Power amp wattage vs cab/speaker wattage?

bencam1997

Going to be using a seymour duncan powerstage 200 on a pedalboard with my quad cortex, so i can run straight into whatever 4x12 is at rehersal rooms if the PA is low quality. Question is, I dont see many 200w speaker cabs, is this a problem?

Danny1969

No, it's only around 100 watts into a typical 8 Ohm cab  ... to be honest the amp is likely to thermal it's self off before a typical 100 watt guitar cab is blown 

andy_k

My Marshall 4x12 is rated at 300 watts, and I'm guessing anything 4 x 12 would be appropriate for 100 watt valve amps ( don't see many videos about blown 4 x 12 cabs, but haven't really looked ).
Impedance is the main issue, but I'd look at the Powerstage manual closely and see what it says.
There was an interesting set of videos recently, where the annoying German bald guy blew up a brand new 100 watt Marshall handwired / modded plexi by using a Fryette loadbox.
The ability to run high power / high gain amps at full blast for extended periods through loadboxes / attenuators, doesn't appear to mean that we should be doing it.
Power ratings on amps are measured for maximum clean signal, and class D digital stuff is quite different to class A/B valve equipment, it is always going to be a bit of a gamble using some anonymous unlabelled cab in a rehearsal room, and if you don't own it you need to be careful.
I very much doubt you will be playing your rig at the levels that could cause damage, but if something blows you could easily be expected to replace somebodies worn out cab with something new, could be an expensive lesson.
The videos I mentioned above are interesting because Steven Fryette responded with a nice lesson in how the power ratings of this kind of equipment are measured, and it is generally overdesigned so the cheapest component should be the first to fail .
A fuse is a lot cheaper than an output transformer, and class D amplification always seems to highlight its high power ratings, heat is the enemy here, so if you are playing hard for extended periods you could well have some issues.
I had the same thoughts when I had to get a cab to suit a Victory V4 pedal amp, rated at 180 watts into 4 ohms, 90 into 8 ohms, 45 into 16 ohms.
It was designed this way to be loud enough for live use, with 45 watts into a 16 ohm 4x12 being the most obvious use.
In my case I wanted a 1 x 12, and ended up with a Fane F70 loaded Zilla cab, so 90 watts into 8 ohms, and at home I cannot set the amp any quieter, I literally had to change the chicken head knobs for something that would let me get really low and not be easy to adjust.
We often think we need high power amplification, where in reality we need reliability, so it is best not to push things too hard for long periods, I bet the Powerstage has some form of thermal protection, and it may well be using the same kind of class D amp as my V4, so in reality you may be getting a lot less than 200 watts depending on the cab impedance used.
You could be getting close to the limits if you are getting 45 watts into 16 ohms, and playing with a loud drummer, but I doubt it in a rehearsal room.
I played in a loud punk band for a few years with a very loud drummer, and my Marshall Code 50 1 x 12 combo did a good job of keeping up, with the master volume never getting close to half way.
It wouldn't have stood a chance on a big stage though, which is where the PA comes in, very different situation.

ICBM

If the 4x12" is a vintage or reissue Marshall with 25W Greenbacks it will be 100W but at 16 ohms, so the amp still can't deliver enough power to be any risk to it - I don't know the figure for the Power Stage into 16 ohms, but it could be as low as 50W and will definitely be less than 100. (It depends how well-regulated the power supply is, the power doesn't always drop off linearly with impedance.)

On a modern-style Marshall cab with the switched inputs, you can still use the 16-ohm input not the 4 - although these cabs usually have 75W or 60W speakers (ie a 300W or 240W cab), there's no reason to stress the amp running it at 4 ohms if 16 is loud enough. Any other cab of more than 100W rating at 8 or 16 ohms, or more than 200W at 4 ohms, will be fine - which is pretty much any modern 4x12" I can think of.

For what it's worth the guitarist in the band I play bass in has a Laney Loudpedal 60W solid-state amp and a Marshall 2x12", and he's loud enough to compete with a fairly loud drummer and me with a 450W Ampeg bass amp in a big room, so I think you'll have plenty of volume.

Danny1969

The Seymour Duncan Powerstage ranges use Icepower modules, like the Tonemaster amps. I've fixed a couple of them. You can check the specs with Icepower ... yours is a 200AS2 I think and about watts into 8 Ohms ... operation into 16 Ohms isn't recommended 

bencam1997

Interesting, so if Im using a 1x12 or something that isnt a high wattage cab im risking it? Didnt realise products like the powerstage were so limited in what you can use them with

Danny1969

Well common sense comes into play ... if you turn up any source of high wattage, be it an amplifier head or an amplifier in a guitar pedal format to an output wattage more than the voice coil of the connected speaker can stand  then yes you risk of blowing the speaker. 

That's not a limitation of the Powerstage products .. it's up to the user to match the source to the load

BillDL

https://www.seymourduncan.com/wp-content/uploads/2020/06/Powerstage-200-Tech-Specs.pdf

ICBM

bencam1997 said:

Interesting, so if Im using a 1x12 or something that isnt a high wattage cab im risking it? Didnt realise products like the powerstage were so limited in what you can use them with

It’s a limitation of all amps. You can’t run a 100W valve amp into a single 25W speaker and expect it not to blow the speaker either.