MSSCF
Hugo, the difference in base resistors is interesting. Assuming that the pos and neg current of the opamps is equal, this means that the top and bottom output transistors need different base current for the same collector current, meaning they are not really matched. The difference is about 7mA base current for what was it, 320mA quiescent? Quite lot. Hmmm. What is the output DC of the opamps without signal? Probably 100mV or so pos?
Do you have any idea of the actual THD from this circuit?
BTW, if you say " 320mA across Rx", do you mean 320mV? That would give some 700mA consupmtion, not 1.32A
Bernhard, can you post a schematic of your design? I think yours is different, probably really "supersymmetric". Hugo, your circuit really is a bridge amp. Nothing wrong with that, just that the name is less fancy. It remains to be seen (heard) which gives better overall performance.
Jan Didden
Hugo, the difference in base resistors is interesting. Assuming that the pos and neg current of the opamps is equal, this means that the top and bottom output transistors need different base current for the same collector current, meaning they are not really matched. The difference is about 7mA base current for what was it, 320mA quiescent? Quite lot. Hmmm. What is the output DC of the opamps without signal? Probably 100mV or so pos?
Do you have any idea of the actual THD from this circuit?
BTW, if you say " 320mA across Rx", do you mean 320mV? That would give some 700mA consupmtion, not 1.32A
Bernhard, can you post a schematic of your design? I think yours is different, probably really "supersymmetric". Hugo, your circuit really is a bridge amp. Nothing wrong with that, just that the name is less fancy. It remains to be seen (heard) which gives better overall performance.
Jan Didden
Jan, look at post 220, this is it, just added pots to the 135ohm resistors to adjust offset.
But the offset doesnt matter anyway.
Currently I run it with inverted Ops but it makes no difference.
Speaker connected between the outputs.
Also see my sine wave post 218.
Re: MSSCF
To measure the exact positive & negative current of the opamp I would have to add some 1ohm resistors in their circuit.
So lets assume that current is ok. That means the transistors should be matched. They aren't for the moment.
The DC output from the opamps is 125mV.
If you send me a distortion analyser or know another way to measure the THD I can post it.
320mA = 320mA, not 320mV. This is about 300mV across the source resistors.
So the total power consumption is 320*4 = 1.28A. Together with the opamps this is about 1.32A nicely balanced between the two power supplies.
The schematic I used is originated by JH; I thought it was SuperS.
So, the only thing to do is cross the feedback resistors?
Bernard, please clarify your post #220. Who is "he"? and "yours"?
/Hugo - "And Whaaat Is He To You"
janneman said:
To measure the exact positive & negative current of the opamp I would have to add some 1ohm resistors in their circuit.
So lets assume that current is ok. That means the transistors should be matched. They aren't for the moment.
The DC output from the opamps is 125mV.
If you send me a distortion analyser or know another way to measure the THD I can post it.
320mA = 320mA, not 320mV. This is about 300mV across the source resistors.
So the total power consumption is 320*4 = 1.28A. Together with the opamps this is about 1.32A nicely balanced between the two power supplies.
The schematic I used is originated by JH; I thought it was SuperS.
So, the only thing to do is cross the feedback resistors?
Bernard, please clarify your post #220. Who is "he"? and "yours"?
/Hugo - "And Whaaat Is He To You"
Netlist,
"he" is Nelson and "you" are you and "mine" is me. See post 218.
I realized it too, that something was missing but it was too late to edit...
So I think your design is not supersymmetric because the current from the OPs does not flow from one side to the other, and feedback is not from the other side,
and my design might also not be supersymmetric because I have no feedback and my OP is not a currentfeedback OP.
Maybe it even sounds better without feedback 🙄
Guess what I have in mind
Raise power 
"he" is Nelson and "you" are you and "mine" is me. See post 218.
I realized it too, that something was missing but it was too late to edit...
So I think your design is not supersymmetric because the current from the OPs does not flow from one side to the other, and feedback is not from the other side,
and my design might also not be supersymmetric because I have no feedback and my OP is not a currentfeedback OP.
Maybe it even sounds better without feedback 🙄
Guess what I have in mind
Raise power
Bernhard said:
Guess what I have in mind
Raising power comes to mind now, thats true, but what about
trying to substitute the transistors with mosfets or darlingtons like Nelson suggested?
