How do I check output voltage on my Marshall Super Lead 100 vintage 1971 head?

[firehouserecording]

The ceramic resistors sound like fun. Do you care to elaborate on that process?

Thanks,

Paul

[g1]

You will need to connect a 16ohm 25watt resistor across each of your speakers (from + to -). Now you have the equivalent of 4 fifty watt 8 ohm speakers. So wired up the same way as it was, you will have a 200watt 8ohm cabinet.

[firehouserecording]

Okay, that seems simple enough. Thanks.
Attenuator or resistors- any opinions on how different they will sound?

Thanks,

Paul

[52 Bill]

Either way you are reducing the power going into the single cabinet. Adding the resistors inside the cabinet will work, but if you want to use the cab in other applications the added resistance will be a factor.

The simplest version would be to add a 100 watt 16 ohm load resistor to the output of the amp through the other speaker jack. Remember that it will get hot if you are playing loud.

[firehouserecording]

So that would do the same as adding a second 100 watt cab without the sound?
Would that cut my volume down 50% with the same basic distortion level?

Thanks,

Paul

[Gtr_tech]

Here's an idea....get a smaller amp that you can safely run wide open without risk of damage to either the amp or the speakers.

You have to keep in mind that while a superlead 100 is a "100w" amp, it will do close to 100w fairly clean...the higher plate voltage versions can put out close to 150w. Once you start driving it into output section clipping it does *more* than the rated 100w. The high amplitude clipped wave sent to the speaker heats up the coils beyond what they are rated to withstand...then they burn open.

My advice would be to quit beating up this vintage amp before you roast it. An attenuator of any type will increase the chance of damage. Why? Because since you can run it all day long without blowin' yer head off, chances are you'll run it balls out into the att for longer times. I'm not gonna go into the technical details of this, but the long and short of it is you have a much greater risk of blowing the output transformer and/or arcing tube sockets.

If it were me, I'd use some sort of 50w SLP clone and beat that up since it has no vintage value....

[firehouserecording]

It's not a wife, dude. It's guitar head. I've been playing it for 14 years already without any issues other than 5 blown speakers. Just because I know it'll make you cry, I'm gonna stick it the freezer for an hour when I get home.

[Gtr_tech]

Great. After that....pour gas all over it and set it on fire. Dude.....

[Gtr_tech]

And don't take my word for it....
http://www.seattle-attorney.com/guitar/2204_hangtag.jpg

[firehouserecording]

Oh, I get it. Yeah, I definitely don't want to void my warranty.

[J M Fahey]

What warranty?
After you burn it, you'll have to buy another amp anyway.
Go ahead, it's your amp.
You needn't take advice from *anybody* on how to destroy it.

[firehouserecording]

I appreciate your replies, Juan. What I don't need is to be told to use a 50 watt clone. I want to find the best way to run the Super Lead 100 through my 25 watt greenback cab. Are you saying that adding resistance or an attenuator is destructive?

Thanks,

Paul

[Enzo]

Hey come on guys, do we really need to be pissing at each other?

If you use attenuators, it is more stressful on the amp. The amp is working as hard as it can into the attenuator, The attenuator is doing its job of wasting away the majority of the power, leaving only a small portion of it for the speaker. This is like driving your car down the highway with the parking brake on to slow you down to a nicer speed.


If it gets you the results you want, then so be it, use an attenuator.

[Steve Conner]

Well, let's look at the two sides of the argument.

On the one hand, the 100 watt Marshalls are known for running "on the edge". They make more than 100 watts and that results in considerable stress on the tubes and output transformer when overdriven. Any kind of attenuation only makes things worse, because it removes the volume limit that would result from your (or your bandmates' or neighbours') threshold of pain and lets you crank it really flat out.

On the other hand, maybe that's just what you have to do to get the true sound of rock.

I'm going to argue that you don't need to worry about getting the amp to work with a 25 watt Greenback cab because you just fried all your Greenbacks anyway. Replace them with some higher wattage speakers and crank it back up.

[DrGonz78]

I spent roughly and at least 9,240 hours jamming on a JCM2000 tsl 100 watt amp with a 1960a cabinet, never ever blew a speaker. They use Celestion G12T-75 speakers in those cabs and I suggest that is what you need in you cab. The greenbacks are cool or whatever... Fact is that they are underrated with this head. I like the idea of modifying something to make it work but why not just get new speakers that you won't be able to blow out as easily.

P.S. Just don't come home and put your wife in the freezer!! lol!