star ground for power tubes and ct, or soldered to chassis?

[Chuck H]

I think it's relevant to note that Leo was late in the hum bucking pickup game. Even by years. Most of his early circuits were example circuits from tube guides. Later circuits were not designed by Leo exclusively. He was a smart man that knew what he wanted to achieve based on what had gone before. Not an innovator in anything but his greatest claim to fame. Making the electric guitar a manufactured product. That was his greatest stroke. The amps, of course are amazing. his was the good fortune to be on the ground floor. This takes nothing away from his ability to read the market and locate areas of growth for the amplifier end of Fender. Much of that was in the hands of hired individuals.

Leo did always keep to his own ideals though. Not much known is that the designers of the dreaded first series post CBS changes to Fender amps were in fact employees hired by Leo. With Leo out of the picture they were free to pitch their upgrades at CBS management and thus the changes. Leo may or may not have eventually given in to these supposed upgrades. It's impossible to know now.

In short I'm just saying that Leo was the right man for the job. But the companies success and relative goodness of the amps is more about the timing and the fact that those are the amps that guitars were designed around and then more amps were designed around the new guitars and then more guitars were designed around current amps, etc. ad nauseam. In other words, the amps sound good because that's what we know amps to sound like. It's hard to imagine a world without the BF Fender paradigm. But if it hadn't been Leo, we might have a whole different ideal for what vintage amps should sound like.

[NateS]

Good points. Having been one myself for a short while, I'm surprised I didn't see it sooner. Perhaps where Leo's true innovation lies is in manufacturing engineering. Making profitable products out of ideas.

[Alan0354]

genius does not limit to designing a tone stack, a ground connection. Being at the right time, making and marketing the right product, knowing how to use talents to get innovation products out..........Those are intelligence.

It is easy to say other people have that idea, but when come to business, you put money where your mouth is. He had to foresight to put his money, savings into something that turn out to be legendary, that by itself is a talent. I personally do not believe in luck, it's all hard work, critical thinking, anticipation of the market, predicting what the market wants. Those are just a genius and talent as designing a good circuit.

FYI, I did a patent search on Leo Fender. I found close to 30 patents all by C. Leo Fender!!!! Each might be not that big a deal. But the totality is incredible!!!!

I admire Leo Fender, there are few if any has as much contribution in the guitar industry as him.

[Tooboob]

You might enjoy one of these: http://www.ebay.com/sch/i.html?_trks...at=0&_from=R40

I've got black T-shirts with the Strat and Les Paul patent apps.

I got a swamp ash Tele with a broken truss rod cheap, put on a cheap neck, got a pro setup, and piled lots of money into it, but it's still a Tele, except for the Kinman Broadcasters that I always run in series. I have quite a few guitars, but I keep reaching for that Tele. Hard to believe that with over 50 years of industry innovation, the first try might have been the best, and I don't think it could be cheaper to make. I love my DRRI too.

Let's not forget Ted McCarty, Seth Lover, Les Paul ... and those nerds at RCA.

Note that the J-bass neck pickup is single-coil and hum cancelling, and people objected to humbuckers at first because there was too much distortion.

[Alan0354]

You might enjoy one of these: Stratocaster patent shirt | eBay

I've got black T-shirts with the Strat and Les Paul patent apps.

I got a swamp ash Tele with a broken truss rod cheap, put on a cheap neck, got a pro setup, and piled lots of money into it, but it's still a Tele, except for the Kinman Broadcasters that I always run in series. I have quite a few guitars, but I keep reaching for that Tele. Hard to believe that with over 50 years of industry innovation, the first try might have been the best, and I don't think it could be cheaper to make. I love my DRRI too.

Let's not forget Ted McCarty, Seth Lover, Les Paul ... and those nerds at RCA.

Note that the J-bass neck pickup is single-coil and hum cancelling, and people objected to humbuckers at first because there was too much distortion.

