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Hammond 290-series Guitar amp PTs
#4
Hi Daryl

That would be a Super Champ X2, rated at 15W using 2x 6V6.

The amp has a full and proper tube power amplifier with a proper output transformer that matches the push-pull tube stage to an 8R speaker. Why do you need to change it? There are lots of mods you can make to the PA, but changing the OT is not the first one that comes to mind - if at all. And as always, do not waste your money on Mercury Magnetics. Total hype and not as good as "generic" brands.

"Autoformers" are auto transformers )single winding with taps and a shared end for input and output)designed for audio, generally for low-quality public address systems. Note that such systems should NEVER have full bass response, let alone extended bass response, as this low-frequency content becomes more of a background "rumble" than sounding anyways musical. Background music systems are explicitly that - BACKGROUND and should therefore be unobtrusive.

In a PA system, the power amp may have a 70V line transformer built-in, or simply be rated at such high 8R power that it can produce 70Vrms output directly. The latter would have to be rated for close to 800W into 8R - not too common. In typical systems, the driving OT has a step-up voltage ration that matches the amp's nominal rated voltage output (what corresponds to its 8R output) to the 70V line. Then at each speaker location is a smaller autoformer to tap a portion of the power.

None of the 70V system transformers are applicable to your guitar unless you wish to distribute the sound through such a system, with notably reduced fidelity /altered tone compared to the combo speaker. Using an over-sized line AT may reduce the fidelity loss.

Have fun
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Messages In This Thread
Hammond 290-series Guitar amp PTs - by K O'Connor - 01-10-2022, 05:35 PM
RE: Hammond 290-series Guitar amp PTs - by K O'Connor - 11-06-2022, 08:55 PM

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