mikeks said:
Actually the output inductor is a bandaid. If one can build a stable amp without the need for it and produce them in production volumes (inspite of all of the variations) , I say this speaks for itself.
There is a level of knowledge gained from years of actually living this stuff that is evident in everything John says. Chose to discuss or argue; the pursuit of knowledge is a personal thing.
One other point. Any impedance stores and releases energy back into the signal path in very complex ways (they perform their function through interference). Thinking that a coil or capacitor disipates (or somehow just makes the energy it's filtering go away) is simplistic. To think that you insert a coil in series with the output and the effect is benign is interesting, even if your dealing with "textbook perfect" devices.
I've looked at the Halcro picture a number of times and I get the feeling there is quite a bit of religious engineering going on there. Which is fine, but luckly they are in a market segment where only a limited number of people can scrutinize their success or near misses.
Mike.
Nothing special, rather low actually. I use more than 60dB in my designs and they are quite reliable, even drive ES speakers.
Output inductor is 1.4uH, damped by 10R, with 10R/100nF Zobel.
I endorse Mike B's comments strongly. You can't beat decades of experience in the field. I do not understand the 'stand and deliver' attitude against John; we should all try to be more respectful.
He's been in the business of technology + sales; throwing up one less than perfect result of torture testing from years back is not very productive if done as a mortal challenge.....
Hugh
Output inductor is 1.4uH, damped by 10R, with 10R/100nF Zobel.
I endorse Mike B's comments strongly. You can't beat decades of experience in the field. I do not understand the 'stand and deliver' attitude against John; we should all try to be more respectful.
He's been in the business of technology + sales; throwing up one less than perfect result of torture testing from years back is not very productive if done as a mortal challenge.....
Hugh
well stated, hugh.
h*ll, if i was jc, i'd quit wasting my time ...
there are some designs where using the coil may help high frequency distortion numbers (check old Hitachi Power MOSFET databooks, for example).
in such case, "bandaid" sounds like a pretty apt description to me.
mlloyd1
BTW, some nice internal shots of JC2 preamp here.
looks sweet, john!
how can i see the insides of the amp?
h*ll, if i was jc, i'd quit wasting my time ...
there are some designs where using the coil may help high frequency distortion numbers (check old Hitachi Power MOSFET databooks, for example).
in such case, "bandaid" sounds like a pretty apt description to me.
mlloyd1
BTW, some nice internal shots of JC2 preamp here.
looks sweet, john!
how can i see the insides of the amp?
AKSA said:
Nelson also stated somewhere that he does not (any longer) use an output coil; the reason he cited was again the sonic signature it imposes.
Assuming that all other design and stability aspects are well taken care of, in my experience, it seems that amplifiers delivering very limited current with perhaps, a single pair of output devices cannot get away without an output inductor. Whereas when the output stage is capable of delivering enormous amounts of current, it can deal with complex loads usually without the need for an output inductor and also without bordering on instability.
Why this militant attitude towards JC, may I ask? He is a very successful designer and a commercial success as well. If his philisophy and approach have gradually changed with experience, it only points to the fact that he is willing to learn and does not think that he has arrived. That is maturity compared to many others who seem to pose that they "know better".
Please don't drive away from this forum experienced designers who are willing to spend their time and energy discussing sometimes trivial issues and most times, those of technical merit.
Assuming that all other design and stability aspects are well taken care of, in my experience, it seems that amplifiers delivering very limited current with perhaps, a single pair of output devices cannot get away without an output inductor. Whereas when the output stage is capable of delivering enormous amounts of current, it can deal with complex loads usually without the need for an output inductor and also without bordering on instability.
Why this militant attitude towards JC, may I ask? He is a very successful designer and a commercial success as well. If his philisophy and approach have gradually changed with experience, it only points to the fact that he is willing to learn and does not think that he has arrived. That is maturity compared to many others who seem to pose that they "know better".
Please don't drive away from this forum experienced designers who are willing to spend their time and energy discussing sometimes trivial issues and most times, those of technical merit.
John Curl:
"I didn't believe it at first either. I had to be shown with an A-B test. However, I NEVER used more than 2uH, and I was using less that 1uH, before I gave them up completely."
Hi John,
I'm trying to find something I can point to to explain why your experince has shown MOS devices to be fragile at high supplies. I agree with Kanwar's approach as a means to protect the output devices from shorts. Could this have been related to the problems you've seen or do you think this was caused by something else?
Tony
"I didn't believe it at first either. I had to be shown with an A-B test. However, I NEVER used more than 2uH, and I was using less that 1uH, before I gave them up completely."
Hi John,
I'm trying to find something I can point to to explain why your experince has shown MOS devices to be fragile at high supplies. I agree with Kanwar's approach as a means to protect the output devices from shorts. Could this have been related to the problems you've seen or do you think this was caused by something else?
Tony
MikeBettinger said:
An output inductor is no less of a “bandaid” than the other design compromises that are necessary to ensure a comparable degree of stability phase margin when driving a capacitive load without one. It’s up to the designer to opt for the design compromises that he/she is comfortable with and design along those lines.
The lone fact that a designer may have a commercially successful amplifier design on the market that doesn’t require an output inductor to ensure stability when driving capacitive loads does not mean that his amplifiers are any more or less competently engineered or any more or less “HiFi” than other design utilising the opposite design approach.
Also, nobody is saying that the function of the inductor is benign. If this were so it would have no purpose. The contention to the nebulous claim that even a small inductance can have a disastrous effect on an amplifiers sound quality revolves around the fact that the impedance of the inductor is a very small part of the complete load impedance ultimately presented to the output of the amplifier.
And yes, there is a lot of religious bunkum involved in some aspects of Halcro’s design philosophy. That’s necessary for any amplifier manufacturer seeking to extract $40k from customers for a pair or monoblocks. However, this doesn’t override the fact that their amplifiers are competently engineered performers, even with their output inductors.
Cheers,
Glen
The output coil is an application specific tool.....
In professional environments the amplifier's outputs are connected to speakers with passive crossovers and the connecting wires are as much as 25meters long which in some case even run in close proximity with RF prone area as well as mains AC cables, which would eventually make the amplifier prone to oscillations if without output coil....
You all guys consider the output coil as a sonic degrader, well i agree with you all because the application environment of your amps is not in a Hell as pro-arena, rather than its the "Home Sweet Home" or a demonstration room or maybe your living room....Niether the connecting wires are 25Meters long in this home application amps....I have seen various hi-end amps in recording studios, Audiophile's home and enjoying pretty "Heaven" like well good environment...
Run any Home specific amp without coil with 25 meter high capacitance cable with dreaded passive crossover of JBL SRX750 Tops....and See the Smoke machine in action....
In professional environments the amplifier's outputs are connected to speakers with passive crossovers and the connecting wires are as much as 25meters long which in some case even run in close proximity with RF prone area as well as mains AC cables, which would eventually make the amplifier prone to oscillations if without output coil....
You all guys consider the output coil as a sonic degrader, well i agree with you all because the application environment of your amps is not in a Hell as pro-arena, rather than its the "Home Sweet Home" or a demonstration room or maybe your living room....Niether the connecting wires are 25Meters long in this home application amps....I have seen various hi-end amps in recording studios, Audiophile's home and enjoying pretty "Heaven" like well good environment...
Run any Home specific amp without coil with 25 meter high capacitance cable with dreaded passive crossover of JBL SRX750 Tops....and See the Smoke machine in action....
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