Princeton reverb build in a trainwreck chassis

[norburybrook]

The footswitch is working in reverse fro the reverb and trem but if I switch the cable connections at the amp end it makes a horrible noise and stops working.

The connection to the reverb FS must be shielded but the connection to the trem FS does not have to be shielded. So, if you have a typical Fender two button FS, you need to swap connections at the FS end. May be easier to just swap the switches around.

Or, you could swap the connections INSIDE the amp if your layout permits.

Or just swap the label everything else on this amp is the wrong way round so why not the switch


M

[sluckey]

Even better! Follow the electron to the path of least resistance.

[norburybrook]

OK biased up to around 22/23mv and the trem did indeed come into range. p.s. note to self don't try and Bias with the bias trem on ....LOL .....

I have a box of old 12*7 valves with no marking so i tried a random one in the verb spot...perfect...I have e a NOS AT7 coming as well.


I've got it plugged into the Alnico cream cab at the moment.

Dear lord...what a perfect sound....really is just ...well perfect...it has clarity and no harshness, the reverb is beautiful and the trem.....oh lordy lordy ...subtle and sweeeeet.

man this thing sounds good


M

[martin manning]

[norburybrook]

had a lovely sunny day today so made the cabinet. It's not based on anything in particular I just made up the dimensions , I think it's height and width are similar to the width and height of a princeton but I've made it deeper so it has more volume so should be a bit 'bigger' sounding. I found some engineered pine so used that, it's great, easy to work with and incredibly light.

tomorrow tolex and grill cloth.

any reason not to use fat short wood screws to hold the speaker in? sometimes it's hard to get a screw the right length when using those pressed in metal inserts, they're often too long and poke into the grill.

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M

[didit]

Hello -

Cool seeing this all came together so well. Clean work as always. Cabinet looks to be exactly the correct size.

An answer for that last question first. Presumed referring to T-nuts, there's durability long-term with those. I've had to add them more than once to boxes where wood screws did the job badly. With care in measurement, you should be able to get correct length bolts that mate cleanly and clear grill fabric.

Question - did you power PI off the same B+ node as original schematic as designed, or to the node higher in the string?
.
You had one recommendation for JS-1250. It and their EJ-1240 are are two recent signature Eminence speakers that one might anticipate are different but both well suited for this style amp. Preference for me would be Alnico, but that's personal taste versus something measured.

Best .. Ian

[norburybrook]

Hello -

Cool seeing this all came together so well. Clean work as always. Cabinet looks to be exactly the correct size.

An answer for that last question first. Presumed referring to T-nuts, there's durability long-term with those. I've had to add them more than once to boxes where wood screws did the job badly. With care in measurement, you should be able to get correct length bolts that mate cleanly and clear grill fabric.

Question - did you power PI off the same B+ node as original schematic as designed, or to the node higher in the string?
.
You had one recommendation for JS-1250. It and their EJ-1240 are are two recent signature Eminence speakers that one might anticipate are different but both well suited for this style amp. Preference for me would be Alnico, but that's personal taste versus something measured.

Best .. Ian

Ian, I wired it exactly as the original but added grid stoppers and up rated bias filter cap and up rated dropping string resistors. Oh and added a BIAS pot.

I've ordered a canabis rex , I htought I'd give it a try, everyone seems to love them in these amps and I've never heard one so i thought it was worth a try. The cream alnico is sounding lovely so I can fall back on an alnico if I don't like the eminence.

M

[Colossal]

Dear lord...what a perfect sound....really is just ...well perfect...it has clarity and no harshness, the reverb is beautiful and the trem.....oh lordy lordy ...subtle and sweeeeet.

man this thing sounds good

That's awesome, Marcus. Always great when an amp is extra special! Did you add a grid stopper to the entrance of the cathodyne?

EDIT: Oh, I think you were answering Ian when I was typing: you added grid stoppers

[didit]

Ian, I wired it exactly as the original but added grid stoppers and up rated bias filter cap and up rated dropping string resistors. Oh and added a BIAS pot.

Would encourage trying out that isolated higher voltage point in B+. Adds about 30% more headroom for the cathodyne to swing. Should be easy to test. This, together with grid stoppers, made most of the few I tinkered with.

I've ordered a canabis rex , I htought I'd give it a try, everyone seems to love them in these amps and I've never heard one so i thought it was worth a try. The cream alnico is sounding lovely so I can fall back on an alnico if I don't like the eminence.

I have a C-Rex, and like it. Not tried with a Princeton, but should sometime. Was favoured in a Deluxe Reverb, until the D120F came along. Warm. Recall it took some sparkle off, undesirably in that case but helpful with other amps.

