# Best Grounding Scheme Method Aluminum Amp Chassis?



## RickyLee

I have an aluminum chassis which is the only one I have that will fit in this slightly smaller JMP style headbox I want to use. Figured I might as well do something with it.



I am thinking I should try some type of star grounding scheme or maybe even an above ground reference scheme like you see in the JCM900 SL-X.

This chassis has no welded studs to go off of anywhere, as in for the wall plug Earth Ground, so bummer there.


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## jack daniels

Ask AMS, he has all the answers...


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## RickyLee

I was just reading that it is possible to bond solder to aluminum. I have an old high wattage iron to try and the trick besides heat is to scratch the surface of the aluminum with the solder tip while soldering/heating to remove the oxide film from the aluminum. If you sand or scratch the aluminum first, it will just come back instantly as it has air contact.

I will try a combination of a stud with a wire all bolted to the chassis as well as trying to bond it with solder. That will be my power cord Earth Ground. Then will try looking at the SL-X above Ground schem and star Ground everything to that point with an aprox 800 ohms above Ground. I am going to look at the SL-X schem here in a bit . . . .

ADD: Crap, I am even thinking might as well go for DC heaters while I am at it. This build will probably go in the high gain direction. At least 4 gain stages if not 5 or the 5th can be an added Lead stage.

I have a set of 30W transformers, so this could get very interesting for sure.


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## neikeel

There is this:






Or this:




Both work ;-)


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## RickyLee

@neikeel: Thanks for the schems. That lower 1959 looks very close to what I did on my PlexiRod build. And it is a very quiet amp with lots of gain on tap.

The top one looks like an aluminum chassis. Is that what they actually are, aluminum chassis schemes? Would that 1959 be what the first Marshall aluminum chassis did or is that an upgrade to quiet those old aluminum chassis Marshalls?


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## RickyLee

This is what the SL-X schem is. The entire amp circuit is star Grounded to one point which is 22 ohms above chassis Ground.

http://www.drtube.com/schematics/marshall/2500-60-02.gif


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## john l

neikeel said:


> There is this:
> 
> 
> 
> 
> 
> Or this:
> 
> 
> 
> 
> Both work ;-)



I too like the Larry method, its much quieter then the buss on the back of the pots and interestingly enough it seamed to make little tricks like DC elevating heaters more effective. My 4 stage monster is set up this way and its disturbingly quiet for being such a chugger.


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## danfrank

RickyLee said:


> I was just reading that it is possible to bond solder to aluminum. I have an old high wattage iron to try and the trick besides heat is to scratch the surface of the aluminum with the solder tip while soldering/heating to remove the oxide film from the aluminum. If you sand or scratch the aluminum first, it will just come back instantly as it has air contact.



Aluminum oxide DOES NOT come back instantly; especially where you live where it's as dry as a bone. It will happen rather quickly in humid places like the gulf coast or the east coast, but not where you are. Just use a steel screw and a couple of star washers, you know, the kind that digs into the chassis when you tighten down on the screw. Unless you're in the habit of pouring beer or soft drinks over your amp regularly, you won't have a problem.
As for soldering onto aluminum, it can be done with "acid flux" like ruby fluid, but acid flux is generally a no-no with electronics. Acid flux WILL dissolve any aluminum oxide that may have formed at your connection. It will also disolve any copper, so this is why this is done before the amp building starts. If you plan on going this route, drill all holes that your chassis needs, then solder the studs onto the aluminum chassis using acid flux. After this wash the hell out of your chassis with a solution of baking soda and water and use a stiff nylon brush; this will neutralize the flux residue. After that, wash thoroughly with plenty of water and dry.



RickyLee said:


> ADD: Crap, I am even thinking might as well go for DC heaters while I am at it. This build will probably go in the high gain direction. At least 4 gain stages if not 5 or the 5th can be an added Lead stage.



