Which Radio Spares JTM 45 OT clone?

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Lefty Lou
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Which Radio Spares JTM 45 OT clone?

Post by Lefty Lou » Wed May 23, 2012 11:23 pm

I have a modified (JTM45/JTM50) head for which I'm considering changing the OT from a Mercury Magnetics 050 JM OT to a Radio Spares Deluxe JTM45 OT clone. I'm interested in any metro forum member experiences with Metro, Marstran, ******, and MM versions of the Radio Spares Deluxe JTM45 OT in your JTM45 amp or other amp(s) particularly when using KT66 tubes and GZ34 rectifier sections. :thumbsup: BTW, What's up with the ******* when you type in Chris (you know who), is there some angst that I sense from the moderator(s) against this transformer guru that I'm not aware of? :scratch: :whistle:

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Re: Which Radio Spares JTM 45 OT clone?

Post by EFK » Thu May 24, 2012 1:01 pm

Both the metro and marstran are excellent transformers made by Heyboer. To be blunt, they're the middlemen. You can just call Phil at Heyboer directly and tell him you want an *exact* copy of the RS JTM45 transformer. They can make it various ways, i.e. different lams and different degrees of interleaving, depending upon what it specified and how much you want to spend. Since the original was a general hi fi replacement, it will basically be most expensive to get an exact clone made as high quality steel was used and it was fairly well interleaved. But they have the specs, so just go to them directly and get it done.

Of course I've heard great things about ******'s OTs as well but I've never tried one.

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Re: Which Radio Spares JTM 45 OT clone?

Post by neikeel » Thu May 24, 2012 2:39 pm

I had an MM in my JTM45 clone. It always felt stiff and did not break up nicely. I replaced it with a Metro specc'd Heyboer Drake type. At the same time I lowered the V1 cathode cap to 25uF and replaced the extremely closely matched NOS GEC KT66s with a pair of similarly testing but slightly mismatched (8mA at idle) GEC KT66s.
The change was amazing, lots of harmonics, grind, crunch and break up in the mderate volume range, wind it up >8 on the dial and prod it with a pedal and it screams.
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I was going to sell it as it never quite 'did it' for me, now it is a keeper 8) .

Bear in mind what tones you are after. The RS types do have a cleaner more hi-fi sound (I do have an original Deluxe) if that is what you want get the RS type but if you want a rocker get a good quality Drake type. All three of the ones you describe are specc'd well.
Chris M and George had a dust up provoked by a well known ex-forum member who pushed his luck with them both ironically, and now the name is **** out. He did post here to pay respects to Ben (Stunt double) Wise and I think dips in to the forum now and again.
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Re: Which Radio Spares JTM 45 OT clone?

Post by Lefty Lou » Fri May 25, 2012 2:22 am

neikeel, are the "stirrer upper's" initials J.M. and (does/did) he have his own amp business? It's also interesting about the Dagnall OT version mentioned, Magnetic Components have a version of the Dagnall JTM45 OT (but not the RS Deluxe version) I wonder how the MC Dagnall version is to be compared? My JTM45/JTM50 head uses Groove Tubes "Silver" Saratov KT66 singles (in an un-matched pair) that could be off by as much as 5% from each other but still sound tremendous in this amp. The output tranny is a ( MM O50 JM ) 50 watt plexi tranny designed for EL34's, and the power tranny is a Heyboer JTM45 power tranny w/vintage turret board and original NOS marshall components (no Sozo's, Mallory's, etc). The modified output is around 46 to 48 watts RMS. I've been pondering over whether or not I should replace the ( MM 050 JM ) output tranny with the MM 045RS-L (Mercury Magnetics Radio Spares Deluxe OT) to closer match tube, output, and cabinet impedances and to see if I can gain that much more "tonal majesty" in a manner of speaking by using the MM 045RS-L tranny. Decisions decisions. :scratch:

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Re: Which Radio Spares JTM 45 OT clone?

Post by OnTheFritz » Fri May 25, 2012 2:54 am

Lefty Lou wrote: Magnetic Components have a version of the Dagnall JTM45 OT (but not the RS Deluxe version) I wonder how the MC Dagnall version is to be compared?
It's not a Dagnall, as they never spec'd a 45 or even 50 watt OT for Marshall. It's Drake.

MC's 50 watt OT sounds great, have not tried the 8k JTM 45 OT.
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Re: Which Radio Spares JTM 45 OT clone?

Post by Lefty Lou » Fri May 25, 2012 8:46 pm

OTF you made a very good point, I got Dagnall and Drake names confused. Somewhere it was stated that Marshall typically used Dagnall transformers for their 100 watt amps and Drake transformers for their 50 watt amps, is this correct?

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Re: Which Radio Spares JTM 45 OT clone?

Post by Lefty Lou » Fri May 25, 2012 8:52 pm

One would tend to think that an "audiophile" designed transformer such as the Radio Spares Deluxe OT transformer would not elicit the great harmonic overtones that a great classic guitar OT could provide, and I've heard everything from accolades to ho-hums about this transformer.

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Re: Which Radio Spares JTM 45 OT clone?

Post by neikeel » Sun May 27, 2012 12:15 pm

Lefty Lou wrote:neikeel, are the "stirrer upper's" initials J.M. and (does/did) he have his own amp business?
No MA.

