Joe:
Here's a diagram of my exact test setup:
To be certain I wasn't being fooled by the scope, I connected a 22k resistor to ground (as pictured) and obsevred a 1 kHz square wave ground referenced. The result is identical to the floating output (between the drains of the fets) I must be missing something terribly simple. Also, I tried the circuit with and without the source resistors (just to be sure) to no avail. I'll check everything thoroughly (values, connections, etc.) and have another go.
Thanks again.
Mike
Here's a diagram of my exact test setup:
To be certain I wasn't being fooled by the scope, I connected a 22k resistor to ground (as pictured) and obsevred a 1 kHz square wave ground referenced. The result is identical to the floating output (between the drains of the fets) I must be missing something terribly simple. Also, I tried the circuit with and without the source resistors (just to be sure) to no avail. I'll check everything thoroughly (values, connections, etc.) and have another go.
Thanks again.
Mike
Mike -- From your test setup and reported 100 Hz rolloff, my best guess is that R21 and R22 are actually 220K ohms instead of 220 ohms. In addition, given the "open loop" topology you're using, R1 and R2 at 10K ohms also may be rolling off the HF too soon in conjunction with the diff pair input capacitance. I'd consider replacing them with 1K values.
I'm referring to circuit23.zip so we don't get confused. I get the gut feeling to disconnect the lower ends of R4 and R5 and run them to earth. Make R9 and R10 zero ohms.
One way to set the bias is to offset M1 and M2 gates a little negative but it will be very touchy. Probably unusable.
GP.
One way to set the bias is to offset M1 and M2 gates a little negative but it will be very touchy. Probably unusable.
GP.
Circlotron, Joe: I was thinking of using a modified current mirror in the LTP to control the output current along the lines of what Joe had suggested. I'll draw it up and show you what I mean. Not sure if it would work, but maybe worth exploring. Thanks for your recommendations. I'll try them soon.
Thanks
Mike
Joe: your guess about the 220k resistors is pretty insightful and would emulate the effect, but I've checked them. In your experience, are there any known problems with these experimentor plug-boards? I think Grey said that he built his Aleph-X on one and is not having problems.
Thanks
Mike
Joe: your guess about the 220k resistors is pretty insightful and would emulate the effect, but I've checked them. In your experience, are there any known problems with these experimentor plug-boards? I think Grey said that he built his Aleph-X on one and is not having problems.
Sorry Mike, I don't have much experience with plug-in boards. I use one occasionally, but generally prefer to go from simulation to PCB layout, as I think I expose more problems that way.
That said, as a service tech years ago I learned that common airborne pollutants can deposit a semi-insulating film on contact surfaces over time. So if your plug-in board or components have any age on them, I'd probably at least try cleaning and reseating the component leads. As you say, the problem does resemble a high impedance (film?) in series with the gates of the input pair.
That said, as a service tech years ago I learned that common airborne pollutants can deposit a semi-insulating film on contact surfaces over time. So if your plug-in board or components have any age on them, I'd probably at least try cleaning and reseating the component leads. As you say, the problem does resemble a high impedance (film?) in series with the gates of the input pair.
I have designed and built a two stage solidstate circlotron amp without any couplingcaps. It uses 2SK170GR in the input/feedbackstage and IRF 9530 in the outputstage.
Its only giving me about 14 watts a channel but with more heatsink and bigger transformers i could get 50-60 watts.
It souds way better than my zen version 4 i tried prior too this design.
Right now it has current feedback, but it is easely changed too supersymmetry feedback.
Its only giving me about 14 watts a channel but with more heatsink and bigger transformers i could get 50-60 watts.
It souds way better than my zen version 4 i tried prior too this design.
Right now it has current feedback, but it is easely changed too supersymmetry feedback.
I could not post the picture, but i have it on another swedish hififorum.
www.hififorum.nu/forum/topic.asp?TOPIC_=32287
www.hififorum.nu/forum/topic.asp?TOPIC_=32287
Small correction:
I said "hopefully the attached schematic works", what I meant to say is "hopefully attaching the schematic works".
I am thinking of designing and building a circlotron/susy soon.
I am thinking of using a balanced line zen type or reflected cascode front end, then drive a balanced circlotron output. Probably use local or global feedback. I'm shooting for 100 watts class A into 8 ohms. I'll try low power version first just to see if my ideas work.
