Guitar Amp Wiring and Lead Dress

[R.G.]

I updated my thoughts on wiring practice, and added drawings. The first link is the longer version, with explanations for what is happening, why the suggested practice is good, and - to me, at least - what's going on to make it that way.

This grew from the two-page list I had in mind to about 50 pages while I was writing it up, way too much for a casual reader, so I did a "cartoons" version, with just the drawings and a few sentences for each.

Full Version:
https://www.dropbox.com/scl/fi/vpijj3al ... y7v7f&dl=0

Cartoon Version:
https://www.dropbox.com/scl/fi/soyg9csg ... 7dzrx&dl=0

[Turret]

Perfect timing, thank you

[Matthews Guitars]

That's a very good guide. I specifically note that you included the recommendation, in the cases where the power cord is a 3 wire grounded cord and directly attached to the chassis, that the ground wire should be the longest, the last to break, should the power cable be pulled out. This is excellent, and shows great attention to detail. That is a very thorough guide.

Well done.

[Turret]

Yeah, its a treasure. I did my own layout for the #124 and since I cannot go "monkey see, monkey do", and I still want a quiet amp, I will be studying this a lot. Thank you R.G., for decades of great resources

[stephen_w_keller]

I've been a fan of John E. P. Hynes "Gothik Ring" method:

https://www.geckoamps.com/P1-Gothik-Rin ... t_2017.pdf

Here is a (now ancient AX84) P1-eX layout using the technique:

https://www.geckoamps.com/P1-Gothik-Rin ... k-ring.pdf

[R.G.]

The Gothic Ring setup is a nice, tidy way to deal with two amplifier sections of a duotriode. Either flying the heaters above or way below the signal/component leads is good as well - distance reduces crosstalk by the square law, so using a Z=axis separation is good.

This setup is good where you can have two amplifier sections each with its own tag-strip on opposite sides of the socket. It does bring up a consideration about grounding;; the difference between local decoupling caps and remote power filtering caps. It is GREAT if your chassis supports having the power filter and/or decoupling filters right beside the duotriode socket as the link shows. Current needs above X frequency are supplied by the local cap, and only a highly filtered, more-like-DC current runs down the wires back to the first filter cap. The filtered return current in the wire(s) back to the first filter cap carry much less high frequency content, and this lowers the possibility of oscillation.

But it doesn't eliminate it. the wire returning power to the first filter cap negative sthas a DC offset from the DC part of the current and an AC component below what the local filter cap can produce. If the ground return wire to the first filter cap negative has other sections' power ground returns attached to it, this gets right back to the "ground" voltage being different at each section (or socket, in the Gothic Ring setup), and leaves the possibility of either high frequency oscillation or motorboating. If there is one and only one wire from the tube/socket/section to the filter cap negative, that would prevent interaction through ground-wire resistance. If other sections share part of the ground current return wire, the interaction is still there.

Whether it actually produces ill effects depends on how big each current is and how much this introduces "ground bounce" signal into each stage. Mostly you'll get away with it if the ground wires are not long. Sometimes you won't. As I mentioned, there is more than one way to get quiet, effective grounding. Star grounding is just the only way to know ahead of time that wiring won't introduce ground noise issues.