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Old 11th December 2005, 03:02 AM   #41
jcx is offline jcx  United States
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a quick sim of a "half cell" suggests a fair amount more gain can be had by using a cfp for your follower - mosfet bias permitting, but probably hopelessly complcates overload behavior
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Old 11th December 2005, 04:50 AM   #42
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Hi jcx,

A CFP instead of the BC546C? The gain's huge already, believe me.



" probably hopelessly complicates overload behaviour" - as it is I've had to put in a clamp diode to stop the base collector forward biassing and switching on the MOSFETs at clipping on the off cycle.

Cheers,
greg
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Old 15th December 2005, 04:00 AM   #43
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Just as a matter of interest I decided to sim my design with a Leach cascode front end (pictured below) to check for PSRR. This can be compared with my cascode front end at post 40 -

http://www.diyaudio.com/forums/showt...965#post786965


Cheers,
Greg
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Old 27th December 2005, 12:41 AM   #44
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Well Hi all,

Between festivities and libations I decided to build a new piece of test equipment to test my amps - a 10KHz tailored impedance square wave generator. I needed one which had sufficiently fast rise time and worked into a capacitative load, so I could bypass the Rinput filter and test closed loop character. A very fast rise time better stimulates the UHF character of an amplifier.

Spec : 10KHz, rise time < 400nS , fall time < 100nS. Zout 47R //1000pF.

Here is the GB300D with it's output . no 160KHz input filter.

Cheers,
Greg
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Old 27th December 2005, 01:19 AM   #45
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Greg top performance mate! you should publish it at stereophile.com

happy festive season mate
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Old 27th December 2005, 01:39 AM   #46
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I think not mastertech,

Interestingly the rise and fall times are virtually those of the square wave generator... so I guess I'll need to do an even faster one.

That's the trouble with building really fast amplifiers, in this case full gain bandwidth >5MHz, is that your equipment has to be upgraded as well.

Perhaps I should stick to ordinary amps in pretty boxes and high bias reviews. Real challenging stuff. Then find some marketing person to shout how wonderful it is - without even hearing it ???

Cheers,
Greg
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Old 27th December 2005, 05:16 AM   #47
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Home sweet home

What is the V/DIV on your picture Greg? Without it seems difficult to ***** the result!

5V/div??

\Jens
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Old 27th December 2005, 05:41 AM   #48
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Hi Jens,

When I cropped the photo I left in the V/div selector. 1V /div.

It's roughly 1W. The sq wave gen's just a lashup at present. Needs a box, connectors and a pot for functionality.

Cheers,
greg
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Old 27th December 2005, 06:00 AM   #49
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Quote:
Originally posted by JensRasmussen
Home sweet home

What is the V/DIV on your picture Greg? Without it seems difficult to ***** the result!

5V/div??
Jens, you can actually see the knob at 1 V/div. Check the black stripe on the knob.

Greg,
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Old 27th December 2005, 07:46 AM   #50
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Quote:
Originally posted by amplifierguru
Hi Jens,

When I cropped the photo I left in the V/div selector. 1V /div.

It's roughly 1W. The sq wave gen's just a lashup at present. Needs a box, connectors and a pot for functionality.

Cheers,
greg

I know, I was unsure about the x5 botton......

I often use a x10 probe, I thought that you might do the same

How about a rail to rail pic?

\Jens
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