Re: The Potato Amp?

In article <1140933911.866627.93680@xxxxxxxxxxxxxxxxxxxxxxxxxxxx>, "Andre
Jute" <fiultra@xxxxxxxxx> wrote:

John Byrns wrote:
In article <1140717246.836709.81270@xxxxxxxxxxxxxxxxxxxxxxxxxxxx>, "Andre
Jute" <fiultra@xxxxxxxxx> wrote:
John Byrns wrote:

Please forgive me if I have asked this question before, but how did your
Potato Amp come by its name?

Potato Amp is not the amp's name; it merely describes a single-tube
amp. Any single-tuber is a Potato Amp. It is a pun: tube-tuber-potato.
I don't know who first made the pun. I heard it first from Dan
Schmalle, known as Dr Bottlehead, of VALVE and Elecronic Tonalities of
Poulsbo WA, makers out excellent low-priced kit amps. It is a nice
consideration whether an amp built with two tubes in one envelope (per
channel) is still a potato amp. An example would be Dan's Single-Ended
Experimenter's or SEX; I had a sidebar in my original review for Glass
Audio of the SEX amp on the lexicography of potato amps but the editor
preferred to give the sidebar space to an advertisement...

Thanks for explaining the meaning of a "potato" amp so that it could
penetrate my occasionally thick skull.

I would consider "an amp built with two tubes in one envelope" to fit this
definition, in fact I am sort of fascinated by the idea of push pull
"potato" amp using a transformer for phase inversion. Do you know of any
suitable dual triodes, something roughly on the order of two 417s in a
single envelope?

Tomorrow I'll probably regret answering this now as I am wiped. The
twin-triode Dan chose for the SEX, the 6DN7 is two dissimilar tubes in
the same octal envelope, so it won't do.

The tube that comes automatically to mind is 6AS7 but that isn't
anything like a 417A.

I assume the reasons you choose the 417A must include one or more of
the following:

1. High gain

2. Works direct out of CD (2V signal peak is good)

3. Decent current capability.

Steve Bench built an amp with a bank of 417A but I can't now remember
whether it was PSE or PP.

Tell us more of your parameters. Where would the signal come from, can
your IST be a step up as well as splitter, how much power do you want?

Hi Andre,

While the 417A doesn't particularly stir my audio passions, I am starting
with your SE 417A "potato" amplifier as the baseline. From my perspective
the specifications of an ideal push pull "potato" amplifier would be a
maximum output of 2 Watts, which could be driven to a 1 Watt output with
the 2 volt peak signal from a CD player that you quote.

The input transformer can have a voltage step up, the transformer I have
in mind has a voltage step up from the primary of 3X grid to grid.

I have in mind some sort of dual triode tube with an anode resistance some
where in the neighborhood of 1,700 Ohms, a transconductance as high as
possible, and an anode dissipation rating sufficient to provide a 2 Watt
output.

Any thoughts?


Regards,

John Byrns


Surf my web pages at, http://users.rcn.com/jbyrns/
.

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