Dayton Wright

Try here:

http://www.dayton-wright.com/Preamplifiers.html

Good Luck

You will find the SPA preamp sold on ebay from time to time. During its day it was the equal of anything offered. I used modified XG-8 speakers with the panasonic leaf tweeters until they burnt out. Hard to service and get filled with sufahexafloride gas. I think the electrostatic doc may still fix them. They were special speakers especially when stacked. At the time they were introduced only Threshold and Krell amps could drive them as they dipped to 1 ohm and probably below. Mike Wright is a true genius and a very nice person. Do a google search on Dayton Wright and you will find him.

I have a DW SPA preamp and rebuilt it with newer resistors and caps - better output op amp and power supply etc etc . a nice design in it's time it is dated and even the best parts will only take it so far. I also have the DW SG equalizer and 4 pairs of XG 10's waiting for the time and space to get a double pair going out of them.