As a comparison a 84dB sensitive speaker with 2,7 Ohm minimum would need 2 x 270W to sound as loud as my speakers with 2 x 3,125W into 8 Ohm.
Well Actually I do not know for sure that it cannot be done - perhaps some fancy design with distortion cancellation - that's beyond my range of knowledge but I'm interested to hear this opinion from an experienced professional designer.
For the simpler designs that interest me they always seem to sound better when biased at least into heavy AB. 500 - 1000mA.
Why use fancy complicated designs to try and eliminate something that simply disappears with higher bias. For me simple is best.
yes - good point
I saw a design by a guy called chater in a collected designs book where he used op amps to make sure the o/p transistor never turned off and it was supposed to sound very good - and I can imagine that it could be great.
Do we think lower high order distortion in higher bias designs is purely down to less switching noise ?
When running single supply and Constant current source this is correct. But if you run dual supply one will be constant current and the opposite site will modulate the supply.
The best way is to use a push pull stage in differential mode. This way the current from drawn from the output sinking will be added from the output sourcing. This way in theory the current draw in class A will be constant.
Optimum bias depends a lot on the gain step. with BJT it is very straight forward - 25mV drop across the emitter resistor.
For Mosfet we need to take in account what the gfs of the chosen mosfet is.
- Sonny
Even in non- switching you will have a steep roll of in the bias current. The faster the slope is (di/dt) -> more high order harmonics will be generated.
But if you can switch a mosfet really fast off and on and slew really fast from the point where one goes off and too the point where the other goes on you can reduce the harmonics a lot and be really green. (4 - 8 watt idle for an 50 - 100 watt @ 8R amp).
I think Mikelm knows what i mean.
The TSSA V1.5 is not perfect. I am the first one to say it!
But given the design rules that it should be simple and stable i Think it is a good compromise between performance and simplicity.
If i would make a version of it and not listen to what other thinks the AMP would twice as many parts and it would be All bjt design. But that is not the case here.
Still with twice the number of parts it would only be 2 stage design.
The present design Will maybe get changed resistor values and lower gain when i have completed the build and test.
But given the design rules that it should be simple and stable i Think it is a good compromise between performance and simplicity.
If i would make a version of it and not listen to what other thinks the AMP would twice as many parts and it would be All bjt design. But that is not the case here.
Still with twice the number of parts it would only be 2 stage design.
The present design Will maybe get changed resistor values and lower gain when i have completed the build and test.
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that was a great discussion - thx Sonny.
You seemed to confirm what I suspected but didn't really know for sure.
You seemed to confirm what I suspected but didn't really know for sure.
Not since yesterday where i asked you if it was possible to switch from 50+50 to 100+100, and gave you my adresse and friends name that will do paypal transfer for me.
Regards Marc
I don't think i have the TSSA V1.5 up and running before next week.
I have been lazy in ordering the 2SJ79 and 2SK216. 😱
I have been lazy in ordering the 2SJ79 and 2SK216. 😱