Btw you need to decide what tones you seek, cleaner crystalline tones = RS type or dirtier crunch = Drake type.
Neil

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Re: Which Radio Spares JTM 45 OT clone?

Post by EFK » Sun May 27, 2012 1:04 pm

I've always found the RS style transformers to add a hint of a nasally kind of honk (over multiple amps in which I've used them) - something I personally like to hear. Really, the only way to decide what you want to hear is to A/B the two in your amp, b/c every amp will be a bit different depending upon components used, tubes etc.

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Re: Which Radio Spares JTM 45 OT clone?

Post by shakti » Sun May 27, 2012 1:45 pm

Agree about the honk... Or even more like a bit of quack! You can get a good feel for how it sounds from Mayall's A Hard Road album. Peter Green played an early block logo with presumably an RS on that album.
JTM45 RS OT, 1973 18W, JTM45/100, JTM50, JMP50 1986, JMP100 "West Coast", AC15, AC30, BF Super Reverb, Boogie Mk 1, Hiwatt CP103, DR103

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Re: Which Radio Spares JTM 45 OT clone?

Post by Lefty Lou » Sun May 27, 2012 8:23 pm

[/quote]Btw you need to decide what tones you seek, cleaner crystalline tones = RS type or dirtier crunch = Drake type[/quote]

I love great clean tones that I associate with some vintage Fender tube amps, and I like crunch but I like a more "balanced" smooth even crunch in a manner of speaking (ala Carlos Santana). I'm primarily a (blues/rock/classic rock) aficionado. From what I'm understanding it sounds as though I'd be better off sticking with my MM "Tone Clone" 050 JM Plexi OT (designed for EL34's) but using my KT66's with the TAD GZ34 tube rectifier. I still get great clean tones and smooth overdriven balanced "crunchy" tones. I don't want to get into the high volume clean headroom thing. Am I off base? Or am I just unclear about the term "audiophile" when used in the context of guitar amplification?

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Re: Which Radio Spares JTM 45 OT clone?

Post by EFK » Mon May 28, 2012 3:05 pm

I think you may be overthinking it a bit. Take my advice for what it's worth, I have built a pretty good number of straight JTM amps as well as JTM inspired amps, and while you can hear a difference between different types of OT, assuming you are alternating between quality OTs, it's not so dramatic that it's like night and day - especially, if you are just winding the amp up to max. Think of it as different flavors of the same amp. The RS OT might have been *intended* to be a general hi-fi replacement, but it's not going to turn a JTM45 into a sterile hi-fi circuit. It's still a Bassman/JTM circuit - you can't drown the greatness of it as a guitar amp. I sincerely recommend you buy a good quality RS OT, temporarily wire it in place in your particular amp, and try it out. A/B the two and sell the one you least prefer. Or just store it for another amp, because of course there will be another.

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Re: Which Radio Spares JTM 45 OT clone?

Post by Lefty Lou » Mon May 28, 2012 7:44 pm

EFK wrote: I sincerely recommend you buy a good quality RS OT, temporarily wire it in place in your particular amp, and try it out. A/B the two and sell the one you least prefer. Or just store it for another amp, because of course there will be another.

That may have to be the case EFK, a local amp tech and engineer swears by the MM 045RS-L "Deluxe" OT and even says he's placed one in a twin (must've been the tweed twin) to excellent results. The (JTM45/JTM50) build was done by Jack McCallister of Mourdian Amps. I'm not sure about what mods I might have to reverse that Jack did in order to make the MM 050-JM OT work. There may have to be slight alterations or changes made in order to accomodate the MM 045RS-L "Deluxe" OT. Whatever it is that needs to be done in addition to swapping out the transformers, I would still like to use the Saratov KT66's.

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Re: Which Radio Spares JTM 45 OT clone?

Post by BillYoung » Thu Mar 05, 2015 4:28 pm

WHERE DO YOU GET THE GERMINO SPEC HEYBOR OUTPUT TRANSFORMER ?

BILLYOUNG606060 AT GMAIL DOT COM

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Re: Which Radio Spares JTM 45 OT clone?

Post by jnew » Mon Jul 27, 2015 2:20 am

Lefty Lou wrote:I have a modified (JTM45/JTM50) head for which I'm considering changing the OT from a Mercury Magnetics 050 JM OT to a Radio Spares Deluxe JTM45 OT clone. I'm interested in any metro forum member experiences with Metro, Marstran, ******, and MM versions of the Radio Spares Deluxe JTM45 OT in your JTM45 amp or other amp(s) particularly when using KT66 tubes and GZ34 rectifier sections. :thumbsup: BTW, What's up with the ******* when you type in Chris (you know who), is there some angst that I sense from the moderator(s) against this transformer guru that I'm not aware of? :scratch: :whistle:
The MM's 045JT RS-L is MAGIC. Specifically designed for KT-66's, or 6.6K primary, It's the best sounding OPT Trans. I've ever heard and I've used it with KT-66's, EL-34's and fat bottle 6CA7''s. Can almost guarantee it makes any amp into something truly special, provided all else in the circuit is dialed. Outstanding clarity and harmonic content with fantastic dynamic feel. 8)
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