Pavel Macura's MOSFET Power Follower

[Jay]

Originally Posted by diegomj1973

The sound with my two way loudspeaker is wonderful.

Remove those LM7808 and LM7908 (replace with LM317 based regulator) and you should hear more wonderful sound.

I have never found any implementation where the LM7808/7908 IC doesn't hurt the sound, more so in a transparent/simple circuit like this.

[diegomj1973]

Hi Jay!
Thanks for your reply and advise!. I had thought about replacing LM7xxx by LM317 and LM337, but it happens that the LM337 will suffer a significant deterioration in its impedance and PSRR from the 2 or 3 KHz and more. (the PSRR can be as low as 30dB).
I want to implement the cascode CCS mode (with two units of the LM317, instead of using the LM337).

Can you advise me any other options?

Greetings

[Jay]

Hi Diego,

I don't understand electronics as well as you. Your schematic confused me. Are you sure that the regulator capable of supplying class-A amp current? What amp is this? What is the wattage? Are you sure you can get 0V at the output (direct coupled)? If so, I think this is an improvement, provided that the power supply is upgraded. I like chokes for this purpose.

[diegomj1973]

Originally Posted by Jay

Hi Diego,

I don't understand electronics as well as you. Your schematic confused me. Are you sure that the regulator capable of supplying class-A amp current? What amp is this? What is the wattage? Are you sure you can get 0V at the output (direct coupled)? If so, I think this is an improvement, provided that the power supply is upgraded. I like chokes for this purpose.

Jay:

The circuit is a voltage follower based on mosfet. Voltage gain is slightly less than 1. The circuit has current gain. LM317T regulator serves as a source of constant current of 0.5 Ampere. The circuit operates in pure Class A up to a maximum power of 0.95 watts (on an 8 ohm load). Currently I use it connected to the output of a CD player that delivers 2 V rms maximum, so the maximum output power at 6 ohms is 0.66 watts.
I have intentions of changing the constant current source for improved high frequency response. Would using two LM317 units operating in the cascode mode.

PS: Sorry for my English.

[Jay]

Originally Posted by diegomj1973

The circuit operates in pure Class A up to a maximum power of 0.95 watts (on an 8 ohm load). Currently I use it connected to the output of a CD player that delivers 2 V rms maximum, so the maximum output power at 6 ohms is 0.66 watts.
I have intentions of changing the constant current source for improved high frequency response. Would using two LM317 units operating in the cascode mode.

Is this a headphone amp? I think most headphones have higher than 8 ohm impedance? I'm not familiar and do not have experience with headphone amps...

And, are you sure you already have good enough analog amplification after the DAC inside your CD player?

[diegomj1973]

Jay:

I use this amp with normal speakers, I do not use it with headphones. My listening room is not very large. Its output power is more than enough for me. Could be used with headphones, but reducing its power output.

You can watch a recording I made on Youtube.

Search for "Common Drain MOSFET Amplifier. Pure Class A (part 1 ) ... to ... ( part 6)"
Grettings