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building a princeton clone

jmt

Member
Messages
4
first time posting here, so apologies if I'm in the wrong spot.
I want to build a Princeton reverb clone head from scratch, have not built an amp before, but I'm extremely handy, good with this sort of thing (soldering, building etc).
I have found a few good lists of the parts online (Hoffman) I'll need, and have looked at several kits (mojotone, allen, others). However, I am pretty set on adding a few tweaks/mods to this baby (deluxe transformers, mid pot, gain, others?).
However, I am wondering about the parts.
How do I tell a "good" potentiometer/capacitor/resistor from a crappy one? Can I just pick this stuff up at radio shack? I have a U-do-it electronics near me, and would love to go there and just pick everything up. I'm trying to keep the cost down. I can fab the chassis and cabinet, and have a few different speaker cabs (I like to mix and match heads and cabs...s'fun)
thx...
jef
 

mark norwine

Member
Messages
17,189
My advice....buy a kit from Mojo.

The materials are first-rate, complete and well labeled.....and you won't be left wondering "what do I need to scrounge up next?"....

No, you can not source what you need from Radio Shack. Some stuff, maybe. But everything? Nope...

Also: do not "mod" while building. If this is your first build, build it 'straight' and get it to work. That alone might be a challenge. Once it functions, THEN mess with it.
 

dazco

Member
Messages
15,168
Really? Mojo...i just checked the price on a blackface PR with NO speakers and NO tubes and WITHOUT shipping it was $817 ! Am i missing something here? A fender RI WITH tubes and speaker is about that much ! That was a bit shocking. They must be selling them somehow, so what is it that would make someone buy a kit instead of the fender RI when the fender is much cheaper, not to mention would have 3 times the resale? (if you could even sell the kit at all)
 

Kenny Blue

Silver Supporting Member
Messages
3,632
Really? Mojo...i just checked the price on a blackface PR with NO speakers and NO tubes and WITHOUT shipping it was $817 ! Am i missing something here? A fender RI WITH tubes and speaker is about that much ! That was a bit shocking. They must be selling them somehow, so what is it that would make someone buy a kit instead of the fender RI when the fender is much cheaper, not to mention would have 3 times the resale? (if you could even sell the kit at all)
I coincidentally was looking at Mojo kits a bit earlier this morning.

I think maybe you were possibly miss reading the pricing for the Princeton Kit.
Mojo offers that kit complete, or without various items, ie Cab, Speakers, Tubes....

The Mojo kit for the Princeton head without Cab, or Tubes ( no Speakers ) is $547.99
 

oldhousescott

Gold Supporting Member
Messages
2,860
Well, the point of DIY is not so much to save money as it is the satisfaction of playing something you've built, and to build it the way you want it to be (IMO, YMMV, etc.)

I'd recommend buying your passive parts (resistors, caps, pots) from Hoffman. His prices are a tad higher, but all his stuff is geared toward tube amp building and it's high quality. Plus, he ships faster than anyone in the business. He doesn't carry the Micalex sockets, though, and I've come to prefer them for my infrequent builds. You can get those from Antique Electric Supply or Watts Tube Audio and probably some other vendors.

Since you're bending your own chassis, I would go with a standup type power transformer. That way you only have to drill holes, not cut out a square for a laydown type PT. Edcor Electronics USA has good iron at reasonable prices. I'm sure you can find a PT from among their many choices in their Class X products. You could get your output transformer there too, but I would look at the ones David Allen sells. Of course, you can always spend a good bit more and spring for the Mercury Magnetics iron.

Be sure to build your head cabinet tall enough to get plenty of separation between the transformers and the reverb tank. Too short a head cab, and you'll get hum induced in the reverb circuit.
 

Don A

Gold Supporting Member
Messages
6,307
Mojo puts their kits on sale from time to time as well. I paid under $700 for my Mojo PR combo kit around Christmas 2012 and $375 for a tweed Champ kit last Memorial Day, both with free shipping (shipping is still free on domestic orders over $100).

You really can't compare it to a Fender re-issue PR. It's built like the old Fender amps. The re-issue is not.


 

jmt

Member
Messages
4
yea..I guess building it first, then modding would be the way to go, but I want to make sure I have room on the front for a couple extra knobs, etc
did see a "small parts kit" for a tweed Princeton for about $170 from mojo, but didn't see one for a Princeton reverb...I def want to change out the transformers...I play bright and clean with ONE heaping spoonful of greasy dirt...
 
Messages
2,910
Well, the point of DIY is not so much to save money as it is the satisfaction of playing something you've built, and to build it the way you want it to be (IMO, YMMV, etc.)

I'd recommend buying your passive parts (resistors, caps, pots) from Hoffman. His prices are a tad higher, but all his stuff is geared toward tube amp building and it's high quality. Plus, he ships faster than anyone in the business. He doesn't carry the Micalex sockets, though, and I've come to prefer them for my infrequent builds. You can get those from Antique Electric Supply or Watts Tube Audio and probably some other vendors.