The key to good grounding and a quiet amp is to have each stage have it's own ground path to it's respective filter cap. What you don't want is for the ground returns of the different stages to criss cross each other. This is an invitation for ground loops which is what the ground "hum" noise typically is. Using the chassis is a TERRIBLE way to implement a ground system in an amp. Early amps were made this way because the manufacturers didn't know any better.


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## RickyLee

danfrank said:


> Aluminum oxide DOES NOT come back instantly; especially where you live where it's as dry as a bone. It will happen rather quickly in humid places like the gulf coast or the east coast, but not where you are. Just use a steel screw and a couple of star washers, you know, the kind that digs into the chassis when you tighten down on the screw. Unless you're in the habit of pouring beer or soft drinks over your amp regularly, you won't have a problem.
> As for soldering onto aluminum, it can be done with "acid flux" like ruby fluid, but acid flux is generally a no-no with electronics. Acid flux WILL dissolve any aluminum oxide that may have formed at your connection. It will also disolve any copper, so this is why this is done before the amp building starts. If you plan on going this route, drill all holes that your chassis needs, then solder the studs onto the aluminum chassis using acid flux. After this wash the hell out of your chassis with a solution of baking soda and water and use a stiff nylon brush; this will neutralize the flux residue. After that, wash thoroughly with plenty of water and dry.
> 
> The key to good grounding and a quiet amp is to have each stage have it's own ground path to it's respective filter cap. What you don't want is for the ground returns of the different stages to criss cross each other. This is an invitation for ground loops which is what the ground "hum" noise typically is. Using the chassis is a TERRIBLE way to implement a ground system in an amp. Early amps were made this way because the manufacturers didn't know any better.



Thanks for the great info.

Using the scheme you mentioned of tying each gain stage Ground to its respective filter cap Ground is what I did on my PlexiRod. Very quiet amp indeed as it turned out.

But on this aluminum chassis, would I not be better using a star Ground layout. BUT, run each stages Ground direct shortest route to its respective filter cap Ground. Then try to minimize Ground runs to the star point, by consolidating wires and avoiding criss crossing of course? 

My method above would probably have to use filter caps mounted on the turret board vs the chassis mounted filter cans.


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## danfrank

Hi,
Yes, star grounding is good also. What you want to avoid, for example, is attaching the grounds from the 1st 12AX7 tube to the 1st filter cap ground closest to the PT.
One more thing I forgot to mention which is important is to attach the chassis ground to circuit ground at only one place. This helps a lot in avoiding ground loops. Some people like to tie the 2 grounds together at the input to the amp, but I find this way to be finicky, sometimes it works good for me, other times, not so much. What I like to do is attach both grounds at the 1st filter cap coming from the rectifier; this becomes my "star" point and I attach a lug to one of the screws that holds this cap to the chassis which then goes to the (-) lead of that capacitor.


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## ampmadscientist

RickyLee said:


> I have an aluminum chassis which is the only one I have that will fit in this slightly smaller JMP style headbox I want to use. Figured I might as well do something with it.
> 
> 
> 
> I am thinking I should try some type of star grounding scheme or maybe even an above ground reference scheme like you see in the JCM900 SL-X.
> 
> This chassis has no welded studs to go off of anywhere, as in for the wall plug Earth Ground, so bummer there.



You actually have 3 grounds to the chassis:
1. Safety Ground (from power lead)
2. Power supply grounds
3. Audio circuit grounds

PART 1: Safety Ground Wire
The safety ground connection to the chassis (from power receptacle) is attached w/ half steel half aluminum stud. (one method)
Aluminum side of the stud is welded to chassis or bolted using aluminum hardware (nuts and washers).
Sure, welding is always better because oxygen cannot get between the 2 aluminum parts.
In aluminum to aluminum hardware contact, grease such as NO-OX-ID prevents oxide between aluminum parts from interrupting the contact.

The steel side of the stud w/ steel hardware is for connecting your copper saftey ground wire usually w/ a ring terminal. The ground wire is crimped and soldered to the ring. The steel hardware and your ring should have similar plating to prevent oxide from forming between the parts, thereby losing contact.
After you get your ring tightened down to the steel side of the stud w/ steel hardware, you can also solder the steel / plated parts together. (actually the best way is to solder steel / copper / plated parts together)

No, you cannot solder copper wire to aluminum...in case you were wondering about this.

