[78-L] RCA dealers' phono? (OT?)

[Malcolm Rockwell]

Ah-HAH! Thanks fro the clarification.
Malcolm

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On 3/11/2011 10:33 AM, J. E. Knox wrote:
> Greetings from FixitLand!
>
> Malcolm Rockwell wrote:
>
>> If the 5Y3 is the rectifier and the 6K6s are the push-pull power
>> amp (they are),
>> then it only stands to reason that the other two (6SQ7s?) are very
>> probably the preamp stage.
> Nope -- the schematic is quite clear: 6J5 is the first (preamp)
> stage, one 6SQ7 is a 2nd voltage-amplifier stage, the other 6SQ7 is a
> phase inverter. One could perhaps say that the three tubes together
> comprise a "preamp" feeding the push-pull output stage, but that term
> usually refers to an amplifier that brings a phono-level or low-level
> stage up to a line level. Here, we have a crystal cartridge which is
> already pretty much at line level; the 6J5 medium-mu triode doesn't
> add a bunch of gain but it is the first stage of the amp. It's also a
> metal-shell tube (rather than the 6J5-GT glass tube), and the shell
> is grounded, providing shielding. The 6SQ7s' shells are grounded too.
> That unit would likely hum up a storm if unshielded glass tubes were
> used.
>
> Take care,
> J. E. Knox