Changes between an original '65 Princeton Reverb and the reissue. Go!

Smgbad

Silver Supporting Member
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2,272
So are the only real differences the ground switch being obsolete, the modern power tube cage, and the components being PCB mounted instead of handwired? Just curious as I have a '67 BF, '78 SF, and a new '65 PRRI and can't hear much of a difference between the BF and the '65 PRRI. The treble seems a bit higher, but you can tame it by simply turning the treble knob down. Any other notable differences? Any component values that changed?
 

mortatort

Member
Messages
1,029
and speaker.


I'm a vintage Fender dude and I really like the PRRI and DRRI. That said, I've noticed a fairly distinct difference in sound. Still in the same neighborhood but perhaps a different street. All in all though, I think they are a great representation of the originals.
 

Figaro

Silver Supporting Member
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12,440
The PRRI does not have a pine cabinet. I think it's voltages are a little higher, which is not necessarily a bad thing. Good amp for the money USED.
 

wyatt

Member
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4,168
I have no reason to think they altered the circuit, nor would they have any reason to do so, but I haven't compared schematics.

Suppliers and manufacturers of OEM parts and components have all changed, and tolerances (in general) have gotten tighter. Where as your BF and even SF would have been built with wider tolerance parts that have drifted in value over the years. Caps drift up, resistors drift down and electrolytes wear out. The condition of all of these affects tone. But, a difference in speaker alone can have massive affect.
 

slider313

Silver Supporting Member
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8,134
The trace wire on the pcb is much thinner than cloth covered wire and the lengths are much shorter, the 1/4 watt resistors are half the size of the originals, the small radial coupling caps can't be compared to the blue molded "Ajax" caps, the cheaper transformers, newer Russian, Slovak or Chinese preamp tubes and it's not a finger joint pine cabinet. All these thing have an affect on sound in some respect.

I've yet to hear a DRRI sound even close to an original. I can hear a difference.
 

phsyconoodler

Member
Messages
4,315
I find the biggest difference is indeed the transformers.They are made in China these days for Fender and I am not a big fan of them at all.
I swap out tubes,speaker and output transformers on the PRRI and they come to life.Other than maybe a couple of better quality tone caps in the signal path,they are pretty good as is.Not like the originals I'm afraid but acceptable overall.IMHO.
 

Gillespie1983

Member
Messages
2,375
I love my PRRI. I compared it to a friend's 64 PR. They were very similar, but each had subtle personality qualities. Can't say the 64 PR was "better" tone; just more authentic tone for a 64 PR. Duh.
 

HawkeyeKane

Member
Messages
1,326
Primary differences...

-Transformers are outsourced overseas. Fender should consult Mercury. That's all there is to it.
-Electrolytic cap values are higher since wall voltage has been gradually on the rise over the last 50 years
-Today's Jensens are obviously not the Jensens of yesteryear
-PCB circuit lines are, as slider mentioned, far thinner than a PTP handwired board, therefore less efficiency in conductance
-Current production tubes are of different (I won't say lesser) quality construction

All in all, it's still a good amp for the money, and it comes as close as Fender's gonna go to reproduce the original. But the old addage rings true. They don't make 'em like they used to.
 

Figaro

Silver Supporting Member
Messages
12,440
I find the biggest difference is indeed the transformers.They are made in China these days for Fender and I am not a big fan of them at all.
I swap out tubes,speaker and output transformers on the PRRI and they come to life.Other than maybe a couple of better quality tone caps in the signal path,they are pretty good as is.Not like the originals I'm afraid but acceptable overall.IMHO.
Please tell which output transformer and tone caps you use.
 

DrRaoulDuke

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173

pdf64

Member
Messages
6,948
added grid stoppers on the 6v6s
Well spotted!
With the values used, I don't think that the addition of 1k5 control grid and 470 ohm screen grid stoppers will have much effect on circuit audio performance.
changed the rectifier to a 5AR4
There are PR AA1164 K-FD drawings for both GZ34 (=5AR4) and 5U4 rectifiers https://el34world.com/charts/Schematics/files/Fender/Fender_princeton_rev_gz34_aa1164.pdf
In reality, I've no idea what the ratio split between the versions actually made was :confused

The RI has a few other additions too, eg 6 protection diodes, bias pot, higher value bias supply reservoir cap, ground loop suppression resistor (R60), mains current inrush suppressor. As above, I don’t think that any of it will change the sound much.
 
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HotBluePlates

Member
Messages
9,835
... The RI has a few other additions too, eg 6 protection diodes ...
Do you have any insight on the purpose of D1 and D5 across the 1Ω cathode resistors?

If the forward voltage drop of the diodes is supposed to be 0.7v, they wouldn't do anything until 700mA is flowing through the cathode resistors. At that point, sure the 1w resistors will only have 1/2w dissipation, but the tubes are well-done and trying to pull 1.4A from the B+ supply?
 

pdf64

Member
Messages
6,948
Yes, I think they're just to avoid the resistors requiring replacing in the case of a tube shorting, thereby saving a warranty return.
I think that really a HT fuse should have been fitted.
At least the current inrush suppressor RT1 in the PT primary circuit allows the use of a F type primary fuse, so hopefully it should blow fairly quickly and save the PT, if a shorted power tube etc draw HT fault current.
 

harvey j

Member
Messages
1,276
The trace wire on the pcb is much thinner than cloth covered wire and the lengths are much shorter, the 1/4 watt resistors are half the size of the originals, the small radial coupling caps can't be compared to the blue molded "Ajax" caps, the cheaper transformers, newer Russian, Slovak or Chinese preamp tubes and it's not a finger joint pine cabinet. All these thing have an affect on sound in some respect.

I've yet to hear a DRRI sound even close to an original. I can hear a difference.
How would you know unless they were both new?
 




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