The Essential Safety Protocol for Marshall (Tube) Amps.

[V-man]

Some know/have heard of “The 4 Rules of Firearm Safety.” Not everybody knows that you can (hypothetically) outright ignore one of the first 3 and nothing happens. You can even violate 2 of the first 3, and should an unintended “BANG” take place, nobody gets seriously hurt. The point is the redundancies of this safety system allow for: A) hyper-vigilance; and B) the ability for our dumb fallible human asses to catch what’s going on before mistake becomes tragic mistake. The same discipline should apply to tube amp operation, particularly with the ownership of muliptiple heads, cabs, attenuation units and moves for studio/gig use.

Last week I pulled the speaker cable from attenuated unit A to transfer attenuation to B. Pulling a speaker cable is/should be the equivalent of a loaded firearm with the safety off. Those anticipating the punchline, No. Amp A was not then powered without a load later, but another potentially worse SNAFU developed: while playing musical chairs with cable leads, I managed to set one of the speaker cables (B speaker out to A speaker out) back into A, giving B no load and setting A to receive God knows what damage from B’s output.

Thanks to one stupid move from my dumb, fallible, sleep-deprived human ass, I staged an event that risked damaging TWO amplifiers simultaneously. But for the “4 Rules of Firearms Safety,” I might have done just that. To my knowledge, no perceptible damage was caused.

This protocol is likely the reason why:

1. NO LOAD
ANY amp with no load gets a solid connector jammed into the input jack to indicate there is no lead attached. -Others have pointed out a safer practice is to disconnect the power cable. Go with your preference of max safety or convenience seeing how either should prevent negligent powerages.

2. SET VOLUME
ANY amp (particularly NMVs) should be backed down to 0-1 and any amp changing speaker cables MUST be backed down to 0-1

3. NO SIGNAL
When disengaging Standby and hearing no signal come out (at low-dialed volume), IMMEDIATELY hit Standby, (consider powering off thereafter) and trace all speaker cable origins/destinations.

4. IMPEDANCE ORGANIZATION
If switching frequently between different impedance cabs, consider markers that remind you of what’s going on (i.e. blue-based speaker cable for 16 ohm cab, red for 8 ohm cab and/or markers to sit on top of head -maybe a small red or blue block or a post-it with 8 or 16) to keep track.

5. BONUS: KNOW THE “PINK“ FROM THE “STINK”
Rather fucked up title, but I bet you remember it! Classic amps have 2-4 speaker outs and that’s it. Modern amps can have multiple D.I.s, FX Loops, etc running back there that a careless shuffle could have you plugging your speaker cable into anything but the speaker output. Consider distinguishing these input/output jacks. Some later Marshalls have used Orange nuts to distinguish Speaker outs. They are a cheap replacement, as is hobby paint or nail polish on a black speaker jack nut to do the same. If you reach back habitually and don’t look/cant see, lo tech solutions like a sticker or taping a dime (something tactile) above the speaker jack lets your finger’s confirm it’s not “the wrong hole!”


Yes, Solid Connectors in the bin may play a vital part for your gear still… ironically by preserving amps rather than ruining pedals. Clearly, this amp has no load attached per the protocol.


Bright jack nuts help with quick confirmation that you are accessing speaker outs in the back of a populated amp.




These are my protocols. If you have other or better, feel free to share.

 

[Sustainium]

Excellent advice, thanks for taking the time!

 

[junk notes]

Well, we are all different and have different experiences and episodes, but I guess that you are seeing it right,

and does not hurt your tone to be cautiously colorful.

 

[BlueX]

Well, we are all different and have different experiences and episodes, but I guess that you are seeing it right,

and does not hurt your tone to be cautiously colorful.

Maybe I just got OCD, but why aren't 1x16 green and both 1x8/2x16 white?

 

[Calebz]

I'm with you on rule 1, but I approach it differently.

No load=no power.

If there's no cab attached, there's no power cable attached either. 100% guarantee my dumb ass can not accidentally cook something if there's no power😄

I also color code the ins/outs I most commonly use. Back of the amp, cables themselves, and on the pedalboard in/out panel.