Since you're bending your own chassis, I would go with a standup type power transformer. That way you only have to drill holes, not cut out a square for a laydown type PT. Edcor Electronics USA has good iron at reasonable prices. I'm sure you can find a PT from among their many choices in their Class X products. You could get your output transformer there too, but I would look at the ones David Allen sells. Of course, you can always spend a good bit more and spring for the Mercury Magnetics iron.

Be sure to build your head cabinet tall enough to get plenty of separation between the transformers and the reverb tank. Too short a head cab, and you'll get hum induced in the reverb circuit.
The above is what I did. I got my chassis off ebay with faceplates and boards, majority of parts from Hoffman, and OT/PT/reverb transf from David Allen.
 

mark norwine

Member
Messages
17,189
Be sure to build your head cabinet tall enough to get plenty of separation between the transformers and the reverb tank. Too short a head cab, and you'll get hum induced in the reverb circuit.
This is just a general FYI....y'all file it as you see fit.

The statement above is true.....sort of.

If the pan's output jack is too close to the power transformer, you will get hum.

But if you turn the pan 180 degrees, the input jack will be near the PT, yet there will be no hum.

The reason is that the output transducer is high impedance, and is highly susceptible to the radiated field given off by the PT. But the input transducer is low impedance, and isn't affected.

I've successfully added reverb to modded Bassman & Bandmaster heads....the clearance between the PT & the pan is about the thickness of a piece of cardboard. But if the pan is oriented so that the input transducer is under the PT, there's no hum at all.
 

dazco

Member
Messages
15,168
I coincidentally was looking at Mojo kits a bit earlier this morning.

I think maybe you were possibly miss reading the pricing for the Princeton Kit.
Mojo offers that kit complete, or without various items, ie Cab, Speakers, Tubes....

The Mojo kit for the Princeton head without Cab, or Tubes ( no Speakers ) is $547.99
No, i didn't miss that, in fact i used it. Were talking princeton combo as the fender RI is, and no speakers and no tubes was $800+. You quoted no cab too. Point is, with speaker and tubes and everything the complete amp is well more than a fender RI ! And you have to assemble it !
 

jmt

Member
Messages
4
wow...thanx all for responding....and please feel free to pile on with more advice/tips/comments...I'm all ears...
 

Diablo1

Member
Messages
620
No, i didn't miss that, in fact i used it. Were talking princeton combo as the fender RI is, and no speakers and no tubes was $800+. You quoted no cab too. Point is, with speaker and tubes and everything the complete amp is well more than a fender RI ! And you have to assemble it !
When you buy a Fender RI, you are getting a wave-soldered PCB amp. The construction method is great for lowering the cost of the amp build, but not so good for long term reliability, durability and ease of repair. They also use lead-free solder, which is known to have long term reliability problems because of whisker growth. The military uses lead-tin solders for this reason. When you build a kit amp, you can use lead-tin solder and the amp is built exactly like they built them in the 1960s, so they are easily repairable.
 

Kenny Blue

Silver Supporting Member
Messages
3,632
No, i didn't miss that, in fact i used it. Were talking princeton combo as the fender RI is, and no speakers and no tubes was $800+. You quoted no cab too. Point is, with speaker and tubes and everything the complete amp is well more than a fender RI ! And you have to assemble it !
I see what you mean. Well I was just kind of going with what the OP asked in his post ... which was he wanted to build it himself, that he was building a head cab himself and already had a speaker cab... and so he basically just focusing on what it would take to build the chassis itself.
 

jmt

Member
Messages
4
right with the chassis. I'm not planning on being very picky with it. I heard a great story about a guy who builds amps using old .50 caliber bullet boxes for chassis....they're cheap, steel, built like a tank, and also...how effin cool would it be to have a bullet box be your chassis? I've also checked with industrial suppliers that make a variety of metal boxes..steel, aluminum....that are reasonably priced. I don't mind cutting and drilling it myself as needed. I've seen chassis made out of old radios, suitcases....the possibilities are endless
right now I'm most interested in learning about the differences between good quality parts and crappy ones. It's been my experience that the most expensive is not neccesarily better....but I'm not well-versed in the world of amp electronics, so I don't really understand the difference between a good capacitor and a crummy one...
 

dazco

Member
Messages
15,168
But also, with something like a PR there are so few caps you really don't have to worry about the extra cost of good caps. The boutique caps like sozo however i think are just not necassary. I tried then for a year or so and ended up back with mallory and actually feel they are better. Those are cheap, and maybe not the right choice for a fender clone but the point is the same....caps are cheap aside from the boutique stuff, so the $ isn't an issue. The big cost issues are chassis, trannys, cabinet, tubes, and speaker. the guts are cheap. Look at classictone tranny sets. they are cheap as any and people love them. I use then and they've been as good or better than others i used such as heyboer and hammond. Build your own cab and save a good bit too. But any way you look at it, unless you have some of the parts already and/or make some yourself like the cab or chassis, building an amp is NOT cheap. My 50 watt marshall style amp without speaker or tubes, homebuilt cab, blank self drilled chassis cost be over $600 to build using mostly the cheapest parts. It's NOT a shortcut to a cheaper amp if thats what u want. IMO it's a way to get exactly the amp you want similar to building a fender from ebay parts. I loved JCM 800's but I felt they weren't nearly the best they can be so i built what i felt would be and it worked out.
 






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