Using that method, you are not dependent on steel or copper (plated parts) screwed or bolted directly to aluminum. This is the worst possible method.
A. Dissimilar metals contact causes oxide between the parts to form.
B. The oxide is a perfect insulator.
C. This is the main concern - that dissimilar metals will lose electrical conductivity, and there will be no ground to the chassis.
D. No matter how tight the hardware is, the oxide can (for sure) still form between the dissimilar metals.

NO-OX-ID grease: It's actually intended for aluminum to aluminum parts contact only.

*HOW COME it has to be like this?*

*Because people DIED! This is why the electrical grounding rules (for aluminum) were created.*

Yes it is a law. 

E. Electricians / Manufacturers are not allowed to ground aluminum using dissimilar metals that are screwed to each-other.

F. You cannot use the aluminum chassis as a Current path. This is illegal.


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## ampmadscientist

jack daniels said:


> Ask AMS, he has all the answers...



Actually, it's NEC that has the answers. (National Electrical Code)

You probably should go earn yourself an NEC certificate.


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## ampmadscientist

danfrank said:


> Hi,
> Yes, star grounding is good also. What you want to avoid, for example, is attaching the grounds from the 1st 12AX7 tube to the 1st filter cap ground closest to the PT.
> One more thing I forgot to mention which is important is to attach the chassis ground to circuit ground at only one place. This helps a lot in avoiding ground loops. Some people like to tie the 2 grounds together at the input to the amp, but I find this way to be finicky, sometimes it works good for me, other times, not so much. What I like to do is attach both grounds at the 1st filter cap coming from the rectifier; this becomes my "star" point and I attach a lug to one of the screws that holds this cap to the chassis which then goes to the (-) lead of that capacitor.



Star grounding is the noisiest method.
Because power supply noise is introduced into the audio ground.

*because the noise is AC, and AC travels both directions. It's not a one way path to the chassis.

The quietest method: Audio and power supply ground is separated, the resistance of the chassis is in between the two.
(or other methods)

*In many newer amps, you will see a resistor between the power supply ground and the preamp audio ground.

* In older amps, the chassis acts as this resistor. The resistance of the chassis between power supply and audio ground might be 10 ohms or more....and this is how it was done in the old days.

The power supply is grounded on the PT side of the chassis.
The audio is grounded on the opposite side of the chassis.


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## ampmadscientist

PART TWO:
The aluminum chassis cannot be used as a current path. (it's a safety code violation)
Which basically implies that filter cap grounds + other power supply grounds and power tube cathodes are hard wired back to the center tap of the power transformer...
instead of using the aluminum chassis as the current path.

And now you start to understand why Marshall, Boogie, Silvertone (actually Danelectro), etc...stopped using aluminum and changed over to a steel chassis.


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## Thiez

My marshall build has an 3mm aluminium chassis. I basicly used the 'larry grounding' but wired it as some kind of buss instead of using the chassis.


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## ampmadscientist

Thiez said:


> My marshall build has an 3mm aluminium chassis. I basicly used the 'larry grounding' but wired it as some kind of buss instead of using the chassis.


As long as the aluminum is not a current path...
As long as there are no dissimilar metals used to attach the ground to aluminum...
Then you have done a good job.

You remind us that it's all possible to do it the right way. I mean, it's more effort but still possible.


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## GIBSON67

Good thread, thanks!


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## coldengray

I have done the vintage ground bus soldered to the back of the pots, and I have done Larry. When comparing the two directly using a Metro Headmaster through the same cabinet I heard no difference in the noise floor. YMMV.


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## mickeydg5

GIBSON67 said:


> Good thread, thanks!


Does your avatar provoke beastiality?
According to the internet, yes.





That is funny right there!


