12AT7 has the lowest impedance for TU-8500
How does it sound in comparison?
From the designer point of view, 12AT7 is the best for TU-8500.
It has the lowest impoedance
The 12AU7 has a plate resistance of 7,700 ohms
The 12AT7 has a plate resistance of 10,900 ohms
The 12AT7 is actually the higher of the two.
A better selection may be the 5751 with a plate resistance of 5,800 ohms.
That is if the TU-8500 can handle the higher filament current of
175 mA (at 12.6v) over the 12AU7 filament current of 150mA (at 12.6v).
Without a schematic of the preamp section, and how exactly the tubes are being used, this is all pretty much moot.
jeff
The schematic is in the manual
The 12AU7 has a plate resistance of 7,700 ohms
The 12AT7 has a plate resistance of 10,900 ohms
The 12AT7 is actually the higher of the two.
A better selection may be the 5751 with a plate resistance of 5,800 ohms.
That is if the TU-8500 can handle the higher filament current of
175 mA (at 12.6v) over the 12AU7 filament current of 150mA (at 12.6v).
Disregard this with the 5751 I read the plate resistance wrong
The 12AU7 has a plate resistance of 7,700 ohms
The 12AT7 has a plate resistance of 10,900 ohms
The 12AT7 is actually the higher of the two.
Victor may have meant the output impedance of the preamp.
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