Hawksford

Hi,

Thanh, do you mean Dr. Malcolm Hawksford?

Schematic of what, exactly?

Cheers,

I didn't know he had a book out. He was a lecturer of mine at university, and even back 30 years ago he was more than slightly eccentric. He seems to have got even more eccentric over the years.

He has come out with some innovative ideas in audio though.

Thanh,

I don't know exactly what you are looking for, but some of
Hawksfords publications are available on the net at
http://wes.feec.vutbr.cz/~gratz/Download/Hawksford.ZIP
(most probably illegaly, but the link has already been
published on this forum before).

This may help:

http://www.essex.ac.uk/ese/research/audio_lab/malcolms_publications.html

Werner said:

This may help:

http://www.essex.ac.uk/ese/research/audio_lab/malcolms_publications.html

Click to expand...

Wow! Thanks for that link, and thanks to Essex university for making the papers freely available.

thanh said:

I want to watch his cascode stage.But i like feedforward very much.Christer!You know!you are a intelligent man.Thanks you!

Click to expand...

Intelligent because I remembered and found a link that had
been posted on the forum before??? OK, I actually did find
that link myself by googling maybe half an hour or so before
somebody else posted it on the forum, but that hardly requires
much intelligencce either.

thanh said:

Oh!I don't know that site had been posted
Christer!Thanks a lot!

Click to expand...

I just happened to remember it. Although you could probably
have found it spending some time searching the forum, the
search function in general isn't good enough to find things
unless you know approximately what you are looking for
and often you need to remember who posted it to cut down
the number of results to a manageable size. Some people
think you no longer need a good memory when we have
computers and the internet. I have found it to be quite the
opposite, a good memory is very useful. In this case I
remembered who had posted the link. If I hadn't known
that, I probably wouldn't have tried searching for the post
just to be helpful.

At the same address you can find Cordell.zip file with very interesting article published by Robert R. Cordell in1984 (A MOSFET power amplifier with error correction)
The Cordell's power amp has following parameters:
P = 50W per 8 O
THD (20Hz - 20kHz) <0.001%
SR >300 V/ms
DF >5000
S/N 108 dB

Look at the post #5. There is an address with Hawksford's zipped article about correction of distortion in power amplifiers. When you replace Hawskford with Cordell, in address, you get the second mentioned article. I think that you should not copy Cordell's amplifier exactly, because it's from eighties, but you learn a lot about some ideas which are explained very well.

I have a very detailed app note published by Siliconix for a Mosfet output amp using Hawksford's error correction techniques.
It appeared in a very useful book that Siliconix produced in the 1980's about power Mosfets.

I could scan the article if anyone is interested.

No problem, there's another guy wants a copy as well. I'll scan it either tonight or tomorrow night.

The author of that app note is Cordell. The schematic is nearly identical to the AES paper he wrote.

Which I've posted here a few times before for folks reference- what the heck, why not once more?






and







You guys ought to listen a bit to why JC, CH, JH and others are "pushing" this "philosophy"- it's not becuase they think they're going to realize more commerical success if you accept the benefit of their experience for where you direct your efforts.

OTOH, in the spirit of "If you meet the Buddha on the Road, kill him", maybe you all need to get to your own level of knowledge the hard way- by spending quite a few years building different circuits and listening to them, then scratching your head when you don't like the way they sound (after the initial honeymoon wears off) and building new ones. I've been doing that myself since the mid 70's; these other guys variosuly longer or almost as long.

No reason any of you should take Charles or anyone else's advice or recommendations for a development direction and short circuit 5-10 years of experimental work. That would be too easy...

Do it the hard way, instead. Fight over semantics, go totally off topic. Ignore other people's experience. It's fun to watch.... up to a point.

You can learn more that way, too, if you're willing to actually make the effort and honestly build and compare a lot of alternatives, instead of deciding that only silver or only black chassis or whatever point you're fixated on can lead to audio nirvanna, and just build that. It will just take longer, if you repeat all the work of others that have preceded you...



DISCLAIMER:

I have known CH for almost 30 years, and as they say, I have a little insight into his character and integrity, and what a long strange trip it's been. I don't always agree with him 100%, but I very much respect the things he's achieved and the fact that his designs and efforts are putting food on the table and a roof over the head of he and his employees. It takes a lot more to make a successful small company with longevity than just a few interesting schematics and SPICE simulations of circuit's you've never built or listended to.

I built a high power variations on the Cordell circuits (some tweaks and changes to the input stage, and eventually a VERY different MOS output stage) 15 years ago; the final version sounded better than the reference copy I built of his AES paper circuit, and met my client's desires and requirements, but I wouldn't go down that road for myself.

Got something else in the works (actually, it has been for three years... Just have to find time away from work to finish the PCB layouts...

Regards,

Jon