Marstran 784-139 VRS 128 Output transformers

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Marstran 784-139 VRS 128 Output transformers

Postby bluze81 » Sat Jan 17, 2009 9:21 pm

Hi I have a number of Marstran transformers in my builds,just ordered my first 128 output for a JTM 50 style clone I am doing, is there a difference in specs, between the 139 output and the 128 output transformers? just wondering about any tonal difference of the two, thanks
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Re: Marstran 784-139 VRS 128 Output transformers

Postby Brian Wallace » Sat Jan 17, 2009 9:33 pm

The 128 has a buried 100V winding and should have a bit of a bass bump to it compared to the 139.
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Re: Marstran 784-139 VRS 128 Output transformers

Postby bluze81 » Sat Jan 17, 2009 9:49 pm

Hey Thanks Brian, cant wait to get it installed and give a listen, every output transformer I have purchased from you sounds great! Steve
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Re: Marstran 784-139 VRS 128 Output transformers

Postby Brian Wallace » Sat Jan 17, 2009 11:01 pm

How about some sound clips of the two different OT's? Post them in the clips section.
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Re: Marstran 784-139 VRS 128 Output transformers

Postby bluze81 » Sun Jan 18, 2009 3:21 pm

As soon as I get the 128 output thats on back order I will then do some comparison clips, thats a good idea, I dont think anyone on the forum has done this? the reasons for me posting the question is I read a forum post somewhere that the 784-139 and the 784-128 were identical in tone, I had doubts about that statement ,Steve
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Re: Marstran 784-139 VRS 128 Output transformers

Postby Roe » Mon Jan 26, 2009 7:20 am

brian how does the drake type 119 ot compare to the 132?
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Re: Marstran 784-139 VRS 128 Output transformers

Postby 57lpjr » Wed Feb 04, 2009 11:35 pm

Here are some pics of a JTM50 Chassis and some parts that I got recently...

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It's steel and needs a good cleaning, one corner needs to be spot welded and it may need to be replated...

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it came with a repro Plexi Panel that the holes don't line up on correctly...

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I found a Black Flag / Reverse Logo Plexi front panel from Ceriatone but their back panel has the IEC cutout and I have an original Bulgin for it so need to find a blank somewhere.

I'll be getting a Marstran 1202-118 PT and am trying to decide between the 784-128 or 784-139 OT's since both seemed to be in use with a GZ34 Rectifier and EL34's according to the list here on the website...

I have a nice modded JTM45RI (Marstran OT, hand wired board and KT66's - will post pics of the soon to arrive modified smallbox head, by smallbox, w/repro block logo, "Clapton" knobs and back panel w/cutout for the cord) and a '70 Metal Panel 50 watter so I figure this'll nestle right in the middle...

Which OT should I go with?
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Re: Marstran 784-139 VRS 128 Output transformers

Postby Hamilton » Thu Feb 05, 2009 2:37 am

If you're going with a "blackflag" panel, go with the 128. Here's mine :

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Re: Marstran 784-139 VRS 128 Output transformers

Postby David B » Thu Feb 05, 2009 12:41 pm

Hamilton wrote:If you're going with a "blackflag" panel, go with the 128. Here's mine :

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Very nice :D got any transformer shots?
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Re: Marstran 784-139 VRS 128 Output transformers

Postby Brian Wallace » Thu Feb 05, 2009 6:22 pm

Pony up Hammy. :)
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Re: Marstran 784-139 VRS 128 Output transformers

Postby 57lpjr » Thu Feb 05, 2009 11:55 pm

Yes, more pics would be nice!!!

Brian - you can expect and order tomorrow for some transformers...
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Re: Marstran 784-139 VRS 128 Output transformers

Postby LordAli » Wed Feb 02, 2011 7:03 pm

Hmm. Nice.

I bought 784-128 and after about a half year of testing I'm afraid i've got a lot of bass made by transformer :shock: . I would like more highs and little more mids. Amp run through 1960A cabinet. I hope that preamp modifications fix it :lol: . I never thought that 100V winding can have such significant influence on upper frequency range of amp. Next time I'll try some transformer without 100V winding. :idea:
JMP50-X1 (JMP50 Combo version loaded with Vintage 30)
JTM50 head (some strange amp of that kind)
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