Baby Zen amplifier

[renjiish]

dear nelson,
i want to make 5 watts zen amplifier using irf510,since i have excess irf510's in my stock.can you tell me what all changes i have to make in the circuits.i have one good quality 24v/4A transformer with me.with these two things can i make baby zen
renjish

[Nelson Pass]

Funny you should mention, I just built something like that
a couple weeks ago.

18 VAC secondary feeding a CRC (cap resistor cap) filtered
supply at about 23 volts, and what looks like the original
Zen circuit but with the 610 (510 will work just as well) on the
bottom and a 9610 P channel or 610 N channel current source,
and about a 1.2 amp bias.

The feedback network has much higher values (lower capacitance
on the Mosfet so it has a higher impedance) and the distortion
is a little higher than the original Zen, but it sounds good on
compression drivers. Clipping starts at about 4 watts rms, 8
watts peak.

It's a little anemic compared to the Zen, but the top end is
better extended, and its much kinder to source impedances.

I've worked up a version without feedback which has a .5 to 1
ohm resistor on the Source of the gain device, and it makes
a nice current source amp as well. If you have a Lowther or
Fostex, it would give you a chance to play in that sandbox.

If one of the locals here doesn't work you up a schematic, it
or something like it will show up on www.passdiy.com in a
couple months. The key thing is a well filtered supply - you
don't want the noise figure to compete with 4 watts.

[tomtt]

ben duncans amp-02 project showed truly advanced thinking
about noise in power supplys, yet i haven't seen any one
utilize such in diy(except for the amp-02)

[renjiish]

dear nelson
yesterday night i made this circuit and tested it,but without speakers.it was taking 1 amp bias current .power supply is not properly regulated.today i will test it with speakers.
what is your opinion about this circuit.please comment

[Nelson Pass]

Originally posted by renjiish
dear nelson
yesterday night i made this circuit and tested it,but without speakers.it was taking 1 amp bias current .power supply is not properly regulated.today i will test it with speakers.
what is your opinion about this circuit.please comment

I like to regulate my current source a little better, so I use a
(npn in your case) bipolar transistor to sense the voltage across
the Source power resistor, setting it at about .65 V. This is not
as simple as your circuit, but gives better regulation. You can
see it in the later Zen circuits.

After that, it looks like Bob's Your Uncle. Remember that this
circuit likes a low an impedance as seen by the Gate of the
gain Mosfet, so you try to keep the source and feedback
impedances as low as possible.

Also, if you tend to bias the gain device at a higher D-S voltage
you will get lower distortion at high frequencies, so add a couple
volts to the DC output voltage, and it will sound a bit better.

And.... this wattage on an IRF510 is pushing it, so be prepared
to heat sink this well, or lower the current, or get a bigger
transistor.

[renjiish]

Dear Nelson
Thank you for giving me such a nice advice
Yesterday I connected it to my speakers, the sound quality was very good especially mid and high’s, but there is lacking of bass and the volume is also very low. So I removed the feedback, volume increased little more.
Today I will try to do what you have told me. I will change the BJT to MOSFET as current source. But I don’t want to change the IRF510’s, since I have some pieces in stock.
Regards
renjish

[mastertech]

dear nelson
yesterday night i made this circuit and tested it,but without speakers.it was taking 1 amp bias current .power supply is not properly regulated.today i will test it with speakers.
what is your opinion about this circuit.please comment
--------------------------------------------------------
class A!!!!!!!

[moe29]

I was reminded of this "Baby SOZ" reading this thread.

http://www.passdiy.com/gallery/soz-p7.htm

They had a nice write up about the amp, but unfortunately their
provided link is dead now...

I did some searching, and dug up the page using the
Internet Archive Wayback Machine. Check out this link for a what
was archived if you're interested.

http://web.archive.org/web/200301050...la+anatomy.htm