Hello Kindhornman,
As a general rule any harmonics which are not present at the input of the audio product but are there at the output cause coloration and to some people this can be desirable, but I am sure if you heard the original tape master before it was transmitted it would of sounded much better than what was coming out of the Luman radio.
Transparency (all this being equal) in a signal chain is a good thing and can sound very good.
Phoenix,
I was kind of being tongue in cheek in that reply, just razzing Scott and Richard. 😀
I was kind of being tongue in cheek in that reply, just razzing Scott and Richard. 😀
Well, why dont you tell us what YOU think they are (there are two circuits on the page you linked)
I know you did not. Same as I have not neglected a possible presence of 8th harmonic if accompanied by 2nd and 3rd. I have only neglected 8th as a single product of circuit non-linearity.
I know Ed will demonstrate the the obviously audible -140dB artifacts any day now.
The math of smooth non-linearities also precludes certain amplitude distributions of higher harmonics even when lower ones are present.
Look it was a sort of a joke, Richard made a statement to Waly, without a lot more knowledege of what Waly is doing how does one base where -100dB or so of 8th comes from? My experience with ferrous metal harmonics is that they are mostly odds and there would have to be big evens to intermodulate.
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We measured mostly 3rd (+ further odds), a nice example was a coaxial cable placed in a steel "shielding" tube, this used in a High Power Testing plant. The steel tube acted like a transformer and you had 3rd of 50Hz everywhere 😀
This is rather dissapointing performance for a amp which compromises 56 active devices for the input stage alone. This level of performance was achieved 30 years ago using a 1/4 of the devices.
Ok, why is it a VFA, and what are the CFA principles it follows (and, if so, why isn't it a CFA)?
Of course, it's disappointing
. Three days later, I guess everybody now understands why I am not posting the schematics 
.Perhaps you could quote the brand and the model of one of those 30 years old amplifier able to do 800W/4ohm, with the same level of distortions, using only 14 active devices in the front end?
I would be curious about the specification and the schematic, in particular because 30 years ago, modern RET power bipolar devices with Ft=30MHz did not exist.
Feedback is to a high impedance node.
It uses two buffers as input, in this case its 2 Jfets, it could have been two diamond buffers ie LM6172.
The inputstage will have deliver current on demand to TIS,same as CFA.
Which high impedance node, at the output? If so, why is this specific to a CFA or VFA?
Due to symmetry (you can fold the schematic both along the horizontal and vertical center lines, opposite nodes are at the same potential), the amplifier uses in fact one jfet at the input.
So why is this not a CFA?
Hi Scott,
There's that great sarcasm -- But, that is a totally different subject.... it is not electronics. For myself, I dont have an interest in that subject. I dont see it as the relevent issue about ferrous materials and distortion and how much IMD or what ever is produced; how and what levels etc. It probably needs its own forum as it is brought up so often. maybe something called - What has a bearing on sound and how do we know?
For others who want to know more, just google on distortion from ferrous materials and the like. Here's one of a zillion (nothing seems to be directed to audio, so this will have to do or do your own T&M). I'm looking for prior art in ferrous metals which might be used in LF and at power amp signal levels.
www.ieee.li/essay/passive_imd.pdf
Thx-RNMarsh
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might be a CFA.... [I havent looked at your schematic]. But the Industry has defined the topology for CFA and its major characteristics which defines it. We have, earlier, described that topology and it's characteristics. If your circuit fits that description then its a CFA. Should not be hard to determine by established industry norms.
Thx-RNMarsh
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Richard,
That link is somewhat incorrect but I did find what I think you are referring to. This is the active passage on the second page of the document that I found:
The use of ferromagnetic materials such as nickel or steel within the current path, especially at high power levels, can also generate PIM due to the nonlinear voltage to current ratio and hysteresis effect of these materials.
That link is somewhat incorrect but I did find what I think you are referring to. This is the active passage on the second page of the document that I found:
The use of ferromagnetic materials such as nickel or steel within the current path, especially at high power levels, can also generate PIM due to the nonlinear voltage to current ratio and hysteresis effect of these materials.
Speaking about heavily copper plated component leads in audio, if this is a concern, you may want as well to consider the effect of the solar total eclipse of August 11, 1999.
Waly,
They never refer to copper cladding so I can only assume they are talking about pure ferrous metals somewhere. I have no stick in this game, just posting what was in the pdf Richard pointed to.
They never refer to copper cladding so I can only assume they are talking about pure ferrous metals somewhere. I have no stick in this game, just posting what was in the pdf Richard pointed to.
I don't think so.
JC's topology has all the properties I can think of a CFA (low impedance inverting input, current on demand, for low closed loop gains - ULG modulation by the feedback network, etc...). By all the criteria I have seen here, that is a CFA. I wonder what would make anybody (including JC) believe it is not?