For a while I just thought the circlotron looked weird and overly complicated, but recently I have opened my mind and started taking a look at it. I just have a couple of points I wanted clarified.
1. I see a lot of people referring to this circuit as a 100% feedback arrangement (a cathode follower), but it seems that tying the plate supply to the cathode of the opposite tube would result in only 50% of the total plate swing being seen in the grid circuit, so it seems that drive requirements would be half of that for a cathode follower output stage or similar to a McIntosh style amp?
2. I just need an output transformer with half the turns ratio as normal to build one of these, since the entire primary is still driven when one tube cuts off?
1. I see a lot of people referring to this circuit as a 100% feedback arrangement (a cathode follower), but it seems that tying the plate supply to the cathode of the opposite tube would result in only 50% of the total plate swing being seen in the grid circuit, so it seems that drive requirements would be half of that for a cathode follower output stage or similar to a McIntosh style amp?
2. I just need an output transformer with half the turns ratio as normal to build one of these, since the entire primary is still driven when one tube cuts off?
1. Yeap !
2. Yeap !
The main drawback is having the two PSU "swinging" at signal rate . . . and in opposite directions !
You have to design them with lo capacitance between them and to ground, this includes the transformer windings.
If not, it's like adding few nanofarads between plates.
Of course, an OTL version driving a few ohms load doesn't care about even a full microfarad shunt cap
In short, Circlotron moves some problems from the OPT to the PSUT but in opposite direction: you MUST have an hi linkage inductance and lo shunt capacitance between HV secondaries and others.
Using two PSUT puts this inductances and capacitance in serie, better than nothing !
Yves.
2. Yeap !
The main drawback is having the two PSU "swinging" at signal rate . . . and in opposite directions !
You have to design them with lo capacitance between them and to ground, this includes the transformer windings.
If not, it's like adding few nanofarads between plates.
Of course, an OTL version driving a few ohms load doesn't care about even a full microfarad shunt cap
In short, Circlotron moves some problems from the OPT to the PSUT but in opposite direction: you MUST have an hi linkage inductance and lo shunt capacitance between HV secondaries and others.
Using two PSUT puts this inductances and capacitance in serie, better than nothing !
Yves.
Hi Yves.Must say this maintransformer two separated secondary capacitance have some `interference` only in old style Circlotron Tube Amp,with Tube rectifier PSU(EV for example),in this case each secondary have center tap conected to two,source`(oposite Circlotron cathodes),betwen two cathodes is Load(OPT),here some AC(sonic) power exist in main transformer secondary.1. Yeap !
2. Yeap !
The main drawback is having the two PSU "swinging" at signal rate . . . and in opposite directions !
You have to design them with lo capacitance between them and to ground, this includes the transformer windings.
If not, it's like adding few nanofarads between plates.
Of course, an OTL version driving a few ohms load doesn't care about even a full microfarad shunt cap
In short, Circlotron moves some problems from the OPT to the PSUT but in opposite direction: you MUST have an hi linkage inductance and lo shunt capacitance between HV secondaries and others.
Using two PSUT puts this inductances and capacitance in serie, better than nothing !
Yves.
But any way even here major AC(sonic)power travel thru Electrolytic Capacitor(Smoothing Filter)not thru main transformer(Here is Your missunderstading).With modern SS bridge rectifier we have two separated main transformer secondary(for two phase output balanced bridge) without center tap and when we use modern SS bridge rectifier only `inverse` capacitance is junction capacitance of each SS diode in rectifier bridge(40-80pf) in series with main transformer both secondary capacitance(resulting in minor comon mode capacitance).Remember AC(sonic)power travel thru the Output Power Tubes,Smoothing capacitor and Load.DC component only suply output Balanced bridge,To increase AC(sonic)power travel thru the each smothing Capacitor(and linearise fiter capacitor transfer characteristic and whole Amp) I always install SS clamp diode(UF5408) parallel with each two Smothing filter(electrolytic Capacitor),important thing is to keep SS bridge rectifier snubber blocks low as posible and conect both secondary in same manner to both SS rectifier bridge( this second is to avoid noise&hum).All the Best
Hi banat,
We don't speak about the same problem !
"Nanofarads" that usually appears between secondary windings of the same transformer are not hidden by any rectifiers unless you put a choke in serie with BOTH wires.
Of course, individual transfos improve the situation.
But I agree with the utility/necessity of some snubbers blocks.
Yves.
We don't speak about the same problem !
"Nanofarads" that usually appears between secondary windings of the same transformer are not hidden by any rectifiers unless you put a choke in serie with BOTH wires.
Of course, individual transfos improve the situation.
But I agree with the utility/necessity of some snubbers blocks.
Yves.
Thanks, Ives. I was pretty much sure I was right but had read in several places that it was 100% feedback, but didn't see how that could be true.
Zero Cool, I know it is not fashionable to say here, but if I were to build an OTL circlotron I would use transistors! I live in a warm place and don't need a space heater.
Zero Cool, I know it is not fashionable to say here, but if I were to build an OTL circlotron I would use transistors! I live in a warm place and don't need a space heater.
