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Memory distortion, crap or serious?
Memory distortion, crap or serious?
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Old 11th March 2004, 03:45 PM   #11
IanHarvey is offline IanHarvey  United Kingdom
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Doug Self has investigated thermal distortion here:

http://www.dself.dsl.pipex.com/ampin...d/thermald.htm

It's untrue to claim that thermal distortion is not detectable with steady-state measurements, as the graphs show.

I'm also unconvinced that simulations which show the output DC offset drifting at a few mV/sec after a signal peak actually translate into distortion at audio frequencies.

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IH
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Old 11th March 2004, 03:46 PM   #12
Svante is offline Svante  Sweden
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So, they have a new way of measuring that includes the effects of time varying systems? Why don't they show the results?

Until then, the verdict is: crap.
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Old 11th March 2004, 04:00 PM   #13
Steve Eddy is offline Steve Eddy  United States
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Quote:
Originally posted by IanHarvey
Doug Self has investigated thermal distortion here:

http://www.dself.dsl.pipex.com/ampin...d/thermald.htm

It's untrue to claim that thermal distortion is not detectable with steady-state measurements, as the graphs show.
It's worth noting that Self's measurements are of a monolithic power opamp, where the low current input and VAS stages are built on the same slab of silicon as the high current output stage.

And as Self notes, "There is absolutely no such effect to be seen in discrete-component power amplifiers."

se
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Old 11th March 2004, 05:27 PM   #14
Pjotr is offline Pjotr
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Hi all,

Thanks for the replies so far. Although I vote the promo-talk on the links I gave as totally nonsense, a Google search on “memory+distortion+amplifiers” brought up some serious links but mostly related to HF amps.

The talk about electrons leaving traces of flux in semiconductors made me thinking of the slugs that sometimes entering the house from the backyard and leaving twinkling traces on the kitchen floor

Thanks JF for the peufeu link. There are 2 links there at the end to patents that holds serious stuff regarding thermal modulation. But if that makes really sense to audible artefacts in SS audio amps? I doubt …

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Old 11th March 2004, 05:47 PM   #15
JohnG is offline JohnG  United States
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However, as far as I am aware, this is only an issue when going from a forward to reverse bias state on the junction, and will only take a few pico seconds (or nano at the VERY worst) to take place. So, to say that this will effect the sonic character of an amplifier seems to me to be total BS, as I just can't see it even applies in a fully class a circuit, and for anyother type of circuit (with the possible exception of class D perhaps) the frequency range it will effect will be inaudible and hence of now significance what so ever.
Although I'm not qualified to comment on memory distortion per se, the above quote refers specifically to reverse recovery in diodes turning off. In diodes of substantial current ratings on the order of an amp or more, recovery time can easily exceed 100ns, and in standard recovery diodes, can be several microseconds. Similar phenomena can occur in BJTs, but I'm not sure of the time-scale there. It is primarily a large-signal issue, but power amps generally deal with large signals.

John
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Old 11th March 2004, 05:48 PM   #16
Mark25 is offline Mark25  United Kingdom
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A magnet can induce a "memory", type effect in a piece of steel, due to the magnetic domain hysterisis. Although this is totally unrelated, it is at the same atomic "level", as current flow. I don't know enough about current flow through semicondutor junctions to relate it, just thinking aloud really.
Mark
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Old 18th July 2018, 10:38 PM   #17
Aklankrisztian is offline Aklankrisztian  Hungary
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Serious.
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Old 19th July 2018, 04:02 AM   #18
stratus46 is offline stratus46  United States
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Quote:
Originally Posted by Aklankrisztian View Post
Serious.
Did you hire a detective to find a thread that old? After 14 years do you think anybody cares? FWIW I vote for crap.

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Old 19th July 2018, 08:49 AM   #19
forr is offline forr  France
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Quote:
Originally Posted by stratus46 View Post
crap
Memory distortion seems to be insignificant not to say immeasurable.
However the circuits proposed to avoid any potential trace of it are very linear and really interesting.
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Old 19th July 2018, 09:26 AM   #20
davidsrsb is offline davidsrsb  Malaysia
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memory distortion is a poor term for what is really thermal intermodulation
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