01-05-2012, 09:42 PM
(01-05-2012, 12:01 PM)Joe Wrote: I've been wondering if there were ever transistor-based versions of these, ie a mechanical movement driven by transistors, or did they go straight from valve to digital?
Yep, transistor ones were made, typically 1 M ohm per volt, a good valve VTM with a decent diode probe would typically be 2 to 3 M ohm input impedance to the probe and would be good from approx 20 hz to 100 mhz.
If you can't get the diagram then try to reverse engineer the circuit, shouldn't be too difficult on a quiet day. The 12AU7 might well be a balanced amp, if it is then I doubt if it is the simple wheatsone bridge type Valve VTM.
Lawrence.
