Re: lateral mosfets vs. bjts in audio amplifier design

[Eeyore]

Indeed. Its just about impossible to make a profit in "pro audio" now adays.
Too much stuff on the market.

Thankfully there are still a few areas with profit left in them.

Graham

 

[Eeyore]

No its doesn't. Its a push/pull class AB current drive to the mosfets, and
secondly, you don't need much. 20ma class drive is way more than enough for
at least 500w at 200Khz power BW.

I thought he was wrong about that. I confess I didn't look it up again at the
time but my 1200B does exactly the same as your approach Kevin.

Graham

 

[Eeyore]

Yes. Wafer probe.

That must be some fine machinery !

Grham

 

[Eeyore]

"Pro" audio design seems like an infinite chain of stolen circuits.

Only in China.

To reseach the issue fully would take you months full time.

Graham

 

[Eeyore]

0.01% IMD @ 20Khz/19Khz at all power levels. 1db flatness to 50Khz power BW.

I don't claim that this is necessary, but my take is that it is sufficient.
I won't buy a PA amp if it is say, 0.1% at 20khz.

As far as what I am interested in as a personal achievement goal, its
probably 0.001% IMD at 20khz, 1db flatness to 1Mhz power BW.

How about flatness in the audio band ?

Graham

 

[Eeyore]

Lets not kid ourselves, "all" circuits are stolen, whatever the field. Its
that simple. Show me *any* design, and I will show you a bit of is in a
prior design. Like diff pairs, current mirrors, cascodes, are all the same
building blocks we all use.

But these are simply 'prior art', not actually 'stolen'.

Coming up with a genuinely new configuration these days is increasingly
difficult, although the USPTO will probably still give you a patent on it !

Graham

 

[Jamie]

Jamie wrote:




You're the fool. You are nothing more than a disgusting piece of pig
excrement.

You're just jealous because you can't do it. Bloody typical of idiots.

LOL!!!

Right... now go back to your room before the hall police see you
wondering around..

 

[Eeyore]

Right... now go back to your room before the hall police see you
wondering around..

WTF are you babbling on about ?

You contribute nothing here except bad / erroneous / stupid and retarded
info.

GET LOST ! And stay lost !

Graham

 

[Eeyore]

Eeyore wrote

JF

Did you have something useful to contribute or were you simply dumbstruck by a very
simple question ?

Graham

 

[Eeyore]

---
Not true.

In the dim recesses of time, an idea flashed into being which was unique
and was fleshed out electromechanically into our being here, now, so
_that_ circuit wasn't stolen.

On a more mundane level, some of us work through the problems of design
without resorting to directly infringing the work of others, whether
that prior work exists or not.

Oh Good Lord, you mean you accept my work as original ?

Graham

 

[Jamie]

---
The hall police are responsible for bringing you to task for your
wandering around.

The mind police are responsible for bringing you to task for your
wondering around.

JF

I must be getting the same illness as you know who. Just hope I
still have some more years to go before I get as bad as him. Or I'll be
the next one wondering why I am wandering around and going no where!.


http://webpages.charter.net/jamie_5"

 

[Eeyore]

advantage.

That's certainly true.

Mostly.


Yours, maybe. Not mine. I hate to copy circuits, even my own.

Likewise. I was really pleased back in 1988 to design a new mic amp topology that
used twin feedback paths in order to handle signals over a 70dB range with a
single rotary control for gain that was close to dB linear. And the only serious
cost plus was dual gang pot in place of a single one.

Graham

 

[Eeyore]

You live in your own little fantasy world where you actually have
some value.

More than just 'some' my friend.

This guy just gave me a reference btw.
http://www.ibd-uk.com/members/jones-martin.htm

Look at his credentials ! A totally charming chap btw and we think very alike. We
worked on 2 successful projects (one of which I turned round from a 'runaway'
into a full blown commercial success) and stay in occasional contact to this day.
They were radar projects btw lest you think I only do audio.

Graham

 

[Eeyore]

More than just 'some' my friend.

This guy just gave me a reference btw.
http://www.ibd-uk.com/members/jones-martin.htm

Look at his credentials ! A totally charming chap btw and we think very alike. We
worked on 2 successful projects (one of which I turned round from a 'runaway'
into a full blown commercial success) and stay in occasional contact to this day.
They were radar projects btw lest you think I only do audio.

---
RADAR, huh?

Here's open-ocean PPI marine collision avoidance I was doing in 1972:

(View in Courier)

TX TRIG>------[MS1]---[MS2]----A
AND Y---A _ _____
RX VIDEO>-----[CLIP]-----------B NOR Y--+-->ALARM
+--B |
| _ A--+
+--Y NOR
B--+---O |
| |<-- SET
[R] O |
| |
GND +V

To start with, the SET switch is made, momentarily, causing the ALARM
signal to go false.

