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Post subject: 78 Princeton Reverb Tube Layout
Posted: Tue Mar 10, 2020 12:07 pm
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Hey folks! Just picked up a 78 Princeton Reverb. The tubes were removed and bubble wrapped for shipping, but I can't seem to figure out what goes where in the pre-amp stage. The amp seems to be using a different set of tubes to give it some additional headroom.

Anyway, here's what I have:
12AT7
12AT7
12AX7
12AU7 (This tube was the only one left in during shipping and was located in V1)

Any idea where these other ones go? Thanks!


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Post subject: Re: 78 Princeton Reverb Tube Layout
Posted: Fri Mar 13, 2020 1:45 am
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Joined: Fri Feb 05, 2010 4:31 am
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Location: Province de Québec, Canada
12AU7 and 12AT7 are low gain tubes
Amp will work fine with less gain / overdrive


Original tubes layout
7025 is a "high"performance 12AX7 , I always put good and quiet 12AX7

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Post subject: Re: 78 Princeton Reverb Tube Layout
Posted: Fri Mar 13, 2020 2:28 am
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Location: Tombstone Territory
Actually the now-discontinued 7025 was a low-noise dual triode, used in lieu of a 12AX7 because of its superior S/N ratio which helps to keep the amp quiet at idle. It's "mu" characteristics were similar in most other respects to the standard 12AX7.

Arjay

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"Here's why reliability is job one: A great sounding amp that breaks down goes from being a favorite piece of gear to a useless piece of crap in less time than it takes to read this sentence." -- BRUCE ZINKY


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