The Frugalamp by OS

[KLe]

ostripper, this is looking very nice ... what is the PSRR

[ostripper]

(see below)
OS

[Steve Dunlap]

Originally posted by ostripper


I didn't mean to point out a problem , but I don't want to be
a contributer to burning amps .


I've tried both including or omitting the diamond current
stage in the NFB loop with little effect other than ,with the
isolated current stage, no change with load. (As you pointed out.)

Another interesting note is that by degenerating the darlington
(470r - 2.2k) like a standard EF type 2, "tames" a little
bump at 5MHz (I think that is where this thing "likes" to oscillate)
and sets the phase margin.

I already did the carlos thing and no fire , so I know it works. I tested what would happen if my vbias died and it
is the safest I could imagine.. just 300ma (severely overbiased).
Idiot proof, much better than a typical amp. A total short at
the output would just burn the basestopper resistors.

It seems DIYaudio has gone "krill crazy" these days, even
carlos (no trashbin or buckshot) likes it, 3 seperate diamond
topology threads... you started it all ,steve, thanks!
BTW..., yours(krill) is most like the Nakamitchi 620, except they use an EF'ed diamond which is the thermal compensation .
(attached)
OS

Anything that contributes to the stability of the amp is welcome. I certainly have no issue with you pointing it out.

I haven't seen the bump at 5 Meg in the open loop design.

Audio Research placed the input pair on the hear sink for compensation in the solid state amps they released in the mid 70s.

I am glade I stirred up a little interest. I really appreciate the reception my design has received here.

[keantoken]

Hi.

Ostripper, have you come across Andy_C's models for the 2SC4793/A1837 devices? Andy hasn't seemed to put these up on his site yet so here they are. Also there's a link to his MJL spice models.

For anyone who hasn't gotten them yet.

http://www.diyaudio.com/forums/showt...83#post1656283

http://andycpublic.50webs.com/spice_models_1.htm

- keantoken

[keantoken]

Also, While I was looking at your schematic in post 699 I though of the Baker clamp.

http://home.mira.net/~gnb/audio/bakerclamp.html

Not exactly similar, but interesting.

- keantoken

[ostripper]

Thank you for the baker clamp link , I sucked the articles into
my pdF creator and cropped them so they will read nice.

I went to the Knoxville TN. Eagles concert and listened to 24
QSC 1KW amps. At first they sounded strained , later in
the show I saw the engineer "fiddling" with the board and
the sound became more to my liking.

Compared to my last concert , RUSH , in 1985 - albany, N.Y.,
with Altec lansings and 4.1 surround at 50KW+ ,the eagles
sound system "blew chunks". The performance was good,
considering the age of Henley and Walsh.

Dang ticket cost a fortune for a 3.5 hour show.(see below)
OS

[keantoken]

In your schematic you posted, what is R28 for?

- keantoken

[ostripper]

R28 was put in to reduce the gain of the vas, not essential,
I was just playing..

[jkeny]

Os If you get a chance I would recommend catching a Leonard Cohen concert - excellent value for money by superb musicians - memorable experience. Don't know what sound system was used but the sound was intimate in an open air venue which says a lot for the sound engineers.

Your amp has me intrigued - is the magic in the input stage or the whole circuit. I'm interested in an output stage only which my tube based input stage will feed.

You are using global feedback which I would lose so would there be much advantage to yours Vs the Krill output stage?

[ostripper]

is the magic in the input stage or the whole circuit

No magic, but the cfp inPut stage and holman (apt) based
front end is the best as compared to a standard topology.

The krill /nakamitchi diamond OPS has slightly better
distortion figures with global feedback but as Steve pointed
out it would go "open loop" if it burned out ,also NFB would be affected BY differences of loading on the output.

The sound of the diamond seems to be the same either
way as I have tried it.

The whole circuit is one of the best I've done both simulated
or prototyped. Only basic matching is desirable for the
diamond itself (ksa1381/ksc3503).
os