This not only minimizes the chances of me doing something stupid, it makes stage setup quick, easy and stupid-proof.

Yay for colored electrical tape😄

 

[PelliX]

I like #1 a lot. A sort of lock-out-tag-out system for amps... not a bad idea, really!

2. SET VOLUME
ANY amp (particularly NMVs) should be backed down to 0-1 and any amp changing speaker cables MUST be backed down to 0-1

What's the goal here? Preventing hearing damage because there's such difference in volume between cabs that it might be unexpectedly loud? Or are you referring to swapping cabs with the HT *on* and thus reducing the signal while doing so?

 

[Ronquest]

If you forget to connect your speaker don't shut the amp off, just plug the speaker in.
Turning the amp off without a load can cause more damage from flyback.
The sudden on/off change in voltage to the transformer causes the voltage spike and potential arc/short. It's like an ignition coil in a car.

 

[Matthews Guitars]

You can buy colored sets of jack nuts if you really want to. They're available online and easy to find with a search "Colored Cliff jack nuts" will take you there.

 

[fitz]

No load=no power.

If there's no cab attached, there's no power cable attached either. 100% guarantee my dumb ass can not accidentally cook something if there's no power😄

This is what I do.
Before I disconnect a speaker cab, I disconnect the power cord.
Before I connect a power cord, I check both ends of all speaker cables and amp impedance setting.

I swap around pedal boards more so than speakers, so I color code my loop cables with a wrap of red tape on either end of the return cable.

 

[PelliX]

If you forget to connect your speaker don't shut the amp off, just plug the speaker in.
Turning the amp off without a load can cause more damage from flyback.
The sudden on/off change in voltage to the transformer causes the voltage spike and potential arc/short. It's like an ignition coil in a car.

Granted, I'm not a car mechanic, but I'm familiar with the concept of flyback from electric motors, relays, etc. I don't quite see what's supposed to get damaged here; the OT will be fine. I fail to see how this is going to hurt the valves themselves, either. While I concur that in theory the assertion is correct, I doubt whether it really makes a practical difference here?

 

[TonalEuphoria]

I'd like to add some.

5. Don't point your Marshall in the direction of anyone you are not willing to sonically destroy their loves of disco.

6. Know your target with your Marshall and what their behind looks like.

7. Keep you fingers off your volume knob until you are ready to lay down deadly tone.

And

8. Always bring spare tubes, lest you enter the tone fight with not enough ammo.

 

[Jethro Rocker]

Very good points.
I never switch around enough stuff at home to care and like @Calebz and @fitz above, I only plug in one amp at a time to AC power.
Best I do is put white tape above the fx return jack on most amps as most stages are dark and from above reaching around it is hard to read. Saves using flashlight.

 

[Dr.Twang!]

I included this on a Craigslist ad for a very loud converted amp a few years ago:
”This appliance is NOT suitable to be used by any person or persons (including children) with limited physical, sensorial or mental ability, or by persons with insufficient experience and/or knowledge to operate such an appliance. Children under 14 years of age must be kept away from this appliance at all times.
This device is capable of producing very high sound pressure levels (in excess of 90 dB), which may cause temporary or permanent hearing damage. Exposure to extremely high noise levels may cause permanent hearing loss. Use care when setting and adjusting volume levels during use. Wear hearing protection if continuously exposed to such levels”

 

[El Gringo]

Some know/have heard of “The 4 Rules of Firearm Safety.” Not everybody knows that you can (hypothetically) outright ignore one of the first 3 and nothing happens. You can even violate 2 of the first 3, and should an unintended “BANG” take place, nobody gets seriously hurt. The point is the redundancies of this safety system allow for: A) hyper-vigilance; and B) the ability for our dumb fallible human asses to catch what’s going on before mistake becomes tragic mistake. The same discipline should apply to tube amp operation, particularly with the ownership of muliptiple heads, cabs, attenuation units and moves for studio/gig use.

