Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: dmp on November 30, 2015, 09:50:53 am

Title: Princeton'ish build
Post by: dmp on November 30, 2015, 09:50:53 am

Here is a amp build I completed earlier this year. It is based on a Princeton Reverb circuit using EL84s as the output stage.
I had a salvaged organ chassis and speaker baffle to build around. After getting it going, I upgraded to a new output transformer to get 4,8,16 ohm outputs (and a better sound than the stock Triwec), and more durable speakers (Celestion g10 vintage).
I have a post PI master volume on the back, a switch for fixed or cathode bias, and a three-way switch for feedback: none, princeton (med), or twin (high).
 

Title: Re: Princeton'ish build
Post by: dmp on November 30, 2015, 09:56:07 am

Pine cabinet made with box joints. Two 10" speakers. I'd like to add tilt back legs when I find something to use that fits the character of the amp.

 

Title: Re: Princeton'ish build
Post by: sluckey on November 30, 2015, 11:06:39 am

That really looks good! The AO-43 is a very versatile platform for many different 15-20 watt guitar amps. I'm surprised you replaced the Hammond OT. I like that transformer. Just wish it had multiple output taps.

Title: Re: Princeton'ish build
Post by: tubenit on November 30, 2015, 11:09:51 am

I am quite impressed with that build!  Thanks for sharing the photos and info.

With respect, Tubenit

Title: Re: Princeton'ish build
Post by: dmp on November 30, 2015, 11:18:36 am

Thanks guys
I hadn't planned to replace the OT - or the speakers - but the lack of 4 & 16 ohm taps drove me to get the new OT. I did play the amp quite a bit with the original and I do like the new one more.   I pretty sure the original was Triwec, not Hammond. The code on it was 5247105.
I replaced the speakers because they were rattling at high volume (high distortion). I put in the Celestions and I still have the rattle  :BangHead:

Title: Re: Princeton'ish build
Post by: shooter on November 30, 2015, 11:53:44 am

Quote

still have the rattle

Make sure it's not the chassis doing the rattle, 2 of my homebrew cabs rattled, both turned out to be chassis, not speaker, one still rattles if the screwdriver I have jammed 'tween cab and chassis and comes loose :think1:

Title: Re: Princeton'ish build
Post by: dmp on November 30, 2015, 12:00:27 pm

I think it must be something like that. Shouldn't be too hard to find with a little time to troubleshoot. I just assumed it was a bad speaker.

Title: Re: Princeton'ish build
Post by: Ed_Chambley on December 01, 2015, 04:16:15 pm

Nice Build.  I have a 2, 10" Princeton'ish build as well.  I tried a single 12, but preferred the 2 10's.

The cab style reminds me of an Ampeg.