Posted by strieb (A) on July 31, 2008 at 08:12:47

In Reply to: RE: Questions about the TU-875 posted by vkung on July 30, 2008 at 22:39:40

Victor: Thanks for your prompt and forthright reply.

The preamp that was originally designed to complement the ST-70 was the Dynaco Pas 2 /3 series. Two R's in the Pas are in parallel with the input impedance of the ST-70 ... thus ... R1 (62K) + R2 (510K) + R3 (470K) in // equals a load of (nominally) 50K Ohms.

Perhaps the best way to procede goes like this: build the TU preamp. Then meter the output impedance. In accordance with whatever the result may be, the assembler can do adjustments by adding in R's — either in series or in parallel so as to bring the TU close to presenting a load that is a tenth of the input impedance of whatever amp is being used. AFAIK, a 10:1 ratio is the usual target. Cheers ... Lorne
Sonic Lizard

Edits: 07/31/08