Can you capture Belgium Radio1 in Munich?
There is a wonderful saxophone (jazzband) playing tru my new amp 😎
/Hugo
Well, I guess I'll have to take a break from
taxes (March 15) and ponder what you've got -
I'll post something tomorrow.
In the meantime, keep experimenting!
taxes (March 15) and ponder what you've got -
I'll post something tomorrow.
In the meantime, keep experimenting!
Bernhard said:
🙁
😱
Remember who gave you the idea and have your good time.
I am on the way to the Class Exclusive. 😉
Thanks for the coffee, Hugo.
JH
JH, all I liked to say is, that it seems this small bias current is far too small and the circuit does not work classA anymore.
May be you also will find a different way to keep this going...
May be you also will find a different way to keep this going...
Netlist, one question is answered, your LM6181 is the one and only current feedback OP, so your chances are best...
Re: Re: MSSCF
Not wanting to split hairs, but the total power consumption is about 700mA since the same current that goes through the pos half goes through the neg half...
Jan Didden
Netlist said:
Not wanting to split hairs, but the total power consumption is about 700mA since the same current that goes through the pos half goes through the neg half...
Jan Didden
Bernhard said:Thanks, and again the one from me:
Do we have supersymmetry
Because in his circuit
> the feedback goes to the other side = different from yours.
> he did not split and ground resistor 19 = different from yours.
> he got feedback = different from mine.
> there should be current feedback OPs = different from mine ( and yours ??? )
Bernhard,
Are you sure the schematic is correct as posted? There seems not to be any control of the output nodes.
Jan Didden
Re: Re: Re: MSSCF
You are correct here.
/Hugo - Wonders how an artist can become a 'tax-man'..
Except from the 400mV offset at outputs, this amp performs great!Bernhard said:
janneman said:
You are correct here.
/Hugo - Wonders how an artist can become a 'tax-man'..
Ok, I got a pair of LM6181 🙂 from the coffee shop round the corner so maybe this is another chance.
Another
is to feedback the other side Transistor output to the noninverting input of the Op and also run the OP in noninverting mode.
so maybe this is another chance. Another
is to feedback the other side Transistor output to the noninverting input of the Op and also run the OP in noninverting mode.
OK, I have reached my first conclusion, which is that this schematic offered up earlier in the thread, will not work with only one input driven.
If the left input is driven and the right input is not, then the op amp on the right hand side will resist the current from the op amp on the left hand side in order to keep its - input at ground potential. As a result, we see that grounding the output of one side makes at least one half of the circuit work, but certainly not as intended.
Even if both inputs are driven, SuperSymmetric operation will not occur as the op amps will resist each other's errors in the same manner.
I turn now to the other arrangement with the + inputs driven, and I'll let you know what I get.
If the left input is driven and the right input is not, then the op amp on the right hand side will resist the current from the op amp on the left hand side in order to keep its - input at ground potential. As a result, we see that grounding the output of one side makes at least one half of the circuit work, but certainly not as intended.
Even if both inputs are driven, SuperSymmetric operation will not occur as the op amps will resist each other's errors in the same manner.
I turn now to the other arrangement with the + inputs driven, and I'll let you know what I get.
Attachments
Bernhard said:
What has happened her
Why rising the voltage to 24V?
Can't see the LM6181 in the circuit.
Did you build it? Are the 1.5k's there to limit the voltage across
the OP's?
Keep us informed from that coffeeshop 😉
In the meantime I made a mosfet version; seems to work fine on the sim. I'll post results when I build it.
One thing bothers me: Nelson agreed with JH about his circuit in
post http://www.diyaudio.com/forums/showthread.php?postid=133973#post133973 and post
http://www.diyaudio.com/forums/showthread.php?postid=136660#post136660 and never said it wasn't an X.
Now, my circuit is based on JH's and jan tells us that its a bridged amp????
post #221/Hugo – wants to build X
Also, I conclude that Bernhard's smoke circuits would not be X circuits as they do not have feedback from the output, and any errors generated by the output stage will not be reflected back to the other side, in fact, errors on the part of each op amp appear to be re-amplified out of phase, the opposite of cancellation.
To raise power.
Yes, it is the old one.
Niet.
First I will try feedback to +input.
If that fails, I will go on with the LM6181.
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