Last week I pulled the speaker cable from attenuated unit A to transfer attenuation to B. Pulling a speaker cable is/should be the equivalent of a loaded firearm with the safety off. Those anticipating the punchline, No. Amp A was not then powered without a load later, but another potentially worse SNAFU developed: while playing musical chairs with cable leads, I managed to set one of the speaker cables (B speaker out to A speaker out) back into A, giving B no load and setting A to receive God knows what damage from B’s output.

Thanks to one stupid move from my dumb, fallible, sleep-deprived human ass, I staged an event that risked damaging TWO amplifiers simultaneously. But for the “4 Rules of Firearms Safety,” I might have done just that. To my knowledge, no perceptible damage was caused.

This protocol is likely the reason why:

1. NO LOAD
ANY amp with no load gets a solid connector jammed into the input jack to indicate there is no lead attached.

2. SET VOLUME
ANY amp (particularly NMVs) should be backed down to 0-1 and any amp changing speaker cables MUST be backed down to 0-1

3. NO SIGNAL
When disengaging Standby and hearing no signal come out (at low-dialed volume), IMMEDIATELY hit Standby, (consider powering off thereafter) and trace all speaker cable origins/destinations.

4. IMPEDANCE ORGANIZATION
If switching frequently between different impedance cabs, consider markers that remind you of what’s going on (i.e. blue-based speaker cable for 16 ohm cab, red for 8 ohm cab and/or markers to sit on top of head -maybe a small red or blue block or a post-it with 8 or 16) to keep track.

5. BONUS: KNOW THE “PINK“ FROM THE “STINK”
Rather fucked up title, but I bet you remember it! Classic amps have 2-4 speaker outs and that’s it. Modern amps can have multiple D.I.s, FX Loops, etc running back there that a careless shuffle could have you plugging your speaker cable into anything but the speaker output. Consider distinguishing these input/output jacks. Some later Marshalls have used Orange nuts to distinguish Speaker outs. They are a cheap replacement, as is hobby paint or nail polish on a black speaker jack nut to do the same. If you reach back habitually and don’t look/cant see, lo tech solutions like a sticker or taping a dime (something tactile) above the speaker jack lets your finger’s confirm it’s not “the wrong hole!”

View attachment 127657
Yes, Solid Connectors in the bin may play a vital part for your gear still… ironically by preserving amps rather than ruining pedals. Clearly, this amp has no load attached per the protocol.


View attachment 127658 Bright jack nuts help with quick confirmation that you are accessing speaker outs in the back of a populated amp.




These are my protocols. If you have other or better, feel free to share.

Very well said and an important safety reminder . Thank You !

 

[ITburst]

This is what I do.
Before I disconnect a speaker cab, I disconnect the power cord.
Before I connect a power cord, I check both ends of all speaker cables and amp impedance setting.

I swap around pedal boards more so than speakers, so I color code my loop cables with a wrap of red tape on either end of the return cable.

I also pull the power cord and don’t plug it back until confirmation of a speaker cord.

When I was swapping heads I would also leave my guitar cable plugged into the head/cab I was playing last as a reminder not to switch on the one with no guitar cable.

I noticed you colour code your loop jacks. I’m still finding my way around tube amps, but is plugging the loop backwards dangerous? Or is that just for your setup convenience?

 

[fitz]

When I was swapping heads I would also leave my guitar cable plugged into the head/cab I was playing last as a reminder not to switch on the one with no guitar cable.

That's exactly what I do with my little 2 headed Egnater rig.
And I only use one power cord that I swap back and forth for the two heads.

I noticed you colour code your loop jacks. I’m still finding my way around tube amps, but is plugging the loop backwards dangerous? Or is that just for your setup convenience?

I don't think it's dangerous to the amp or pedals.
When I've plugged the loop cables in backwards, I just get nothing coming out and start looking for incorrect connections.
I've tried labeling the cables with printed "Send" & "Return" stickers, but a quick red tape wrap on the return cable is easier to put on, and even easier to figure out.