Hi sonnya 😉
Yes and also input cap, some decoupling caps etc. Intention of this sch is to show basic principle more clearly, it is not final product sch.
Did you test TSSA first post sch yet? This feedback bridge doesn't have any injecting current, which imediately brings two benefits, thermal stability plus no modulation of injecting current, simply because it isn't present. 😉
Yes and also input cap, some decoupling caps etc. Intention of this sch is to show basic principle more clearly, it is not final product sch.
Did you test TSSA first post sch yet? This feedback bridge doesn't have any injecting current, which imediately brings two benefits, thermal stability plus no modulation of injecting current, simply because it isn't present. 😉
Aha thanks, missed them, were posted in between I wrote ... 🙂
Hej not bad at all considering four trannies only and to be symmetrical. Input BJT-s, splitted feedback bridge and biasing are working properly. Lowering distortions is a matter of more sophisticated schematic. 😎
Hej not bad at all considering four trannies only and to be symmetrical. Input BJT-s, splitted feedback bridge and biasing are working properly. Lowering distortions is a matter of more sophisticated schematic. 😎
No, it is not bad at all.
The same circuit could use njw0281/njw0302. With an higher idle in the input pair (10mA) and with good cooling it would be easy to do a class a amp with them also. Maybe even remove the collector resistors??!?!!! 😀
The same circuit could use njw0281/njw0302. With an higher idle in the input pair (10mA) and with good cooling it would be easy to do a class a amp with them also. Maybe even remove the collector resistors??!?!!! 😀
Why No DC Servo?
I think I will prefer the bipolar if the distortion is close. But how close? 😉
I'm curious why DC servo is not discussed with SSA circuits. It is hard to get a low THD without compensating other factors such as the DC offset (at least from simulation).
I will be building this TSSA but cannot yet decide on which circuit to build. Zero DC --> terrible THD. Good THD --> terrible DC.
I don't know what is the worse acceptable DC, 0.2 volt may be? But I think with such a simple circuit highish THD is okay, 0.3% may be?
I have tried a -0.2V offset with 0.02% THD (1kHz, 2V input sinewave, 2N5401/5551, tho low noise TR performs better). May be I need to aim for 0.1V?
I think I will prefer the bipolar if the distortion is close. But how close? 😉
I'm curious why DC servo is not discussed with SSA circuits. It is hard to get a low THD without compensating other factors such as the DC offset (at least from simulation).
I will be building this TSSA but cannot yet decide on which circuit to build. Zero DC --> terrible THD. Good THD --> terrible DC.
I don't know what is the worse acceptable DC, 0.2 volt may be? But I think with such a simple circuit highish THD is okay, 0.3% may be?
I have tried a -0.2V offset with 0.02% THD (1kHz, 2V input sinewave, 2N5401/5551, tho low noise TR performs better). May be I need to aim for 0.1V?
DC servo circuit cannot influence the distortion profile since it has the bandwith of influence of a few Hz or even less. Why we didn't put any effort on DC servo yet? Simply because there's no need, since the output DC fluctuations are within +/-50mV, of course if the input pair is thermally coupled. This DC offset at power amplifier's output terminals is none of practical importance, it is more cosmetic to have 0,5 mV here. For musical sources and preamps I agree, this value has to be below 1 mv.
Hi buzzforb 😉
TSSA schematic from post #1, built by sonnya, all together four transistors only and as you can see from the pics very promising results.
Attachments
That looks a great deal like one of my amps, although I think his is neater. I have one laterals and BC5XX, sp might as well
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no additional VAS please - the idea is simplest possible. To heck with THD, if it sounds good it is good 😀
Just my small contribution...
You prob already have a schematic but I enjoy it and it's late so it may be incorrect 🙂 !
Lazy cat mentioned that cap maybe beneficial so I assumed I could omit it for the neatness of my board please tell me if I'm wrong!
You prob already have a schematic but I enjoy it and it's late so it may be incorrect 🙂 !
Lazy cat mentioned that cap maybe beneficial so I assumed I could omit it for the neatness of my board please tell me if I'm wrong!
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I love it, such a simple pcb. Some thoughts...
a) make the pcb longer and cover the power devices, then screw through the pcb, through the power device into the heatsink. You can eliminate the separate pcb mounting holes.
b) are you sure you can get 2W rated trimmers of that size ? you may need a power resistor in parallel with a lower wattage trimmer
c) leave a little space between the caps
d) move the resistors a bit further away from the power device leads which will tend to want a fair bit of solder around them
IF I understand correctly, the extra cap helps ensure balance between the two feedback loops, which will minimize even order distortion. I don't think it's a big issue to leave it out.
a) make the pcb longer and cover the power devices, then screw through the pcb, through the power device into the heatsink. You can eliminate the separate pcb mounting holes.
b) are you sure you can get 2W rated trimmers of that size ? you may need a power resistor in parallel with a lower wattage trimmer
c) leave a little space between the caps
d) move the resistors a bit further away from the power device leads which will tend to want a fair bit of solder around them
IF I understand correctly, the extra cap helps ensure balance between the two feedback loops, which will minimize even order distortion. I don't think it's a big issue to leave it out.
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Who wants to minimize even order distortion🙂 Question. If paralleling a resistor with pot, you want the power resistor to be smaller than pot so that it takes the heat, correct
Why not?
I could easily do TSSA BIGBT HP since it is much simpler than SSA and potentially even better performer. 😎
Why not?
I could easily do TSSA BIGBT HP since it is much simpler than SSA and potentially even better performer. 😎
do it, doit, do it....
Marc