You can use Google Patent and do "Leo Fender" search and you get all for free. I downloaded a lot of patents in pdf files.

https://www.google.com/?tbm=pts#q=Le...atents&tbm=pts

[elipsey]

Uh... that's cool. So should I solder my grouds chassis, or....?

[R.G.]

Do not solder your grounds to the chassis.

The power transformer CT wire goes directly to the first filter cap negative. Anything else will cause hum.

Do not use the chassis for the speaker common return. Get this slightly wrong and ground the input jacks to chassis and you can set the power amp to oscillating; worse, just having funny resonances in the sound.

You can do bus grounding or star grounding for the circuits. Don't use the chassis as the bus. Don't let the current returning from high current places ( such as the power tubes) return through the same ground conductor as the preamp tubes unless that ground conductor is massive. How big is "massive"? What exactly does "through the same conductor" mean in a single bus system? These are hard to answer for busses. They are easy to answer in star or modified star ground systems.

[elipsey]

tyvm

[elipsey]

Problem:

My cap can contains an internal ring bus:


I can't even tell what order the caps are conencted to the bus, because it's all covered with glue.

Should I get a new one?

Will the ground tabs on those 1-3/8" C&E caps fit properly in my 1-1/8" chassis hole?

How do you deal with those multi section cans that only have one shared ground tab?

[R.G.]

I can't even tell what order the caps are conencted to the bus, because it's all covered with glue.

One of the most useful tools on my bench is a homemade precision probe. "Precision" because it lets me probe very tiny places, and "homemade" because it's a composite of a sewing needle and a chopstick from a fast food Asian place. I drilled a tiny hole into the end of the chopstick, epoxied a sewing needle into it, sharp end out, and then soldered a wire to the needle and ran it up the chopstick, covering the whole mess in heat shrink. With the other end plugged into a meter, I can get the sharp end onto SMD IC pins. I can also do what I'd do here - poke it through the glue to contact the cap pins so I could tell for sure what wire went where.

Should I get a new one?

Not if you're already committed to this one on your chassis.

Will the ground tabs on those 1-3/8" C&E caps fit properly in my 1-1/8" chassis hole?

Unknown, captain.

How do you deal with those multi section cans that only have one shared ground tab?

The older ones had a different grounding arrangement than the cap cans like you have here. But you just live with it.

A lot of the decisions depend on your physical arrangement, as you're finding.

Here's what I might do, faced with a similar situation. If you're going to have to use that cap can, and it necessarily requires twist locking to the chassis, make that point be your one connection to the chassis, and your star ground point. Since only the first filter cap is critical to rectifier pulse buzz issues, put in a new first filter cap ahead of this. Tuck a 22uF/450V axial cap right under the rectifier(s) to eat the big pulses, and use a 10 ohm or so resistor from the new first filter cap (+) to the rest of the filter caps. This forces the charging pulses to go in/out of the new first filter cap, and then the DC from the first filter flows off to the caps you have now free of the big pulses. They will filter the ripple voltage and will not have to deal with the rectifier pulses in the rectifier return wire.

Or you can do it the easy way; connect that joined ground cap can to the chassis, connect the rectifiers there, and hope it's not too bad. It might even not be too horrible. If you have to count on luck, do it.

[elipsey]

Do not use the chassis for the speaker common return.

What's the best way to isolate a switchcraft jack if you don't have any of those little shoulder washers?

Should I use cliff jacks for speakers instead?

Should the speaker ground go on a star with the first filter ground?

[gui_tarzan]

as well as writing machine boot code, detailed control of printer mechanisms, system boot code,

My head just exploded. I absolutely, unequivocally HATE programming. My hat is off to those of you that can do that.

[NateS]

Shoulder washers are cheap enough I don't think I'd substitute. The isolated jacks I bought look more delicate than plain old jacks. (Why are we using 1/4 jacks for this still, especially in homebrews where we make other mods out the wazoo?)