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## ampmadscientist

coldengray said:


> I have done the vintage ground bus soldered to the back of the pots, and I have done Larry. When comparing the two directly using a Metro Headmaster through the same cabinet I heard no difference in the noise floor. YMMV.



When you have the bias too cold, it works like a noise gate.
It's not a fair contest unless the bias eliminates crossover distortion before clipping.
Then, you will really hear what noise is there, instead of masking it by shutting the output off with cold bias.

With a scope, you can really see the differences in noise levels.
But w/ aluminum chassis, the safety issues change with age....it's not just the noise you need to worry about.

READ THIS
It's not just a noise floor issue. It's a safety issue.
Learn this: aluminum chassis needs special grounding precautions.


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## guitarmike2107

ampmadscientist said:


> *HOW COME it has to be like this?*
> 
> *Because people DIED! This is why the electrical grounding rules (for aluminum) were created.*
> 
> Yes it is a law.
> 
> E. Electricians / Manufacturers are not allowed to ground aluminum using dissimilar metals that are screwed to each-other.
> 
> F. You cannot use the aluminum chassis as a Current path. This is illegal.



Hello Ampmadscientist, do you know what section this is covered in the NEC, I cant find anything along these lines in my copy.

250.8 does say that connections that rely solely on solder are not allowed.

IEC 60065 discusses earth bonding and says that bonds between materials with Electrochemical potential above 0.6v should be avoided, connections with an aluminum chassis with zinc plated steel parts is well below 0.6v and so is allowed by that code (see Annex F + section 15.2)

In addition to this Marshall still use aluminum chassis for the 1974x amplifiers in all countries.


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## ampmadscientist

RickyLee said:


> I was just reading that it is possible to bond solder to aluminum. I have an old high wattage iron to try and the trick besides heat is to scratch the surface of the aluminum with the solder tip while soldering/heating to remove the oxide film from the aluminum. If you sand or scratch the aluminum first, it will just come back instantly as it has air contact.
> 
> I will try a combination of a stud with a wire all bolted to the chassis as well as trying to bond it with solder. That will be my power cord Earth Ground. Then will try looking at the SL-X above Ground schem and star Ground everything to that point with an aprox 800 ohms above Ground. I am going to look at the SL-X schem here in a bit . . . .
> 
> ADD: Crap, I am even thinking might as well go for DC heaters while I am at it. This build will probably go in the high gain direction. At least 4 gain stages if not 5 or the 5th can be an added Lead stage.
> 
> I have a set of 30W transformers, so this could get very interesting for sure.



They are talking about the SAFETY GROUND, not the circuit path ground.
The SAFETY GROUND does not normally carry current. (unless a short circuit occurs)
You guys have been *using the chassis as a high voltage current circuit path.*
That's where the problem starts.

Amp makers used to use the chassis for a filament current path too...
(that has also been stopped)

No you cannot solder to aluminum.
*Whoever posted that is full of shit.




*

Just because you make a pool of solder on the aluminum...or scratch the chassis...does not mean that it's soldered.

Solder MUST flow. Not pool...a pool of solder is not a connection to aluminum.

The solder can pop / crack right off of the aluminum, it's a superficial connection. The solder cannot flow / bond into aluminum.

Aluminum has to be tig or mig welded.

1. The best method: is not to use the aluminum as a circuit path.
2. Safety mains ground should be permanently attached to the chassis, so it does not depend on screws alone.

All commercial products: *have removed the aluminum from the circuit path.* Otherwise it won't pass safety regulations.

Aluminum Chassis CAN be used but: the circuit grounds are all copper wire or copper traces on the circuit board.

The safety ground (mains ground) is attached to the chassis.
Current does not pass thru the aluminum (anymore). That's the real point of the safety precautions.


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## ampmadscientist

guitarmike2107 said:


> Hello Ampmadscientist, do you know what section this is covered in the NEC, I cant find anything along these lines in my copy.
> 
> 250.8 does say that connections that rely solely on solder are not allowed.
> 
> IEC 60065 discusses earth bonding and says that bonds between materials with Electrochemical potential above 0.6v should be avoided, connections with an aluminum chassis with zinc plated steel parts is well below 0.6v and so is allowed by that code (see Annex F + section 15.2)
> 
> In addition to this Marshall still use aluminum chassis for the 1974x amplifiers in all countries.




