Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: 12AX7 on July 13, 2013, 12:54:26 am
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Long ago i asked for a princeton w/o trem and was shown several schematics. Some fender, some variants some here have built. I have an amp i can build into a princeton by simply changing the preamp section, but the amp would them be a LTP PI version, which was one of the ones i was shown. The question is, what will the LTP version sound like compared to a typical 60's princeton with whatever that PI they use is called? What difference will it make tonally?
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A LTP actually produces more than unity gain, and a cathodyne splitter only produces unity gain at best.
BUT a LTP gets less overall gain out of the two 1/2s of the triode than you would if you had that same bottle configured as a driver stage and a properly balanced cathodyne splitter.
BUT a LTP has a potentially higher clean output swing than a cathodyne, so if there is enough clean gain going into the LTP, then you can get a bigger clean signal coming out of the LTP than you could out of a cathodyne.
Hence we see lots of amps (like BF amps) with a couple of stages before the LTP, whereas the likes of a 5E3 or a brown or BF (non-reverb) Princeton has two stages and a cathodyne. So the latter two amps get less overall gain (but more than enough to push a 6V6 grid into clipping) than your typical 6L6 based BF amp (or even a BFDR).
Now a BFPR is slightly different, because you have 3 stages before the cathodyne (albeit that the dry signal gain going into the third stage is heavily attenuated in order to get more wet signal into the blend), whereas your non-reverb BF Princeton only has the 2 stages in front of the cathodyne, so it has less potential gain than a BFPR.
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So then they really don't sound different as long as the preamp gain is enough aside from the differences in the preamp itself ?
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The sound is different when they're pushed. I like LTP amps overdriven. Cathodyne amps sound a bit muddier
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Thanks. I think i'll go with the LPT circuit. Makes it easier too since it's already there.