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Old 8th September 2011, 12:56 PM   #261
Elvee is offline Elvee  Belgium
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Quote:
Originally Posted by terranigma View Post
My concern is C3, coupling cap at input. My source has DC if it refers to ground, thus requires a cap at input of amplifier which is a compromised solution that I dislike -imho-. If I use balanced as source, then there is no ground referenced signal and there is no DC, then there is no need a cap in signal path.
You could try something like this.

It will short one output to ground in AC, but in your case this shouldn't be a problem.

The common mode range of the input is something like |Vs|-4V
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Old 8th September 2011, 08:11 PM   #262
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Quote:
Originally Posted by Elvee View Post
You could try something like this.

It will short one output to ground in AC, but in your case this shouldn't be a problem.

The common mode range of the input is something like |Vs|-4V
A discrete amp with balanced input! Although its other unusual features, this will be a great significant feature for me anyway. Maybe it is not opamp style but my aim is not related with this as you know.

Thank you for great support.

Last edited by terranigma; 8th September 2011 at 08:15 PM.
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Old 12th September 2011, 01:26 AM   #263
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Quote:
Originally Posted by wakibaki View Post
Attachment 225174

Attachment 225180

Attachment 225181



w

If you see anything else don't hesitate to point it out.
If there isn't any termal issue between Q1 - Q2 (Q4-Q3 in original schematic) PCB layout is very good but if they should positioned face to face, is it possible in this layout?

I think I tend to go with 2sc2240/2sa970's and populate parts on vero board. This is not related with current PCB layout.. just not being in a mood of making a pcb.

Regards.

Last edited by terranigma; 12th September 2011 at 01:41 AM.
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Old 12th September 2011, 12:30 PM   #264
Elvee is offline Elvee  Belgium
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Quote:
Originally Posted by terranigma View Post
If there isn't any termal issue between Q1 - Q2 (Q4-Q3 in original schematic) PCB layout is very good but if they should positioned face to face, is it possible in this layout?
Putting those transistors face to face is rather cosmetic: they themselves dissipate a moderate (~25mW) and strictly identical power, and on the board, there are no big sources of heat, therefore placing them side by side is quite sufficient.
You could wrap them in a common heatshrinking sleeve, but that's pure luxury.

Even if there is a one or two °C gradient between them, this will translate into 2 to 5mV DC offset at the output, and nothing else: the Circlophone circuit forces a balanced operation.


Quote:
I think I tend to go with 2sc2240/2sa970's and populate parts on vero board.
That's an excellent choice, and veroboard is fine, I made all my prototypes that way
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Old 12th September 2011, 02:02 PM   #265
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TO5 heatsink is sometimes right size to clamp a pair of TO92, not always.
I see size variations in TO92, usually deviant on the small side of normal.
I got some matched pairs that just fall out of TO5 heatsink.

This pair wouldn't fall out of a heatsink...

No time for sceenshot, my clearwire connection has been failing.
Uptime in minutes, when it connects at all... you might need a
library, search Duncan Amps. I'll bundle in zipfile later.

I want to change floating sense to Taylor, and tail to current mirror,
so I can set a threshold lower than 1 emitter drop, and determinism.
But serf circle becomes unstable whenever I try that arrangement.
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Old 13th September 2011, 09:13 AM   #266
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Why does it ring in clipping without 1 ohm or ferrite in floating sense?
How to change floating sense to Taylor without reversing feedback
of said resistor or bead. It goes crazy whenever I try...
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Old 13th September 2011, 09:33 AM   #267
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That was like the thirteenth attempt to post above. My connection keeps
getting dropped mid-post, while typing. I kept it short, though I shoulda
just typed offline, then quickly pasted. Anyways, thoughts I wanted to add...

The tOObage was merely plausible excuse to invert the input topology at
expense of CFP driver stage. There is no benefit Triode over JFET or BJT
when input impedance is only 10K, and Mu here has absolutely no function.
Plate held constant 30V doesn't bother 6DJ8 made for cascode operation,
but isn't showing us anything a solid state part couldn't do well or better.

Open loop gain is rather low, and drive current is too low for 4 ohm loads.
Both can be fixed by adding drivers back in. Would need to be Darlington
rather than CFP, if N type input stage is wanted with N type output...

I am interested if it is possible to sense one transistor in float, and the
other at the rail? That would enable possibility to cross real transistor
currents, rather than perceived currents at load. Which crossing would
be superior anyways? These crossings would never be same with N BJT
outputs, as bottom one wastes base current into the rail. The top one is
getting an assist from base to emitter and base bypass currents into the
load. Right now, I am crossing at center of Schottky currents, which is
not center of BJT currents...

Elvee's circuit is crossing emitter vs collector current, perhaps not in
exactly equal proportions. Is there some fudge factor built into the
Taylor voltage references at each rail to find the actual center? Note
the resistor at the bottom is only 1/2 that of the top, what was the
reasoning behind that?

Last edited by kenpeter; 13th September 2011 at 09:53 AM.
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Old 13th September 2011, 09:35 AM   #268
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Quote:
Originally Posted by kenpeter View Post
Why does it ring in clipping without 1 ohm or ferrite in floating sense?
How to change floating sense to Taylor without reversing feedback
of said resistor or bead. It goes crazy whenever I try...
Hi Kenpeter
the asc file is impossible to simulate due to absence *.inc file called in directives
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Old 13th September 2011, 11:32 AM   #269
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Generic triode
Generic pspice model dmtriodep.inc you need.
Or rip them out and replace with JFET, U309 seems to work...
Or rip them out and replace with BJT, 2N3904 seems to work...
Or rip them out and replace with MOSFET, 2N7002 seems to work...

Higher loop gain with substitutes may aggrivate ringing after clip.

Last edited by kenpeter; 13th September 2011 at 11:51 AM.
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Old 15th September 2011, 11:36 AM   #270
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Quote:
Originally Posted by Elvee View Post
If it is included in an amplifier having global NF, this will be implicitly realized.
.
Hi Elvee, Kenpeter!
back to xquad idea, you can use 4 IRF610 and input voltage 2V will not saturate irfs...
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