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Duncan Convertible 15-100 watt combo with attenuator (post phase-invertor potentiometer)


Seymour Duncan 100Watt Convertible Amp

-Very flexible; power-dialable from 15-100watts
-variable speaker compression (passive)
-switchable from triode to pentiode power
-cooling fan


-100watts of all-tube power (four Sovtek EL34's)
-12" EV Speaker
-Two identical channels (Gain, Master Volume, Treble, Mid, Bass, Reverb)
with independent reverbs
-effects loop with volume control
-two convenience plugs
-solid cab
-Ideal for studio or stage. This is a great amp and they don't make them anymore. $500 used.

The Duncan Convertible has a post phase-inverter master labeled as an attenuator. One owner says that the "continous variable power" worked great, enabling cranked-up sound at low volumes with no major tone loss. He also said that even without the modules, it is a wonderful amp in terms of features.

> The "variable power" control on the Duncan amp does no such thing.
> It's actually just a fancy active master volume control. When the
> control in question is turned down there's no way you can get the
> output stage to break up, 'cause the function of the control is to
> limit the voltage to the grids of the output tubes. Whatever
> additional distortion you are able to achieve with this control turned
> down is due to preamp and phase splitter overdrive, not output
> clipping.

>>Actually I think the "variable power" control is not as mundane as you
present it. It is actually an addition dual tube (12AU7) section that
limits the power after the inverter by changing the apparent load as
seen by these tubes. It is after the phase splitter tube itself. It adds
some really neat sounding distortion even at low volumes. It is not, as
you say, output tube clipping.


> 2. This amp has the ability to use from 5 watts RMS to 100 watts RMS
>of power. This feature is subtle at best at lower volumes...but VERY
>drastic at higher volumes. When you're jamming with a band...and you
>want maximum clean headroom, you can dial the power amp to 100
>watts...and get crystal clear clean tone. OR you can dial it down to
>a lower wattage, and get the power amp to break up sooner...for leads
>and so forth. By the way, this variable power is adjustable w/ a
>volume pedal (plugs into the front jack near the variable knob). You
>can continuously sweep variable power settings right during a
>performance.

>>The "variable power" control on the Duncan amp does no such thing.
It's actually just a fancy active master volume control. When the
control in question is turned down there's no way you can get the
output stage to break up, 'cause the function of the control is to
limit the voltage to the grids of the output tubes. Whatever
additional distortion you are able to achieve with this control turned
down is due to preamp and phase splitter overdrive, not output
clipping.

>>By the way, the power amp section of the Duncan 100 was designed by
hifi tube guy Roger A. Modjeski, who makes Music Reference tube hifi
amps and sells RAM Labs tubes. The preamp section was done in-house
at Duncan.

[to do: company page, harmony central, dejanews]

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