPT for this would be a high nickel, parafeed (no gap) single ended transformer.
The only reason, I can see, to run into A2 would be to get more power.
I have 96db speakers and don't play that loud so power is not an issue.
Thanks for the link.
Stephens Trusonic had an OTL amp way back. They built a 500 ohm speaker for it.
The problem is a 500 ohm VC gets heavy.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Edits: 08/20/11
Reason for use the OPT ``split bobbin `` coil configuration for Circlotron output power stage is to get the perfect primary load symmetry & balance for both Circlotron PP output power stage phase , since the Circlotron topology use the whole OPT primary coil , not only the half of the OPT primary coil which is normal for classic based OPT tube PP Amp .
That`s mean equal OPT parasite capacitance & stray inductance for both half of the output Circlotron PP power stage & more important is to get minimum and Equal parasite capacitance between primary and secondary Circlotron OPT coils .
Usually there is no any DC flowing thru the Circlotron OPT primary coil ,so there is no appearance of switching transients ! , (accidentaly same as for SE parafeed configuration ), and central primary coil earth tap it is necessary only to get the ground reference point for driver stage unit & power stage bias , since the Atmasphere OTL Amps use two equal 600R resistors from each ``floathing `` speaker terminals conected to Amp star ground point for that , that is the reason why yours OPT CT don`t have to be grouded at all.
The best iron core for Circlotron output power stage it is not critical as for standard SE or PP based Amps ,and it is physically much smaller than ordinary PP OPT for the same projected output power , but in the same time it is with much wider both high & low Audio frequency ends response .
For low step up/down ratio request quality toroids finish the job 100 % , but for higher step up/down Circlotron OPT ratio the double C core iron with middle inserted split bobbin coil is far the best solution !
- Hi impedance VC is not heavier than low impedance VC ,since the high impedance coil is made of very tiny isolated Cu. wire ,this type of speaker it is ``excited`` with average relative high voltage signals from OTL Amp but with relative low average signals peak current for the same distributed power .
Friend of mine have reconed 12``/ 15W speaker with 2500 ohm VC !!!,``excited direct via condenser from 6l6 SET anode (parafeed), Sonic difference is huge compared with normal OPT based 6l6 SET ,and thats excellent system sound it is the normal appearance for pure tube OTL Audio !!! .
Best Regards
__
Enlightened Evolution-Astral Projection
Edits: 08/20/11
Back in the early 70s, I had a double pair of KLH9 ESLs wired in series and driven by a large home-made Futterman amplifier, using eight 6LF6s per monoblock. One wonders why I ever moved on from that, the point being that the series arrangement made for a nice load on the Futtermans.
Because Your Nuts! like most here at AsyLum.But you Are a Diyner so i say your ok.An you no what thats worth.....
I guess I'm not nuts in this sense, since I have hardly changed my setup since the eighties---NYAL OTL3 + Stax F83's. Someone suggested I should run the panels in series instead of parallel, which would be possible but not trivial, so I didn't do it. The only change I have made is to get some subwoofers, designed by Roger Modjeski, for which I am very grateful. On the other hand, I am nuts about Patricia Barber, having flown to Chico three times to see her at the Green Mill. I do admit to some terror about the future of my amps---I have some extra tubes, but who will bias them correctly when the time comes? BTW my NYAL amps are, I suppose, class B and have lots of feedback, but I like the way they sound and they don't run that hot. These are good facts, I think.
Thanks for all the great information.One thing...
"since the Circlotron topology use the whole OPT primary coil , not only the half of the OPT primary coil which is normal for classic based OPT tube PP Amp ."
In a normal Class A PP amplifier the whole OPT primary is used by each tube.
Only in Class B is the output primary use one half by one tube and other half by the other tube.
"The best iron core for Circlotron output power stage it is not critical as for standard SE or PP based Amps"
This is not true at all.
If there was concerns like DC being present, etc. then compromises are made.
When there is no DC present then there is no reason for compromises.
The best transformer has no air gap in the core and has a core made of the highest permeability allowable for the power level intended.
The signal source (when it's pure AC as in this case) is only part of the equation as to it's impedance.
The transformer is not going to know if it's being feed from a PP circlotron or single ended parafeed or differential coming from a single ended to balanced bridging transformer or differential output opamp or whatever.....
