Arny Krueger wrote:

When the first generation SS audio test equipment like the HP 331-334
first hit the market, residuals *instantly* improved by like an order of
magnitude.

http://mywebpages.comcast.net/mnowlen/hp334a.htm

Heath made a cheap clone of this box (IM5258) that I was able to improve so
that it had mid-band residuals in the 0.001-0.003% range.

Neat !

Do you fancy posting any more info about that ?

Graham