[PeterR]

Plugged it in, and to my great shock and surprise it worked right away

JFET input stage (2SJ109), AD797 for voltage gain, IRF610/9610 output stage (it's snowing outside and I'm cold, so they're running at 80mA bias).
RMAA measurements into 32 ohms (-101 dBA noise, 99.2 dBA DR, 0.0044% THD, 0.0096% IMD) are basically the same as for the soundcard alone (Delta AP2496). No nasties on the scope either, so it's time to think about a case

...

Update:
Finally managed to take pictures of the amp in the Par-Metal case:

Still on the to do list: those brass screws need to get black and the knob sits a little too far from the faceplate...

 

[Nisbeth]

Uhhhh, very nice!

/U.

 

[Glassman]

cool, schematics?

 

[Iron_Dreamer]

Looks neat, what is it?

 

[rsaavedra]

Sorry for my DIY naivete in electronics, but what type of amp is that Peter? Pimeta, ppa, something else?

In any case, it looks really awesome!

 

[morsel]

Looks promising, Peter. How do you like the sound? I've been champing at the bit to do a MOSFET output amp for some time now.

 

[PeterR]

Quote:

schematics?

See attachment, power supply is a standard LM317/337 job.
Quote:

Sorry for my DIY naivete in electronics, but what type of amp is that Peter? Pimeta, ppa, something else?

Something else

(hacked together by myself)
Quote:

Looks promising, Peter. How do you like the sound? I've been champing at the bit to do a MOSFET output amp for some time now.

Thanks. The most qualified comment I can make right now is "wow", I'll go into more detail once the new toy syndrome has worn off a little...

 

[Budgie]

Nice! Very sophisticated looking topology, too!

 

[aos]

Some of your resistor values in output stage are asymmetrical. Is it because 610 and 9610 aren't really complementary even though they're marketed as such? I think I remember they're not all that similar. Also, did you consider Hitachi MOSFETs?

Looks nice, both design-wise and implementation-wise.

 

[00940]

nice

What is that pot ?

 

[Nisbeth]

Quote:

Originally posted by 00940 What is that pot ?

Looks like an Alps "Black Beauty". Also known as the 40 mm, this is the Blue's bigger brother

/U.

 

[ppl]

Now there is a Person that believes in High Open Loop gain and lots of Negative feedback. I like the three transistors Current Mirror Or as some have called the Wilson Current Mirror. You might consider replacing R11 and R12 with Jfet Current sources. Nice Design.

 

[Voodoochile]

Nice sounds, and you can use it as a handwarmer!
Really nice, Peter. Looking forward to your further impressions as you get settled into it.

 

[PeterR]

Quote:

Originally posted by aos Some of your resistor values in output stage are asymmetrical. Is it because 610 and 9610 aren't really complementary even though they're marketed as such? I think I remember they're not all that similar.

Similar enough, most of the asymmetry is to force about 6mA current draw from the opamp.
Quote:

Also, did you consider Hitachi MOSFETs?

I did and probably will try them one day. This whole project started however with me looking at a pile of IRF610s and wondering what I could do with them (and it just took 10 dozen or so other parts to get rid of two of them, am I not efficient?

)
Quote:

Looks nice, both design-wise and implementation-wise.

Thanks

Quote:

Originally posted by Nisbeth Looks like an Alps "Black Beauty". Also known as the 40 mm, this is the Blue's bigger brother

Right, ALPS RK40.

Quote:

Originally posted by ppl Now there is a Person that believes in High Open Loop gain and lots of Negative feedback.

LOL, yes I know that's politically incorrect these days

But I'm not dogmatic about it, my Zen uses 16 dB or so feedback...
Quote:

I like the three transistors Current Mirror Or as some have called the Wilson Current Mirror. You might consider replacing R11 and R12 with Jfet Current sources. Nice Design.

Thanks!

 

[PinkFloyd]

wow Peter!

That looks like the skyline of New York...... awesome stuff! What are you going to case her up in?

Pinkie.