Starting JTM45 Build. Have a few questions please.

[playloud]

What @neikeel said, re impedances. I also believe I've read (sadly don't have personal experience) that Marshall used both 6.6k and 8k taps with the RS OTs. Not sure if this was related to 5881s v. KT66s or was simply haphazard (wouldn't be surprised!)

use the hamond OT if the transforfer does not come with a data sheat you can screw it up . you can make a plate with counter set bolts for the choke plate no new holes

It looks like he has all the data sheets (see first post).

 

[fperezroig]

Hi Mark,
Thank you for kindly mentioning me in your build thread.

I own some stock of mustard capacitors. Did not think about selling, since I do not have many. However, if you need some for your build I will send you a set very well priced.
If you are struggling to find any other part, let me know, since I could probably be of help.
Just found some boxes with original vintage Radiospares bias trimmers, for instance, that you might also like to use. I'll drop one for free in case I send some components to you.

Cheers,
Fran

 

[RiverRatt]

I built a great ValveStorm JTM45 in a Bluesbreaker sized 2x12 combo cab. I can share a few things that helped me along. I had to use grid stoppers on the output tubes. Seems like it’s a thing with Metro/ValveStorm JTM45’s. I used Heyboer transformers and a ClassicTone 20H choke. I’ve read all kinds of posts saying that a 20H choke is overkill, but I decided to do it anyway. If you can find one of those for sale, snag it. It has a nice vintage look and it sounds great.

Speakers, speakers, speakers. I stressed more over this than any other part of the build. Celestion alnico blue, Ruby, Greenbacks, etc. and finally got a pair of UK made Greenbacks. I was happy with the tone I guess, but it didn’t blow me away. That happened when I put in a Scumback M75 and a Celestion G12T-75. Let the haters hate. It sounds damn good. Those Scumback M75 speakers are wicked good.

IMO you hit a point of diminishing returns chasing vintage and boutique caps. I used the standard ValveStorm small parts. To me, it’s the best Marshall I’ve ever played through. Dead quiet, and it absolutely roars when you crank it. One final tip - definitely spend a little more for a pair of GEC KT66’s. I went thru several Chinese tubes before I broke down and got the real deal. The later GEC tubes with clear glass were $250 for the pair. While I was waiting for the GEC tubes to arrive, I biased up a pair of Tung-Sol 5881’s in it. If these GEC’s take a sh!t on me, I’ll probably go back to those. They sound very good as well.

 

[Pete Farrington]

I've read (sadly don't have personal experience) that Marshall used both 6.6k and 8k taps with the RS OTs

I recall reading an expert (maybe George Metroupolis) recounting that RS DeLuxe were only ever wired to 6k6 on the primary and 15ohms on the secondary.
And that applied to the 2x12 combo too, where the 15ohm speakers were wired in parallel. Thereby presenting a 3k3 load to the output valves.