Saturday, February 20, 2010

Somebody needs a JTM45

And that would be me. I've never actually owned a "head". I've only had combo amps. But when I've used a head I've had the best sound. So, uh, well maybe I'm just a slow learner here. I wonder if I want a closed-back cabinet with 10" Celestions... or Webers...

OK, so here's my learning curve about the JTM45:

There are six tubes in a Marshall JTM45.

Two of them are power tubes: KT66's. To get a matched New Old Stock (NOS) pair you're going to be laying out upwards of seven hundred bucks. So my big questions be:

  • Can I use lower wattage (read: "cheaper") tubes and get a nice cranked sound out of them at a lower volume? (As far as I know, no.)
  • Or, can the amp be run with only one power tube? (As far as I know, no.)
  • Or, will EL34's (which are more in the range of $300 for a matched pair) work and still make the amp sound groovy (although not exactly like a JTM45)? (As far as I know, yes.)

There are three 12AX7's.

And a single rectifier tube, a GZ34.

Here's an interesting (so I thought) comment regarding the quality of different tubes from the MetroAmp board:

The consensus I am hearing is that VA KT66's are very good in relation to the tone quality compared to the holy grail GEC/Genelex/Gold Lion KT66's. This is good news and in fact the difference I hear between the GEC's and the VA's is that the GEC's have more push in the upper mids, where the VA's are a little thinner - notes on the B string are as fat as those on the G and D strings. Think of it as going from say a set of 9's to a set of 12's for string gauge, and you start to understand my interpretation.

Here's a page of information on mods for the Marshall JTM reissue.

What does all this mean? It means that somebody has to buy me a GMP45 Head.


Lindsay Stewart said...

I've never gotten a tone I liked out of a Marshall. They always seem to have too much of something or need to be pushed beyond comfortable volume to find the sweet spot. My old Vox AC-30 on the other hand sounded friggin' incredible at low volumes or at high volumes. Not having a separate gain stage for overdrive though, you had to have a stomp box if you didn't want to deafen yourself to get skronk. That said an Ibanez Tube Screamer in to that old Top Boost sang like crazy. Wish I'd never sold that thing. Stick with the Traynor!

Andrew Bellware said...

I'm going to throw a Celestion in an isolation cabinet (probably one I build) and put THAT inside my Whisperroom. Then I'm turning the amp up to 11.
(The JTM's are 38?-watt amps. They're vastly less "angry bees" - sounding than the later Marshalls.)