NAD: It's here! AFD100 in the house!

[purpleplexi]

My take  - it's a bunch of components. One of them is playing up. It can be replaced. I don't want my money back or another amp. I just want this great amp to work properly so's I can go gig with it.  At the moment I can't - well I don't have it but unless a problem is diagnosed and fixed I won't feel confident doing so. Where does that leave me?

Marshall are the bedrock of reliable, working, gigging kit - I just want reliable working gigging kit.

[Dmoney]

Maybe the bedrock, but whether that has been continued... I'm not so sure. I've had Marshall's with bad reps hold up to some bad things, but then I have friend who constantly have TSL's and DSL's (for example) in for repair.

I feel bad for you... like you say... you want the amp the work, but there has to be a point where it either gets fixed, or you have to give up. Obviously that point is totally down to you.

[purpleplexi]

Yep. I have to say I had a TSL for years and years without even a blip. 100% perfect reliability. I didn't turn it on once for 2 years and it was still perfect next time I used it.

We'll just have to see what Marshall find. Hopefully something.

[HTH AMPS]

does the amp work fine with the power scaling turned all the way off (i.e. no power scaling) ????

if so, I'd tend to err on the side of living with the amp and just using the master volume (IF you really love the amp and want to keep it).

my take is that Marshall should've sorted this before release - surely this must've come up during testing if there are two people on this board with the same issues.

[Twinfan]

Yep, it works fine with the power on full - I tested that myself.  Sounds dead thin though, you need some power amp beef in a JCM800 at lower volumes!

[HTH AMPS]

Yep, it works fine with the power on full - I tested that myself.  Sounds dead thin though, you need some power amp beef in a JCM800 at lower volumes!

agreed - JCM800s need VOLUME.

still, its a stage amp, so thats fair enough.

how you get it sorted.

[gwEm]

it sounds like a relatively common embedded firmware bug you get when sampling the value of pots.  obviously the resistances changes over time, due to temperature, dust and vibration. if it is on the edge of a certain key value, you can get oscillation between the two - which is twinfan's theory.

its a classic problem, and i've seen it myself. its solveable by adding some hysteresis into the system - a bit like with an analogue thermostat. you can also take a moving average - or do both.

of course it may not be the cause.

[purpleplexi]

Yep, it works fine with the power on full - I tested that myself.  Sounds dead thin though, you need some power amp beef in a JCM800 at lower volumes!

That is the problem precisely. I could live with the volume wobbling about a bit if it didn't sound so tinny with it. The posts you see on youtube, the guitarist magazine review and Marshall's own vids have a really ballsy sound - as did the one I tried in the shop. If the one I tried sounded like mine I'd have run like a thief.

I found another guy on the Marshall amps forum who isn't happy with his.

[Twinfan]

purpleplexi - I'll send you a PM.  We need to sort this out.

Dave

[HTH AMPS]

purpleplexi - I'll send you a PM.  We need to sort this out.

Dave

class action  PDT_003

[purpleplexi]

See this thread on the Marshall amps forum

http://www.marshallforum.com/marshall-amps/23918-afd100-problem-help.html

[jpfamps]

As far I understand with the "Power Scaling", Marshall refused to pay the London Power licencing fee ($5 an amp), and seem to have "developed" their own system.

From reading this thread, it seems they are using some form of DAC to code the changes in power level.

Kevin O'Conner outlined how to do this in one of the Ultimate Tone series (TUT4 or 6, I can't remember), although I'm not sure whether the circuit shown was an example of a "tried-and-trusted"  circuit, or entirely theoretical.

Regardless, I remember thinking that at the time that this seemed a rather complicated method of controlling the power output of the amp, which lets face it doesn't need to be that accurate (we've managed to cope with inaccurate volume controls on guitar amps for at least 75 years!).

Now it would be an astonishing co-incidence if Marshall, given that they were already looking at London Power circuits, completely independently came up with the digital method of controlling the power output.

Sadly it looks like it has bitten them on the back side, some what.

[FernandoDuarte]

Hummm good to see you guys are summing strenghts... I'm completely choked that Marshall did it... Man, it's a celebration model, few units, BIG money and it doesn't work? Come on....

Hope you guys get it sorted!!!!

BTW, some amps comes with a schematic of it, does this AFD100 comes?

[Twinfan]

Nope - no schematic Fernando.

I've subscribed to the Marshall forum so there's now at least three of us there with an issue.  Not good for Marshall is it?

[Dmoney]

Not good at all!