Valves?

[Mats A]

Does this amp have EL34´s? Does Yngwie use EL34´s in his amps?

[surfnorthwest]

We don't know yet what power tubes the amp will have. We do know that like the AFD100 they will be interchangable. I am curious as to how many preamp tubes the amp will have.

[Mats A]

Me too. If it´s a DOD built in as a boost it may only have 3 valves like a regular old Marshall.

[DSL100 Dude]

I would guess EL34's. Just makes sense for a Super Lead.

[Mats A]

Surfnorthwest did the amp Chris played at NAMM have EL34´s in it

[Beano4Ever]

Hi Guys,
New to the forum here but I saw the youtube clips that surfernorthwest was kind enough to put up. I am really interested in this amp so I thought I would jump in and start posting. As far as the valves go, on Marshall's site http://www.marshallamps.com/product.asp ... e=OVERVIEW it says these are going to have EL34's but I imagine that is subject to change before the builds actually start.

[surfnorthwest]

The amp comes with EL34s. Chris was playing through a Marshall 1960AX in that video (greenbacks) You can install any tubes or combination of tubes. I suspect in the end EL34s will be the best sound.

[Beano4Ever]

I have been thinking about how tubes other then EL34's will sound when ran through the output transformer which was designed for EL34's? For example if I get this YJM I will most certainly want to run KT 66's in it on occasion. Its such a great tube and I really love the sound of them, however will I still get the same sonic qualities that I would get if I were running it through an amp that had an OT specifically designed for KT66's? I am afraid it will be missing something running tubes it was not primarily designed for.
Anyway, at a minimum it will be a fun experiment.

[DSL100 Dude]

Wouldn't that be the point of the auto bias?

[Beano4Ever]

Wouldn't that be the point of the auto bias?

I mean yes the tubes need to be biased but I still don't know if proper biasing alone eliminates the problem of the the primary impedance of the OT vs the tubes. For example in a EL34 1959 I think the OT has a primary impedance of around 1.75 k, however 4 KT66's like to see around 4k and the OT primary impedance on a KT66 designed amp is around 4.0 k.

I just don't think its going to be the same as running them with an OT designed specifically for the KT66's, obviously the amp will work properly and will still probably sound good but I wouldn't be surprised if there are losses in the lows & highs and slightly less power overall but I def. could be wrong.

[DSL100 Dude]

That is the kind of talk best left to Steve and Santiago.

Even though I work in an electronics based industry and have been in it most of my adult life, I understand enough to know that I don't know their stuff.

So, I just plug it in, Dime it and the chyt sounds good or it don't. :rocker

[Beano4Ever]

[quote="DSL100 Dude"] I just plug it in, Dime it and the chyt sounds good or it don't. :rocker [/quote

lol.. true dat!

[Papus]

I'm with DSL100Dude

Class 5 with bedroom trick or Marshall Major, I say to the world:

DIME THAT PUPPY!!!!!!!!

[Beck-Ola]

By the way, biasing the tubes has nothing to do with the impedance match between the output tubes and the transformer. Biasing involves setting the "idle" of the tube.

The internal resistance of the tube is part of the tube's characteristics and not adjustable. A transformer is specified to match as closely as possible to the output impedance of the tubes when the amp is designed. There's rarely a perfect match for that matter but the closer the match the more efficient the transfer of power and more power potentially produced. It's the slight variances that help make each amp sound slightly different. Even with some mismatch it can still sound darn good. If they can be biased correctly given the adjustment's leeway and if they can physically fit then KT-66s should probably work all right even though the match isn't perfect. Hope that's helpful.

[Mats A]

I asked Santiago this some time ago and he said there was no difference with the transformers if i remember correct. Don´t remember all he said though. The post should be somewhere on the JVM forum.

-- Tue Jan 18, 2011 4:55 pm --

This is what Santiago said in a post on the JVM forum

there is nothing as a "perfect primary impedance", it is always a compromise between output power and distortion. In any case, EL34 and 6550, KT88 have similar "optimum" load impedances, around 3000-3500 ohm for a pair if I remember correctly, but you can check the datasheets which give you that data.

On the other hand, tubes like 6L6, 5881, etc deliver max output power with impedances around 6k to 7k but if you load them more, you get just a bit of less power and different distortion figures. Again, some datasheets also give you those curves.

The AFD100 output transformer is the same as Marshall have been using for ages, no black magic here either.

You can always play with impedance mismatch to "optimise" the different output tubes. For example plugging a 16ohm cabinet into the 8 ohm output will give you "better match" to 6L6 but at the end is a matter of taste and player preference.