Re: 12DW7/amp question

[The Bernadettes <mdestefano@xxxxxxxx>]

George,
    The 12AX7 is the inverter.  If you tried it, you'd find a 12DW7 wouldn't
even fit in the 6AT6 socket, it's much smaller socket.  BTW, if you do this
12DW7 sub on a Harvard, you may wanna try subbing a 6AV6 in the 6AT6 socket.
The 6AV6 is a higher gain version of the 6AT6.  It would make the amp more
feedback prone but it would also make it more crunchy sounding.  The gain factor
on a 6AT6 is 70, on a 6AV6 it's 100.  In other words the 6AT6 is the single
triode version of a 5751, the 6AV6 is the single triode version of a 12AX7.
Another tip; when buying either 6AT6 or 6AV6 single triodes, buy several, these
single triodes are prone to being microphonic.  When I batches of them, I
frequently find almost half of them to be so microphonic that they're useless.
Thankfully, these single triodes are fairly cheap NOS.

Don D.

George Brooks wrote:

> Don DiStefano wrote:
>
> The 12DW7 works
> great for harp on cathodyne inverters by lowering the gain on the input side
> of
> the inverter but keeping a high gain triode on the output side providing a
> strong signal to the power tubes.  This allows you to raise the gain (or
> volume)
> on the first gain stage of the amp before feedback.  You can then experiment
> with a 12AX7, 5751, or 12AY7 on the first gain stage tube position.  I do
> this
> with my tweed Harvard which uses a cathodyne inverter and it works great.
>
> Aside from the power tubes and the rectifier, my tweed Harvard has a 12AX7
> and a 6AT6.  Which one do you sub with a 12DW7?  Put another way, which tube
> is in the inverter?  Many thanks in advance.
>
> George