Hi all.
New here. My name is Duke.
I'm looking for answers, and hope someone has some ideas.
I am an electronics tech, just not an engineer.
The secenario: A friend obtained an old Hammond PR20 Tone Cabinet. Since none of us have an organ to connect it to, we decided to see about modding it for guitar.
I downloaded the schematics from Capatin Foldback's site (Lars Mikael...a nice, helpful person), and proceeded to experiment. Here's his site, BTW: http://www.captain-foldback.com/
I emailed him, and he said I needed a transformer to interface a 1/4" jack to the G1 and G2 inputs (and ground) of the three amplifier sections. So, I ordered one from Tonewheel General and installed it. (It's the HS122XB Input Transformer here:
http://www.tonewheelgeneral.com/build_page.php?category=Leslie+Speaker+Parts&subcat=Transformers
I also connected a grounded cord, switch and fuse for power. Checked all the tubes...all very good.
Lit up the first time. I knew I was going to have some level problems even before I plugged anything in. I took a POD 2.0, and a Yamaha DG Stomp over to see what they would do. Well, they only put out a few volts, cranked. They played, but volume was low. I knew that would happen, so I plugged each into an ART Tube MP preamp, and pushed the +20dB button. NOW, it was getting closer. But the highest clean signal (before clipping) I could get out of the combinations was about 16V. (I had an O'Scope measuring, and I was also testing with a sine wave from a signal generator).
The PR20 G1 and G2 input lists 24VAC at the test points, and Lars said that's approximately what a Hammond will feed it.
The thing actually sounded pretty good, but I know if I can get it to put out more and make those tubes work a bit harder, it might even sound better.
So, there's my dilemma. I'd like to be able to take a small signal from a preamp unit, whether it's my homebrew guitar pre, a POD, a DG Stomp..etc., and bump it to ~24V...without having to add a Tube MP, etc.
Do I do it before that tiny Hammond transformer, which would be easier because it's only +/-? Or do I do it after, with both legs run to something before entering the amp?
HOW do I even think about it? Can a different transformer work at the input, and get rid of that Hammond one, which seems to be a 1:1...no boost? Do I build an active circuit boost? Would it have to be tubes, or would something S.S. work?
Like I said, it works now, and it actually sounds pretty good, but I think I can get a lot more air to move from those 4 speakers.
Any ideas will be appreciated.
Thanks,
Duke
New here. My name is Duke.
I'm looking for answers, and hope someone has some ideas.
I am an electronics tech, just not an engineer.
The secenario: A friend obtained an old Hammond PR20 Tone Cabinet. Since none of us have an organ to connect it to, we decided to see about modding it for guitar.
I downloaded the schematics from Capatin Foldback's site (Lars Mikael...a nice, helpful person), and proceeded to experiment. Here's his site, BTW: http://www.captain-foldback.com/
I emailed him, and he said I needed a transformer to interface a 1/4" jack to the G1 and G2 inputs (and ground) of the three amplifier sections. So, I ordered one from Tonewheel General and installed it. (It's the HS122XB Input Transformer here:
http://www.tonewheelgeneral.com/build_page.php?category=Leslie+Speaker+Parts&subcat=Transformers
I also connected a grounded cord, switch and fuse for power. Checked all the tubes...all very good.
Lit up the first time. I knew I was going to have some level problems even before I plugged anything in. I took a POD 2.0, and a Yamaha DG Stomp over to see what they would do. Well, they only put out a few volts, cranked. They played, but volume was low. I knew that would happen, so I plugged each into an ART Tube MP preamp, and pushed the +20dB button. NOW, it was getting closer. But the highest clean signal (before clipping) I could get out of the combinations was about 16V. (I had an O'Scope measuring, and I was also testing with a sine wave from a signal generator).
The PR20 G1 and G2 input lists 24VAC at the test points, and Lars said that's approximately what a Hammond will feed it.
The thing actually sounded pretty good, but I know if I can get it to put out more and make those tubes work a bit harder, it might even sound better.
So, there's my dilemma. I'd like to be able to take a small signal from a preamp unit, whether it's my homebrew guitar pre, a POD, a DG Stomp..etc., and bump it to ~24V...without having to add a Tube MP, etc.
Do I do it before that tiny Hammond transformer, which would be easier because it's only +/-? Or do I do it after, with both legs run to something before entering the amp?
HOW do I even think about it? Can a different transformer work at the input, and get rid of that Hammond one, which seems to be a 1:1...no boost? Do I build an active circuit boost? Would it have to be tubes, or would something S.S. work?
Like I said, it works now, and it actually sounds pretty good, but I think I can get a lot more air to move from those 4 speakers.
Any ideas will be appreciated.
Thanks,
Duke