AFD100 Marshall 'Slash' Amp Power Scaling

The AFD100 power output circuitry makes this amp a real breakthrough in the world of amp heads. But is it REALLY as good as they say?

Marshall AFD100 'Appetite' SLASH Amp NEW Power Scaling Reduction Circuit from Marshall Amplification

What have we here... the bedroom players dream come true. Imagine cranking up that tube amp of yours to flat out on the preamp and the power amp with everything on eleven like the 'good old days'.

It sounds like a good idea right? Wrong - for many reasons none the least for what it would do to your hearing. I came from those times and I can tell you that when you REALLY feel those notes hit the back of your neck you know that's as far as the volume will go - yes I really did do that sometimes. But that is then and this is now.

Firstly, it would be likely if you play at home (in these stupid law times) that you would get a piece of paper with a fine on it, maybe an ASBO (for those that don't know what one of them is, its a bit like a restraining order from the rest of the world) and maybe even a few broken noses from your neighbors (you know how they can be at anything after 10:00 pm).

Secondly, running an amp with every knob on 10 (no not just the master and pre) will give you a crap sound. I learned that a very long time ago.

Thirdly, you will be wearing out the amp at some rate and the inevitable WILL happen - pop, spark, bang - then you go quiet.


Marshall amplification is not operated by a bunch of fools. They KNOW their market for kit and I'm sure they would agree that while amps are sold for large arenas and stages, there is a veritable army of guys who are 'bedroom' guitarists. Actually it might be a garage or an outhouse but it's all basically the same problem with a tube amp.

You have to TURN IT UP to get those tones - no matter whether you pedal the front end of the amp or have the best preamp in the world - tube distortion starts at volume - there is simply no getting away from it no matter what any HD500 guy will tell you.

Heres the answer:


I did talk about London amps in my review of this amp on this site so I wont bore you with too much about this.

But basically the Power knob on the AFD100 can allow your amp to run literally flat out with as low as 0.1 watt of output power.

Marshall claim that the sound of the amp is not affected at all. I beg to differ a little.

In my opinion, if you listen REALLY closely (not to the speakers - ouch) you can just about hear a slight change in tone of the amp. I admit that it is not a massive change but it is there.

However - as far as you and I am concerned the days of LOUD are over.

You can literally talk over the volume achievable with this little knob and the amp remaining flat out.

It is more than likely that Marshall will introduce this technology on most if not all new tube amps in future so don't be surprised about it - its that revolutionary. To my knowledge this is the first time Power Scaling of this type has been used by a world leading manufacturer.

Good for Marshall amps and good for you!

The Power Scaling has other effects too - like extending the life of your power tubes by up to ten times - and that's a feature that we all should be grateful of - it will save you a bucket of money over the years. Heres a simple table showing the power scaling and knob position effects:

Knob position relative to time position Power Output Level
7:00 0.1 Watt
8:00 0.8 Watt
9:00 1 Watt
10:00 3 Watts
11:00 5 Watts
12:00 12 Watts
1:00 20 Watts
2:00 30 Watts
3:00 45 Watts
4:00 55 Watts
5:00 85 Watts
5:30 100 Watts

As you can see the scaling does not appear to be linear - its more log than linear. For example at 12:00 its half way round outputting just 12 watts - but by 3:00 its 45 watts.

Be careful with that axe Eugene...


Although I do have a studio and record in there without constraints of noise I actually found this control very useful. By turning down the Power Scaling to reduce the amp output it also reduced the hissing somewhat - at least that's my story and its a useful side effect once again.


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