February 2008 \ Features \ Product Spotlight \ The BluesBreaker Revisited

The BluesBreaker Revisited

John Wiley
Premier Guitar February 2008

(2 of 5)

Hitting the streets in 1990, the Model 1962 “Bluesbreaker” reissue was plagued with discrepancies out of the box. The cabinet was undersized by some 30 percent, with a depth barely over 9”, while the original measured in at 10.5”. The reissue’s overall width was almost 30”, while the original was 32”. The most reasonable explanation for these differences would come from the use of output tubes originally selected for the Model 1962. Although the very first combos incorporated the smaller 5881 vacuum tube, Marshall designed the Model 1962 for the more prevalent but enormous Coke bottle-shaped KT66 vacuum tube. The usage of this particular tube necessitated the deeper 10.5” cabinet.

Likewise, the cabinet’s construction differed significantly from original specs. The Model 1962 Series I was built using pine planks for the cabinet with multi-ply birch baffles; the Model 1962 Series II was completely constructed with multi-ply birch plywood (more about these Series differences in a moment). The reissue used particle board for the cabinet and plywood baffles.

Finally, the speakers supplied in the original combo were G12M “Greenbacks,” rated at 20 watts each. This speaker utilized an Alnico magnet, providing sweet, warm tones and a smooth midrange – an essential ingredient for that “British chime.” At 20 watts, the speaker could barely keep up with the tremendous overdrive of the amplifier when it was at full volume. Marshall, however, equipped the Bluesbreaker reissue with 25-watt Greenbacks, featuring ceramic magnets. While they lacked the chime of an Alnico magnet, they could withstand twice the wattage and had a fine sound of their own.


The Model 1962 Backstory
However, before we dig in and modify our reissue Bluesbreaker, it would behoove us to understand where it all started. In 1964, while the Beatles made their first appearance on the Ed Sullivan Show, and the Civil Rights Act of 1964 was enacted, Marshall was busy introducing its very first combo. Because it was the very first series, it is historically referred to as the Model 1962 Series I. Interestingly, the 1962’s model number did not refer to a particular year or significant event in time. Until the 1980s, Marshall’s distributor and financial backer Rose-Morris used these numbers arbitrarily, using the prefix “19” for all of Marshall’s product line.

Jim Marshall wanted his new range of combos to be versatile; as a result, he designed the Model 1962 with two 12” loudspeakers and used the JTM45 bass chassis (Model 1986) electronics. The Model 1962 was described in the Marshall catalogue as a “Bass/Lead” unit, making it an extremely versatile amplifier that could be used by guitarists and bass players alike.



But just how close was this new variant to the original Model 1962? To the true Marshall collector, and to the rare few who actually owned the genuine article, the differences were immediately apparent.




In addition, a second combo with four 10” speakers – the same configuration used in the Fender Bassman – was offered to players. Marshall’s 4x10 version was referred to as the “Lead” and utilized the JTM45 treble chassis (Model 1987) electronics. This 4x10 configuration, designated the Model 1961, was designed for guitar use only. Both Model 1962 and 1961 were purposely marketed as the British equivalent to the vastly popular Fender Bassman, and they offered quite a bargain for British and European musicians. The Model 1961 retailed for a scant $165 American dollars and the Model 1962 retailed for $170, while the Fender Bassman was nearly double at $300. Both models went into production in late 1964.


Cabinet and Construction
The cabinet dimensions for the Model 1962 (2x12 configuration) were 30” wide by 24” high by 12” deep. The 1961, incorporating four 10” speakers, maintained square proportions, measuring 28” wide by 28” tall and 11” deep. The Model 1962’s width is 2” wider and 1” deeper than the 1961’s to accommodate the dual 12” speakers.

Marshall amplifiers would also gain a reputation for their ruggedness. Marine ply birch was used for cabinet construction, as the laminated layers of glued veneer plywood provided greater overall strength than a singular plank of yellow pine, which was the wood of choice for Fender amplifiers. These early Marshalls did not use the “finger-lock” joints that would become standard on all Marshall cabinets a few years later.

The BluesBreaker Revisited
The Marshall ads above suggested the reissues matched the originals; in reality, there were significant differences
Marshall cabinets were also visually appealing and had the look of richly appointed furniture. Black PVC (polyvinyl chloride) material, similar to the General Tire invention known as “tolex,” was used for the entire exterior of the cabinet. This smooth, black fabric was different from the black “Levant” tolex Marshall would use later.

Accenting the cabinets was Marshall’s elegant grill cloth. The company’s catalogue referred to this early cloth only as, “contrasting speaker grills,” not actually describing the color or pattern of the cloth material. However, it was known as the “white” grill cloth and had thin, horizontal gray lines running through it. Also included on the earliest models were three leather straps, attached to the top of the cabinet and similar to the Vox AC30. These amplifiers weighed in at a very heavy 70 pounds, and the sheer weight meant that it wasn’t long before the leather straps would stretch and break. In early 1965, an improved, single plastic strap which was stronger and larger in size replaced the leather ones.

The very first Marshall combos produced in late 1964 used what was known as “Vox-style” cooling vents, which allowed the heat produced by the transformers and vacuum tubes to escape efficiently. Two vents were installed into the top of the cabinet, similar to the Vox AC30. The vents were rectangular in shape and had a metal screen riveted inside.