I'd return the speaker ground to the same point your power tube cathodes and the filter cap bypassing the OTCT go to,

[R.G.]

What makes grounding hard is that we're all taught electronics in terms of voltages, not currents. We get taught about currents, but as a purely secondary issue. We all get exposed to "measure this or that voltage, then think of what current that makes/lets flow". Grounding is the other way round. Currents flow in ground conductors, and that makes a voltage happen in the ground conductor by Ohm's law (or the bigger case, Maxwell's Equations if very fast signals and edges are involved). Let me pontificate a bit, in the interest of better understanding.

Quiet grounding involves knowing first what currents have to flow in the ground conductors, and then arranging things so that the voltages generated by these currents flowing do not get amplified unintentionally by other parts of the circuit. Star grounding is a start-from-zero, belt-and-suspenders massive overkill. It can be proven to work at low frequencies first time, every time, if implemented strictly because each ground current flows in a different conductor. They CAN'T overlap and get amplified in some unintended way.

But for all but trivially small circuits, there are so many ground wires needed that pure star grounding always gets simplified into local stars which are for one limited section of circuit where "it can't hurt... can it?" based on knowledge of the circuit, plus several wires to an overall star point for the entire mess. This is generally good enough.

Well-thought-out buss grounding (or just pure-luck schemes! ) can be even better, because of the nature of active devices all being inverting. If you can use -or luck into- inverting stages to cancel AC ground currents, the residual AC component of the ground current can be reduced, perhaps to near zero. Or you can luck into several stages cancelling ground currents from one bigger stage. The reason I keep typing "luck" is that very few people really understand what currents flow in their circuits' grounds well enough to do this in a deliberate fashion. Generally, someone saying that buss is better than star is a marker for the person saying it responding like an addicted gambler - they had one or two lucky encounters early, and they're convinced that they can recreate that lucky high. Not always, but often.

But it is possible. At frequencies much above audio, field effects tend to make return currents follow the signal conductor in a ground plane if they can, so at higher frequencies, and especially at many-MHz RF situations, ground planes make sense, as the field effects force the return currents to sort themselves out - they *WANT* to go where they should. This is the origin of ground planes being good, but not a panacea for audio circuits. Mostly at audio planes are good because they put a lot of sheer copper mass in the ground lines and lower the bulk conductivity.

With that load of rambling as background, back to your questions:

What's the best way to isolate a switchcraft jack if you don't have any of those little shoulder washers?

Careful painting of the bushing with a few layers of insulator-filled epoxy. This is still marginal. You'll have to carefully deburr the hole in the chassis, and ideally paint it with epoxy too. Shoulder washers are better.

Should I use cliff jacks for speakers instead? Should the speaker ground go on a star with the first filter ground?

Speaker outputs are special. They're quite high currents, and they have the potential to cause significant offsets in the conductors that carry them.

Ideally, the speaker return (not ground, notice) should go back to the transformer winding that generated it. It will anyway, and connecting it as straight back to the winding as possible keeps it from causing other issues.

This is complicated by the need for the secondary "common" to be attached to signal ground for the purpose of returning the output signal to the PI for feedback. My preference would be to first satisfy the current loop for the speakers by connecting winding to speaker jack tip, then speaker jack bushing/sleeve to the winding, then connecting the "common" end of the winding to the signal ground at the PI it's going to be sending feedback to, and then connecting the speaker "hot" signal through the feedback R/C to the PI input. Currents flow in the shortest path to the places that need them.

[Enzo]

I have yet to see a shoulder washer that cannot be lost, misplaced, or forgotten. I have yet to see a jack nut that cannot loosen. All of those things can bring your jack bushing into contact with the chassis.

Just my opinion, but I much prefer NOT using specialized things. I hate setting up systems that require odd cords for example. So I much prefer the very simple Cliff jack to shoulder washers. There is always an exception, but USUALLY we don't find someone later deciding "metal jacks are better" and replacing them. They are by their nature insulated from chassis.