Transformer article

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Transformer article

Postby Brian Wallace » Sat Dec 13, 2008 5:39 pm

I was lucky enough to be asked to write a short article on the Radiospares Deluxe transformer.

Here is the text from the article as well as some pictures and diagrams.

Radiospares output transformer. A brief summary of its sound, history and use in the Marshall JTM45.

“From a lock-up garage in North-West London, J H Waring and P M Sebestyen established a company called Radiospares Limited, which began operating from a small building in nearby Birchington Road, supplying radio repair shops with spare parts for radios. It was from there that RS began its journey to becoming the market leader it is today. From the very first day of trading, in 1937, RS had the simple objective to provide a replacement part for every job. For more than 60 years RS has been dedicated to a single purpose: service excellence.” Excerpt from RS components website.

Between 1962 and 1965 the “RS Deluxe” transformer was used in the Marshall JTM45 amplifier. Though the RS Deluxe was seen as a cheap Hi-Fi audio transformer not intended for guitar amplification purposes, Ken Bran and Jim Marshall foresaw the possibilities, changing the way we listen to amps today. Highlighting E-bay sales, the “RS Deluxe” audio transformer has become one of the most sought after and expensive transformers used in the JTM45 amplifier.
Despite the fact that the RS Deluxe appears in every Radiospares catalog from 1958 through to 1970 it is unclear how long the RS Deluxe was sold by Radiospares. The manufacturer of the RS Deluxe is also a mystery since Radiospares mainly rebranded items for sale and did not manufacture them. I have seen many examples similar to the RS Deluxe from Partridge, Haddon and Parmeko but nothing that would indicate indisputably who made them. Recently, an E-bay auction claimed that the manufacturer of such transformers was R.F. Gilson, however the conclusiveness of this claim has not yet been proven.
The tone of the RS Deluxe in a JTM45 is fairly even overall complimenting the frequency response between its highs and lows. When played through Alnico speakers and a Stratocaster, the sound ranges from a crisp chimey tone with clarity to a great classic rock crunch. However, when played through Greenbacks and a Les Paul, the tones range from a clean blues tone to a hard rock grind.
The only down side to the transformer that I have found is it’s secondary wiring. The secondary taps can only be wired for one choice at a time unless you are willing to use an elaborate switching and wiring scheme to allow the standard 4, 8 and 16 ohm selections. Overall, I have found the RS Deluxe to be rich in harmonics when pushed yet have a full smooth clean tone.

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Re: Transformer article

Postby dai h. » Sat Dec 13, 2008 9:00 pm

nice! Brian one question if you don't mind, how is the primary usually hooked up in an original JTM45? 6.6k?
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Re: Transformer article

Postby Brian Wallace » Sat Dec 13, 2008 9:42 pm

Yes, 6K6 is the only way I have seen these wired.
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Re: Transformer article

Postby dai h. » Sat Dec 13, 2008 11:42 pm

cool thanks. Was wondering because I remembered reading something about possibly being 8k in some so there was some confusion.
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Re: Transformer article

Postby Brian Wallace » Sun Dec 14, 2008 12:18 pm

I've seen posts like that as well and they mentioned that the 6K6 wiring was rare. Well I must be the luckiest guy in the world then since all I have ever seen is 6K6. ;)
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Re: Transformer article

Postby David B » Sun Dec 14, 2008 1:41 pm

Brian,

Great article :D I also remember seeing a post somewhere stating RS OT's wired predominantly 8K, can't remember where.
Does the goofy secondary wiring contribute to how the transformer sounds?

Though the RS Deluxe was seen as a cheap Hi-Fi audio transformer not intended for guitar amplification purposes


Wow huh, look what they go for now!
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Re: Transformer article

Postby dai h. » Sun Dec 14, 2008 6:25 pm

was thinking possibly it was less from being "goofy" and more from the particular way it's wound(compared to the other Marshall OTs with the more conventional 4/8/16 taps), but I might be completely wrong on that
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Re: Transformer article

Postby David B » Sun Dec 14, 2008 6:32 pm

Hi Dai,

I should have said goofy secondary windings :oops:
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Re: Transformer article

Postby dai h. » Sun Dec 14, 2008 7:58 pm

don't worry you did! :mrgreen: I was just thinking more in a broad general sense of how the physical windings could become more complicated if (in trying to reduce inter-winding capacitance) you tried to not lay winds next to ea. other and how that might result in having a greater than usual number of outside taps (due to the complicated scheme) and provide a *possible* explanation for the goofiness.
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Re: Transformer article

Postby Brian Wallace » Sun Dec 14, 2008 8:42 pm

The secondary's were wound with a combination of different coils joined in parallel or series depending on what ohms was required. This is a far cry for the very simply series winding found on guitar transformers. Goofy indeed. ;)
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Re: Transformer article

Postby David B » Tue Dec 16, 2008 2:27 pm

Seen some PT secondaries wound like that (multi-coiled) as well, wonder that the reason is for the more complex arrangement?
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Re: Transformer article

Postby Vintageheadbox » Sun Dec 21, 2008 1:56 pm

Hi Everyone. Brian did a Great job on his article in the 1st issue of Vintage Amplifier magazine. Brian will be doing More!
His contributions as well as others make this Mag work,, Thanks Brian..and to Date the Mag has taken almost 8000 hits
since Dec 12th...
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Re: Transformer article

Postby Brian Wallace » Sun Dec 21, 2008 8:54 pm

Jerry,

Thank you for asking me to write about something that I have a true passion for. I hope the online rag does extremely well.

I have the next article about half written. This will be on the next OT in the JTM45 history, the ever mysterious transformer with the selector on it. :lol:
Remember....You can fix it with a little extra energy and a positive attitude. ;)
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Re: Transformer article

Postby Vintageheadbox » Sun Dec 21, 2008 11:42 pm

Very Cool Brian.. I also put advertisements on the Site for all that are contributing..
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Re: Transformer article

Postby Brian Wallace » Mon Dec 22, 2008 8:17 am

Vintageheadbox wrote:Very Cool Brian.. I also put advertisements on the Site for all that are contributing..


That's very nice of you to do that. 8)
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