Output Transformer for 50 Watt Marshall

darkbluemurder · Post by **darkbluemurder** » Tue Aug 15, 2006 12:54 pm

In another thread I posted about my bad sounding Marshall. I am considering an upgrade OT. It's a 50 Watt amp with 2 EL 34s. The amp is now wired as a Master Volume amp with a bit more overdrive on tap. The voltage divider after the 2nd gain stage is replaced by another volume control since I also want to get cleaner sounds if I want them.

I am looking for as much as possible detail from the OT, yet I want it to have a lot of punch. Which one would you recommend (MM, Heyboer, Marstran, OEI, other)?

Thanks very much for your input
Stephan

kt77 · Post by **kt77** » Tue Aug 15, 2006 2:45 pm

Partridge clone form Heyboer...hey, you said 'detail' and 'punch'

darkbluemurder · Post by **darkbluemurder** » Wed Aug 16, 2006 3:12 am

kt77 wrote:Partridge clone form Heyboer...hey, you said 'detail' and 'punch'

Of course I could take that route but that would probably take it too much away from a Marshall. Maybe I need to be a bit more specific about what I want to achieve:

1) styles of music: with a Marshall usually EVH, AC/DC, classic rock, no metal

2) guitars: Les Pauls, Teles

3) benchmarks: I have a JMP 100W 1959 model (year 1979) which sounds good with any circuit tried (must have a very good OT - seems to be the original one) and a modded SLP reissue which also sounds good with the original transformers. I also have a JTM 45 reissue with the original transformers and a Hoffmann PTP board. This amp also sounds very good. They all sound a lot better than this 50 Watter, and I once used the same preamp in the JTM 45 RI and the 50 Watter. They have the clarity and the Marshall sound, and you can hear the character of different guitars played through it. The 50 Watter doesn't have all this. I want to get the 50 Watter to be in the same league as the others, or at least near to them.
I am just puzzled that the original Marshall transformers which in some discussion threads are believed to be not as good as some custom irons seem to be so much better than the TAD 50 Watt replacement I have in the 50 W (which to be fair was a lot better than the original transformer).

Hope that helps in your analysis. Otherwise I might simply trash this amp for the parts to save myself more headaches.

novosibir · Post by **novosibir** » Wed Aug 16, 2006 8:28 am

darkbluemurder wrote:I am just puzzled that the original Marshall transformers which in some discussion threads are believed to be not as good as some custom irons seem to be so much better than the TAD 50 Watt replacement I have in the 50 W (which to be fair was a lot better than the original transformer).

The Drake OT's used in the 50W Marshalls, especially buildt from the mid 80' onwards were terrible differing from year to year. Although they've always had the same part's number (784-139), they were buildt with different qualities of the sheet metal - mostly they've had a dark iron (assuming M29), but sometimes also a shiny one. Sometimes the sheet metal was very wimpy attached into the bobbin, so that due to the bigger gap between the E-type and I-type sheets the primary inductivity (bass response) was very low.

When the OT still is new and the varnish inside still not hardened, you may 'improve' a bad OT - put it into a stove and heat it up to 60

OnTheFritz · Post by **OnTheFritz** » Wed Aug 16, 2006 12:48 pm

I plan on buying a 139 50 watt OT from Brain real soon for my re-issue.
He told me his are hand made, based on tear downs of originals from the late 60's, and seems to me (IMO) to be the best repro out there, especially for the price.

http://marstran.com/50W%20OT%20139.htm

Post by **VelvetGeorge** » Wed Aug 16, 2006 2:24 pm

Brian's OT is a good choice. To me, the MM O50JM is better than the stock 50W OT that heyboer offers. I heard Brian's in his souped up 50W build and it killed. So you can't go wrong either way.

george

Flames1950 · Post by **Flames1950** » Wed Aug 16, 2006 5:31 pm

VelvetGeorge wrote:Brian's OT is a good choice. To me, the MM O50JM is better than the stock 50W OT that heyboer offers. I heard Brian's in his souped up 50W build and it killed. So you can't go wrong either way.

george

Since you've got nothing but time on your hands

it must be time for you to buy some 50-watt trannies to tear down so Heyboer can build you a 50-watt Metro tranny as good as they make for Brian.

darkbluemurder · Post by **darkbluemurder** » Fri Aug 18, 2006 7:00 pm

Pulled the trigger on a Marstran. I'll report about the results.

darkbluemurder · Post by **darkbluemurder** » Sun Apr 01, 2007 5:31 pm

Well it took me a while to find the time to finish this project but finally I did. The Marstran 50W OT was a further improvement. It has a little less midrange than the TAD 50W and a more typical Marshall sound to my ears. The amp sounds good now even though it still cannot quite touch my modded JMP 100W.

Thanks for all your input.
Cheers Stephan