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Post subject: Princeton Reverb (AA1164 circuit)
Posted: Sun Jul 18, 2010 7:04 am
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I'm restoring a couple of AA1164 circuit PR's. Wondering if there is any new tricks to increase the drive on the reverb circuit. As you prolly already know, the Deluxe Reverb (AA868) uses both halves of a 12AX7 to drive and recover the reverb:

http://www.kbapps.com/audio/schematics/ ... ab868.html

As well as both halves of a 12AT7 for the phase inverter.

The PR uses a half of 12AX7 for reverb and other half for PI work:

http://www.el34world.com/charts/Schemat ... AA1164.pdf

Any comments would be appreciated! Thanks & try to keep cool.


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Post subject: PR 1164 edit
Posted: Sun Jul 18, 2010 7:06 am
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I meant the vibrato (tremolo) section, not the reverb...


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Posted: Sun Jul 18, 2010 8:29 pm
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BMW, glad to hear you are looking at and comparing schematics. As far as I know, there are no reputable mods to increase the input signal into the driver stage of the PR. The very best tubes and in spec caps & resistors would be my approach. IMO The veiled sound of the PR's, is it's strongest appeal. Just a minor point; check the schem- the signal comes out of the first 12AX7; passes through a.02 cap; then a portion of it goes to the 12AT7 grid. This would usually be considered the reverb driver. The PI is a cathodyne or split-load type, again adding to that"veiled" sound, producing slightly less than unity gain. Very different in characteristics of the long -tailed PI used in the DR. The Vib is also interesting, in that it oscillates the fixed bias of the power tubes, rather than oscillate and dump the pre amp signal to ground. IMO these all add up to one of Fender's best amps. Keep at it, BMW. Now, if I would get around to fixing and selling my Bassman, I could build a PR or maybe a 15Watt TrainRex. Art

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Posted: Sun Jul 18, 2010 9:09 pm
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The Princeton Reverb's "bias-wiggle" tremolo was Leo's first design and was initially introduced in the tweed 5E9 Tremolux. It was shared with the blackface Vibro Champ and silverface Bronco as well. This circuit was used in the '63 Vibroverb instead of the more elaborate two- or three-tube "harmonic tremolo" circuit developed for the Vibrasonic and other brownface amps of the era. This afforded sufficient space on the chassis for the required tubes used for the Vibroverb's built-in reverb.

Arjay

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Posted: Mon Jul 19, 2010 3:03 am
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A good bias of the power tubes can make big difference in tremolo


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