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20th November 2007, 09:14 PM  #2811  
diyAudio Member
Join Date: Sep 2006

Quote:
Hi Andy, Cool! I've also wondered about doing it with some kind of arrangement using triacs, but have not done it. Cheers, Bob 

21st November 2007, 02:40 AM  #2812  
Account disabled at member's request
Join Date: Aug 2005
Location: Toronto

Re: 2SK1530 and 2SJ201
Quote:
.SUBCKT 2SJ201 1 2 3 * Node 1 > Drain * Node 2 > Gate * Node 3 > Source *************************** .PARAM pi=3.1416 .PARAM Cgdmin=143p .PARAM Cgdmax=2677p .PARAM a=0.31548599 .PARAM B={(Cgdmin + 0.5 * pi * Cgdmax) / (1 + 0.5 * pi)} .PARAM C={(Cgdmax  Cgdmin) / (1 + 0.5 * pi)} M1 4 5 3 3 PMOS5 RG 2 5 1m RD 1 4 1m ;RD 1 4 0.198 DDS 1 3 DDS CGS 5 3 1414p GGD 2 1 VALUE={ if( V(2,1) < 0, {C * tanh( a * V(2,1) ) + B}, {C * atan( a * V(2,1) ) + B} ) * DDT(V(2,1)) } .MODEL PMOS5 PMOS ( LEVEL=5 L=2U W=0.5m ;+ EKVINT = 1 + cox = 3.6e4 + xj = 2e7 + vto= 1.72 ; threshold voltage, adjust this value at will + gamma=6 + phi=2.4 + kp=8.5e2 + e0=2.0e+11 + ucrit=2.67e+13 + dl=0 dw=0 + lambda=1.1305e5 + ibn=1.0 iba=0 ibb=3.0e8 + weta=0.0 q0=0 LK=2.9e7 + leta=0.0 rsh=0.0 ) ************************************************** ******************** .MODEL DDS D( N=1.55178 IS=2e8 RS=0.01 CJO=1544p M=0.4786242 VJ=0.423139 BV=200 ) ************************************************** ******************** .ENDS .SUBCKT 2SK1530 1 2 3 * Node 1 > Drain * Node 2 > Gate * Node 3 > Source *************************** .PARAM pi=3.1416 .PARAM Cgdmin=42.8114p .PARAM Cgdmax=1216.887p .PARAM a=0.31548599 .PARAM B={(Cgdmin + 0.5 * pi * Cgdmax) / (1 + 0.5 * pi)} .PARAM C={(Cgdmax  Cgdmin) / (1 + 0.5 * pi)} M1 4 5 3 3 NMOS5 RG 2 5 1m RD 1 4 383m DDS 3 1 DDS CGS 5 3 850p GGD 2 1 VALUE={ if( V(2,1) > 0, {C * tanh( a * V(2,1) ) + B}, {C * atan( a * V(2,1) ) + B} ) * DDT(V(2,1)) } .MODEL NMOS5 NMOS (LEVEL=5 L=2U W=0.5m ;+ EKVINT = 1 + cox = 7e4 + xj = 1e8 + vto=1.97 gamma=5.9999694 phi=3.4298218 + kp=7.95e2 + e0=2.0568449051e+11 + ucrit=2.6680517254825e+13 + dl=0 dw = 0 + lambda=1.1305e5 + ibn=1.0 iba=0 ibb=3.0e8 + weta=0.0 q0=0 LK=2.9e7 + leta=0.0 rsh=0.0 ) ************************************************** ************************** .MODEL DDS D ( N=1.5517725590608 IS=2e8 RS=0.009989 CJO=405.936p M=0.560182 VJ=2.403248 ) ************************************************** ************************** .ENDS 

21st November 2007, 05:50 AM  #2813 
diyAudio Member
Join Date: Jul 2007
Location: Central Berlin, Germany

Regarding my output stage idea, this morning I now see something that uses the same concept, a feedback loop that just holds the added voltage drop across both output emitter resistors constant. Nobody less than Bruno "UcD" Putzeys designed it (together with Sander Sassen), a really straight design:
ExtremA, classA strikes back? I need to study that in detail. And like I intend to do, they did it as a bridge design which I think is only of true benefit with class A. Seems I'm not on a completely false track...  Klaus 
21st November 2007, 08:50 AM  #2814  
diyAudio Member
Join Date: Apr 2003
Location: London

Quote:
that particular idea is quite old and was published by Allison in 1972 according to Ben Duncan's book: Cheers Alex 

21st November 2007, 09:36 AM  #2815  
diyAudio Member
Join Date: Nov 2003
Location: Amsterdam

Quote:
Also have a look at: E.M. Cherry, "A high quality audio power amplifier" in Monitor Porc. IREE Aust., Jan/Feb 1978, pp 18, and referred at in Electronics World, June 1997, p. 476. Cheers, Edmond. 

21st November 2007, 12:27 PM  #2816  
diyAudio Member
Join Date: Nov 2003
Location: Amsterdam

Re: Re: Re: Re: Re: Re: hec != hoax ?
Quote:
Quote:
See below how I've eliminated the distortion of the drivers. Admittedly, it's a quick and dirty solution by using CFP stages and current sources, but nevertheless it gives optimal results. Also notice that I've slightly adjusted the compensating caps so that the NFB loop in both circuits has the same Ft, 2.8MHz. For results, see next post. Cheers, Edmond. 

21st November 2007, 12:29 PM  #2817 
diyAudio Member
Join Date: Nov 2003
Location: Amsterdam

hec != hoax ?
(continuation)
The THD20 in ppm at various power levels into 8 Ohm 1.0W : HEC: 22.28 NFB: 22.17 10 W : HEC: 54.55 NFB: 54.88 100W: HEC: 60.27 NFB: 54.00 As one can see, not only the THD figures are almost identical, but also the gain and phase plots of both amplifiers (see below) closely match each other. I hope that these figures provide enough evidence that HEC is nothing more (or less) than NFB in disguise. Cheers, Edmond. 
21st November 2007, 02:03 PM  #2818 
diyAudio Moderator Emeritus

Hi, Edmond,
Very interesting What is the input and output impedance of each approach? 
21st November 2007, 02:16 PM  #2819  
diyAudio Member

Re: hec != hoax ?
Quote:
Hmmm. Too good to be true, almost. Could it be that what is limiting the THD levels in each case, is what the two versions have in common  i.e. the input emitter followers (Q2,3, Q20,21)? These are outside the hec loop as well as the nfb loop if I'm not mistaken. Jan Didden
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21st November 2007, 02:41 PM  #2820  
diyAudio Member
Join Date: Nov 2003
Location: Amsterdam

hec != hoax ?
Quote:
The input and output impedance are frequency dependent, so I hope you don't mind that I'll show you them at only 20kHz. Zi HEC: 2.17MOhm, NFB: 1.97MOhm. Zo HEC: 3.3mOhm, NFB: 3.6mOhm. At all other frequencies they are also almost identical. Cheers, Edmond. 

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