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Old 25th February 2012, 12:39 PM   #191
ontoaba is offline ontoaba  Indonesia
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@ Edmond
It need to be tweaked until drop voltage closest to sinewave. May be there is some differences in models, like 1N4148.
tina 4148: IS=1n, N=1.7, VJ=750m, MJ=330m, EG=1.11

@padamiecki
It is attached, but using spice level 3. A bit and more different, with level 1 that used in LTspice, but it is more accurate.

@kenpeter
Thanks for the concept, yes less quick in response and less stable but has better gain loop.
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Old 26th February 2012, 02:11 PM   #192
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Quote:
Originally Posted by ontoaba View Post
@ Edmond
It need to be tweaked until drop voltage closest to sinewave. May be there is some differences in models, like 1N4148.
tina 4148: IS=1n, N=1.7, VJ=750m, MJ=330m, EG=1.11
[...]
Hi Ontoaba,

I have tried the 'Tina' diode, but to avail. Frankly speaking, if the compensations depends that much on model parameters, I don't think that the way to go.

Cheers,
E.
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Old 28th February 2012, 10:11 PM   #193
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Yes, it need to be tweaked that will have different resistors value for different active devices, my sim circuit also can't reach what soulution do. But nonfeedback triple EF with low distortion and non switching is very cute.

Any news from AB2?
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Old 29th February 2012, 01:09 PM   #194
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Edmond, has the quad core (h bridge topology) been discussed in this forum before ??

Sorry for the offtopic but seems you have a much better memory than myself.
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Old 1st March 2012, 08:01 AM   #195
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@Ontoaba > Any news from AB2?
No news.

@Homemodder > quad core
Never heard of it, except from Intel.

Cheers,
E.
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Old 1st March 2012, 11:27 AM   #196
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Also known as h bridge ???

How about AD8047 ?? Another reference could be analog devices MT-056 tutorial, theres a patent too but Id have to look it up again.
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Old 3rd March 2012, 08:53 AM   #197
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Also known as h bridge ???

How about AD8047 ?? Another reference could be analog devices MT-056 tutorial, theres a patent too but Id have to look it up again.
Hi Homemodder,

Oh, now I see what you mean by 'quad core'. The Stochino amp has a quad-core input stage.
Please look here: The high slew rate design that time forgot?

Cheers,
E.
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Old 3rd March 2012, 09:51 AM   #198
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I should have thought of the stochino, I have one of those built, excellent amp. I dont think it quite operates like the quad cores thou, I must do some simulations of it.
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Old 7th March 2012, 09:59 AM   #199
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Default H-bridge

>I dont think it quite operates like the quad cores thou
Have a look at the R and C that 'bridge' the two tales together.

Also look here for another way to linearize the IPS:
John Curl's Blowtorch preamplifier
and here:
John Curl's Blowtorch preamplifier

Cheers,
E.
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Old 15th March 2012, 08:50 AM   #200
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Hi Edmond. I'm posting this for curiosity, I don't know how much it falls in the realm of so-called "improvements".

I simulated your ABII circuit with VN22xx/VP22xx driving C5200/A1943 (the FJP models from Fairchild are actually better than all the other models). I discovered that matching the Cgs of the complementary drivers caused their capacitive currents to cancel, partially. This current arising from the rectified half-sine base current of the output BJTs. Perhaps the remaining bump is a residual of gm-doubling appearing across C2/C3, and badly summing base currents.

I found the lowest distortion when the current through Q3 and Q4 (my schematic) was lowest (this may be for the non-cross-collector version). The lower current used in these transistors the more accurate the CCS and tempco stuff had to be, and of course it was an "approaching zero" thing. I had the idea of using the class-I circuit outside of a feedback loop, maybe as a bench audio-purpose buffer if not for listening.

When messing with my K-multipliers, I found the BC550C/560C to have the best low-Vce behavior (about 1.3V Vce), better than anything else I had access to. I recently found the BC327-25/337-25 (BC807/817) to be better, maybe the lower Hfe class would also be an improvement. In any rate I think quasi-saturation may be important here, it may screw everything up and it is not modeled in the simulator. I think small NXP BISS transistors may be good here, like the PEMZ7 and it's cousins (dual packages available). It should work really well at low-Vce. 15V max Vce, so horses for courses. It's like the 2N5769/5771.

Would it be beneficial to seek out BJTs designed for good log conformance?
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