LightSpeed Attenuator vs. GoldPoint SA1X

Hi Yuhengdu, Here's one below on the Luminous Audio Axiom. I'll look at some other sites on Lightspeed threads for you for the Goldpoint comparison if there is one I'll post it here.

http://forum.audiogon.com/cgi-bin/fr.pl?aamps&1276356977&openflup&1324&4#1324

Cheers George

Here is another comparison with similar DIY Slagle Autoformer Modules TVC based passive preamp like the Axiom. Still looking for one with the Goldpoint.

http://forum.audiogon.com/cgi-bin/fr.pl?aamps&1248137240&openfrom&1&4#1

Cheers George

Thank you! So lightspeed is ldr based? How about the tortuga preamp?

Yes there are a few clones trying to get around having not to quad match the LDR's which is very labour intensive.
Ones I know just dual match (the series and the shunt ldr's) which is half way there to get the best out of it.

And then some now don't match at all, and use a forced matching auto calibration type circuit circuit (like a active feedback circuit) to force match the LED/LDR's. This saves a lot of labour. But this can be desctructive over time to the led/ldr's (as I stated in the Lightspeed diy thread linked) and then it can also lead to not having a very low lowest level volume. Like revving your car passed it's redline all the time, something's got to give after a while.

http://www.diyaudio.com/forums/analog-line-level/80194-lightspeed-attenuator-new-passive-preamp-276.html#post4475116

I have found quad matching is the only way to go, to still use the labour intensive way of hand quad matching the series and shunt led/led's over 5 different current points, it the only way for me, and gives the best reliability, lowest low level volume and a nice logarithmic feel to the volume control progression, and best sound.

Cheers George

Is it impossible to do a balanced version of LDR passive volume control? Thanks.