The current path is not through the aluminum chassis: Marshall removed and isolated the current path from the chassis.

The grounding lug is (welded) soldered and screwed (both) to the chassis. And this screw would have a lock washer / lock nut.
The wire is normally crimped and soldered (both) into a grounding lug.

The wire is mechanically attached (crimped) and electrically attached (solder).
(both)

The lug is mechanically attached (screw lock nut) and electrically attached welded / soldered (both).

There are no safety ground connections which depend on solder alone....or should not be.

Except PC boards which do depend on solder alone : all of them do. But the current is all on the board, not the chassis.


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## zebrarock

Hi, a question a little out of the topic, di guitar grounding issues may depend on a bad amp grounding ? My guitar produces buzz when i don't touch it, while it stops when i touch every metal part. Classic problem. I open my guitar but all connection to ground seem to be ok. So is this due to my amp


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## ampmadscientist

zebrarock said:


> Hi, a question a little out of the topic, di guitar grounding issues may depend on a bad amp grounding ? My guitar produces buzz when i don't touch it, while it stops when i touch every metal part. Classic problem. I open my guitar but all connection to ground seem to be ok. So is this due to my amp



No, non è dovuto all'amplificatore.
Può essere causato da pickup single coil.
Può essere causato dalla mancanza di schermatura all'interno della chitarra.
Il cablaggio all'interno della chitarra dovrebbe essere un cavo schermato.
I controlli all'interno della chitarra possono essere schermati con metallo che riduce il rumore.
Se la schermatura all'interno della chitarra è sottile foglio di metallo, o vernice di schermatura, non è molto efficace.

Stai usando pickup single coil? Che tipo di chitarra stai suonando?

No it is not due to the amplifier.
It can be caused by single coil pickups.
It can be caused by lack of shielding inside the guitar.
The wiring inside the guitar should all be shielded wire.
The controls inside the guitar can be shielded with metal which will reduce the noise.
If the shielding inside the guitar is thin metal foil, or shielding paint, it is not very effective.

Are you using single coil pickups? What type of guitar are you playing?


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## zebrarock

Gibson les paul std 1990, there is the metal plate into the pot box, my pickups are alnico II pro slash with shielded bride wire. Brides are joint to pots. there is no shielding inside..


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## ampmadscientist

zebrarock said:


> Gibson les paul std 1990, there is the metal plate into the pot box, my pickups are alnico II pro slash with shielded bride wire. Brides are joint to pots. there is no shielding inside..



The guitar has no metal shielding around the pots and wires inside?
Sorry, but I'm not sure I understand.

To shield the insides, there should be metal around the controls and wiring.
Do you have this metal shielding can inside the Les Paul?






This is the best method, which will reduce noise and hum the most effectively.

Also: all the wires in the guitar should be shielded wires.






If the shielding is only foil, or shielding paint, it is not nearly as effective.

1. The best type of metal to use for shielding is mu metal.
Thick Copper will also work, but if it is thin it does not work as effectively.

2. Multiple layers of shielding, with space in between, is very effective.

La chitarra non ha una schermatura metallica intorno ai vasi e ai fili all'interno? Scusa, ma non sono sicuro di aver capito. Per proteggere l'interno, ci dovrebbe essere metallo intorno ai controlli e al cablaggio. Avete questa protezione metallica all'interno della Les Paul? Questo è il metodo migliore, che ridurrà il rumore e il ronzio più efficacemente. Inoltre: tutti i fili della chitarra dovrebbero essere cavi schermati. Se la schermatura è solo un foglio o una vernice protettiva, non è altrettanto efficace. 
1. Il miglior tipo di metallo da usare per la schermatura è mu metal. Anche il rame spesso funzionerà, ma se è sottile non funziona altrettanto efficacemente. 
2. Gli strati multipli di schermatura, con spazio intermedio, sono molto efficaci.