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Comments

(11 comments) display by
UsernameComment
frank
on 12/03/2012
manque le poid est necesaire savoir aussi
Duke
on 06/24/2011
I have a mojo large size combo. Huge sound difference when compared to the reissue marshall.
John Moleksi
on 07/01/2010
Where is the best place to buy a kit from in order to try to build a better bluesbreaker? I can build the cabinet myself.

zaphod_phil
on 11/09/2009
Great article, but it's wrong where it says "the speakers supplied in the original combo were G12M “Greenbacks,” rated at 20 watts each. This speaker utilized an Alnico magnet..." G12M 'Greenback' speakers, even the original 20W ones, have always had a ceramic magnet. The Celestion G12 Alnico Silver and Blue speakers are the alnico models. I was surprised to see such a fundamental error.
John
on 10/15/2009
I have a Metro Amp JTM45 build. I sourced out for some vintage parts so this is a custom build from a Metro Amp kit. I am replacing a pair of June 1962 Mullard EL34's with some new Gold Lion KT66's tomorrow. I have a Swanson custom build Marshall Style 1 combo with a pair of original Dec '64 Celestion Pulsonic speakers with the original cones and paper. I am hopeful this will be tone nirvana...not that the '62 Mullards are not. I am also running a vintage Mullard AX7 in V1.
Lord Valve
on 11/19/2008
Since it's rumored I may know a little bit about tubes, I'll pass this on... ;-)

The Reflektor-production "Tung-Sol" KT-66 isn't a KT-66. Rather, it's a set of the Reflektor-production "Svetlana" 6L6GC guts mounted in a metal-based KT-88 bottle. It doesn't sound like a KT-66, nor spec like one. (I'm not saying it sucks or anything, but it isn't a KT-66, and if you like the tone it produces, you can get it cheaper as a Reflektor/Svetlana 6L6GC.) The JJ KT-66 is an unknown quantity at this point; like the Tung-Sol, it's mounted in a KT-88 bottle. I haven't had time to do any testing on the dozen sample pieces I have. Stay tuned. The Groove Tubes KT-66s used to be made in Russia by HP. No more are available. I don't know what GT is using for KT-66s these days, but I wouldn't be surprised if they are Shuguangs. The "Valve Arts" KT-66s mentioned in the article are from Shuguang. They do indeed sound excellent, although (like most Chinese power tubes) they don't last as long as I would like. Probably the best currently available KT-66 is the Reflektor-production "Gold Lion," a clone of the original GEC KT-66. The new (I don't like to use the term "re-issue") Gold Lions are probably as close to the originals as you are going to find; you'll need to take out a second mortgage if you want real ones. Although it doesn't matter in this particular application, the Gold Lions are serious eye candy - they look like someone cared.
I like that. They sound great, too.

Lord Valve
NIC
on 09/24/2008
Thanks, this is great information and i have a reissue bluesbreaker which i would love to convert to the original specs however i live in New Zealand and the voltage here is 220-240v. My question is "where do i find a suitable output transformer rated at 240v"? can you help me? Nic in NZ
Rick
on 08/12/2008
I have examined the Mercury Magnetics RS output transformer in detail and find it in no way similair in design or measured characteristics to the real RS Deluxe output transformer.. It does not use the same winding geometry nor the same type of core material.. It does not even sound remotely the same. Nice push for Mercury through...Brain at Marstran makes a much closer replacement. Also, Merren Audio makes a repro with the original style Tag-Board..
You need to research a bit more before leaping to such conclusions.
Brian Myers
on 02/13/2008
Hi,
Great stuff, except! in the table
"The following is a listing of the basic differences between the original Model 1962 and the Model 1962 “Bluesbreaker,” as reissued in 1990:"

It lists the "original" [as compared to the reissue] depth as 10.5 " but thats the series II It should have read 12" deep.
Thanks for a great read!
Brian

JoeZ
on 01/27/2008
I thought I'd share a couple of other tidbits I've picked in my pursuit of an authentic sounding "Bluesbreaker" combo amp.

Original Radiospares output transformers were hardwired for 16 ohms output. It's my understanding that Marshall used only 16 ohm Celestion speakers and in 2 x 12 1962 Bluesbreakers combos, wired them in parallel for 8 ohms. This "mismatch" is vital for Beano tone. I'm not an electronics expert, but I've been told by knowledgable amp gurus that this arrangement works for this amp's transformers and tubes.

Makers of accurate reproductions of JTM 45's and 1962 combos include Germino Amplication (I highly recommend working with Greg Germino who provided me with a special order Style II cabinet upon my request, although he prefers the Style I), Retro-King (Style II) and Blockhead (Style I) with kits available from Metropolous, Mojo and others. As far as I know, only Metropolous and Blockhead offer a tremelo circuit on their BB's.

The matter of speakers is the subject of significant discussions on guitar-related internet forums. The consensus seems to be that the speakers in Clapton's 1962 were AlNiCo's, mostly based on the sonic evidence, which also seems likely since ceramics were only first being introduced in late '65 and widely used in '66. Based on dates in Doyle's book only the recently reissued Celestion G12C-25 ceramic speakers could have been available for use in Marshall combos before April '66 recording of the "Beano" album. Power handling ratings on AlNiCo's seemed to have increased during the sixties and it also seems that Celestion used speaker cones from Pulsonic 102 003 and Kurt-Mueller H1777. Their were probably numerous variations. There's some reluctance to use relatively expensive Celestion Blues rated at 15 watts each in a Bluesbreaker combo since the rated power is reported somewhere between 30 and 45 watts. Further it seems that the speakers used in Clapton's speakers may have had different cones and othe



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