Tweed champ vs princeton (5f1 vs 5f2a)

[martinman]

Hi Everyone,

I was reviewing the layout of both amps and it seems there is only a very small difference: 1) tone pot, 2) extra stage of filtering. Can someone explain why the extra filtering stage is needed? What does this actually do? The rest of the amp - component values all are the same.

[sluckey]

Can someone explain why the extra filtering stage is needed?

They both have the same number of filtering stages. The Princeton just has twice the capacitance for the first stage. Any single ended amp benefits from extra filtering up front. The Champ was Fender's cheapest, bottom of the line amp, mostly aimed at students or beginners. The Champ had a cheap 8" speaker that did not reproduce low frequencies very well so you did not notice the power supply hum. The Princeton's larger speaker was better at reproducing low frequencies so the hum would be more noticeable, hence the larger first stage filter cap.

[Mark]

Personally I think it is a no-brainer build the Princeton over the Champ. There is more real estate available if you want mod the amp, the tone control is a plus and it can be switched out with a pot with a DPDT switch.

Use a fat stack output transformer too, I found the output transformer contributed the most to the Champs lack of bass response. I'd tried 12" speakers and the output transformer gave me the biggest increase in bass response.

[pops]

Or build the champ with a tone control and a 12" speaker. Could even parallel the 6v6 if you want. There are a lot of cool mods to a champ and a killer sound that a princeton just can't compare.

[Mark]

A 5F1 Champ with a tone control is called a 5F2 Princeton.

http://www.turretboards.com/layouts_sch ... mp_5f1.gif

http://www.turretboards.com/layouts_sch ... n_5f2a.gif

I've done most of the mods out for these amps which is why the Princeton chassis is the way to go.

http://www.tdpri.com/forum/amp-central- ... ntrol.html

[pops]

And they say age has no benefits, confusion, memory loss, bla bla bla.

[Mark]

I've heard people say the larger Princeton cab sounds better than the Champ cab too. The larger baffle board would help too whether a 8" or 10" speaker was used.

I've experimented with using a 6L6 or two 6V6's, the increase in volume isn't worth the extra tube, however the 6L6 has a firmer bass response while the 6V6 has the nice creamy tone. The stock Champ power transformer cannot handle a correctly biased 6L6. It will run hotter than the output tube.

I've tried the extra filtering stage to get rid of the hum, it's okay till the amp starts distorting then it provides additional sag which may not be wellcome.

I've put an additional gain stages on the Champ this sounds good to a point, but real estate is an issue which is where the Princeton chassis comes into it's own.

Once you go beyond this sort of thing it's time to consider stuff at the AX-84 forum.

Oh yes, always check the bias of the output tube, it's not uncommon for the 6V6 to be biased beyond the recommended 12 to 14W (100%) dissipation.