.. Ian

[norburybrook]

Ian, I wired it exactly as the original but added grid stoppers and up rated bias filter cap and up rated dropping string resistors. Oh and added a BIAS pot.

Would encourage trying out that isolated higher voltage point in B+. Adds about 30% more headroom for the cathodyne to swing. Should be easy to test. This, together with grid stoppers, made most of the few I tinkered with.

I've ordered a canabis rex , I htought I'd give it a try, everyone seems to love them in these amps and I've never heard one so i thought it was worth a try. The cream alnico is sounding lovely so I can fall back on an alnico if I don't like the eminence.

I have a C-Rex, and like it. Not tried with a Princeton, but should sometime. Was favoured in a Deluxe Reverb, until the D120F came along. Warm. Recall it took some sparkle off, undesirably in that case but helpful with other amps.

.. Ian

Ian,

Thanks, I hope it doesn't take the sparkle off, I like a bit of sparkle Looking at the frequency plot for the cannabis Rex it has quite a spike around 2k, I would thought that would make it a bit bright! Did it take long to break in? that's another issue with some speakers, they can sound awful until broken in.

Regarding the P.I. is it just a case of taking it off a node further up the B+ chain? do you have that node then going to 2 places? or swap them?


M

[didit]

Thanks, I hope it doesn't take the sparkle off, I like a bit of sparkle Looking at the frequency plot for the cannabis Rex it has quite a spike around 2k, I would thought that would make it a bit bright! Did it take long to break in? that's another issue with some speakers, they can sound awful until broken in.

Regarding the P.I. is it just a case of taking it off a node further up the B+ chain? do you have that node then going to 2 places? or swap them?

It was several years ago, so fuzzy memories. Recall it stiff sounding, so putting it in a box and running it loud for a few days. I have done that more than once so perhaps confusing myself. It's now installed in a Traynor YGM-3, which was a good match.

Illustration might help. Just unwire from the shared filter node that the preamp is using and move it onto the otherwise unconnected node up one step. One might reasonably ask why it's this way initially.

Princeton B+.jpg

Best .. Ian

[norburybrook]

OK, well after a few days I've finished so far.

Tolexing and grill all done. While i was waiting for the speaker , an eminence Cannabis rex, I thought I'd check a few things over, one of which was the reverb tank. I 'd just thrown it in there and it was sounding great however i thought i should check it. The princeton wants an 8 ohm fender reverb tanks but the one i had actually measured 600ohms !! which i thought was way off so ordered the correct one.

The new one is in and of course it has the classic fender reverb scenario of a sweet spot between 1 and 2!! the old tanks I had was lovely in the fact that you could dial it in easier as it was up around 6 or 7 and a big sweet spot. Whats the best way to deal with this/ a lower output valve? Ay7 Au7?

Edit: tried an AY7 no difference.

The Cannabis rex? the jury is still out, it's new so i think it needs a break in, i still prefer the Alnico cream in my other cab but i'll let the dust settle on the rex.

Is there a way to have a slower range of trem? Again,like the reverb it's all around 1 or 2 for me.

edit: Just done a google and adding extra 0.1 cap in parallel with the other 0.1 caps will do it

OK pics.

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M

[norburybrook]

well the internet is a wonderful thing....So i've solved all my issues.

Send (Dwell) Pot ...perfect

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added an extra 0.1uf cap to trem cap in parallel ......again...perfect.

why didn't Leo think of these things

[sluckey]

The new one is in and of course it has the classic fender reverb scenario of a sweet spot between 1 and 2!! the old tanks I had was lovely in the fact that you could dial it in easier as it was up around 6 or 7 and a big sweet spot. Whats the best way to deal with this/ a lower output valve? Ay7 Au7?

The single best mod for the original Fender reverb circuit is to replace that 100K linear pot with a 100K log pot. You may want to do this even though you now have a dwell pot.

The slow trem thing is to add a .01 (not .1) cap across one of the existing .01 caps. I bet that's what you did even though you are saying .1

[norburybrook]

The new one is in and of course it has the classic fender reverb scenario of a sweet spot between 1 and 2!! the old tanks I had was lovely in the fact that you could dial it in easier as it was up around 6 or 7 and a big sweet spot. Whats the best way to deal with this/ a lower output valve? Ay7 Au7?

The single best mod for the original Fender reverb circuit is to replace that 100K linear pot with a 100K log pot. You may want to do this even though you now have a dwell pot.

The slow trem thing is to add a .01 (not .1) cap across one of the existing .01 caps. I bet that's what you did even though you are saying .1

yes that's what i did

Steve i think it was a post from you on another forum I found when i googled so thanks. Dwell pot is great I don't know if i can be bothered now to take fit a log verb pot as it's working really nicely.



M