In harr--(at)--oundsmith.com (harry kolbe soundsmith inc.) writes:

>>Mike Glantz wrote:
>>>
>>> A couple of months ago, someone posted a short article saying
>>> that someone had done some research which demonstrated a new
>>> way of measuring distortion which would explain why tubes sound

>A paper entitled "Measurement of a Neglected Circuit Characteristic"
>was read at the 100th Convention of the Audio Engineering Society,
>May 11- 14 1996 in Copenhagen. The author of this paper is Gerard
>Perrot and it is available as Preprint # 4282 (T6) from the AES.
>This paper presents a measurement method for circuit memory.
>The author proposes and I agree that the signal "memory" of
>cicuits and cicuit components is a form of distortion that correlates
>well with listening test.

In brief: current through components heats them up, causing shifts in
operating parameters so that the circuit in the moments after a loud
sound is different from the same circuit after not so loud sounds.
Perrot has a patent on a solid state circuit topology that eliminates
this. The AES paper is well written, as is the patent. He's also
written a broader paper on the problem, including some earlier
discussions published in the French magazine l'Audiophile under the
pseudonym "Hephaistos" that explains these theories, and measurements
to reveal them.

--
David Josephson / Josephson Engineering / San Jose CA / davi--(at)--osephson.com

Index:

AB crossover	Amp Classes Defined	Amp Classes Explained	Amp Mods Harmful
Bass Cutoff Frequencies	Bias adjust safeguard	Bias Cathode Resistors	Bias Shift
Biasing methods	Biasing	Channel Switching LDRs	Choke Input Filter
Circuit Memory	circuits	Drop B+	Eyelet board
Fender Response Curves	FET source follower	Filament Cathode Ground	Fixed to Cathode Bias
FM Transmitter Voltages	Grid Blocking	Identify Power Trans Leads	Load Impedance
LV No PC boards	Output impedances	PC Boards	PCB amp problems
Phase Inverter Resistors	Pilot Light Tone	Rectifier voltage drops	Resistor Design
Resistor Max Voltage	Resistor noise	Reverb Tank Types	Reverb tanks
Screen Grids	Standby Switch Ratings	Standby switches	TAME Digest
Tone Circuits	Transformer Design Book	Transformer Info	Transformer Placement
Zener Voltage Drop