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Edits: 08/20/11 08/20/11
``In a normal Class A PP amplifier the whole OPT primary is used by each tube , Only in Class B is the output primary use one half by one tube and other half by the other tube.``
- Nope , this is not true at all ! Regardless to class of operation with the single source PSU connected to CT of classic PP Amp OPT each tube always use only one half of the transformer primary coil !
About OPT again :
Each type of tube Audio OPT it is one big compromise in itself !, even Circlotron OPT it is .
Some Amps topology just allow less OPT performance compromises , some Amps topology require more OPT performance compromises .
So the best Amps OPT it is actually No OPT at all , but just OTL !
Best Regards
__
Enlightened Evolution-Astral Projection
"- Nope , this is not true at all ! Regardless to class of operation with the single source PSU connected to CT of classic PP Amp OPT each tube always use only one half of the transformer primary coil ! "That is only true in the DC.
Let's take a pair of 300b output tubes with a common cathode bias resistor.
The AC signal path will only include the power supply (CT of OPT) and the common cathode resistor for the imbalance.
If the tubes were perfectly linear and perfectly matched there would be no AC traveling out of the CT of the output transformer or across the common cathode resistor at all.
Take a look at the differential (forced balanced) and parallel feed differential examples in the link below.
I have ran my Class A1 PP 300b amp with and without a cathode cap and hear no difference at all. Not at the levels I play them.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Edits: 08/20/11 08/20/11 08/21/11
Hi Tre` !Don`t want to abuse this respected OTL Asylum forum with OPT staff but ,Yours attached schematic from Mr.Lynn Olson tutorial on 2004 European Triode Festival presentation it is incorrect and can lead the reader to false conclusion that each tube use the whole OPT primary coil , or Raa load !
Here is my explanation :
Each Basic PP Amp is formed from two equal basic SE Amp joined together ,and need at least double separate SE OPT Ra primary coil load for normal operation ( 2x SE Ra = PP Raa ) .
Best Regards
__
Enlightened Evolution-Astral Projection
Edits: 08/22/11
You show loop one with positive polarity sinewave input giving no inversion on the plate output. That is an error.
You show loop two with negative polarity sinewave input giving a proper inversion on the plate output. This is correct.
So you diagrammed a cancellation instead of a double boost in output current.
One tube operating and one cut-off except for DC will have one tube energizing the whole primary through mutual coupling to the other polarity as in class AB operation. With both helping, the load is easier as in class A operation. Both work. They are however, in different operating points.
Mr. Kurt.s without my sincere intention to belittle or insult you !!! , but a You sure in that what you claim ?
Found that the present level of your ignorance and misinterpretation of basic phenomena inside of a simple tube PP Amp electronic circuit represented in my posted schematic it is incredible !
Best Regards
PS: Now I can clearly see the reasons why Mr. Karsten sometimes loses self-control and react emotionally when he has to deal with some ignorant people.
__
Enlightened Evolution-Astral Projection
This forum is your place to go to get all your ideas fucked up in your brain. Enjoy it.
Perfect!Let's look at your schematic.
If the tubes are linear then when the current increases in one tube, the current will decrease, by the same amount, in the other tube.
So the AC current flowing through the Power supply/common cathode node will be equal and opposite.
Equal but opposite current is the same as no current at all and the AC signal path will bypass those nodes and include the whole primary winding and the both tubes only.
If there is no net AC current through the cathode resistor/power supply node then we are left with one AC current loop just as Lynn shows.
The current loops you are showing are for the DC only.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Edits: 08/22/11
If we galvanic separate both B+ supply for both separate SE Amps joined together in one PP Amp via two separate equal OPT primary coil we should expect that yours `` AC power path flow `` well be interrupted , and this Amp well be out of function ,unable to operate , but no !, this separate B + Amp well work with the same performance as Amp from my first attached schematic regardless to class of operation , still having two separate DC current loops .
Only real AC power appears and flow on the OPT secondary coil via load(speaker),on the primary side of OPT AC power appears but only virtually ,being generated from pure PP DC current flow through the both primary loops.Best Regards
__
Enlightened Evolution-Astral Projection
Edits: 08/22/11
"Amp well work with the same performance as Amp from my first attached schematic regardless to class of operation , still having two separate DC current loops "That is not true for (at least) 2 very obvious reasons.
Now each tube is operating into 1/4 Raa instead of 1/2 Raa.
The cathode bypass caps are now 100% in the signal path and so are the power supplies.
