Marshall AFD100 owners

[lame guitarist]

Any of you AFD owners screwed around with other combinations of tubes? I was wondering if I should try some winged C el34 and some gold lion KT88 in together.

What kinda preamp tubes has anyone gotten great results with?

Not sure if its just me but I found the stock tubes kinda lifeless in that amp, amp doesn't breathe or have mojo

 

[born_hard]

Yeah, the stock power tubes are very bright. I guess, you need very loud stage volume to enjoy it. Or maybe some better brand of tubes...
Anyway, what i did: 3 Tesla EL34 brown based and left 1 6550. Killer.
The best thing in this amp is the auto bias feature, so you can combine all types of tubes and it will bias them automatically!
So go on and experiment.

 

[LP Freak]

Yeah, the stock power tubes are very bright. I guess, you need very loud stage volume to enjoy it. Or maybe some better brand of tubes...
Anyway, what i did: 3 Tesla EL34 brown based and left 1 6550. Killer.
The best thing in this amp is the auto bias feature, so you can combine all types of tubes and it will bias them automatically!
So go on and experiment.

This is bad advice. The circuit is a push pull and you need to use the same type of tubes throughout reguardless if it's autobias.

 

[Anonymous]

Yeah even in amps where you have individual tube bias (like Fortin), it's not recommended to not use pairs.

PS to me KT88s are the opposite of mojo

 

[djpatb]

I have one and I've been meaning to play with the power tubes, but haven't done it yet.
I have a quad of Winged C EL34's laying around. I'll try to pop them in there soon and report back.
I did swap out preamp tubes though. I got a mix of Ruby, Penta Labs and Sovteks from Doug's Tubes.
My goal was to reduce some hiss and sweeten things up a bit.
I only noticed a slight improvement.

 

[Kapo_Polenton]

It's a bit of a harsh circuit in the first place though isn't it? Dicking with tubes won't make THAT much of a difference. When I did one of the many incarnations of the #36/39 mod in my DIY, it was rather hissy and cut quite a lot. With the wrong pups that could be too much high end. I think the key is the alnico II's he uses soften the attack just a tad.

 

[lame guitarist]

I have a few ruby 12ax7 hg pre's kicking around and a pile of TAD pre's. going to try them.

I would rather keep things in pairs with regards to the power tubes, going to experinent with combining winged C 6L6 and EL34 and also the KT88's. Also maybe some Mesa 6L6 and EL34

I am not really finding the amp overly harsh. I have been using it with a bogner or mesa rec 4/12. I have some standard marshall cabs with the 75's in them so might have a try there. In the bogner or mesa I just find the tone quite flat. No real character unlike a bogner or other marshall

 

[LP Freak]

I don't know the whole lowdown on AFD but I'm thinking it's not a head you can mix and match different types of power tubes....even in pairs. Correct me if I'm wrong though.

 

[Michi]

We had one in the band briefly (our other guitarist had it) and from what I remember you can't mix different kind of tubes in it any way. You can use different types as sets but not with each other.

 

[blackba]

Keep going, you guys are killing any remaining GAS I still had left for an AFD100.

On my Silver Jubilee, the =C= EL34's sound awesome in it.

 

[lame guitarist]

Going to give marshall a call and find out! Heard a few people saying they have, guess its better to be safe than sorry though and find out from marshall

 

[jerrydyer]

auto bias for different types of tubes ?? that means it has four seperate auto bias circuits of some kind? whatever. I'd love to see the schem on that. sounds like hype and BS. its prob just some safe zone for anything which would explain your quad of tubes not doing to well. get a quad of something that is matched and already tested to be on the hot side in the same circuit. like a groove tube higher numbered quad. ? Im betting a fresh quad is going to solve your prob. the original 36 and 39 were on the edge of tooooo much so keep that in mind. borderline unstable and easily pushed to oscilations.

 

[LP Freak]

Going to give marshall a call and find out! Heard a few people saying they have, guess its better to be safe than sorry though and find out from marshall

That's the problem these days....there's too many people with there hands inside amps when they don't have a clue.

 

[lame guitarist]

Going to give marshall a call and find out! Heard a few people saying they have, guess its better to be safe than sorry though and find out from marshall

That's the problem these days....there's too many people with there hands inside amps when they don't have a clue.

Definately, A simple phone call can be the difference as well between a few hundred bucks repair job!

 

[LP Freak]

Going to give marshall a call and find out! Heard a few people saying they have, guess its better to be safe than sorry though and find out from marshall

That's the problem these days....there's too many people with there hands inside amps when they don't have a clue.

Definately, A simple phone call can be the difference as well between a few hundred bucks repair job!

Well I'm curious what Marshall has to say.

 

[lame guitarist]

Going to give marshall a call and find out! Heard a few people saying they have, guess its better to be safe than sorry though and find out from marshall

That's the problem these days....there's too many people with there hands inside amps when they don't have a clue.

Definately, A simple phone call can be the difference as well between a few hundred bucks repair job!

Well I'm curious what Marshall has to say.

They are closed over here just now, not open for about another 14 hours. Will update tomorrow

 

[djpatb]

AFAIK you can't combine different types of power tubes. That would be pretty tricky to get them matched as integrated quads.

From the manual...
NOTE: It is possible to have different octal pentode or tetrode power valves installed in your AFD100.
Some popular options include EL34s, 6L6s, 5881s, KT66s, KT77s and KT88s.

It doesn't tell you to mix them.

 

[baron55]

Auto bias is a pretty simple concept actually. I have some buddies of mine who have actually made these circuits. You have a small Integrated circuit with firmware that measures the tube current and plate voltage of each tube, the circuit simply adjusts the -grid voltage to each tube based on current. According to Marshall, their circuit also keeps the tubes from max plate dissipation when the amp is dimed.

An adjustment on the back sets the bias threshold based on desired taste. Basically at lower volumes the amp will be biased much hotter but still not exceed plate dissipation and at louder volumes biased colder.

This is no more complicated that the Integrated circuits for MIDI control, mapping etc.

But in tube amps, it adds too much expense for the cheaper mass produced amps. But could be a good thing to prevent amp failure from tube meltdowns.

 

[born_hard]

Regarding mixing tubes i read this hear:
http://marshallroadhouse.com/viewtopic. ... 2&start=15

I think, we need to ask the man himself: Santiago Alvarez.

Btw, i run this set (3xEl34 and 1x6550), since a couple of months and the sound is great and none of the tubes failed till now.

 

[lame guitarist]

Shot an email off to Marshall's technical supprt. Thought it would be better having it in writing if they come back and say you can mix. That way if it turned out the amp got damaged due to this then I have it in writing that marshall say you could.

Will post what they respond with soon