Marshall 18 vs. Matchless Spitfire/Lightning

[guitback]

Can someone tell me how they compare? I am specifically looking at the power sections. I am trying to ascertain the difference in feel, tone, etc. I am looking at the schematic for both right now and they seem somewhat similar. Is one more inherently tighter (more headroom)?

[dartanion]

The Matchless amps are pretty much built in the vein of a Vox. The clean tones will be a bit more bright and stiff than the Marshall, but pretty close. The issue I have with the Matchless designs is in the PI. They use the Vox style cold biased PI that causes a fizzy distorted tone that drives a lot people completely nuts, me included! The Marshall uses a warm biased PI and some slight power section changes that makes the distorted tones WAY BETTER. The drawback of buying a 1974x is the suspect transformers. There are tons of reports of both the PT and OT going south. I would look to kit, clone, or boutique variant.

[guitback]

Thanks for the reply. I have built both a Marshall 18 watt and Spitfire/Lightning clones but I never really looked at the power section or the PI very closely to see the differences. I have a Spitfire clone now and it is certainly "touch sensitive" in that it cleans up when you back off or roll off the volume pot on the guitar. However, when pushed, it has a tone that lacks definition. I know all amps smear when pushed, but I suppose this is a different "kind of smear!" Fizzy does seem to describe it. Fizzy (as opposed to "crunchy"); I hate trying to describe characteristics with cliches. Oh well, that's all we can do.

[bigeric]

I think the spitfire is a more versatile amp. I personally have used mine for 10 years. The one I have roars. No fizzy distortion here. I played a new 18 watt marshall with the 2x12 cab and it sounded good but next to the spitfire with matchless 2x12 cab it was no contest. The marshall had one sound. These rigs have a much less focused sound with way less sizzle. This is my opinion of course.

ps
I also am running a 2x12 cab 25 watt webers at 4 ohms. Dimed its downright scary.

[guitback]

If you don't mind, how did it differ soundwise?

My Spitfire definitely seems more "complex" (jeez, I hate to use that term) and maybe even more focused or present, but it isn't as, oh $hit, I don't know any other way to say it than "chunky" or "70's rock." It seems smoother than the 18 watter I built.

[dartanion]

If you are looking for more headroom in an 18watter, there are a few things you can do to increase it, but not a lot. These changes have to do with the power section as the distortion primarily comes from the power tubes in these babies. You can switch to fixed bias, SS rectification, add NFB, but then again it will be a 20watter then ala a 2061. You can also change the grid leaks to a lower value say 220K for a bit more headroom. If you want to get rid of the fizziness in your Matchless clones, remove the 1K2 cathode resistor on the PI a replace it with an 820 ohm like in the Marshall. This should take care of it!!!

[dartanion]

FWIW - Most folks on the 18watt.com like the Spitfire over the Lightning. IMHO the lightnings hotter plexi like preamp accentuates the fizz in the PI.

[jokerjkny]

my 18 watt marshall is much more midrangey and the drive has a nice thickness to it. yet, it had very little headroom. my old lightning was a fun amp for cleans and semi-dirty, but the pushed dirt was a little too fizzy for me.

both together however did make a very fun two amp setup.

[epluribus]

No idea how ancient this thread might be, but I'm about to start building a Spitfire clone--sort of.

I note that most all of the mods to turn a Spitfire into an 18 Watt can be done with a simple ground lift and some judicious parallel-wiring of caps and resistors. Other fairly simple changes involve changing Rp on V1 (one switch), putting a bypass on the input grid resistor (another switch). The biggest change would involve using a DP/DT to trade Volume/Tone networks entirely, and maybe using a push-pull to ground lift the tone pot altogether just for fun. Four switches total to mod the gain stage circuitry.

The power rail might be a bit touchier. For one, I suspect that the two amps show differences in their respective voltage charts, as there are some subtle differences in the builds. (Anybody got an 18W voltage chart?)

Besides that, the schemos show slightly different filtering and use different rectifiers. My initial thinking is that you might get away with nothing more than a sag resistor on a switch for a good approximation of the two power supply behaviors, possibly ganged with a dropping resistor to handle the B+ differences. A single DP/DT would handle that...five switches.

Hm...

--Ray

...and then there's always the notion of two switchable front ends...one 12AX7 and one pentode-type... :beer