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Old 29th June 2003, 05:23 PM   #21
Electrons are yellow and more is better!
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Andy and Sonny, thanks for your emails. Andy, 2 uF without overshoot or ringing, how many amps of ANY kind will manage this? Rather far from a difficult speaker.

I don't expect that CFA is substantially better than a VFA but it caught my interest. The headphone amp I designed was a complete "desktop product" and bam it worked. No instability or other bad behaviour.

I gather that much that a high power amp, CFA style, is much harder to make good.


BTW: What do you call a product which is only designed in a computer or by pen and paper and no part is tested before the pcb is made? The pcb is made and bam it works. In swedish desk = "skrivbord" =>"skrivbords produkt"

Sometimes "skrivbordprodukt" is a negative word. Things that are produced but they have not been developed too much....
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Old 29th June 2003, 06:40 PM   #22
andy_c is offline andy_c  United States
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Quote:
Originally posted by peranders
Andy, 2 uF without overshoot or ringing, how many amps of ANY kind will manage this? Rather far from a difficult speaker.
I see that you and I have the same tendency toward overkill . I believe it can be done.

Quote:
BTW: What do you call a product which is only designed in a computer or by pen and paper and no part is tested before the pcb is made?
I don't know of any English phrase that corresponds directly to that idea. There is a phrase that describes the approach of going bit overboard on the analysis side of things. It is "analysis paralysis". I've sometimes heard this phrase used by management types who don't completely appreciate what's required to get a product right the first time, especially when the requirements of the product are difficult. But sometimes this phrase can be right on target too...
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Old 29th June 2003, 07:05 PM   #23
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Default He may not know you........

But we do!

My experience with them for power amps is that eventually it became necessary to isolate the output with a series inductor.....a few nH worked. I think.....

Nothing we did in the output stage seemed to effect the way it measured.......distortion, bandwidth, slew rate, etc......blah, blah.

CFAs for amp or low-level stuff sounded the same, and while very good.....there was something odd about them. We abandoned them.

Have fun anyway.

Jocko
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Old 30th June 2003, 07:05 AM   #24
Electrons are yellow and more is better!
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Quote:
Originally posted by andy_c
I see that you and I have the same tendency toward overkill . I believe it can be done.
I like also nice step response and I will give it a try to achieve that but I also give it up when it's a clear overkill and I don't succeed...
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Old 30th June 2003, 07:25 AM   #25
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Hi Jocko,
Quote:
CFAs for amp or low-level stuff sounded the same, and while very good.....there was something odd about them. We abandoned them.
Ummm, what kind of odd, if you can put it into words.

Eric.
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Old 30th June 2003, 10:02 AM   #26
Electrons are yellow and more is better!
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Help... simulation guys!

How do I get a frequency sweep as plot with SwitcherCAD? I have messed around with a file which had it in the beginning. I get only time at the X-axis instead of frequency.

I notice also that the high impedance node is critcal and also the feedback resistor (all accordning to theory!)
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Old 30th June 2003, 10:24 AM   #27
sonnya is offline sonnya  Denmark
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you have done a transient response. You need to do an .AC like

.AC DEC [step] [start] [stop]

.AC DEC 100 100 100meg

for 100step/decade start=100Hz, Stop = 100MHz

Set "AC" voltage on your source to 1mV
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Old 30th June 2003, 11:42 AM   #28
Electrons are yellow and more is better!
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Does the SPICE model consider the variations of fT with collector current?

Using a Wilson current mirror doesn't add a thing compared to using a simple one. Is this really true in the real world?

Now I have located the choice of step analizes and sinus sweep. The program is not a wonder of user interface
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Old 30th June 2003, 11:49 AM   #29
Electrons are yellow and more is better!
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Default Re: He may not know you........

Quote:
Originally posted by Jocko Homo
CFAs for amp or low-level stuff sounded the same, and while very good.....there was something odd about them. We abandoned them.
Jocko, can you develop the "something odd", please?
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Old 30th June 2003, 11:55 AM   #30
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Default He's back!!!!

Good.....I can send the requests I get for simulation help to you, ol' buddy.

Per:

Not sure that any of the variations in current mirrors/sources made much difference. Except maybe in the realm of how likely they were to drift.

About the sound...........long story short......the dealers really hated the first product that we made with CFB. Nearly caused a full-scale revolt.

They complained about dynamics. Lifeless, unemotional, all that subjective stuff that drives us engineers crazy. One of them insisted that I buy a particular CD to hear for myself why he didn't like it.

I'll spare everyone the name of the CD, but let us say that I didn't like his CD and we parted ways.

Later, we developed a power amp with CFB, in conjunction with another company. I sent protos out for evaluation. Same complaints. Some were astute enough to figure out that it sounded exactly like that previous product that we made. And none had any idea either used CFB. Of course, they wouldn't know what CFB was anyway.

My buddy did market his version. I received calls from people who heard its debut at CES, and suggested that I talk him into not relaesing it. Same complaints.......
unemotional......uninvolving.....lifeless. Again, from people who knew nothing of its topology.

Any help? No......probably not. Best that I can do.

Jocko
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