Tubes Circlotron(OTL)classA/AB sounds FAR Better than SS Circlotron (OTL)classA/AB.Heat delivery is Allmost the same for both and depends from bias class only(admit SS have no filament).Any way Circlotron topology is right choice(SS or Tube)for excelent sounding power Amp(I prefer Tubes).Good Luck
Here is old Electro Voice A50 Circlotron amplifier with 2x 6550,OPT primary 1,2Kohm,fixed biased near to class B(for long output tubes live).Specs are quit good for early 50`but for 2010 tof course PSU cood be much simplier with modern SS device(dirt cheap).Like the way of variable voltage/curent feedback in this Amps which allow to find optimum damping factor for diverse Load(speaker).For further info you can visit great Net site:Circlotron History Page . For pure OTL Circlotron Atmasphere S30 are good example,only 5x6as7 and 3x6sn7 per chanel(2x30w/8 ohm,2x45w/16ohm,overall feedback only 2db).For further info found thread on this site:`What Tubes For Tube Amp`(here Mr Karsten(Atmasphere) published M60 schematic)
f course PSU cood be much simplier with modern SS device(dirt cheap).Like the way of variable voltage/curent feedback in this Amps which allow to find optimum damping factor for diverse Load(speaker).For further info you can visit great Net site:Circlotron History Page . For pure OTL Circlotron Atmasphere S30 are good example,only 5x6as7 and 3x6sn7 per chanel(2x30w/8 ohm,2x45w/16ohm,overall feedback only 2db).For further info found thread on this site:`What Tubes For Tube Amp`(here Mr Karsten(Atmasphere) published M60 schematic)Still, interesting thought - full wave bridge rectifier, the actual transformer secondary is only 'connected' to the filter caps in the peaks of the secondary voltage waveform (conduction angle depending on current draw). If two such supplies were used for a circlotron, the secondary transformer windings see variable capacitance based on an intermodulation of the mains waveform and the output from the amplifier - in the peaks of the mains waveform, it's practically the true capacitance between windings/ground, whereas in other parts of the mains waveform these capacitances get charged and discharged through the various diodes. It seems to me that this would inject a rather hard to define portion of intermodulation products into the output - perhaps not overly significant if the capacitances between windings were kept low.
An alternative solution would be a pair of center-tapped windings with two diodes each for full wave rectification. Because each of the center taps represents one balanced output of the circlotron amp, the independent secondaries are always connected to the output signal and the capacitances may be much better defined, in particular if some care is taken to add electrostatic screening between windings.
Finally, a split bobbin or even better C-core or R-core transformer with electrostatic shielding may be used to completely separate the two windings physically. This way the capacitances the amp output sees would largely be towards the ground center point, a nice thick cardboard or similar separator can make these quite small, indeed.
Actually old split bobbin tehnique is always the best way to made Circlotron OPT(EI or C core trans or autotrans).This tehnique which is not complicate achive next:keep both OPT primary impedance,resistance,capacitance same,and keep betwen primary bobin kapacitance low.All The Best Ilimzn
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Any hollow state OTL is going to require a lot of finals in order to move the bigamps through the speeks. (Unless you can get those special, Hi-Z speeks originally designed for hollow state OTL use.) A pair of power MOSFETs can do that with ease, but VTs are not low voltage, high current devices.
I've looked at a whole bunch of possible types for finals, but those 6AS7 dual triodes always look the best. Since you get two triodes with each bottle, that's half the holes you need to make in the chassis.
Here is OPT(autotrafo) for that Circlotron Amp,Rkk-900 ohm,Split bobbin coil.Best Regard
Attachments
Feedback is up to you- you don't need a lot to make a practical OTL, even if its low power.
These days, if sonic performance is your goal, there really is no good argument for 4 ohms, as nearly all transistor amps (as well as tubes) sound better (for different reasons) on higher impedances: 8 or 16. OTOH if sound pressure is your goal and you have a transistor amp, 4 ohms can be more desirable. Although this would seem intuitive, I have found that many people confuse 'sound pressure' with sonic merit...
If you can run a 16 ohm load 4 6AS7G power tubes will get you about 35-40 watts. Higher impedance loads will cause the output section to run at a lower temperature as less power is dissipated in the tubes. Distortion will be lower too. But even with 4 power tubes, there is no call for a speaker load over 60 ohms; I've used 4 8 ohm speakers in series for 32 ohms and gotten a very clean 55 watts out of 4 power tubes, although to take advantage of the higher impedance load I boosted the B+ on the power tubes to nearly 200V (obviously the amp was not class A either).
IOW there is a lot of flexibility once you get your head around the idea that it is possible, practical and reliable.
300wpc Circlotron
I hope you do not mind I have some questions on my HUGE and i mean huge mono blocks..the amp was configured with a 12ax7 voltage gain.. to a 12bl7 driver bootstrapped etc...I thought the amp sounded slow... kinda weird but..anyways I decided to mess around ...did some experimentation on just using the 7199 driving a interstage ..... that did not work. and i dont have a schematic so ...what i am asking ... can someone help me design a good sounding front end to drive the 4.. 2 parallel 6n45c tubes per chanel.....did i mention this thing is a monster!...
Thanks for your help
I hope you do not mind I have some questions on my HUGE and i mean huge mono blocks..the amp was configured with a 12ax7 voltage gain.. to a 12bl7 driver bootstrapped etc...I thought the amp sounded slow... kinda weird but..anyways I decided to mess around ...did some experimentation on just using the 7199 driving a interstage ..... that did not work. and i dont have a schematic so ...what i am asking ... can someone help me design a good sounding front end to drive the 4.. 2 parallel 6n45c tubes per chanel.....did i mention this thing is a monster!...
Thanks for your help
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