Princeton reverb coming together (need some help)

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JoshBernstein
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Princeton reverb coming together (need some help)

Post by JoshBernstein »

Hi everyone,
I've put in a bunch of work on my Princeton reverb build. All that's left is the bias board. I'm waiting on a new 100uf cap for it, as the first one they sent me was dead shorted!

Any feedback would be great.

I've got an amperex bugle boy for the input tube, Sylvania 12au7 for the reverb driver, RCA short gray plates for v3 and v4. New production JJ's for output tubes and rectifier. I plan on using that 10" Jupiter speaker and an old ruby reverb tank I had. Classictone OT and heyboer for the reverb driver and PT.

There's just so many wires in these damn things, I think I'll hold off on the fender builds for a while.
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Last edited by JoshBernstein on Sun Apr 30, 2017 4:06 pm, edited 1 time in total.
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xtian
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Re: Princeton reverb coming together

Post by xtian »

Oh, you're going to love this amp, Joshyboy.
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joeboo88
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Re: Princeton reverb coming together

Post by joeboo88 »

Looks good Josh.
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sonicmojo
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Re: Princeton reverb coming together

Post by sonicmojo »

Love the red theme. Doin' your own thing and not worry about the traditional thing. Cool. What brand of resistors are those?
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JoshBernstein
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Re: Princeton reverb coming together

Post by JoshBernstein »

Thanks everyone!

The resistors are PRP, I got them here:

http://www.partsconnexion.com/resis_prp_main.html
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Mark
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Re: Princeton reverb coming together

Post by Mark »

The 100VDC caps in this amp are huge. I take it that you wanted to build an amp with high quality parts. It should be very quiet.
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JoshBernstein
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Re: Princeton reverb coming together

Post by JoshBernstein »

Well I fired it up today! The clean tone is absolutely amazing, the best I've heard.

I've got a few issues to work out, maybe you all can help. First the reverb sounds kinda odd. Like it floats on top of the note and is very washy. I'm guessing it's the reverb tank, as it's not exactly the one the circuit is designed for -- it's a ruby tank, numbered rrvs2eb2c1b. I also used a 12au7 for the reverb driver. Also a bit of hum is added as the reverb is turned up. Would this be lead dress or tank placement?

Also, at lower volumes the amp is quite quiet. But as I turn it up, I get this weird hiss/hum noise I've never heard before in another amp. Is there anything there anything that should be suspect?

Thanks!
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tubeswell
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Re: Princeton reverb coming together (need some help)

Post by tubeswell »

First thing to check is what all your DC voltages are (B+, and at each filter cap power supply node, each plate, cathode, grid)
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JoshBernstein
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Re: Princeton reverb coming together (need some help)

Post by JoshBernstein »

Will do. I'll post some voltages tonight.
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xtian
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Re: Princeton reverb coming together (need some help)

Post by xtian »

Yes, tank placement can influence hum. And you've got to get the right tank, so the impedances and grounding scheme match the circuit.
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JoshBernstein
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Re: Princeton reverb coming together (need some help)

Post by JoshBernstein »

xtian wrote: Sun Apr 30, 2017 8:25 pm Yes, tank placement can influence hum. And you've got to get the right tank, so the impedances and grounding scheme match the circuit.
Definitely will do. Would I be okay leaving the 12au7 as the reverb driver? Also could I use the Accutronics 9AB2C1B or should I stick with the 4AB3C1B? It would be sweet to have the 3rd spring in there.
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Re: Princeton reverb coming together (need some help)

Post by martin manning »

12AU7 will have increased current over 12AT7, but if nothing has smoked by now, it's probably ok. Neither of the tanks you mention carry the ground through from input to output. The send cable shield must be grounded in your amp, usually by tying it to the return cable shield ground. AB2 is medium decay, AB3 is long decay, both are 8-ohm input, 22k5 output.
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M Fowler
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Re: Princeton reverb coming together (need some help)

Post by M Fowler »

You need to study the reverb pan data the 2 in 9AB2C1B is medium decay and the 3 in 9AB3C1B is long decay.

If switching to 4 type pan 2 spring long tank there is a difference in transducer and Reverb Driver ohms.
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JoshBernstein
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Re: Princeton reverb coming together (need some help)

Post by JoshBernstein »

M Fowler wrote: Sun Apr 30, 2017 10:54 pm You need to study the reverb pan data the 2 in 9AB2C1B is medium decay and the 3 in 9AB3C1B is long decay.

If switching to 4 type pan 2 spring long tank there is a difference in transducer and Reverb Driver ohms.
Looking at the specs, the 9ab2c1b has an input impedance of 10 ohms. The reverb driver has an 8 ohm tap. Is this too significant of a difference for it to sound good? I just thought it'd be nice to have the 3rd spring for a more complex sounding reverb
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JoshBernstein
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Re: Princeton reverb coming together (need some help)

Post by JoshBernstein »

martin manning wrote: Sun Apr 30, 2017 10:29 pm 12AU7 will have increased current over 12AT7, but if nothing has smoked by now, it's probably ok. Neither of the tanks you mention carry the ground through from input to output. The send cable shield must be grounded in your amp, usually by tying it to the return cable shield ground. AB2 is medium decay, AB3 is long decay, both are 8-ohm input, 22k5 output.
Based on this I'll give the 3 spring tank a shot. And I'll ground the two shields together. Thank you!
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