Getting Z-wreck back to stock and question about grounding output jacks

[Dcsocal]

Hi all! Long time lurker, first time poster.
I’ve always been into amps/electronics and am now just becoming familiar with the construction side of things, so please forgive me if the question is dumb!

I picked up a Z-wreck for a great deal. That being said, the price was attributable to some work having been done to it. Someone added an FX loop but appears to have done a decent job. The amp is otherwise untouched. However, I really have no use for a loop and think a loop goes against what a wreck is (unadulterated tone!). To add the loop they:
-added a pot to the backside to control wet/dry mix
-added an impedance selector to where the comfort switch was
-enlarged the 4 and 8 ohm output holes to accommodate cliff jacks for send and return
-relocated the comfort/speed switch to chassis topside (where it isn’t accessible)
-shortened the OT common lead

I’m trying to get the amp back to stock, so I can have access to the comfort switch and have a set of 3 output jacks. While the impedance selector is good quality, I’m a proponent of minimizing possible failure points down the road.

I’ve removed most everything but had a question about grounding output jacks. Can someone identify what kind of wire Dr. Z uses to ground the three output jacks? (Picture attached). Is it just a long, stripped and tinned length of the common lead? If so, I know this won’t be possible and was wondering whether I should use 20 or 22awg bus wire? It’s a bit cramped trying to get two 18awg wires into the lug but that could just be user error.

Also, since the common has already been shortened, Id be pushing it trying to get the lead run over to the 4ohm jack.

Does it matter which jack the common hits first? Running it to the middle, 8 ohm jack would afford me the most slack, but I wasn’t sure if it would be okay to have a bus extending from the middle jacks to each adjacent jack, rather than starting from one end and working towards the other. I’m not sure if that makes sense, but thank you in advance!

[pdf64]

…
Does it matter which jack the common hits first? …

I can’t think of a mechanism or scenario by which that would be the case.
I suggest to use the thickest convenient wire and make to good resilient job of it.
The application doesn’t involve high continuous current.

[Stevem]

When you run the math for a 30 watt RMS amp by means of ohms law we get this.
A 4 ohm load generates 2.9 amps

A 8 ohm load= 1.9 amps.

A 16 ohm load= 1.4 amps.

Inside the amp with its short wires runs 18 gauge wire would be fine, but 16 gauge is not a bad idea unless you need to buy a roll of it,
Out side the amp wire needs may change!

18 gauge wire is good for carrying 5 amps for 8 ft of length.

16 gauge wire is good to carry 5 amps a distance of 12 ft.

[Dcsocal]

…
Does it matter which jack the common hits first? …

I can’t think of a mechanism or scenario by which that would be the case.
I suggest to use the thickest convenient wire and make to good resilient job of it.
The application doesn’t involve high continuous current.

Thank you very much for the clarification! Any idea what kind of technique was being used in the picture to ground the jacks?

[pdf64]

There looks to be a bit of twisted and tinned wire (and the chassis) linking the sleeve terminal of the 3 jacks together.

I suggest not to rely on the chassis as an 0V conductor, especially in the case of 0V connections to the chassis being made via jack and pot bushes.
My experience with alloy chassis is that such connections tend to fail. Much higher torques are needed than can be applied by the fasteners on those, otherwise surface oxidation may eventually develop and break the connection.

[Dcsocal]

That makes sense. I was wondering about how secure the grounds would be particularly considering that two jack holes were made larger to accommodate the cliff jacks. Using washers on each end of the jack has secured the jacks but I do worry about how good of a ground that will provide.

[Phil_S]

Please recognize my amateur status, as such, I am not an expert. I do, however, have a reasonable amount of amp building experience. FWIW, I have a few random thoughts that may be helpful, but take them with a grain of salt.

If bonding a ground to an aluminum or aluminum alloy chassis, use NoAlOx on the connection. This will guard against corrosion. You can buy it at the big box store in the electrical department. It doesn't cost very much.

I don't like making a circuit ground at the input jack, nor do I tack anything to the backs of pots. I know that many people swear by both and I'm not suggesting they are wrong or anything like that. I will run a ground buss from the input jack to the end of the preamp section. Then I'll run a ground wire to the main ground point -- first filter cap ground. I will tell you that it works very well. (Not looking for an argument on this, so, please, let's not.)

As pdf64 says, you can't torque down the input jack tight enough. Drill a hole and run a #10 screw (or M equivalent) through the chassis, use star washers, ring lugs, and a good sturdy nut to clamp it down good 'n' tight. You might even lock the first nut with a second nut, though I don't do that. There is also a compound, Loctite Threadlocker, you can apply.

[Colossal]

Please recognize my amateur status, as such, I am not an expert. I do, however, have a reasonable amount of amp building experience. FWIW, I have a few random thoughts that may be helpful, but take them with a grain of salt..

Offtopic friendly jab

Says the guy with 5556 posts! Stop qualifying your replies and your expertise, Phil! Your self-deprecation is becoming downright toxic Seriously, you are a very competent and accomplished builder and contributor here, and always handy with good advice. Thanks!

/offtopic friendly jab

[Phil_S]

I appreciate the off topic jab. Just don't ask me about corner frequencies or what happens when you change the slope resistor. I have yet to wrap my mind around some of the more technical stuff and I've been knocking my head against it for at least 15 years.

[thetragichero]

Just don't ask me about corner frequencies or what happens when you change the slope resistor.

there's plenty of good calculators out there that as long as you know where to plug in the info it's as good as having the equations memorized