I have a singled ended circlotron design idea using an aleph type current source. It is based on the Penultimate Zen circuit. I don't know if I'll build it.
I also have a design idea based upon the Bongiorno 4229706 patent. It uses CFB amps for the SuSy topology.
I'll post the schematics if your interested.
Tom
I said "hopefully the attached schematic works", what I meant to say is "hopefully attaching the schematic works".
I am thinking of designing and building a circlotron/susy soon.
I am thinking of using a balanced line zen type or reflected cascode front end, then drive a balanced circlotron output. Probably use local or global feedback. I'm shooting for 100 watts class A into 8 ohms. I'll try low power version first just to see if my ideas work.
I have a singled ended circlotron design idea using an aleph type current source. It is based on the Penultimate Zen circuit. I don't know if I'll build it.
I also have a design idea based upon the Bongiorno 4229706 patent. It uses CFB amps for the SuSy topology.
I'll post the schematics if your interested.
Tom
Thanx for the help whith the picture!
I would very much like to se yuor schematics. Im very intressted in designing and building circlotrons.
My current design is that on the picture, and it works very good.
Its a klass a/b design and i use 4 IRF9530 /chanel.
ts by far the best sounding amp i ever had. I will some day modify the feedback to susy-feedback and crank up the quisent current in both stages.
(Sorry my English sucks, but i hope you understand what i mean.)
I would very much like to se yuor schematics. Im very intressted in designing and building circlotrons.
My current design is that on the picture, and it works very good.
Its a klass a/b design and i use 4 IRF9530 /chanel.
ts by far the best sounding amp i ever had. I will some day modify the feedback to susy-feedback and crank up the quisent current in both stages.
(Sorry my English sucks, but i hope you understand what i mean.)
more circlotrons
Please excuse the hype on the schematic.
Note: I have not built or tested any aspect of this schematic.
The aleph section could be replaced with a ordinary current source or even a resistor.
A low power version or preamp could be built with IRF610's for example, with the aleph current source replaced with an ordinary current source.
A problem with this circuit would be the output offset voltage.
Of course these ideas come from tube circuits.
Tom
Please excuse the hype on the schematic.
Note: I have not built or tested any aspect of this schematic.
The aleph section could be replaced with a ordinary current source or even a resistor.
A low power version or preamp could be built with IRF610's for example, with the aleph current source replaced with an ordinary current source.
A problem with this circuit would be the output offset voltage.
Of course these ideas come from tube circuits.
Tom
Re: circlotron madness
circuit.
I think the outer ends of R8 and R9 should both go to the earthed junction of V3+V4.
Hmmm... the resistor Rx that connects U1- to U2- can't be left just floating and connecting two inputs; it will have to have some dc connection (even if via a high value resistor) to somewhere.
Also, what is the reason for R6/D1 and it's neighbour? I can sort of see what it is going to do but I can't see the reason yet.
Tom2, I think there is a drawing error in yourTom2 said:
circuit.I think the outer ends of R8 and R9 should both go to the earthed junction of V3+V4.
Hmmm... the resistor Rx that connects U1- to U2- can't be left just floating and connecting two inputs; it will have to have some dc connection (even if via a high value resistor) to somewhere.
Also, what is the reason for R6/D1 and it's neighbour? I can sort of see what it is going to do but I can't see the reason yet.
circuit errors
Circlotron thanks for asking.
The circuit is a very idealized representation.
Things like compensation and stabilty are not even addressed.
From what I understand of the circuit, at the quiescent point(no signal input, inputs at zero volts), the outputs across the load sit at zero volts with respect to the ground point of the voltage supplies V3 and V4 for the CFB amps(via feed back action of R2 and R3 or R4 and R5). Thus a potential exists across the resistors R8 or R9 equal to the voltage of V4, thus current flow from the output nodes to the negative supply terminal(V4) through each resistor is equal to V4/R8 or V4/R9. Since the circloton voltage sources (V1 and V2) and output transistors(Q1, Q2) form a closed loop, this current must come from the output of the U1 and U2, thus this is the base current for Q1 and Q2, thus sets the circulating bias current for the circlotron loop. The circulating current is thus equal to beta of Q1 or Q2 times current through R8 or R9.
