Propeller Head Plaza Technical and scientific discussion of amps, cables and other topics.

---

[ Follow Ups ] Thread: [ Display  All  Email ] [ Propeller Head Plaza ]

---

[ Alert Moderator ]

---

Re: Memory Distortion

Posted by Steve Eddy on May 19, 2003 at 12:47:41

In Reply to: Memory Distortion posted by greg7 on May 18, 2003 at 20:17:18:

Lavardin puts forth the basis for their amps having excellent sound quality results from having reduced or overcome 'memory distortion' inherent in solid state devices. Bases on the very positive press their amps have received, it seems this is plausible. Any idea how they achieved this? They're quite mum on the actual nuts and bolts so I can only assume they've either found transistors that don't exhibit this and/or found a way to minimize or overcome this and subsequently had a custom transistor design built for them. It's a rather bold, unusual claim so I'm curious what you think.

Nothing particularly bold or unusual about it really. Though seeming bold and unusual certainly helps with marketing. :)

The "memory distortion" they speak of is simply signal-induced thermal modulation of the transistor. Because a transistor's transfer characteristics are effected by junction temperature, changes in junction temperature change the transfer characteristics of the transistor.

Because the junction is built into a slab of silicon which has mass, this results in thermal energy storage, which means that the junction temperature will not fluctuate in unison with the current flowing through it. So the transfer characteristics of the transistor will vary depending on the input signal and the thermal time constant of the silion the transistor's made from. In other words, distortion.

It's fundamentally no different than other forms of energy storage, such as inductors and capacitors which, due to their energy storage have the current waveform time shifted with respect to the voltage waveform.

Lavardin's approach to dealing with thermal distortion is a differential input stage using a current source and feedback network which keeps the current flowing through the input transistors constant. Keeping the current constant keeps the junction temperature constant which effectively prevents thermal modulation of the transistor's transfer characteristics which would ideally translate into less distortion.

It's rather hard for them to keep mum about the actual nuts and bolts seeing as their input circuit is patented and therefore in the public record.

This type of "memory distortion" isn't any sort of new discovery. It's been known of for quite a long time, particularly among those who design monolithic integrated circuits. There are a number of ways it's been addressed. Lavardin's is just one of them.

You can read all about it here:

5,512,858.

se

This post is made possible by the generous support of people like you and our sponsors:

Sonic Craft

---

[ Top of Page ] [ Contact Us ] [ Support/Wish List ] [ Copyright © 2025, Audio Asylum, all rights reserved ]

---

[ General ] [ Speakers ] [ Tubes ] [ Vinyl ] [ Digital ] [ Hi-Rez ] [ Video Asylum ] [ Cables ] [ Tweaks/DIY ] [ Music ] [ Films ]

---