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## zebrarock

No, there is no metal cover over the pots... as in picture #2 they just lay in a metal plate, then pickup wires are shielded and switch wire is shielded. This last wire have a bare wire inside connected both sides, into switch and into pots metal plate. Is the right method ? Does ground wire have to be connectted both sides ?


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## ampmadscientist

Capacitors:

The capacitor (can have film) outside foil connected to one lead, and inside foil connected to the other lead.

film capacitors

The capacitor foil must be facing the correct way, to reduce hum and noise the most efficiently.


condensatori: Il condensatore (può avere un film) all'esterno di un foglio collegato a un conduttore e un foglio interno collegato all'altro conduttore. condensatori a film La pellicola del condensatore deve essere rivolta nella direzione corretta, per ridurre il ronzio e il rumore nel modo più efficiente.


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## ampmadscientist

zebrarock said:


> No, there is no metal cover over the pots... as in picture #2 they just lay in a metal plate, then pickup wires are shielded and switch wire is shielded. This last wire have a bare wire inside connected both sides, into switch and into pots metal plate. Is the right method ? Does ground wire have to be connectted both sides ?



"No, there is no metal cover over the pots..."

Then there will be more noise.

The ground wire should connect to

The pickup ground + shield of pickup.
The metal cases of the pots
The metal plate the pots are mounted to
Th output jack ground
The frame of the pickup switch
The bridge is also connected to ground

All these points should be connected to ground.


"No, non c'è una copertura metallica sopra i vasi ..."
Quindi ci sarà più rumore. Il cavo di terra dovrebbe connettersi a Il pick-up + lo scudo del pick-up.
Le casse di metallo dei vasi La piastra metallica su cui sono montati i vasi Presa jack di uscita La cornice dell'interruttore di selezione Tutti questi punti dovrebbero essere collegati a terra.


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## ampmadscientist

Please listen to this clip of shielding VS no shielding:


Si prega di ascoltare questa clip di schermatura VS senza schermatura:


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## zebrarock

Oh thanks a lot for these videos... i will do some work on my guitar...last question, how much voltage i have to get from my multimeter when check metal parts ? 0 V or near 0V ?


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## ampmadscientist

zebrarock said:


> Oh thanks a lot for these videos... i will do some work on my guitar...last question, how much voltage i have to get from my multimeter when check metal parts ? 0 V or near 0V ?



Set the meter on ohms, there is no voltage.
Set the meter on continuity beep.

It just tells you if the grounds are all tied together- jack ground to volume control ground, to bridge ground, to shielding plate ground.
It just verifies that everything is grounded / connected to ground.

I think what you need is: shielding. Watch the shielding video.


Impostare lo strumento su ohm, non c'è tensione. Impostare lo strumento sul segnale acustico di continuità. Ti dice solo se i terreni sono tutti collegati insieme: terra da terra a terra per il controllo del volume, per collegare il terreno, per schermare il terreno della piastra. Semplicemente verifica che tutto sia collegato a terra / collegato a terra. Penso che ciò di cui hai bisogno è: schermatura. Guarda il video di schermatura. Un sacco di persone dall'Italia si stanno unendo al forum. Sto cercando di renderlo più facile per le persone che non parlano inglese. Per favore perdona il mio italiano, sto solo imparando, spero che tu capisca me.


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## Guitar-Rocker

guitarmike2107 said:


> Hello Ampmadscientist, do you know what section this is covered in the NEC, I cant find anything along these lines in my copy.
> 
> 250.8 does say that connections that rely solely on solder are not allowed.
> 
> IEC 60065 discusses earth bonding and says that bonds between materials with Electrochemical potential above 0.6v should be avoided, connections with an aluminum chassis with zinc plated steel parts is well below 0.6v and so is allowed by that code (see Annex F + section 15.2)
> 
> In addition to this Marshall still use aluminum chassis for the 1974x amplifiers in all countries.





