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Post subject: Princeton Reverb PI ???
Posted: Sun Sep 15, 2013 5:27 pm
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Just wandering which 12AX7, you folks prefer for the Phase Inverter slot ? The circuit is the 1164 with a GZ34. With today's wall voltage, the tube is seeing right around it's max plate volt rating of 250 VDC. Had a late '50's NOS GE puke, after 9 mos(maybe 600 hrs at reasonable levels). All associated components are up to snuff. Art

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Post subject: Re: Princeton Reverb PI ???
Posted: Sun Sep 15, 2013 6:19 pm
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Art,

This is a concertina phase inverter. Not as critical to have balance across the two triode sections. One section is for the PI, the other is for the tremolo/vibrato section. Just get a high testing & quiet 12AX7.


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Post subject: Re: Princeton Reverb PI ???
Posted: Sun Sep 15, 2013 6:22 pm
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I'm partial to the RCA or JAN Westinghouse myself. And because one half of this tube handles the bias-modulated tremolo circuit, I recommend something extremely quiet (long-tail definitely not a good choice).

Could be that your NOS GE died "just because". It was 50+ Y/O, yunno......

Arjay

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Post subject: Re: Princeton Reverb PI ???
Posted: Mon Sep 16, 2013 7:58 am
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very partial to the Mullard CV4024 for the PI in my Fenders and really like the sound of it. Mike Kropotkin at kcanostubes.com turned me on to them. Definite increase in tone for $30.

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Post subject: Re: Princeton Reverb PI ???
Posted: Mon Sep 16, 2013 7:20 pm
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Thanks guys!!! Yeah, I'm hep to the concertina circuit, Steve. Arjay, I think you're right about the tube just taking a dump(it happens), regardless of hours. Guess I've just gotten spoiled with my experience with NOS tubes over the years. Any way, popped in a super low hour RCA 7025,14mm, and it's all fine. Nedo, I'll give a 4024 a try, the next time an amp needs a 12AT7. BTW, Nedo, really appreciate your opinion on the Warehouse speakers. Thinkin about swappin' out the B'Master's Weber Calif for one of those. Thanks Again, Art

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Post subject: Re: Princeton Reverb PI ???
Posted: Mon Sep 16, 2013 8:37 pm
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When one of the beloved RCA blackplate 6V6's in my '65 Princeton Reverb turned microphonic on me a couple of years ago, it about broke my heart to have to replace the pair.

:cry:

Arjay

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Post subject: Re: Princeton Reverb PI ???
Posted: Tue Sep 17, 2013 12:33 am
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The Mullard CV4024 is a 12AT7 type of tube. You should use a 12AX7 type tube in a Princeton Reverb. Since only one-half is being used as the PI, mu counts.


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Post subject: Re: Princeton Reverb PI ???
Posted: Tue Sep 17, 2013 2:05 am
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Indeed. The bias-modulated trem is directly interactive with the bias supply regardless of whether the trem is switched on or not and the insertion loss is substantial. The amp will never develop its design output power with a low-gain phase-inverter tube. Overall tone is likely to suffer as well.

Arjay

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Post subject: Re: Princeton Reverb PI ???
Posted: Tue Sep 17, 2013 6:45 am
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BMW, would normally agree with you, but having swapped out a 12AX7 for the CV4024, to me subjectively it sounds better, both on my Princeton Reverb and my Bandmaster. May have to get a good NOS 12AX7 and try again as I've had the Mullard in there now for a while... but if it sounds good I tend to leave things alone...

Art - glad the info helped, and hope you like the Warehouse speakers as much as I like them.

I did stray from Warehouse when I rebuilt my Tremolux cab and went with Weber alnico 10A125's and am very happy with them.

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Post subject: Re: Princeton Reverb PI ???
Posted: Tue Sep 17, 2013 9:34 pm
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Nedo, the B'Master has a Brit V30 and the Calif. Just thinkin' a change is due, for the Calif. Have lusted after a Tremoluxe for years. You and Steve are very fortunate!! Actually use two 8ohm Weber alnico 10's(model?) for my '55 Valco brute. Yeah, 5 watts of stone-soul sound !!! Art

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Post subject: Re: Princeton Reverb PI ???
Posted: Tue Sep 17, 2013 10:04 pm
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I think you'll find a warmer sound that works great with Fenders. I thought I would like the aluminum dust-cap Californias, but too stiff/harsh for me.

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Post subject: Re: Princeton Reverb PI ???
Posted: Tue Sep 17, 2013 11:55 pm
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Cool !!! How are the waves in Redondo? If I remember correctly, September can get some big breaks on the northside of the Kings Harbor wall. Be Cool & Keep Pickin', Art

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Post subject: Re: Princeton Reverb PI ???
Posted: Wed Sep 18, 2013 10:03 am
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Waves are pretty good, but I only occasionally boogieboard, not surf, and usually we go to RAT beach (Right After Torrance). Finally cooling down here after abnormally hot September (90's in the south bay is hot for here)

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Post subject: Re: Princeton Reverb PI ???
Posted: Wed Sep 18, 2013 2:34 pm
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nedorama,

The 12AT7 prolly gives you a cleaner tone to a louder volume than a 12AX7 in the PI of the PR. If you like that tone, a 5751 may work nicely, too. No problem, inserting a 12AT7 into a native 12AX7 position --- heater or bias-wise.

Tone is the ultimate goal, so whatever works is cool. Most ppl like the buttery-smooth early OD of a good 6V6GT. So they go for the most pre-amp gain possible. And the PR really needs good 12AX7's in all positions, for this goal.


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Post subject: Re: Princeton Reverb PI ???
Posted: Wed Sep 18, 2013 8:01 pm
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excellent points, and may have to try that out in the future - thanks for the difference.

Sadly, the PR has been taking a rest to allow me to use the Tremolux more often. I think it's getting jealous...

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