Routing filament wiring - flat to chassis?

[CitizenCain]

I'm doing an amp rebuild/mod project, replacing a PCB with a handwired tag baord ass'y. The amp previously had the preamp sockets mounted to the PCB, so I've installed some sockets on the chassis. I have my filament wiring installed. I gave it a nice twist and routed it inside along the edges of the chassis, running out to the sockets. The runs are placed flat against the chassis floor.

An online friend and good amp builder himself said that I should move the runs so they arch up and come straight down to the sockets, then I can lay the other leads flatter against the chassis. He said that both flying leads and flat heaters, or flat leads and flying heaters work, but flat leads and flat heaters can cause hum.

I haven't heard of this, but I'm a novice. Seen plenty of pictures of flat leads with flat heaters and my Ceriatone JTM45 is built this way and it sounds wonderful.

Do I need to rework my heater wiring?

[CitizenCain]

Here's a pic of my filament wiring currently.

http://www.visi.com/~sstolle/sundown/checkpt2.jpg

[antik]

Your online friend is correct. But if you do go with flat leads and flat filaments, the wiring for the each should run at 90 degrees to each other to minimze noise. That is also not a bad practice in general. From your layout it looks like that may be difficult to do. The object it to not run signal wires alongside filament wires.

[CitizenCain]

OK, thanks! I think I'll take the time to reroute the heaters while I can still get at them.

I've got the power section wired up, just starting to work into the preamp area now.

[donnyjaguar]

Just convert to DC filaments and not worry about it. :)

[hasserl]

There is nothing wrong with your filament wiring. Just bring the other leads up to the sockets and run them over the filament leads with a nice loop bend so they don't touch. Run them at right angles as much as possible. Solid core wire will help the wires retain the shape as you run them out to the sockets.

I've run the filaments up in the air on some builds and I've run them flat on the chassis in other's, and both work fine.

[Wakarusa]

I agree with hasserl that your flat filament runs look fine. I'll disagree with the preference for solid wire (stranded wire, over the long run, makes a more mechanically reliable solder joint). Also, you don't have to be particularly anal-retentive on the lead layout -- it's not an all or nothing proposition with either filaments flat and leads high or vice versa.

What matters is signal to noise ratio and cross-talk. So you need to take care that leads carrying weak signals don't run parallel to leads with strong signals. Ultimately, it's the control grid leads that need to be clear of both filaments and plate leads. For your normal inverting anode-follower amplifier stages you should be able to run both cathode and plate leads flat to the chassis (still crossing filaments at right angles) and get a very quiet build. For a cathode follower you need to give a bit more care to where the cathode lead ends up.

[CitizenCain]

Thanks, guys. Actually, I did go ahead and rewire the filaments. This is my first time attempting anything like this so I was erring toward the side of caution.

I've got the amp frying right now, forming the caps based on the technique outlined in the Tube Amp FAQ (http://www.geofex.com/tubeampfaq/TUBEFAQ.htm#forming). They've only been used very intermittently over the past couple of years so I thought I'd try that out, too.

No smoke when I hit the switch, I think that's a good sign :D