Champzog Layout & Humdinger Questions

[The New Steve H]

I'm fiddling with the layout for my faux Herzog, using a Champ 5F1 layout as a starting point.

Question. Was Fender smart to put the filter caps on the same board as the amp? I was thinking of stretching the job out over about a foot, with the PT at one end, then the choke and 5Y3, then the 6V6, and then the 12Ax7, down by the inputs.

If I do that, I can put the filter caps on their own little board down by the PT. It will also give me a nice reasonably straight run for the heaters.

Second question: is there any way to balance 5V AC heater outputs with no center tap? The power transformer I'm using (see attached) is different from the one I put in my 5f6a.

The 5f6a job had a center tap on the 6.3V heater coil, but there was no tap on the 5V heaters, and one side of the 5V was the B+ supply, so you couldn't use a humdinger on it. The Champ PT has a 5V heater supply with no center tap, but it's not connected to the B+. Will I have a problem if I put a pot between the 5V leads, ground the wiper, and try to null out the hum?

I received some RG174 cable today, and I'm going to see if I can use it for all of the heaters and any places where noise can get into the amplification chain. I would like to be able to use the Champzog as a head as well as an effect, so might as well kill as much noise as I can.

[The New Steve H]

This will give an idea of the layout I'm considering. That's 4" aluminum channel. The walls are slightly over 1/8" thick. I would cut it down to around a foot in length and cut off the bottom so the remaining C shaped portion is maybe 2/5" high.

[Firestorm]

What are you using the 5V supply for if not a rectifier tube? If you're not using it for anything, then just tape and stow the leads; no current flows in them so there is no hum to contend with.

[The New Steve H]

I got a tube for it! A 5Y3. The red box is the rectifier tube.

[Firestorm]

Then there will be B+ coming off that cathode connection.

To kill hum in SE builds you can add an extra stage of filtering before the OT. 5Y3 to a 40uF cap, then a 100R (10W probably) to a second 40uF. Connect that to the OT. The extra filter drops ripple voltage by an order of magnitude (or so). You can also elevate the heater supply 50V or so and put the 60Hz hum above the range where it can easily get picked up by the tubes.

[The New Steve H]

I don't know where my brains are. Of course, you are right. I looked at the PT specs and went off on a tangent. Thanks.

[diagrammatiks]

for a small layout like that you could probably group the filter caps together.

in terms of grounding it's usually best to put the caps near the stages that they filter.

[The New Steve H]

Got the tubing cut. Starting to look like a project.

[Cliff Schecht]

for a small layout like that you could probably group the filter caps together.

in terms of grounding it's usually best to put the caps near the stages that they filter.

Truth!

[The New Steve H]

Help me out here. I want noisy stuff far from the input region. I know that means keeping the transformers and rectifier at one end. But it sounds like you're saying the caps themselves should be closer to the amplifying circuitry. Can that be right? I just figured all the ripply stuff and diode switching and whatnot should be far from the input area.

I was going to stick a separate board for the filter caps under the power transformer or very close to it. I assumed I would put a ground on one of the PT bolts, as I did with my 5f6a.

[ToneMerc]

I received some RG174 cable today, and I'm going to see if I can use it for all of the heaters and any places where noise can get into the amplification chain.

You make amp assembly so much harder than it needs to be. There's not much if anything that one can do that hasn't been done before.

1. Have you ever seen a guitar or any vaccum tube amp with coax cable on it's heater filaments or it's B+ wiring? Coax is useless in these applications because of the poor signal to noise ratio of high voltages.

2. Would it be wise or even safe to use 26AWG wire in a heater filament application?

TM

[The New Steve H]

Thanks for correcting me. I thought 26 gauge wire could handle a couple of amps, but you got me researching, and I see that it's not a great idea.

I wasn't planning to put it on the B+ connection, though.

Are you saying shielded wire is generally useless on heater supplies? I bought some 20-gauge 2-conductor surplus aviation wire, with Teflon insulation and shielding. It would be convenient to use it instead of twisting my own wire.

[ToneMerc]

Thanks for correcting me. I thought 26 gauge wire could handle a couple of amps, but you got me researching, and I see that it's not a great idea.

I wasn't planning to put it on the B+ connection, though.

Are you saying shielded wire is generally useless on heater supplies?

Yes and if you can manage an ideal circuit/signal wire layout the filaments don't have to be twisted.

http://www.c3amps.com/EnlargementPages/ ... itch4.html

TM

[The New Steve H]

I have to ask. How is the hum removed from that amp? It looks like the fields from the filament wires would be so different, they wouldn't cancel very well. And is that really two bare AC-carrying wires, or is there some kind of clear insulation on there?

It's not DC, is it? I found a schematic some guy did for rectifying his heater current.

I'm wondering if the geometry is the secret. But I know the magnetic fields should wrap around the wires, so it seems like it should smack all of the contacts pretty good.

[The New Steve H]

Okay, I found some info. Reading up on it now. Thanks for the photo.