Somebody explaining this design?

[Winfield Hill]

The scheme correctly "stiffens" the emitters of Q1,Q3, but
blows it by taking the outputs from the emitters of Q2,Q4.

The proper way is left as an exercise for the student ;-)

Perhaps you can spell it out for us.

There are other configurations, but this looks right to me,
for this one. Q2 serves to keep Q1's current constant, more
or less, as does Q4 for Q3. This means the changing signal
current, Vin/R9 (where R9 includes the variable part), goes
through Q2 and Q4, rather than the input transistor pair.
The input pair's nearly constant current means a nearly
constant Vbe voltage, hence the low distortion. I'd like
to see current sources in place of R2 R6 to improve CMRR,
and a maybe mirror for R4 R8, but this is a good start.

There's another scheme I like by Barrie Gilbert, but it
requires six transistors. I'm not sure it performs any
better at low audio frequencies.

 

[Jim Thompson]

Perhaps you can spell it out for us.

There are other configurations, but this looks right to me,
for this one. Q2 serves to keep Q1's current constant, more
or less, as does Q4 for Q3. This means the changing signal
current, Vin/R9 (where R9 includes the variable part), goes
through Q2 and Q4, rather than the input transistor pair.
The input pair's nearly constant current means a nearly
constant Vbe voltage, hence the low distortion. I'd like
to see current sources in place of R2 R6 to improve CMRR,
and a maybe mirror for R4 R8, but this is a good start.

There's another scheme I like by Barrie Gilbert, but it
requires six transistors. I'm not sure it performs any
better at low audio frequencies.

Barrie's scheme is an entirely different manifestation.

...Jim Thompson

 

[Phil Allison]

"Winfield Hill"

Sorry, Phil, I didn't see it. Rereading all 16 articles in
this thread, I still don't see it, where was your article?

** You * posted a link* to it.

But did not read it or see who it was by.

What a posturing ass you are.




........ Phil

 

[Phil Allison]

"Winfield Hill"

Oh, wait, sorry, now I understand: you wrote the article in
question in this thread, http://sound.westhost.com/project66.htm
Sorry, I didn't pay attention to the author's name, assuming it
was Rod Elliott at ESP.

** The second post in the thread says the article is one of mine.

You missed that too.

When did Elliott Sound Products take
your article and design, and how did that come about?

** A few years ago and none of your business.




........ Phil

 

[Phil Allison]

"Jim Thompson"

The proper way is left as an exercise for the student ;-)

** You are nothing but a colossal, pompous troll - Thompson

**** off.




......... Phil

 

[Eeyore]

Perhaps you can spell it out for us.

There are other configurations, but this looks right to me,
for this one. Q2 serves to keep Q1's current constant, more
or less, as does Q4 for Q3. This means the changing signal
current, Vin/R9 (where R9 includes the variable part), goes
through Q2 and Q4, rather than the input transistor pair.
The input pair's nearly constant current means a nearly
constant Vbe voltage, hence the low distortion. I'd like
to see current sources in place of R2 R6 to improve CMRR,
and a maybe mirror for R4 R8, but this is a good start.

Some designs do indeed implement constant current sources in place of R2 and R6.
I suspect it's relatively rarely done on account of the possible introduction of
extra noise generators although I've never totally satisfied myself about the
practical consequences.

There's another scheme I like by Barrie Gilbert, but it
requires six transistors. I'm not sure it performs any
better at low audio frequencies.

What configuration is that ?

Graham

 

[Eeyore]

"Winfield Hill"

** You * posted a link* to it.

But did not read it or see who it was by.

What a posturing ass you are.

....... Phil

Hey Phil, when's your competitor to the AoE coming out ?

Graham

 

[Terry Given]

Phil Allison wrote:




Hey Phil, when's your competitor to the AoE coming out ?

Graham

Bwhahahahaha! Excellent.

Cheers
Terry

 

[Jim Thompson]

Perhaps you can spell it out for us.

There are other configurations, but this looks right to me,
for this one. Q2 serves to keep Q1's current constant, more
or less, as does Q4 for Q3. This means the changing signal
current, Vin/R9 (where R9 includes the variable part), goes
through Q2 and Q4, rather than the input transistor pair.
The input pair's nearly constant current means a nearly
constant Vbe voltage, hence the low distortion. I'd like
to see current sources in place of R2 R6 to improve CMRR,
and a maybe mirror for R4 R8, but this is a good start.

There's another scheme I like by Barrie Gilbert, but it
requires six transistors. I'm not sure it performs any
better at low audio frequencies.

OK. Back from lunch and purchasing a new power supply for my PSpice
machine. Fan on the old one developed a bad case of the "grindies".