Then, the main bang triggers MS1, the RANGE one-shot, which triggers
MS2, the CAPTURE one-shot, on MS1's trailing edge.

In the meantime, clipped video is applied to one of the inputs of the
AND, the other input being connected to the output of MS2, so that the
AND's output will go true if there is clipped video and a high from MS2
on its inputs simultaneously.

When the output of the AND goes high it resets the RS latch made from
the two NORs, and the ALARM output will go low, causing an audible alarm
to sound, which will alert the RADAR operator (or whoever's on watch) to
the fact that an object has just been detected at the range set by MS1.
JF

Funnily enough, they were working on a new collision avoidance radar system when I was
at Kelvin Hughes. That wasn't my project though. I was working on new spec Rhine River
Radar intended for barges and the like using the Rhine (and doubtless other
waterways).

If you're interested I could explain what their problem was and how I told them the
answer from my bed in 30 seconds. That wasn't good enough though, so we had to make a
MathCad model to prove it.

Then they said - help us ! And I fixed it.

Graham

 

[Eeyore]

So you'd be happy with the -3dB @ 20Hz and 20kHz of the 60s and 70s ?

Graham

 

[Vladimir Vassilevsky]

Below 20 Hz sound is not audible, but you can feel the vibration,
(recently tried that),

Actually, the very low frequencies are only causing problems because of
rattling of everything around. For that matter, it is good to have the
steep highpass filter with Fc ~ 25Hz in the audio path. The very low
boom-boom usually happens at about 30..40Hz; there is little point in
going below that.

above 15kHz only the young can hear, above
20kHz only bats I think (and you perhaps),

The nonlinear mixture of 19 and 20kHz will produce the clearly audible
tone at 1kHz. If you want to be reasonably linear at 15kHz, then the
bandwidth should be extended well beyond the audible range.

then there is the speaker...
Looked for a nice electrostat few days ago, bit expensive though.
So, if I want hifi I use the Senheiser headphones.
And 3dB is easily corrected with a graphic equaliser no?
Better amps are wasted on me I am afraid.

PS
till how many MHz can YOU hear?

Not too long ago I had the ocsillation at full power in the amp with the
frequency about 40kHz. I felt that



Vladimir Vassilevsky
DSP and Mixed Signal Design Consultant
http://www.abvolt.com

 

[Eeyore]

Actually, the very low frequencies are only causing problems because of
rattling of everything around. For that matter, it is good to have the
steep highpass filter with Fc ~ 25Hz in the audio path. The very low
boom-boom usually happens at about 30..40Hz; there is little point in
going below that.

Depends. What's the lowest organ pipe note ? Even rock Bass guitar low E is
43Hz IIRC.

The nonlinear mixture of 19 and 20kHz will produce the clearly audible
tone at 1kHz. If you want to be reasonably linear at 15kHz, then the
bandwidth should be extended well beyond the audible range.

No question about it.

Besides, when young, I could 'detect' rather than 'hear' up to 24kHz. And
yes, I could hear bats too.


Or Beyer or AKG.


Graphics are crap. It's like trying a crappy way to fix something that's
fundamentally broken.

Graham

 

[Sjouke Burry]

So you'd be happy with the -3dB @ 20Hz and 20kHz of the 60s and 70s ?

Graham

As you cant hear the quality difference anyway,
why not???
Oh I forgot those people with VULCAN ears, who can hear
the difference beween oxygen content in cables.......
or gold plated mains sockets.....

 

[Eeyore]

Below 20 Hz sound is not audible, but you can feel the vibration,

You're not kidding.

(recently tried that), above 15kHz only the young can hear, above
20kHz only bats I think (and you perhaps), then there is the speaker...

I could hear 24kHz when I was in my early 20s.

Looked for a nice electrostat few days ago, bit expensive though.
So, if I want hifi I use the Senheiser headphones.
And 3dB is easily corrected with a graphic equaliser no?

Why an equaliser when suitable design removes the need ?

Better amps are wasted on me I am afraid.

PS
till how many MHz can YOU hear?

Don''t be silly.

Grham

 

[Eeyore]

As you cant hear the quality difference anyway,
why not???
Oh I forgot those people with VULCAN ears, who can hear
the difference beween oxygen content in cables.......
or gold plated mains sockets.....

Whilst your examples are inderd absurd, a flat frequency repsonse is not.

I work in pro-audio - you don't. I hear things you can't. To me you're simply a deaf ****
and competely irrelevant.

Graham