Noise From Rectified Heater Current?

[The New Steve H]

My Herzog is taking shape, but I just ran into a new question.

I am attaching a schematic. As you can see, this thing has a muting footswitch relay which runs on 6V DC, rectified from the heater circuit. There is a rectifying diode in the heater circuit, along with a 2200 uF cap. I guess the heaters will run on the same DC current without a problem, or the design wouldn't look like this. The heaters appear to be in series with the diode, so they must be using DC.

I'm worried about heater noise. In order to stick the diode, relay, and 2200 uF cap in the heater circuit, you have to break the wires and cram some bulky stuff between them. Obviously, there will be a big gap between the heater wires, and I assume that means a potential for noise.

I don't know what the rectified power will look like. Maybe it's too smooth to make noise. Maybe that's why the cap is so big. But it's a concern.

I assume that if I do it the way the schematic says, there is no point in using a humdinger between the heater leads, since there is no AC.

[The New Steve H]

Another question. It's impossible to rig the amp up so there is no 6V AC in it. The AC wires have to be a few inches long before they get to the rectifier. Should I use a humdinger on the short AC part of the circuit, before it gets to the rectifying diode?

[ampdoc1]

I'd suggest a FWB rectifier. You could mount the FWB and a couple of caps on an small piece of prefboard and mount it on the side of the chassis close to the AC. I used such an arrangement on the relay boards I built and never had any problems.

[diagrammatiks]

the dc for the relay doesn't get rectified until after the heaters.

the heaters are on ac.

[The New Steve H]

Whoops.

I don't get this circuit at all. It's two filaments on AC, then ground, then a paralleled capacitor and inductor (relay) leading into the positive end of a diode. I don't have the slightest idea how the capacitor and inductor interact.

So I assume I'm getting negative DC at the junction of the diode, capacitor, and relay, and it goes to ground through the relay and jack or manual switch?

Sounds like I am still going to have a problem because of the big opening in the AC wires.

I would rather eat broken glass than dig out Horowitz and Hill, but I guess sooner or later I'm going to have to re-learn the fundamentals so I can get inside this stuff.

I suppose it's a good thing the schematics are such a mess. I'm learning a lot of stuff because of the gaps.

[diagrammatiks]

i'm not exactly sure what the diode is doing since if i needed a relay like that i'd just do a full-wave.

are you sure that isn't just a soft start relay?

like what's the function of the relay in the circuit?

the way I'm seeing the schematic...

the dc supply for the relay and the ac supply for the heaters are in parallel.

you can tap the heaters at any point for rectification.

it's all at the same place electronically.

[The New Steve H]

I don't know anything about relays. I just figured they ran on DC (based on what little I know of electromagnets), and I saw a diode and big capacitor, so I thought this thing produced crappy DC for the purpose of running the relay.

The purpose of the relay is to turn the effect on and off. It closes two switches. One sends negative voltage to the output tube grid to mute the amp (see "D"), and the other sends the input straight to the output jack.

I think. I guessed at this, and some people agree. I don't actually know.

If I'm right, the footswitch (or manual switch, when the footswitch isn't there) turns the relay on and off.

You have to remember, this thing is a giant stompbox with two tubes in it, in addition to serving as an amp head. It needs to be footswitchable.

[diagrammatiks]

well I can't tell how that relay is wired from the schematic.

copying the relay circuit as drawn isn't really going to be good or bad.

if it's confusing just build the circuit and then draw out your own relay circuit.

that schematic doesn't even tell you how many volts the relay is...

i mean ultimately it doesn't matter. if it's just to switch a couple of contacts...you can do it anyway you want.

in fact that relay in the schematic is far from the best way to do it.

this guide is pretty good at explaining relays.

http://www.el34world.com/projects/relay_switch.htm

[The New Steve H]

Thanks for the link.

I'm going to try to build it the way it appears, and if it doesn't work, I'll start over and try something else.

[Firestorm]

Kind of a bad drawing isn't it? The little arrow pointing up before the diode is intended to indicate the heater connection, so the heaters are connected semi-normally and the DC supply for the relay connects afterward. Heaters seem to be connected Fender Champ-style with one leg at ground and the other one wired.

If you're set on having a footswitch-driven relay (versus a manual switch), I'd suggest devising the relay circuitry first. Lots of info on that over on the Dumble side. TUT 3 has a chapter on the Herzog, but built without the relay.

[Structo]

Is that output below the input for a direct out?

If you don't necessarily need that I would skip it.
If you want a mute switch just wire in a Standby switch.

If it were me, I would probably wire up the amp the standard way with floating AC for the heaters.

[Firestorm]

Is that output below the input for a direct out?

??? If you don't have the direct out, it's a Champ, not a Herzog.

[The New Steve H]

An effect with no footswitch is worthless. Imagine having to stop playing, walk over to the effect, and operate it with your hand. It just doesn't work.

I believe the left output is for the effect (no speaker) and the right output is for the speaker.

[Structo]

OK, OK

Just sayin'