Calling all mod gurus - New '68 Princeton bright mod needed

[rduval]

I just picked up one of the newly released '68 Princeton Reverbs, great little amp. It sounds great with my single coils but needs treble at 10 all the time.

When I plug in my 335 (or any humbuckers) it's just too dark, even at 10 on the treble. It lacks "sparkle".

So here's what I'm thinking, It has 2 jacks, #2 being -6db; Can I add a small cap like a .001 or .047 or something across the resistor to allow more highs to get through when plugged into that channel?

I'm thinking that the humbuckers are almost always going to be plugged into the 2nd jack anyway so would that work.

Pics attached of input board, I assume R48 would be the one to put the cap across if I were to do it?

Rick

 

[Scott_F]

Re: Calling all mod gurus - New '68 Princeton bright mod needed

amp bright caps are normally connected to the volume pot or the treble pot, or sometimes linking them. Do you have the schematic? I don't have my old Gerald Weber book with all the schematics in it with me. I'll check when I get home. I'd assume they based this off the AB868 circuit. I tried googling it but what I found on the net was blurred.

 

[Scott_F]

Re: Calling all mod gurus - New '68 Princeton bright mod needed

Webers schematic book doesn't have it in there. It goes up from tweed to 65 blackface and just stops.

 

[Agileguy_101]

Re: Calling all mod gurus - New '68 Princeton bright mod needed

Even if the Weber book had a 68 Princeton schematic it wouldn't be what the OP has - it sounds like he has one of the new Silverface reissues.

 

[BrianS.]

Re: Calling all mod gurus - New '68 Princeton bright mod needed

Webers schematic book doesn't have it in there. It goes up from tweed to 65 blackface and just stops.

That's because Gerald Weber hates silver face fenders! At least that is what I gathered from reading his book and all the Ask Gerald columns in the old Vintage Guitar mags back in the early 90s.

 

[Scott_F]

Re: Calling all mod gurus - New '68 Princeton bright mod needed

Can't find on on the net either.

 

[rduval]

Re: Calling all mod gurus - New '68 Princeton bright mod needed

Even if the Weber book had a 68 Princeton schematic it wouldn't be what the OP has - it sounds like he has one of the new Silverface reissues.

Yep, its one of the new 68 reissues (confusing isn't it) so I don't think there will be any easily available schematics.

I did do some experimentation with some caps I had around. I put 2 .001uf caps across R51 which brightened up the 2nd input (-6db) somewhat but I think there'e still more that could be done. I'm no techie I "just know enough to be dangerous" lol but I think this amp could really benefit from a bright switch.

My thinking on this mod is that, since I added the caps across the -6db resistor, I've effectively raised the frequencies that the caps pass by +6db. Can anybody confirm that I'm on the right track?

 

[LReese]

Re: Calling all mod gurus - New '68 Princeton bright mod needed

I have this feeling with my EC Vibrochamp. This might not be too helpful to you, but I'm using an Echoplex pre with mine to make it a hair brighter. Could also go with an EQ.

I don't know if you got the amp new or not, so might be a moot point.

 

[FAC]

Re: Calling all mod gurus - New '68 Princeton bright mod needed

I have a similar issue with the same amp...my single coil guitars sound awesome, but my 335 sounds a bit dull. I like the fact that the amp does not have a bright cap...my drive/distortion pedals sound great, even at low volumes...I think that is why Fender left it off these amps (clipping them is a common mod). So, I just bump up the highs a bit on my Fromel Shape EQ for the 335...the sparkle returns.

Furthermore...I thought a bright cap was supposed to go across the volume pot, and that by about 4 on the dial its effects were no longer felt...that is, it only works at lower volumes?

 

[rduval]

Re: Calling all mod gurus - New '68 Princeton bright mod needed

I gigged with my "mod" last night and it's great. The caps brighten up the 2nd input (the -6db) which is great for my 335, I put the strat into the #1 and it's perfect for there...

Look! I just invented a mod...lol

I also bought the 68 DRRI and I'm going to do the same to the 2nd inputs on both channels.