SCA v1.2
Single ended Current Feedback Amplifier.
It could be done with various power supply voltages and bias cureents, this is just an example I`m testing and listening for months now..
No thump at start up (if all caps are disscharged). No noise or hum of any kind with sensitive speakers 97dB.
Some measurements in a few days.
Single ended Current Feedback Amplifier.
It could be done with various power supply voltages and bias cureents, this is just an example I`m testing and listening for months now..
No thump at start up (if all caps are disscharged). No noise or hum of any kind with sensitive speakers 97dB.
Some measurements in a few days.
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All "critical" resistors and compensation caps on proto could be changed quick, so I will experiment with values if you have any suggestions.
R208 is shorted and it could be some small value, up to 0.5 or 1R (with R205 value adjusted) for higher output impedance, or lower dumping factor.
For now it`s like in the schematic.
R208 is shorted and it could be some small value, up to 0.5 or 1R (with R205 value adjusted) for higher output impedance, or lower dumping factor.
For now it`s like in the schematic.
Why use low voltage MOSFET +jFET ? I used ssm3k339 alone.
NEW class A :Constant Current Push Pull amplifier with single SMPS and hybrid preamp
At 2ma , it has a Gm of 40mS vs 2mS.
NEW class A :Constant Current Push Pull amplifier with single SMPS and hybrid preamp
At 2ma , it has a Gm of 40mS vs 2mS.
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I'm not really shure, what you wanted to say? Input jfet is cascoded, 2SK932 it's a great part, but Vds is only 15V max. J112 is simple solution for cascode, giving constant, "floating" Vds for lower jfet, of about 2V7.
Output stage is half bjt CFP, like in Hiraga amps and another half is modulated mosfet ccs similar to FW amps. .
The sound is very nice, i'm currently listening only one chanel, mono (left and right speaker in parallel).
Btw, something interesting, power supply is a plain diode bridge and one 15mF elna cap, the circuit has decent PSRR. When speaker GND wire is connected to the power supply star ground there is a slight hum/buzz, with ears close to speakers, and with speaker GND wire, connected to pcb star ground, all that is gone and speakers are silent.
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I love it - this is a very nice looking amplifier schematic. I was surprised by the two pole compensation around one device - in that I've found in simulations that it's been necessary to use a compound (two device) VAS to be needed for full benefit from two-pole taken around it - but simulations is not an actual build which you have done.
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