Progress Report; Holy Macaroni this little sucker is LOUD!

[skyboltone]

Here's the latest nephew build. It's a two hole Liverpool using a Hammond Organ 10,500 ohm primary to 8 ohm secondary OT from an AO-29. The PT is a 300-0-300 (with a 256 ohm secondary winding!). This is the same PT that Dr. Z used in the Carmen Ghia. It's also used in the Goodsell 17, Matchless Spitfire (and others).

[IMG:800:600]http://i12.tinypic.com/71g6ued.jpg[/img]

I modeled the Power Supply on Duncan's software and decided to start out with an 18 volt zener at the center tap. It should be about right as soft as this transformer is. I use a 150W Darlington transistor to multiply the half watt zener so it'll work in this application. That's the little TO-220 bug next to the bleeder resistors.

QUESTION:
The Express shows a 500pf mica treble cap while the Liverpool shows a 50pf. Is that right? I stuck in the 50pf but was surprised by that.

Dan

[gearhead]

Very cool.

Natural light? You cut a skylight in that container?

[skyboltone]

Very cool.

Natural light? You cut a skylight in that container?

No, the bench is right at the door which faces Southy Westy kinda. It's nice to work by natural light though. Thanks

dan

[drhulsey]

The Express shows a 500pf mica treble cap while the Liverpool shows a 50pf. Is that right?

Yes You only need a 500 pF if you live on the water

[skyboltone]

Well all the wiring is finished. Same story as others, 1/8th rotation of the V knob gets big response. Bad bedroom amp. The more you push it though, the better the feedback and harmonics get, so it must be about right. I wonder what a 2 meg audio pot would do? I'll tell you one thing, this is not a good rig to be close to going through 4 10"s at 100db/meter. What in the world do you do with a full size one?!

Help needed.

It motor boats real faint like when you turn the presence knob up.

It has a hissy/buzzy background that I took down 50% by putting an .02 ceramic across the zener in my center tap circuit. I'm thinking it maybe needs to be across the whole darlington? Any thoughts on size for the noise cap are much appreciated.

Wow, what an amp! Here's the darlington/zener contraption. I'm using the NPN screwed right to the chassis.
[img:497:280]http://i7.tinypic.com/7xl4iud.jpg[/img]

[briane]

It motor boats real faint like when you turn the presence knob up.

I had the same problem when I brought up my express. The NFB feed wire was running too close to the power tube feeds(from the PI).

I added a small resistor between the tail resistor and the NFB feed wire and it cleared right up.

brian

[skyboltone]

It motor boats real faint like when you turn the presence knob up.

I had the same problem when I brought up my express. The NFB feed wire was running too close to the power tube feeds(from the PI).

I added a small resistor between the tail resistor and the NFB feed wire and it cleared right up.

brian

Thanks Briane. That's kind of where I'm at now. I've got the Power tube feeds twisted and on the deck but the NFB wire runs pretty close. I've converted over to the Express presence control and now have a narrow band of flutter in the middle of the pot ranage. I'm going to clip in the 4,7K tail tomorrow and see where it needs to be to put a stop to it. And by the way, the express presence is much better anyway than the Loverpool design.

Dan

[andrew]

I just converted one of my Rocket clones into a Liverpool and it is insanely loud! Volume on 1 is loud enough.At first it had a bad background hiss and I thought I would change the presence control to a cut control, but it still hissed. Then I put a .01cap across the 150k and now it's quiet. I wonder if I should put a presence control back but use the Express design. If I leave the cut control in where do I connect the 100k feedback? Thanks!

[skyboltone]

I just converted one of my Rocket clones into a Liverpool and it is insanely loud! Volume on 1 is loud enough.At first it had a bad background hiss and I thought I would change the presence control to a cut control, but it still hissed. Then I put a .01cap across the 150k and now it's quiet. I wonder if I should put a presence control back but use the Express design. If I leave the cut control in where do I connect the 100k feedback? Thanks!

I wish I could help Andrew, but I'm not familiar with the cut control scheme. Post it maybe?

[mlp-mx6]

See any Vox AC30 schem.