Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: kagliostro on September 13, 2016, 01:28:59 am
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This is the schematic of the preamp (all you see is preamp) of a (as far as I can know) dismissed Kit of a very big Bass Amp
(http://i.imgur.com/c0sjyEc.jpg)
The Tone Control seems particularly articulate and there are mix resistors (that are unusual to me)
Which is your opinion about (Tone Control and whole preamp) ?
Many Thanks
Franco
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... The Tone Control seems particularly articulate and there are mix resistors (that are unusual to me)
Which is your opinion about (Tone Control ...) ? ...
Looks like they worked very hard and used a lot of parts to get a Mid-shift (meaning a semi-parametric midrange control).
I have no idea if it would sound good... I'd have to build it and listen.
... Which is your opinion about (... whole preamp) ? ...
The preamp looks pretty straight-forward (except the odd tone circuit). Right up until it uses an EL34 to drive a transformer... From that (and because the transformer secondary doesn't appear center-tapped), I'd guess they worked very hard to make a single-ended amp using a big output tube which they wanted to drive in class A2 (class A, but the grid is driven positive because the EL34 driver can supply grid drive-power without its output collapsing).
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It is standard Fender, except chopped-up and mixed back together with mix resistors instead of stacking. Oh, and one of the caps is switchable.
I don't know if it covers "all" the Fender shapes, or if it offers new shapes (it does seem possible to get top-cut). You could build it about as easy as simulate it.
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Thanks HotBluePlates & PRR
.... because the transformer secondary doesn't appear center-tapped
My fault, I apologize, the secondary of that transformer has a CT
this is the whole circuit of the amp
(http://i.imgur.com/192Hr7K.jpg)
Franco