Amp Mad cannot give you the reference where the N.E.C. covers tube amps, because it's not in the code book, period ! I get so sick of that bullshit that he constantly spouts about that. Are there sections about aluminum wiring and uses covered in the code? Yes. But tube amps are not in there anywhere. For the last time "SHUT IT ABOUT BEING A CODE VIOLATION " to wire an amp in a aluminum chassis. If you are correct Amp Mad show the code reference. This is the third time that I've challenged you in this forum to do just that, and you never have, because you can't. God I get sick of this shit ! Get over it .


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## ampmadscientist

Guitar-Rocker said:


> Amp Mad cannot give you the reference where the N.E.C. covers tube amps, because it's not in the code book, period ! I get so sick of that bullshit that he constantly spouts about that. Are there sections about aluminum wiring and uses covered in the code? Yes. But tube amps are not in there anywhere. For the last time "SHUT IT ABOUT BEING A CODE VIOLATION " to wire an amp in a aluminum chassis. If you are correct Amp Mad show the code reference. This is the third time that I've challenged you in this forum to do just that, and you never have, because you can't. God I get sick of this shit ! Get over it .



"....because it's not in the code book..."

It's definitely in the code book.
And those codes *apply to any electrical*, not just tube amps.

Using dissimilar metals to connect a high voltage current carrying ground path to aluminum is prohibited.
It's illegal to wire any house or building or circuit panel or receptacle using copper (or dissimilar metal) to aluminum.
In fact aluminum wire has been banned from use in new residential buildings completely...
It is illegal to connect aluminum to any circuit (to carry current) unless the device you are connecting is specifically approved for connection to aluminum. (the device says- "Al" stamped on it, and is approved to be used for connection to aluminum).
Any time you connect aluminum to a dissimilar metal, there is an approved device specifically rated / approved for that connection.

For example a device to connect copper to aluminum would be marked : "Al Cu" And that marking would be stamped on the device.

*2014 Code Language:*

*342.14 Dissimilar Metals. *_Where practicable, *dissimilar metals in contact anywhere in the system shall be avoided *to eliminate the possibility of galvanic action.

*2017 Code Language:*

*342.14 Dissimilar Metals. *Where practicable, dissimilar metals in contact *anywhere in the system* shall be avoided to eliminate the possibility of galvanic action.
_
110.14 Conductors of *dissimilar metals* shall not be intermixed ...

_"...shall be avoided..."
"...shall not be intermixed ..."

-------------------------------------------------------------------------------------------_

*FYI:
"Shall" is mandatory. Not optional.*

In electrical safety, you don't make the rules that everybody follows.
Even though you may find that convenient...
_________________________________________________________________

Splicing wire connectors are required to be marked for the material of the conductor and for their suitability where intermixed. Splicing wire connectors, such as twist-on wire connectors, are not suitable for splicing aluminum conductors or copper-clad aluminum to copper conductors unless it is so stated and marked as such on the unit container or an information sheet supplied with the unit container. The required marking is “AL-CU (intermixed-dry locations)” where intermixing (direct contact) occurs.

Ref: 110.14 Electrical Connections (B) Splicing

FYI:
In aluminum chassis amplifiers, the circuit path no longer uses the chassis as a current carrying conductor.
The circuit path has been completely separated from the chassis.
The chassis is still grounded to mains ground !
But the circuit path is no longer through the aluminum.

So- you can still use an aluminum chassis. Just don't use it as the circuit path.
Got That?

NOLOX:
This is used and approved for aluminum to aluminum contact only.
It is not designed or approved for connection of dissimilar metals.

No, I'm not shutting up. Tough luck.


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## ampmadscientist

Guitar-Rocker said:


> Amp Mad cannot give you the reference where the N.E.C. covers tube amps, because it's not in the code book, period ! I get so sick of that bullshit that he constantly spouts about that. Are there sections about aluminum wiring and uses covered in the code? Yes. But tube amps are not in there anywhere. For the last time "SHUT IT ABOUT BEING A CODE VIOLATION " to wire an amp in a aluminum chassis. If you are correct Amp Mad show the code reference. This is the third time that I've challenged you in this forum to do just that, and you never have, because you can't. God I get sick of this shit ! Get over it .



