Yes , phase splitter usually exist in Circlotron(Push-Pull) Power Amps.Sometime this is combination of input Gain stage and phase splitter together,Dual Differencial Cascode Gain Stage(Atmasphere Amps)
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Made a blonde moment.
Bridge 1 and 2 connected incorrectly!!
Now all ok and music omcing out of my test speaker on my first OTL
My god those 6080 get hot. I had no idea how hot!!!
I measured across the 5 ohm resistor and get 0.50 Volts.
So as I calculate 0.5/5*1000 = 100 mA through the 6080 on the circlotron circuit.
At about 90Volts across from the floating supply.
Is this correct?
Need to add a CF to the circuit and tweak the balance. I measured 300mV DC across the speaker terminals. Bit too much.
Bridge 1 and 2 connected incorrectly!!
Now all ok and music omcing out of my test speaker on my first OTL
My god those 6080 get hot. I had no idea how hot!!!
I measured across the 5 ohm resistor and get 0.50 Volts.
So as I calculate 0.5/5*1000 = 100 mA through the 6080 on the circlotron circuit.
At about 90Volts across from the floating supply.
Is this correct?
Need to add a CF to the circuit and tweak the balance. I measured 300mV DC across the speaker terminals. Bit too much.
Made a blonde moment.
Bridge 1 and 2 connected incorrectly!!
Now all ok and music omcing out of my test speaker on my first OTL
My god those 6080 get hot. I had no idea how hot!!!
I measured across the 5 ohm resistor and get 0.50 Volts.
So as I calculate 0.5/5*1000 = 100 mA through the 6080 on the circlotron circuit.
At about 90Volts across from the floating supply.
Is this correct?
Need to add a CF to the circuit and tweak the balance. I measured 300mV DC across the speaker terminals. Bit too much.
You beat me to it; I was about to suggest you hadn't crossed over the two power supplies properly! I made the same mistake when I built my circlotron (Alan Kimmel design). One channel worked fine when I first powered it up, but the other gave no sound from the speaker, just a faint tinkling noise from the output tubes themselves. And I had checked and rechecked all the wiring before I powered up! Anyway, I found the two negative HT wires were round the wrong way, and after switching them over, everything was fine.
Yes, OTLs do run hot! I've fitted cooling fans in mine, to keep the chassis temperature down a bit. But they are wonderful amplifiers...
Chris
Lol. This gave me a fright and ran for the off switch. The plates were pulsating!! Thank god nothing arched/exploded or whatever. At least the 6080 tubes are cheap.
I had 2 tubes running, I can't imagine the heat from a whole chassis full of them. No heating required in the winter!!
Now got a lot of work on this to do.
I want to try different front ends/tubes, speaker protection circuits. bias controls between rails as I am only using reference to ground at the moment.
Not sure if to use the simple phase splitter or a differential yet. Might try both. I heard a double differential gives more voltage swing and also positive and negative power rails give more swing but maybe more hum.
But very happy that the circlotron works on my first otl, at least through a tiny 0.5 watt 8 ohm test speaker!
with no fires/explosions/smoke.
I will increase the cathode resistors on the 6080 a little to >10 ohm I think.
Maybe in the the range of 70-80mA is on the safer side.
Chris
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Yes it is possible,but with two same Independent secodary,each secondary conected to own bridge rectifier,with NO conection anywhere to the ground.
One common mistake when measuring output power and/or distortion is to have the scope and signal generator grounded into the AC outlet. This can cause the ground lead of the scope to be at ground potential, shorting the speaker terminal to ground. Distortion will skyrocket.
Here ya go:
http://www.diyaudio.com/forums/tubes-valves/161112-what-tubes-tube-amp-3.html
You might want to read through these threads too:
http://www.diyaudio.com/forums/tubes-valves/168698-small-cheap-otl-schematic-needed.html
http://www.diyaudio.com/forums/tubes-valves/171035-circlotron-questions.html
http://www.diyaudio.com/forums/tubes-valves/168824-designing-otl-circlotron.html
Forgot to say next:Both secondary have to be conected in same maner to the Two bridge rectifier(`in phase`)this is important to avoid Hum in speaker.And second:You dont need phase inverter for Your Circlotron Amps if You have balanced signal from your Preamp(XLR)or from Your PC Soundcard or DAC,Than You need only decent input balanced Gain stage ,balanced Driver/Bias stage and output balanced bridge Circlotron stage.Good Luck
Using an unbalanced input.
Think I will construct a small pentode current sink on the LTP to get a more balanced output.
The cathode resistor didn't balance them sufficiently and I was getting some DC offset on the ouput through the circlotron dummy load.
I see now how symetrical the phases need to be.
Also blew 2 fuses and 1 small transformer in the process (one cold solder joint on the floating supplies diodes.
Sparks flew!!
Think I will construct a small pentode current sink on the LTP to get a more balanced output.
The cathode resistor didn't balance them sufficiently and I was getting some DC offset on the ouput through the circlotron dummy load.
I see now how symetrical the phases need to be.
Also blew 2 fuses and 1 small transformer in the process (one cold solder joint on the floating supplies diodes.
Sparks flew!!
Using an unbalanced input.
Think I will construct a small pentode current sink on the LTP to get a more balanced output.
The cathode resistor didn't balance them sufficiently and I was getting some DC offset on the ouput through the circlotron dummy load.
I see now how symetrical the phases need to be.
Also blew 2 fuses and 1 small transformer in the process (one cold solder joint on the floating supplies diodes.
