Princeton Head Build

[Ed_Chambley]

Hi Guys, I am planning a princeton build for a friend.  It will be a scratch build, no kit.  I was looking over some older forum posts and found layout, schematics and a board mask.  It has  master volume which switches off.  Does that simply turns off the master.  I was actually planning a PPIMV until I saw this.  BTW, I am speaking of the 1164 circuit, blackface.  What are the benefits of doing this?  Also, I found a hammond OT which has 4,8 and 16 ohms taps.  I have heard with the stock ot really does not matter, it can handle the different speaker ohms.  I find this hard to believe.  Whenever I build a head, I usually use a multi-tap transformer.

If anyone has built this Hoffman version, what do you think of it?  It looks just like a fender schematic with a couple of additions like adjustable bias.  Also wold a PT with 330-0-330 work well?  And lastly, would adding a choke be a benefit as the schematic does not show one?

[sluckey]

Sounds like you may be talking about a Princeton Reverb, rather than a Princeton? Can you post some links to the info you're asking about? Several people have built the Hoffman style PR. In fact, it was developed by a couple board members right here on this forum.

[phsyconoodler]

where are you hearing all this stuff?
Here's the deal:most Fender OT's for the Princeton Reverb are 8k primary.If you were to use a 6.6K like the Deluxe Reverb,then you could use any speaker load 4,8,16. Not so with an 8K.But....because the vast majority of people don't dime a Princeton they can handle mismatched loads for years with no damages.
  Adding a choke will just make the amp smoother and maybe a bit quieter.Not a bad idea,but not necessary.
The switchable master?Benefits?You can switch it in or out.That's the benefit.

Everyone says Fender's can handle a mismatched load.They are not really right.The difference is that Marshall's and other amps are not really designed to play as sedately as most play their fender amps.Crank your Fender to 10 with a mismatched load and see what happens.

[mresistor]

I built a Hoffman boarded Princeton Reverb head and simply love it. I built it with a Deluxe OT. It sounds fantastic and has lots of sustain. Barry made up the drawings and they are in the archive thread I believe. Fantastic circuit and I can't imagine anyone not liking the amp.
BTW - I'm currently playing it into a 16 ohm 2x12 box and also use a Weber Mini Mass on occasion, and crank it up to 8 or so with no problems at all. It takes effects very well. This is my #1 amp. 

[Ed_Chambley]

Sluckey, Here is the downloads from the string I was reading.  It was from 2006.  http://www.el34world.com/Forum/index.php?topic=624.50 is where I was reading.

[Ed_Chambley]

where are you hearing all this stuff?

Yes, I agree with you comments, that is why I wrote that I find it hard to believe.  The Hammond OT I was referring to is an 8000 ct and has 4, 8 and 16 ohm taps.

[Ed_Chambley]

Sounds like you may be talking about a Princeton Reverb, rather than a Princeton? Can you post some links to the info you're asking about? Several people have built the Hoffman style PR. In fact, it was developed by a couple board members right here on this forum.

It is a Princeton Reverb.

[Ed_Chambley]

I built a Hoffman boarded Princeton Reverb head and simply love it. I built it with a Deluxe OT. It sounds fantastic and has lots of sustain. Barry made up the drawings and they are in the archive thread I believe. Fantastic circuit and I can't imagine anyone not liking the amp.
BTW - I'm currently playing it into a 16 ohm 2x12 box and also use a Weber Mini Mass on occasion, and crank it up to 8 or so with no problems at all. It takes effects very well. This is my #1 amp. 

Why did you decide on a Deluxe OT? What PT did you use?

[sluckey]

It has  master volume which switches off.  Does that simply turns off the master.  I was actually planning a PPIMV until I saw this...    ...What are the benefits of doing this?

That is a simple crossline MV. The switch simply totally removes it from the circuit. I have the same mv on my Lightning and I hate it. I would much prefer a dual pot post mv. But do you really need any mv on a PR?

Also wold a PT with 330-0-330 work well?  And lastly, would adding a choke be a benefit as the schematic does not show one?

I used a 330-0-330 on my Deluxe Reverb. Should work on a PR also. I think most who built this PR used a choke. I would.

[mresistor]

Ed asked "Why did you decide on a Deluxe OT? What PT did you use?"
I  wanted nice tight output with well defined bass and maybe a little more headroom. I read that a stock DR OT is 25% bigger than the PR OT so that is what I used. I am using a Weber W041318 https://taweber.powweb.com/store/041318sch.jpg   rated @ 6.6K and 8 ohms.
I very much like it and at $26 it was a great deal.
For a PT I selected an Allen/Heyboer TP-25, actually I think I may have picked it up second hand on fleecebay.
http://www.allenamps.com/parts.php#transformers
I wanted to be able to use 6L6's or EL34's if I so desired. Also was part of the reason to go with a DR OT.

The amp sounds great as is. Haven't tried 6L6's in it yet, and probably won't anytime soon.

[Ed_Chambley]

Ed asked "Why did you decide on a Deluxe OT? What PT did you use?"
I  wanted nice tight output with well defined bass and maybe a little more headroom. I read that a stock DR OT is 25% bigger than the PR OT so that is what I used. I am using a Weber W041318 https://taweber.powweb.com/store/041318sch.jpg   rated @ 6.6K and 8 ohms.
I very much like it and at $26 it was a great deal.
For a PT I selected an Allen/Heyboer TP-25, actually I think I may have picked it up second hand on fleecebay.
http://www.allenamps.com/parts.php#transformers
I wanted to be able to use 6L6's or EL34's if I so desired. Also was part of the reason to go with a DR OT.

The amp sounds great as is. Haven't tried 6L6's in it yet, and probably won't anytime soon.

I already have most of the parts except for the OT.  Thanks for the suggestion of using the Deluxe and if I am not mistaken, my 330-0-330 could run a couple of 6L6's as well.

[mresistor]

What's the filament current rating on your PT?  If it's 3A it may be a little close to max with 6L6's. The TP-25 filament winding is rated 6.3V at 4.5A.

[Ed_Chambley]

But do you really need any mv on a PR?


[/quote]
It is so easy to do when building, i usually do it anyway.  I changed my JTM-45 over to the larmar, Larry and Mark to PPIMV and it really is very nice. The pot makes a difference and the PEC pot is $38.   I checked Alpha's and their readings vary considerably.  It has exactly 220 ohms when dimed.  So I put one in my recent Bassman Build and is even better in this amp.  I have been looking at my stock 66 Super Reverb, but I think I will leave that one alone.  I've got one of those my Father gave to me that he bought new and has never been out of the house.  Everything is exactly as it was when purchased.  I wanted so long to mod it, but never have so I have a 73 which I have done all the mods to.  There are really a lot of simple mods for SR that really make them scream.

I am kind of sold on the LARMAR PPIMV.  Replacing the 220 ohm resistors with a pot was really a great idea.

[Ed_Chambley]

What's the filament current rating on your PT?  If it's 3A it may be a little close to max with 6L6's. The TP-25 filament winding is rated 6.3V at 4.5A.

146
   
115
   
60
   
600V C.T. @ 172ma.
   
5V C.T. @ 3A
   
6.3V C.T. @ 5A

[Ed_Chambley]

OOPS, just noticed my PT is 300-0-300.  Think it will be enough?