The negative inputs are low impedance inputs of U1 and U2 because they are CFB amps. You might be right there should be resistors to ground. I was looking at the schematic in
http://www.diyaudio.com/forums/showthread.php?postid=129639#post129639
Post#8 in the Monolithic SuperSymmetry with Current Feedback thread for example.
Also resistors could be added from the positive inputs of U1 and U2 to ground if the inputs are left to float(as seen in other susy circuits).
I think???, the resistor, diode, R6,D1, increases the circlotron circulating current when the corresponding node goes positive with respect to ground. This prevents Q2 from cutting off(since Q1 is conducting more and Q2 is conducting less to force current through the load because of the amplifying action). R7, D2 does the same for Q1 for the "opposite cycle". I thought of leaving them out initially for simplicity. I'm still unclear about their operation
If mosfets are used for output devices then the biasing scheme is obviously different.
I like playing around with circuits in an abstract way, with sometimes no attention paid to if the circuit could actually be built, work or sound good. Sometimes sort of a copy, cut and paste
method to see if different ideas can be combined; not even completely understanding a circuit.
I have many ideas for susy circuits and susy-hybrid circuits.
Do people on this forum find "fuzzy" audio circuits like this one useful? -- or do circuits need to be more diy-able?
Tom
Circlotron thanks for asking.
The circuit is a very idealized representation.
Things like compensation and stabilty are not even addressed.
From what I understand of the circuit, at the quiescent point(no signal input, inputs at zero volts), the outputs across the load sit at zero volts with respect to the ground point of the voltage supplies V3 and V4 for the CFB amps(via feed back action of R2 and R3 or R4 and R5). Thus a potential exists across the resistors R8 or R9 equal to the voltage of V4, thus current flow from the output nodes to the negative supply terminal(V4) through each resistor is equal to V4/R8 or V4/R9. Since the circloton voltage sources (V1 and V2) and output transistors(Q1, Q2) form a closed loop, this current must come from the output of the U1 and U2, thus this is the base current for Q1 and Q2, thus sets the circulating bias current for the circlotron loop. The circulating current is thus equal to beta of Q1 or Q2 times current through R8 or R9.
The negative inputs are low impedance inputs of U1 and U2 because they are CFB amps. You might be right there should be resistors to ground. I was looking at the schematic in
http://www.diyaudio.com/forums/showthread.php?postid=129639#post129639
Post#8 in the Monolithic SuperSymmetry with Current Feedback thread for example.
Also resistors could be added from the positive inputs of U1 and U2 to ground if the inputs are left to float(as seen in other susy circuits).
I think???, the resistor, diode, R6,D1, increases the circlotron circulating current when the corresponding node goes positive with respect to ground. This prevents Q2 from cutting off(since Q1 is conducting more and Q2 is conducting less to force current through the load because of the amplifying action). R7, D2 does the same for Q1 for the "opposite cycle". I thought of leaving them out initially for simplicity. I'm still unclear about their operation
If mosfets are used for output devices then the biasing scheme is obviously different.
I like playing around with circuits in an abstract way, with sometimes no attention paid to if the circuit could actually be built, work or sound good. Sometimes sort of a copy, cut and paste
method to see if different ideas can be combined; not even completely understanding a circuit.
I have many ideas for susy circuits and susy-hybrid circuits.
Do people on this forum find "fuzzy" audio circuits like this one useful? -- or do circuits need to be more diy-able?
Tom
then they are forewarned.XCG's
Here are some more SuSy circuits. They use opamps. (I know---girlie chips)
I would call these circuits "inies" as compared to some of the Nelson Pass gain clone supersymmetry design "outies" (e.g. GC-SS-4a).
IMHO the XGC2 circuit also shows a possible way to modify (for example the GC-SS-2a), so the common mode signal input impedance does not look like a negative resistance.
Also something I found recently.
Look at US patents 6,741,129 and 6,717,467. High frequency stuff though.
Tom
Here are some more SuSy circuits. They use opamps. (I know---girlie chips)
I would call these circuits "inies" as compared to some of the Nelson Pass gain clone supersymmetry design "outies" (e.g. GC-SS-4a).
IMHO the XGC2 circuit also shows a possible way to modify (for example the GC-SS-2a), so the common mode signal input impedance does not look like a negative resistance.
Also something I found recently.
Look at US patents 6,741,129 and 6,717,467. High frequency stuff though.
Tom
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