Heater/Filament Wiring - Twisted or Parallel?

I'm building a Superlead clone and I was playing around with some different wiring methods. I don't care about doing it the "traditional" way or being period correct. My main goal is for it to sound good and for the wiring/layout to be clean.

I was looking at a bunch of Soldano SLO builds and they are so clean and the wiring looks immaculate. Mainly, the heater/filament wiring in the preamp and poweramp. If you don't know, the SLO uses parallel runs of bus wire to connect everything instead of twisting the wires. The result is a much cleaner and more simple build. The SLO does not run DC current... it's still AC. Most people say the wires are usually twisted to cancel out any noise or Back EMF. So, how does Soldano get away with it? I've played 3 or 4 SLO's and they've all been fairly noise-free for a high(er)-gain amp.

I'd like to utilize some build/wiring methods from the SLO in my Superlead build. So, I'd like to invite those of you in the know to discuss the pros/cons of using this type of wiring method. Obviously, in an SLO the tube sockets are installed with them rotated so that the corresponding pins all line up in a straight line so a bus wire can be used.

In addition to just the heater wire, most of the other pin connections utilize this method as well. So that's a plus. These things are just soooo cleanly built, I'd like to move away from the messy wiring of old Marshalls and build something that's super clean.

Here are some examples:















And here's a similar example from Hiwatt:



As opposed to something typically seen, like this:

You do realize you need a different type of power tube socket (a Fender style one) to do a SLO style build, correct? You'd also need to modify the chassis to have the holes for the socket at a right angle to the back of the chassis to put that socket in a Marshall-style build.

Seems like a waste of effort to me unless you are cutting the chassis yourself. Marshall style builds can have twisted heaters and look just as clean. I'd worry more about getting it to sound good...

If you are cutting the chassis yourself, buy some Fender style power tube sockets and go for it...

Steve

sah5150":mdkhgbf7 said:

You do realize you need a different type of power tube socket (a Fender style one) to do a SLO style build, correct? You'd also need to modify the chassis to have the holes for the socket at a right angle to the back of the chassis to put that socket in a Marshall-style build.

Seems like a waste of effort to me unless you are cutting the chassis yourself. Marshall style builds can have twisted heaters and look just as clean. I'd worry more about getting it to sound good...

If you are cutting the chassis yourself, buy some Fender style power tube sockets and go for it...

Steve

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I mentioned the fact that the sockets are installed differently (rotated so the pins line up). I guess you missed that. That's beside the point. Yeah, they can have twisted heaters and look just as clean, but I've yet to see one that actually lives up to that (a Plexi build, that is). So, the point of this thread is to discuss ways of accomplishing that in a Super lead.

Especially since there are people who say the way an SLO is wired doesn't work and causes noise. There are very few amps out there that use parallel wiring like that. I was just curious about my options...

FourT6and2":39bp5oly said:

I mentioned the fact that the sockets are installed differently (rotated so the pins line up). I guess you missed that. That's beside the point. Yeah, they can have twisted heaters and look just as clean, but I've yet to see one that actually lives up to that (a Plexi build, that is). So, the point of this thread is to discuss ways of accomplishing that in a Super lead.

Click to expand...

Yeah, I did miss that, but my question remains - are you cutting the chassis yourself? You'll also need to make other layout changes if you intend to do this. It is doable, but you'd better draw up a layout first or you'll regret it. I don't know what else there is to discuss actually.

I'm actually doing something similar in re-designing my custom amp. My amp is 3 modes - far more complex and the pre tubes are going to be up front like a SLO. Here is a link to my build thread to show you what I started with. This is the inital prototype in the original Marshall-style twisted layout. I've decided the amp will be more repeatable in a SLO-style layout, so I'm in the process of drawing up a new layout. I'll post my layout when it is done and perhaps it will help you:

From Scratch Build Thread

FourT6and2":39bp5oly said:

Especially since there are people who say the way an SLO is wired doesn't work and causes noise. There are very few amps out there that use parallel wiring like that. I was just curious about my options...

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There are actually tons of amps that use parallel wiring like the SLO. For example, take a look at Muller Amplification's Classic - kind of similar to my amp in the idea of the channels. Obviously this layout works and is not noisy in many amps. If you want to do it, think about the effect on the standard Marshall layout, draw it up first and then go for it... that is what I'm gonna do...

Steve

you can twist them up to the point where you wire in the sockets then go straight by then youve prob accomplished what the twist does. on the CCV's the power tubes have a straight line like that pic.

Actually, I just found this: http://www.freewebs.com/valvewizard/heater.html



Here are some key points:

"In this way the wires are kept perfectly parallel and close to each other, which increases opposing field density and encourages the radiated fields to cancel out." That is in reference to how one should wire the heaters, either using twin-wire (bell cord) or tightly twisted wire. However, it seems the main goal is to keep the wire PARALLEL with each other? If that's the case, I can see why Soldano has chosen to go in the direction they have. Many people talk about the twisting of the wires being key, when it may be just that they need to be kept parallel (which twisting does).

Another interesting snippet:

When heaters are wired in parallel [vs. series, not talking about the physical wires being parallel to each other]; power valves should be first in the heater chain, followed by driver valves, with the input stage being last in the chain. This keeps current, and therefore radiated fields, at a minimum around the most sensitive stages of the amp. Even better is to run the pre-amp and power-amp sections from separate heater chains. If signal wires must cross the heater wires, they should do so at right angles.

The common pre-amp valves (ECC83 / 12AX7 etc.) when run from a 6.3V supply, should be wired from one side only [see right], not by looping one heater wire all round the valve socket, which would create a hum loop and cause excessive interference noise (though many amp makers DO make this mistake and get away with it). The wire twisting must be kept very tight right up to the socket, where it matters most. Their pin arrangement is also deliberate, so that the main heater pins (4 and 5) can be orientated towards the chassis wall, allowing heater wires to be run along the wall away from any other sensitive signal wiring.

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All very helpful!

Another option is to run the heater wires elevated above the sockets, themselves.