Sparks flew!!
Circlotron output power stage are very sensitive to unequal(unbalanced) drive signal(rise the distortion quickly).Not sure what kind of topology You want to use for Input/driver stage,anyway You dont have to experiment to much beacose Mr Karsten(ATMASPHERE) allready published M60 OTL Circlotron here,and that OTL Amps is very simple and easy to build ,Everything what You need is allready there for Excelent sounding and reliable OTL Power Amps.BTW,behind that ATMASPHERE M60 schematic is over 30 year of proffesional expirience and development of that product.But if You want to made some experiment and try some another solution inside OTL Circlotron Power Amp design I respect that for sure.Good Luck
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Thxs banat.
Yes I'm using the circlotron concept and floating power supplies but experimenting with different input/driver sections. It's easy to copy someone's design but more fun to come up with something different/unique. (and you tend to learn much more this way).
The concepts are all the same but different topologies can be made.
I need to source some good powerful transformers for the floating power supplies I see now. That shouldn't be a problem here. Big step down transformers will do the job nicely. 300w-500+watt 110 volt trannies are easy to get hold of here due to the influx of 100v USA products and our 220v supply.
So we're looking at 1.9 amps - 3+ amps @ 110 volts un-rectified no?
500w/110v = 4.54 amps
loss after rectification = 4.54 * 0.7 : 3.18 amps.
Well,for output Circlotron power stage(8x6as7g)You need two separate secondary(galvanic separate!)with 110V/1,5-2A(2X) so step down Transf.of 350w min. to 500w max. well do the job for sure,(bigger trans-less heat/better sound dynamic).Here in Europa We have some advantage of 220V-240V~/50hz primary main voltage(less primary current,etc).Must say next:Atmasphere DC coupled(CF-bipolar suplyed) driver/ bias stage is Perfect to drive Circlotron output power stage of 6as7 grids in A/A2/ class and obtain Perfect sound and overall output stage stability,avoid nongalvanic(only AC)coupling via coupling capacitors beacose Sonically cant reach the quality of reproduced sound Never, peak output power too.I made some experiment with 4x 6c45p(triodes)for DC coupled drivers stages for Multiphase(four phase) 4x6c33c-b Circlotron output stage Amps and that work fine but OTL Multiphase Circlotron concept(topology)is totally diferent from M60 topology(classic two phase)and 6c33c-b tube is totaly diferent`Beast`from 6as7.only what You can modificate is input gain stage in case You have balanced source,since you dont have than stick with original M60 dual diff.cascode gain stage and everything well be fine.M Audio-audiophile 192 is OK PC soundcard(and not too expencive) which have balanced Output(3,9v pp), sometime I use that PC card to drive my Amps directly(balanced),so if You want to made some experiment...All the Best
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Thxs Banat,
Just a quick question. The resistors on the cathodes of the output tubes just serve to measure current flowing no?
Should be very low in the range of 1- 5 ohms yes so current is not restricted?
Also the 7.5 ohm and 0.1 cap between the positive and negative rails is the dummy load?
Just a quick question. The resistors on the cathodes of the output tubes just serve to measure current flowing no?
Should be very low in the range of 1- 5 ohms yes so current is not restricted?
Also the 7.5 ohm and 0.1 cap between the positive and negative rails is the dummy load?
Quick answer:Output stage(Circlotron)cathode resistor is there to made several things together:degnerative lokal feedback,beter matching of out power tubes(dynamic matching/ better load sharing/ to prevent effect of `dominant tube in the row`,value betwen 1-5,6 ohm per each kathode of 6as7 tubes is OK(I prefer 3,3ohm/5w).For DC offset measurment Is provided analog meter with asociated switches(steady Bias curent is fixed and non measurable in atached M60 schematic,but this cathode resistor voltage sag is the good place for individual tube bias check).7,5 ohm res.+0,1uf cap in parallel with Load(speaker) (output terminals)is actualy high pass cutoff filter since OTL Circlotron power stage goes easy flat to Mhz range,But that is OTL Amp Not the OPT Amp characteristic.
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Thxs again.
Yes all makes sense. Have to get some more resistors. Only got enough to test 2 tubes at the moment.
Got 5 x 6080's and 5 more coming in the post. Want to try 6AS7g's also, like the shape of those!!
Actually one of them is an RCA made in USA (others are all GE) and it was glowing a bluish colour during some testing.
I swapped that out as I didn't think it was usual.
Hopefully it's the former and not the latter!
Yes all makes sense. Have to get some more resistors. Only got enough to test 2 tubes at the moment.
Got 5 x 6080's and 5 more coming in the post. Want to try 6AS7g's also, like the shape of those!!
Actually one of them is an RCA made in USA (others are all GE) and it was glowing a bluish colour during some testing.
I swapped that out as I didn't think it was usual.
Hopefully it's the former and not the latter!
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It's the tube!
I think the Russian and Chinese versions of the 6AS7 tubes are more capable of sustaining high currents with relatively low plate voltages. The American versions (GE/RCA) are not really designed to do this. I think the Sylvanias are somewhat better, but hard to find.
Hope this helps!
Russian 6H13c is Ok tubes for M6o OTL too,6080 may cause problem if is variant with small grid heatsink.6as7g is ok tube for that M60 OTL.Very important thing anyway:Let the 6as7/6080 tube for PRECONDITION,only heater voltage turned ON without any other voltage aplied for one day and one night,that well prolong 6as7g/6080 life drasticly.I Must go now.Good Luck
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