Hi knowledgeable fretboarders, just wanted to check my thinking before starting to mod my perfectly good amp!!
i have a ‘68 Princeton which is great, but a bit mid-heavy and bassy with humbuckers (and even my Jazzmaster with A2 pickups). I know this is essentially a modified ‘65 so hoping it’s a quick job to ‘reverse’ some of the mods and make the two states switchable.
From TDPR I’ve got the following info on the differences between the ‘68 and ‘65.
- NFB resistor (R10) is upped from 2.7K to 5.6K
- The ‘bottom’ cap (C23) in the tone stack goes down from .047 to .022
- They add an 18K resistor (R34) coming off lug 3 on bass pot
- Reverb return resistor (R30) goes up from 470K to 1M
(
http://www.tdpri.com/threads/’68-custom-pr-schematic-compared-to-’65-prri-and-aa1164.639609/)
I’m ok with reduced NFB and slightly dampened reverb, but I reckon (2) and (3) are easy to do - an extra .022 in parallel with the one already present to make .044 for (2) and a simple short for (3), and short them to ground with a switch to go ‘stock’.
Thoughts??? Since it’s all preamp I’m guessing I can use pretty much any components that do the job without worrying about power handling etc.
Cheers!!
Comments
There's also the speaker, which might be a more important difference.
"Take these three items, some WD-40, a vise grip, and a roll of duct tape. Any man worth his salt can fix almost any problem with this stuff alone." - Walt Kowalski
"Only two things are infinite - the universe, and human stupidity. And I'm not sure about the universe." - Albert Einstein
"Take these three items, some WD-40, a vise grip, and a roll of duct tape. Any man worth his salt can fix almost any problem with this stuff alone." - Walt Kowalski
"Only two things are infinite - the universe, and human stupidity. And I'm not sure about the universe." - Albert Einstein
To help:
WGS G10C - too much bass, very hollow sound and quite ‘hard’ sounding - everything I don’t like about small fenders (but I get why other like it!!)
Emi C Rex 10 - not as ‘full range’ as the 12 and therefore a bit too dark. Would probably break in and be clearer but it took an age with the 12 I had...
Celestion G10 Vintage - I’m certain this would be fantastic in a ‘65, amazing gain tones and super tight bass. Too many mids for the ‘68 though
Celestion Ten 30 (stock) - actually very decent, well balanced and not too much of anything. Biggest complaint is thin bridge pickup tone. Pretty vanilla - I certainly don’t understand the haters.
Jensen P10r RI - has the alnico sweetness, reigned in bass frequencies and a slight scoop to the mids which suites the ‘68 really well for low volume playing at least! I’m happy with it for now anyway...
But it I digress.
"Take these three items, some WD-40, a vise grip, and a roll of duct tape. Any man worth his salt can fix almost any problem with this stuff alone." - Walt Kowalski
"Only two things are infinite - the universe, and human stupidity. And I'm not sure about the universe." - Albert Einstein
I just opened up my 68 Princeton so see what I can do in the there. I can add some wire to skip R34, I'm going to do that now. I'm tempted to try and removed the front panel to have a look at C23.
The main board looks far too much of a pain to remove. Above it's mentioned to add another resistor to R10 in parallel - does that mean I can buy another 5.6k and attach it's legs to the legs of the existing? I think so but I know some of you guys can help clarify.
Thanks.
Pic of my board:
https://imgur.com/a/tbq2uNM
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https://imgur.com/a/uuXOX4T
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0.022uf has more low mids than 0.047uf. You might find it great to fatten up single coils, but can make the amp a bit boomy and muddy. Super Reverb uses 0.022uf but then cuts bass before the phase invertor.
C23 is .022. The blackface re-issue version has .047. My amp is a bit boomy and muddy - exactly as you describe. I've got my info from here: https://guitarampblog.wordpress.com/2017/01/26/fender-65-princeton-reverb-schematic-vs-68/
It's tempting to have a go at replacing it.
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