This is not how a Class A PP amplifier works. In a Class A PP amplifier the power supply and the cathode resistor are only in the AC signal path for the imbalance. A small % of the total.
I can prove all of this with an oscilloscope.
Calculate the amount of DC current change that should flow from one tube being modulated at a given amount. Measure the actual amount flowing through an un-bypassed cathode resistor in a Class A PP amplifier.
The difference is the amount that the other tube is changing in the opposite direction.
The amount of DC current change that is measured is a measure of the imbalance in the circuit.
The "missing" current change is the balanced current that is flowing through the tubes and the whole primary of the OPT to the exclusion of the PS and cathode resistor.
You should read and understand what Lynn Olson has to say. He knows what he's talking about.Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Edits: 08/22/11 08/22/11
My next schematic describe one of the PP Amp type which Really use only half Raa of conventional PP Amp OPT primary coil , it`s anode coupled Circlotron , again two separate SE Amp joined together , sharing common Ra load and still having two separate DC loops , but now with opposite DC peak currents loops direction .``` You should read and understand what Lynn Olson has to say. He knows what he's talking about.```
Found that respected Mr. Lynn Olson interpretation , plot and fable of certain type of electronic circuit in some particular cases have no real life basis , and sometime it is just his personal free view with very speculative nature .
Think that this is my last post here related to non OTL staff , since this respected forum it is primary dedicated to OTL staff .
Best Regards
__
Enlightened Evolution-Astral Projection
Edits: 08/22/11
Instead to loosing my energy arguing , I collect the parts for my new Atmasphere based OTL Circlotron pure tube DIY Amps ,this time with projected modest 2x30W /32 ohm / A class , to play some Crystal Clear Music in my home ! 24/7 !
Mr. Karsten many thanks again for the excellent sounding power Amp design ever and for helping DIY !!!
Best Regards to all
__
Enlightened Evolution-Astral Projection
Install two resistors and remove the cathode bypass capacitor as shown.Drive the output stage with 1kHz.
Measure the AC voltage across each added resistor. Calculate the current.
Now measure the AC voltage across the cathode resistor. Calculate the current.
What happened to the missing current?
That missing current is not flowing through the common cathode resistor and it is also not flowing through the power supply.
It's flowing in a circle that does not include the common cathode resistor or the PS.
It's flowing through the whole primary of the OPT and the tubes and the added resistors.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Edits: 08/22/11
"Each Basic PP Amp is formed from two equal basic SE Amp joined together ,and need at least double separate SE OPT Ra primary coil load for normal operation ( 2x SE Ra = PP Raa ) ."It is true that a Class A PP circuit requires a primary 2 times the impedance that is needed for each tube.
In a Class A PP circuit both tubes are using the whole winding at the same time and the effect is that each output tube is seeing 1/2 Raa.
But in a Class B amplifier 4 times is needed. Each half of the primary winding is only 1/4 of the impedance of the whole.
This is a problem with Class A/B amplifiers. The load shifts as soon as one tube is no longer changing in an equal but opposite way.
As long as both tube are contributing in an equal way the load seen by each output tube is 1/2 Raa. When one tube cuts off (or reaches the non-linear "cutoff region") the load seen by the other tube is shifted to 1/4 Raa.
The same is true with a Class A/B OTL amplifier.
When one bank of tubes reach the non-linear cutoff region and stop contributing equally, the output impedance of the amplifier goes up and that would have the same negative effect as a load change in a transformer coupled amplifier.
In a Class B amplifier each tube always only uses one half of the primary winding and the two output tubes take turns. Each tube sees it's 1/4 of the total primary impedance and that doesn't shift.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Edits: 08/22/11
" Posted by Damir _the real one on December 2, 2004 at 09:40:51
In Reply to: I'm confused... did everybody miss this class posted by Gordon Rankin on December 2, 2004 at 07:03:25:
Well, I mathematicaly described 30:1 turns ratio SE OPT with CT secondary, see below. In short, you can connect one 4 Ohms speaker on the half of the sec., one 16 Ohms speaker across the whole sec., or two 8 Ohms speakers across both halves. In all cases, our tube on the primary will "see" the same reflected impedance and "gave" the same power. Well, let`s reverse the thing:
1.) We have, say 300 turns CT primary (150+150 turns), and 10 turns secondary. Turns ratio from whole primary to secondary is 30:1, or from halves of the primary 15:1.
2.) Let`s connect the speaker of 8 Ohms across the secondary. Then our reflected impedance to the whole primary is (30^2)*8 = 7200 Ohms.