See?
You keep granting yourself an exemption from electrical safety because the NEC doesn't say: "tube amp."

The NEC applies to EVERY appliance, all high voltage devices. not just tube amps.

Electrical safety applies to all things electrical.
You have no exemption from safety.

You KNOW the dissimilar metals corrode.

You KNOW the connection can fail.

You KNOW safety codes protect people from those hazards.

That's enough.

"Mike Holt, Contributing Editor | Feb 01, 2000"
The National Electrical Code is written for people who understand electrical terms, theory, and trade practices. Such persons include electrical contractors, electrical inspectors, electrical engineers, and qualified electricians. The Code was not written to serve as an instructive or teaching manual for untrained persons [90-1(c)]." 

"Learning to use the NEC is like learning to play the game of chess. You first must learn the terms used to identify the game pieces, the concepts of how each piece moves and the layout of how the pieces are placed on the board. Once you have this basic understanding of the game, you're ready to start playing it. 

But all you can do is make crude moves because you really don't understand what you're doing."


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## Guitar-Rocker

No provide the section that applies to tube amps, or for that matter appliances and grounding of aluminum enclosures. It flat isn't in there and you know that fact. Quit lying to the members here.

And for the record I've taken Mike Holts classes, have you?


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## ampmadscientist

Guitar-Rocker said:


> No provide the section that applies to tube amps, or for that matter appliances and grounding of aluminum enclosures. It flat isn't in there and you know that fact. Quit lying to the members here.
> 
> And for the record I've taken Mike Holts classes, have you?



"The Code was not written to serve as an instructive or teaching manual for untrained persons [90-1(c)]."

And "for the record:"
I am a certified electrician. I earned an NEC electrical certification.


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## Guitar-Rocker

Retired Master Electrician here, keep at it you'll get there someday.


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## CoyotesGator

Guitar-Rocker said:


> Retired Master Electrician here, keep at it you'll get there someday.



You Good Sir, are an optimist.


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## ampmadscientist

One of the first things an electrician is taught: do not hook up dissimilar metals to make a circuit or a ground.
This is rudimentary knowledge for an educated electrician.
Now years ago when the Marshall Amp was first designed, aluminum was an acceptable conductor; up until about 1970 when the standards were changed I do believe.

So the amp was built years ago - at first with aluminum as the circuit path conductor.
But since then the aluminum has been removed; out of the circuit path.

The production with an aluminum chassis today has the safety mains ground tied to the chassis....but no dependence on path through aluminum to make the circuit function.


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## zebrarock

So , wanting to build an amp from scratch, which is the best and safest and easiest to deal chassis material to refers to ? Steel ?


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## ampmadscientist

zebrarock said:


> So , wanting to build an amp from scratch, which is the best and safest and easiest to deal chassis material to refers to ? Steel ?


I would use galvanized steel.
Mostly because
a. it's a lot stronger
b. I can solder and bolt the ground lugs to the metal.


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## zebrarock

for example, my 1981 jcm800 2203 do you know what kind of chassis material did use ? was it alluminium or steel ?


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## ampmadscientist

zebrarock said:


> for example, my 1981 jcm800 2203 do you know what kind of chassis material did use ? was it alluminium or steel ?


It's steel of course.

Long ago manufacturers used aluminum, but there was 2 main problems.
a. it bends too easily and is impracticle for large heavy transformers.
b. The ground connections to the chassis can fail because of dissimilar metals contacting each other. Aluminum oxidizes when it's in contact with other metals.

At that point most manufacturers used steel instead, most of them continue to do so.

The amps that are made of aluminum changed the grounding scheme.
The chassis is no longer the circuit path / the circuit path is hard wired instead.

I use the Fender convention which is:
Grounded connections to the steel chassis are soldered and bolted.

And I recommend that anybody who is building an amp follow that Fender convention.


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