Guitar Amp Wiring Notes

[R.G.]

Over time, I wind up writing replies to questions on wiring inside amps. My time is sliced up into little sections, so I have started saving these bits and when I can, sanitizing and interlacing them into some kind of overall whole. Over a period of some months, that finally got linked up into a batch of wirning hints and tips. The first draft is linked below. Comments and corrections welcome.

https://www.dropbox.com/scl/fi/8fscwmvn ... xzn7d&dl=0
Edit: up too rev 2.15, I've updated the link

[Stevem]

Thanks R G!

[R.G.]

You're welcome!

I have had a bug report, so the first draft isn't the final draft. The drawing on page 5 of how AC gets into your amp from the power pole incorrectly shows the neutral wire connecting to one of the live phases. It actually connects to the ground buss bar. The drawing is going to be updated on my next few minutes of tech-time.

[martin manning]

Over a period of some months, that finally got linked up into a batch of wirning hints and tips. The first draft is linked below. Comments and corrections welcome.

I'm giving it a read. My domestic power comes in via an underground cable with three conductors. There is no ground rod near my house, so my guess is the neutral is grounded at the local underground transformer just across the street. Everything else is as described above, with the neutral and ground buses connected inside the breaker box.

[R.G.]

Hmmm. Interesting, Martin. That's really unusual. Are you in North America? I think the electrical codes require an earth ground rod per building here. But maybe there's a building code exception for not more than X feet/meters from the distribution transformer ground or something where you live.

[martin manning]

Yes, North America, my rounded-off geographic location is under my avatar. Now that I think about it, the breaker box is grounded to the copper water inlet pipe.

[Guy77]

Over time, I wind up writing replies to questions on wiring inside amps. My time is sliced up into little sections, so I have started saving these bits and when I can, sanitizing and interlacing them into some kind of overall whole. Over a period of some months, that finally got linked up into a batch of wirning hints and tips. The first draft is linked below. Comments and corrections welcome.

https://www.dropbox.com/scl/fi/e45svs6y ... lfe9b&dl=0

Thank you RG for taking the time create this great reference document.
So much great info here!

Cheers
Guy

[R.G.]

Yes, North America, my rounded-off geographic location is under my avatar. Now that I think about it, the breaker box is grounded to the copper water inlet pipe.

Ah. That makes sense. That was once standard practice. Then we stopped using copper in water inlet pipes.
A long, copper pipe is probably a better earth contact than a metal rod -especially better than my metal rods driven through 4 inches of dirt and four feet of limestone.

[R.G.]

I'm getting a number of comments and bug corrections from the other forum I posted this to, so there will be another update coming.

[didit]

Hello R.G. --

Worthy project and a fine starting draft. I've not read through with an assertive eye but did snag on the following.

You write ::
Excepting for rectifier tubes, all tube cathodes in guitar amps are indirectly heated. That is, the heater resistor is insulated from the cathode itself.

While tube heaters have specific resistance common convention calls it a filament, so suggest you do so, avoiding any confusion. A resistor in common terminology is a component, standalone that one generally hopes doesn't actually double as a heater.

..

[R.G.]

Thanks, didit! I'll add that to the list.

[cdemike]

Really appreciate you putting this together! If I could make some suggestions, the first reference to OTG is on page 8, second paragraph but then gets defined in the fifth paragraph on the same page:
"Generally, the heater winding is center tapped, and the center tap is tied to signal ground (hint – do this at the OTG)."

I'm not sure if this is applies in most disciplines of scientific writing (I'm familiar with medical writing and writing for the humanities per liberal arts writing classes), but it might be clearer if the first use of the phrase also defines the acronym, e.g. "Generally, the heater winding is center tapped, and the center tap is tied to signal ground. Best practice is specifically to place the heater center tap or other ground reference to the 'One True Ground," or OTG (see: 'Wire the rectifiers to the first filter cap correctly')."

My other suggestions are pretty minor:
I think there's a typo on page 17: I think you may have meant "done" rather than "gone" in "In the real world, this is hardly ever gone."
There appears to be a mission period on page 23: "Voltage/capacitance leakage happens from the stray capacitances surrounding every wire[.] There is a bristling bunch of invisible capacitors to every other conductor."
The second em dash should match the opening em dash in this sentence on page 23: " Each capacitor is tiny—a couple of pF or less - but there are lots of them."
An em dash or colon is missing between "resistor" and "air" in this sentence on page 23: "It could be a resistor even air."

[R.G.]

Second draft is on line, link below. Much reformatting, introduced "book type" features, juggled things, corrected some errors and probably introduced new ones.


https://www.dropbox.com/scl/fi/8fscwmvn ... xzn7d&dl=0
Edit: up too rev 2.15, I've updated the link

[printer2]

Link says that it was deleted.

[nuke]

I suspect that means draft 3 is in progress. Nice work.