Reflected impedance across the one or another half of the primary is (15^2)*8=1800 Ohms, or 1/4 of the whole primary.
3.) Let`s connect the tube, or better - for simplicity AC generator that gives 100Vrms no matter of load. We can connect the generator through the whole primary, Raa=7200 Ohms. Our 100 Vrms will give the power Ppr`=U^2/Raa=100^2/7200=1,3889W. That power is "transferred" to the secondary load. Usec is Upr/turns ratio, or Usec`=Upr/30=3,333Vrms, and power is Psec=Usec`^2/Rsp=3,33^2/8=1,3889W.
We can connect our generator across only the half primary, our generator "see" Raa/4=1800 Ohms, and gives power Ppr``=100^2/1800=5,555W. On the speaker - Usp``=100/15=6,667Vrms, Psp``=6,667^2/8=5,555W.
4.) Now, we feel like goin` PP, and connect two identical generators with 100Vrms output, but in antiphase. Connection - one wire from the each generator on the one side of the primary, then remaining two wires connect together and grounding (the same like with tubes). We can now say that we have two generators in series, in antiphase, connected on the primary, and each one gives 100Vrms.
When we measured AC voltage across our primary, we measured 200Vrms!
Now, Ppr```=200^2/7200=5,555W, and our Usec```=200/30=6,667Vrms, and Psp```=6,667^2/8=5,555W.
5.) The question is - what load each tube/generator in PP A class (both tubes working) "see"?
The Law of power conservation - Ppr=Psec. Every tube/generator gives half of the total voltage and half of the total power on the primary (and transferred to the secondary load).
Usec```^2/Rsp = Ugen1^2/Rload1 + Ugen2^2/Rload2
We know that Ugen1=Ugen2=100Vrms, we know Usec```^2/Rsp=5,555W, and we know that Rload1 = Rload2 = Rload1,2 = unknown resistances of the one and another halves of the primary in PP case.
Then we have: 5,555 = 2*(100^2)/Rload1,2 and
Rload1,2 = 20000/5,5555 = 3600 Ohms (half of the total Raa=7200 Ohms).
We can express this with turn ratios, the result is the same :
1/Rsec = 1/(Rload1*(Nsec/Nhalf pr1.)^2)+1/(Rload2*(Nsec/Nhalf pr2)^2)
1/8=1/(Rload1,2*(10/150)^2) + 1/(Rload1,2*(10/150)^2)
and from that Rload1,2 = 3600 Ohms.
6.) Summary and conclusion:
Reflected secondary load across the whole primary is the square of the turns ratio times Rsec, or in this case Raa=7200 Ohms. This load (7200 Ohms) "see" the tube connected across the whole primary.
When we connect the tube across the only half of primary, our tube "see" Raa/4, or in this case, 1800 Ohms.
When we connect two tubes in PP A class, each tube "see" half of the primary resistance, Raa/2, or in this case 3600 Ohms. "
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Banat
Don`t want to abuse this respected OTL Asylum forum with OPT staff
Dont even think about it, go on with info.Thanks for your time
I see sead the Blind man!No i get it an i have tryed the ZerO not for me but Lew i think uses them?
I think that "BAT" is setup diff,more like a two tube Kt88 pushpull output
i would like to see there Schematic,but that for your time
"An Keep Working the Problem"I can Dig that
The BAT VK-60 is a very similar circuit using a differential cascade voltage amplifier and a Circlotron output, driving an autoformer. The original prototype that Victor K. showed in several locations actually used an Atma-Sphere Z-Music autoformer that belonged to his partner, Steve Bednarski.
Thanks for your time RaLph own the BAT
Personally I've never had a chance to see the Victor K. - BAT VK60 - Circlotron circuit design .
But regardless to that I want to say next : With inserting of autoformer in Circlotron output power stage circuit that Amp immediately stop to be the pure DC Amp , + take in account some negative Sonic sides of autoformer iron .
Contrary to that situation yours Atmasphere Circlotron Hi Fi OTL tube Amps use the pure DC Amp output power stage design configuration ! , but Without using of any DC servo loops (usually traced via GNFB loop(s) ) to preserve OTL Amps output power stage DC stability !
That`s extremely rare !, even on the world of SS Hi Fi Amps designs .Best Regards
__
Enlightened Evolution-Astral Projection
Edits: 08/23/11
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