Now I would like to see a computation of the gain of this "marvy"
amplifier.

Win?

...Jim Thompson

 

[Jim Thompson]

On Sat, 10 Mar 2007 15:28:19 -0700, Jim Thompson

[snip]

OK. Back from lunch and purchasing a new power supply for my PSpice
machine. Fan on the old one developed a bad case of the "grindies".

Now I would like to see a computation of the gain of this "marvy"
amplifier.

Win?

...Jim Thompson

Wow! Amazing how-slowly increasing noise goes unnoticed until it
becomes a grind! Changed out the PS and the silence is deafening ;-)

...Jim Thompson

 

[Phil Allison]

"Eeysore = know nothing pommy charlatan and plagiarist."

Hey Phil, when's your competitor to the AoE coming out ?

** Win is not a "sacred cow" to be worshipped by adoring fools.

Just a posturing, self obsessed, boring old fart.

The final stage in the decline of a lives of all obnoxious narcissists.




........ Phil

 

[Jim Thompson]

On Sat, 10 Mar 2007 15:28:19 -0700, Jim Thompson

[snip]

[snip]

OK. Back from lunch and purchasing a new power supply for my PSpice
machine. Fan on the old one developed a bad case of the "grindies".

Now I would like to see a computation of the gain of this "marvy"
amplifier.

Win?

...Jim Thompson

Well? Anyone? Mathematical solutions only... no simulations please
;-)

...Jim Thompson

 

[Fred Bloggs]

"Eeysore = know nothing pommy charlatan and plagiarist."







** Win is not a "sacred cow" to be worshipped by adoring fools.

Just a posturing, self obsessed, boring old fart.

The final stage in the decline of a lives of all obnoxious narcissists.




....... Phil

The circuit is a primitive paradigm, it would have been a simple matter
to include feedback.

 

[Phil Allison]

"Fred Bloggs"


** I really thought someone had put bullet in this criminal fuckwits head.

Musta been dreaming.




..... Phil

 

[Fred Bloggs]

"Fred Bloggs"


** I really thought someone had put bullet in this criminal fuckwits head.

Musta been dreaming.




.... Phil

That will be over my dead body....

 

[Jim Thompson]

The circuit is a primitive paradigm, it would have been a simple matter
to include feedback.

Ehhh? It does have feedback. What do you think those compound
NPN/PNP's are? And the OpAmp has feedback around it.

Please compute the gain for me, Fred ;-)

...Jim Thompson

 

[Phil Allison]

"Jim Thompson"

Please compute the gain for me, Fred ;-)

** The overall gain is: 6.82 times 4000 / Rg

Where Rg is the total resistance between the two emitters.

6.82 is the fixed gain of the op-amp stage = 150 / 22.

4000 is the effective differential collector load - ie 4.4k with 44k in
parallel.

At low gain settings, the max Rg value is limited by the two 4.7k ohms.

At circa 1000 times gain, Rg is affected slightly by the effective emitter
resistance of the two 4403 compounds - about 4 ohms in total.

So, at max control setting the gain is:

27,280 / 26 = 1049

For 100 times gain, Rg = 272 ohms



........ Phil

 

[jure]

The scheme correctly "stiffens" the emitters of Q1,Q3, but blows it by
taking the outputs from the emitters of Q2,Q4.

The proper way is left as an exercise for the student ;-)

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice480)460-2350 | |
| E-mail Address at Website Fax480)460-2142 | Brass Rat |
| http://www.analog-innovations.com | 1962 |

I love to cook with wine. Sometimes I even put it in the food.

what I see is a differential pair of PNP Sziklai connected
transistors (AKA "complementary Darlington" ),
with a Pi emitter tail to the positive rail. Also, there is the
standard feature of the resistor parallel to the "BE" of the second
transistor of the darlington pair.

The differential pair is out of the feedback loop, introducing
offsets, etc.
what is the linear range for this pair ? => dynamic input range ?

would it be better to close the loop to the bases and have a fully
differential system.
Bartlett is my friend...(grin)

Jure Z.

 

[Phil Allison]

"jure"

The differential pair is out of the feedback loop, introducing
offsets, etc.
what is the linear range for this pair ? => dynamic input range ?

** Read the article - you fool.

" The stage has a gain of six or 15 dB and that sets the maximum input level
at about 1.5 volts rms before clipping. This equals an SPL of over 150dB
with a typical microphone! "




........ Phil

 

[jure]

"jure"




** Read the article - you fool.

" The stage has a gain of six or 15 dB and that sets the maximum input level
at about 1.5 volts rms before clipping. This equals an SPL of over 150dB
with a typical microphone! "

....... Phil

way to answer ????? attack ????

Jure Z.