Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Shack on April 25, 2015, 08:58:15 pm
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If I build a PR, with a taller cab to fit in the 12 inch speaker, and use a deluxe reverb output tranny, but keep the power tranny for the PR, and the whole PR circuit, would that work ok?
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Sure, no problem at all. You actually do not need to enlarge a PR cabinet to fit a 12" speaker but it *is* a tightish fit. I have a SF Princeton Rev that I have an Altec 417-8H 12" mounted in, and that particular speaker has a VERY deep spider/frame. I also hotrodded the amp to 35/40 watt with the trannies from a Dynaco 35-watt amp and using 6L6 tubes. I had to rotate the speaker and the OT actually pokes very slightly into the space between spokes on the spider. Best sounding amp I own bar none. To mount a 12", you *may* have to fiddle with the baffle board on an existing PR, but if you are building one from scratch, talking about the cabinet, I am just saying that you can use PR dimensions no problem. If you were to front-mount the speaker you'd have no problem at all.
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sweet thanks....I thought since im building the cab that one inch more could make alot of difference , especially after I looked into the back of my Blues jr, ..another 16 inch high cab with a 12 inch speaker in it.....looks tight :)
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An extra inch would definitely make your life a little easier but is not an absolute requirement. With smaller Deluxe/Princeton trannies you will not have the bizarre issue of them poking into the space between spokes on the speaker...and many speakers, you can't do that anyway.
But speaker placement (eg; the exact place where you cut out the speaker hole on the baffle board) has to be VERY accurately measured, as I recall, the tolerance was less than 1/4". I SERIOUSLY doubt you can take a PR, clone the cabinets' exact dimension and copy the [10" speaker] baffle board and enlarge the hole concentric with the existing hole. That will NOT work. This is the crux of what I'm saying: you'll have to move the speaker-hole cutout SOME and you may have to build the whole amp, mount the chassis, and THEN measure & cut out the spkr hole.
Or make the cab 1" higher. :icon_biggrin:
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If I build a PR, with a taller cab to fit in the 12 inch speaker, and use a deluxe reverb output tranny, but keep the power tranny for the PR, and the whole PR circuit, would that work ok?
I don't know if this is relevant to you now, but...
Having owned a number of vintage Princeton Reverbs, I'd just go ahead and build the full-up Deluxe Reverb. Or if this is a complete scratch-build, make a Deluxe Reverb with one channel (if you don't need 2) and a midrange control for the tone stack with the Princeton's trem circuit.