Perfect, The LME 49710 can be fed with up to 36v...maybe I need and extra psu for that or a voltage divider.... what is the voltage you normally use for Vcc in this circuit ?
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The circuit i build runs on only plus-minus 14V but i made a bridge with two amplifiers per channel.
I build it this way because Holger Barske wants to run this on solar panels.
The circuit is very tolerant on PSU voltage. Just make sure you do not kill the opamp.
I build it this way because Holger Barske wants to run this on solar panels.
The circuit is very tolerant on PSU voltage. Just make sure you do not kill the opamp.
This one looks impressive.
As the ops will run in class B I guess I can be shy with the heatsinks.... What do you recommend as minimum ?
Just one final question.... what is C6 for ?
As the ops will run in class B I guess I can be shy with the heatsinks.... What do you recommend as minimum ?
Just one final question.... what is C6 for ?
This one should be sufficient, even for both channels :
SK 47/75/SA
Yes, this amp is pretty simple but it sounds very good. The way it is done gives a very honest sound. With more idle you can make the sound slightly warmer.
SK 47/75/SA
Yes, this amp is pretty simple but it sounds very good. The way it is done gives a very honest sound. With more idle you can make the sound slightly warmer.
That is the classic Miller cap. It rolls of the open loop gain at 6dB octave.
Without it the closed loop amp would not be stable.
There are other ways like two pole compensation, TMC and similar that should have even less distortion but this solution here works well enough.
Without it the closed loop amp would not be stable.
There are other ways like two pole compensation, TMC and similar that should have even less distortion but this solution here works well enough.
This has been quite instructive.
I will now design the layout and post it here.
I must have all the parts in my stock 2SA1930 2SC5171 BC327 BC337 and the caps.... it will be a breeze 🙂
I will now design the layout and post it here.
I must have all the parts in my stock 2SA1930 2SC5171 BC327 BC337 and the caps.... it will be a breeze 🙂
thank you for pointing that out... indeed collector current is too low for the 2SA 2SC parts.... will need to buy some D44 D45.
Now regarding class B operation, How can I be sure I have enough overlap to minimize crossover dist ? I know feedback will smooth things out but is it possible the transdiodes are not enough to fully open the ops transistors ?
Now regarding class B operation, How can I be sure I have enough overlap to minimize crossover dist ? I know feedback will smooth things out but is it possible the transdiodes are not enough to fully open the ops transistors ?
Due to the lower Ft of the D44/45 parts you may need to enlarge C6 the miller cap. Experiment with 100p to 1n 🙂 if needed.
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It is possible to enlarge the PSSR by splitting the 12K (R5 current setting resistor) in 3k + 6k + 3k, then from the 3K-6K end 6K-3K connection add a capacitor (100~470u) to Vcc/Vss. To add all possible housekeeping, add a diode in parallel to the capacitor K to Vcc, A to 3K-6K and A to Vss, K to 6K-3K. These diodes will empty the capacitors when shutting down. The capacitors also will function as a soft start.
P.s. 3K(2.7K) and 6K(6.8K) will be fine.
P.s. 3K(2.7K) and 6K(6.8K) will be fine.
As i said, the structure of the output stage does not need much idle.
In Douglas Selfs book i found an optimum value of only 15mA.
So first build it and then measure the idle over the low value resistors at the output.
If the sound you get is too " monitor " like you can ramp up the idle up to 150mA.
Watch the cooling profiles not to get too hot.
In my build i used the D44/45 pair and the miller cap was big enough.
Anyway, as Frans said, you can raise the miller cap if you have stability issues.
That makes the amp a little bit slower though. My build goes aprox. to 200kHz -3dB.
In Douglas Selfs book i found an optimum value of only 15mA.
So first build it and then measure the idle over the low value resistors at the output.
If the sound you get is too " monitor " like you can ramp up the idle up to 150mA.
Watch the cooling profiles not to get too hot.
In my build i used the D44/45 pair and the miller cap was big enough.
Anyway, as Frans said, you can raise the miller cap if you have stability issues.
That makes the amp a little bit slower though. My build goes aprox. to 200kHz -3dB.
Found some D44 D45 power trannies in my stock... good... now I have an old Meridian 101 PSU that I would like to use in this project.... the output is +-35v so it is too much for the opamp.... can I use LM317 337 to feed the opamp at 18volts ?
What is 'super' about this regulator, why the zeners in parallel? what are the 1N4184's doing, are the BC's not a bit small for a soft start, or is there some other purpose (that I fail to see) 🙂
P.s. just have a look at the 317/337 datasheet/application-note and use that 🙂
P.s. on the input side use a pair of large electrolytic separated by a 10 Ohm resistor.
P.s. on the input side use a pair of large electrolytic separated by a 10 Ohm resistor.
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