Turning on head accidentally without speaker attached question

PelliX

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I don't remember hearing any 'crackle' I would normally associate with a short.

Where would this crackle come from then? Components dying horrible deaths generally hiss, pop (once) or whine in my experience... :)

If the transistor overheated you would generally see some discolouring or "unintended aerodynamic shaping" (aka melted corners)...
 

SkyMonkey

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Where would this crackle come from then? Components dying horrible deaths generally hiss, pop (once) or whine in my experience... :)

If the transistor overheated you would generally see some discolouring or "unintended aerodynamic shaping" (aka melted corners)...
The suggestion was that the unconnected speaker terminals accidentally touched, for an unloaded short.
 

RLW59

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The suggestion was that the unconnected speaker terminals accidentally touched, for an unloaded short.

That wouldn't make a crackle. When something shorts in the signal chain it makes a signal that gets amplified and reproduced by the speaker. Without a speaker it would be silent.

If you short a kilowatt power line you can sometimes hear a snap from a big spark flying but shorting the speaker spades wouldn't make any acoustic noise.
 

PelliX

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That wouldn't make a crackle. When something shorts in the signal chain it makes a signal that gets amplified and reproduced by the speaker. Without a speaker it would be silent.

If you short a kilowatt power line you can sometimes hear a snap from a big spark flying but shorting the speaker spades wouldn't make any acoustic noise.

I believe that's a little black and white, I've heard crackle from a lot less if you have very small areas of contact. Not sure whether this particular amp would be capable of causing that, but I wouldn't say it's impossible, either.

Whether you're on 110 or 220-250V AC, I'm sure we all wedged a lightswitch half-way to get the bulb to flicker when we were young, right?
 

El Gringo

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I have a VS65R that makes an alarmingly loud POP when I turn it off (no standby).
It has a shorting jack at the input.
If I half pull the guitar lead as I turn it off: no POP.
Okay, I always hit the stand by first when powering down , so no pop . Sometimes after powering down I get a faint sound from unplugging the cord from the jack in the guitar , but it's so faint .
 

El Gringo

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Hi @El Gringo, not dumb at all. I'm not a technician but AFAIK I've mostly seen these used on the inputs to the amp such that when nothing is plugged in, the input automatically goes to ground, so that the amp output will be zero. I believe this is done to reduce noises when plugging/unplugging guitars.

As for the speaker output shorting jack, this was discussed in another thread,

https://www.marshallforum.com/threads/shunted-speaker-output-jack-question.116954/

So it's a form of protection against open circuits when someone forgets to plug in a speaker, or gets disconnected while in use. I've also heard of some guys doing a slight mod to this by adding a fairly high wattage (5W) resistor which acts as a load, instead of having the OT short to ground.

The thing is, no one should rely on having this feature built into their amp (it's hard to know for sure unless you open up the amp and look), and it's not something you should rely on.
:cheers:
Thank You very much for the detailed explanation and I have learned something new today as this is good to know . I have always been very diligent in first hitting power to warm up and then after 5 minutes or so to then hit the stand by and also do the same in reverse as well just to protect the amp(s) . A long time ago probably somewhere in the 80's I set my transformer on fire in my Silverface Fender Twin Reverb , by at first starting to blow fuses and being ignorant and kept replacing them until this one time I started playing and I smelled that nasty electric burning smell and then seen smoke coming out of the back of the amp . I then went to look in the back of the amp and then seen the blue / orange flame coming out of the transformer . This was not cool like in the Cheech and Chong movie and after I got the amp repaired it lost some of it's mojo as it just didn't sound the same .
 

El Gringo

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:agreed:

I do the same thing. All the gear in my music room is supplied by a single high capacity electric power conditioner which has surge suppression, ground fault detection, voltage regulation, and noise suppression. After I'm finished playing for the day I just pull one plug from the outlet and I know that everything is disconnected. You mentioned a power spike and this is indeed a valid concern. A number of years ago my father in law had a large spike run through his house during a heavy thunderstorm. Almost every electrical appliance and small device he had plugged into an electrical outlet was destroyed, even the ones that were shut off. Luckily he had a good insurance policy!
Wow, Incredible about your Father in law as that's just awful to have happen . I have just regular strips and I really should get strips with surge suppression for the protection . Thanks for the advice as it just makes to much sense not to have this type of protection .
 

SkyMonkey

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Okay, I always hit the stand by first when powering down , so no pop . Sometimes after powering down I get a faint sound from unplugging the cord from the jack in the guitar , but it's so faint .
Probably didn't make it clear. The VS65R is a hybrid SS amp and has no standby.
With my DSL I use the standby.
 

El Gringo

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I have a question after reading this thread I want to ask for a recommendation for really good high quality cables for the amp to cabinet cable ? (speaker cable I think is the term ? ) Please ?
 

Jethro Rocker

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I have a question after reading this thread I want to ask for a recommendation for really good high quality cables for the amp to cabinet cable ? (speaker cable I think is the term ? ) Please ?
Obvioisly no shielded instrument cables! Any good 18 to 14 guage speaker cable would be fine as you aren't running large amounts of power. It does not have to be extra thick but don't get a thin cheapie with plastic plug ends.
I use these in 18 guage, 14 would be for longer runs. I only need 3 feet of cable.
Yorkville because my local dealer stocks them.
Multi stranded lamp wire can run 1800 watts so to run a 100 watt amp is plenty.

lg_lg_SC-xx.jpg


14 gauge

md_SC-__R-12[1].jpg
 

Kev ATGNI

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Well guess what I did today FFS

I played a day or two ago with headphones on through a Weber Minimass and the speaker cable removed between the Weber and to the speaker. Come to it today, turns it on and winds up the Rheostat on the weber without the speaker cable in. It was about 1/4 to 1/3 way around the stat, and for about 5 seconds or so before I realised after playing a couple of notes. I plugged the cable in and the amp works but I swear it isn't as loud as it used to be but there was no smell or excess heat. Is there likely to be damage or am I imagining the reduced output?
 

Jethro Rocker

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Well guess what I did today FFS

I played a day or two ago with headphones on through a Weber Minimass and the speaker cable removed between the Weber and to the speaker. Come to it today, turns it on and winds up the Rheostat on the weber without the speaker cable in. It was about 1/4 to 1/3 way around the stat, and for about 5 seconds or so before I realised after playing a couple of notes. I plugged the cable in and the amp works but I swear it isn't as loud as it used to be but there was no smell or excess heat. Is there likely to be damage or am I imagining the reduced output?
No if it works it works. You didn't play much or long. I did that once with the mini Jubilee. Probably like 30 seconds on. No worries.
Carry on.
 

Kev ATGNI

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No if it works it works. You didn't play much or long. I did that once with the mini Jubilee. Probably like 30 seconds on. No worries.
Carry on.
Thanks brother, I can go back into my little room again now that I know I haven't killed my lovely sv20 :)
 
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