Magnatone Guitars!

New for Fall 2013, a complete guide to Magnatone guitars and the stories behind them!

1938-1960 Steel Guitars

1956-1963 Bigsby/Barth Era

1964-1966 Starstream Era

 

Solid State Years

The last of the Magnatone amps were a series of solid-state amps introduced in late 1967 and produced through late 1970. The premium amplifiers were well designed and of high quality but they didn't sell particularly well and the lack of sales, no doubt, influenced Estey's decision to discountinue the Magnatone brand. Contrary to what some might think, the solid-state amps did not completely replace the tube amps. Both amplifiers were made concurrently for a time at the Harmony, PA plant.

Schematics

See Schematics for all solid-state amplifiers.

Developmental years 1964-1966

Solid State amps had been on the horizon for some time, and the industry trend of moving from tube to transistor was something Estey began looking at in late 1964. The competition was getting into transistors, most notably was Gibson with their launch of the Starfire series in 1963. Standel, Baldwin, and Selmer all followed in 1965. J.M. McClintock had recently been place at the helm of Estey following the companies re-emergence from bankruptcy. McClintock wasn't experienced in the musical instrument industry but he was quite hopeful and announced to their distributors in 1965 that a solid-state amplifier would be a reality for the following year.

The change to solid-state was not simply the engineering task of a circuit redesign, there was the assembly process to sort out as well. Component count was much higher for solid-state designs, and the traditional pointtopoint assembly was far from optimal. Estey engineers decided the only way to manufacture solid state amps efficiently was to modernize and use printed circuit board (PCB) technology. PCB and wave soldering had taken hold in military electronics but it was still in its infancy for commerical applications. Here is what Tony Price recalls from his days as Chief Engineer for Magnatone at this time:

"We were cautiously exploring different ways to come up with reliable solid state power amps for Magnatone, such as design them in house or buy an outside design. A fellow named Bob Marks and his son had developed a pretty neat concept that we looked at, but the cost was higher than the market could afford. The in-house approach would depend on what engineering talent we could find, as this was all new stuff at the time."

 

The first attempt at an all solid state product was the M-101 travelorgan. This was an ambitious project! When it was released for production, it was the first portable all solid-state electric organ on the market. The development of it was all carried out in Torrance, but the first production units were not made until Estey had relocated to Harmony. The new wave-solder process was met with some diffculties that likely delayed production until sometime late in 1966, and while the M-101 was very cool and attracted a lot of attention at the July 1966 NAMM show, production figures were not very high.

At the same 1966 NAMM show, a still optimistic McClintock had to make the announcement that the development of solid state amplifiers was slower that he had hoped and that they would instead arrive in 1967.

Production Amplifiers 1967-1970

Another hurdle to overcome was staffing the engineering department. It was proving difficult to attract electrical engineers to the hard-scrabble western Pennsylvania area. Only a few of the Torrance era engineers chose to come to Harmony and by 1967 chief engineer Tony Price had left. Finally, in late 1967 the solid state amplifiers were designed and ready for production. The engineering staff credited with this achievement was headed by Chief Engineer Bob Warren, Paul Bossert who designed the power supplies, Bill Layton who was adapted photocell technology to the original Bonham-vibrato design and mechanical engineer Don Bergstrom.

At the July 1968 NAMM show at Chicago's Conrad Hilton Hotel, Magnatone exhibit highlighted the 300W 105lb. "the Killer" M-35, as well as an 8-foot tall 1000W amplifier.

Unfortunately, the amplifiers had a series of problems that led to a bad reputation, and ultimately disappointing sales figures. The cabinet design and construction had durability issues, plus the initial design used a particle-board speaker baffle with broke apart and required a plywood replacement under warranty repairs. If that wasn't enough, the power supplies had a zener diode issue which also required a warranty repair.

Estey was sold again in 1969 and soon the Magnatone name, the amps, and the guitars were all mothballed in a back corner on the Harmony plant. When Estey was again sold in 1973 (this time to Mattel), manufacturing was moved to nearby New Kensington, PA. The old stock Magnatone parts were sold at clearance sales.

Models

The first solid-state amplifiers came out in 1967 as The Brute Power Series. The four bass and guitar models were the M27, M30, M32 and M35 and the PA series amps were the PS150, PAS150 and PAS300 powered speaker systems. These were designed in the summer of 1967 and released for production in November 1967. The features of the bass and guitar amplifiers closely ressemble those of the tube amp models M7, M10, M12, and M15.

In late 1968 the accordion/organ amplifer models 240SV and 130V were designed and released as well as two new guitar amplifier models, the 150R and 120R.

 

M35 "The Killer" and M32 "Big Henry"

The M32 and M35 amplifiers were designed for bass and guitar/organ. They shared a speaker cabinet and power amplifier unit that was mounted in the bottom of the cabinet. The pre-amp circuit boards were mounted in a "head" unit (called a "preamp deck") that was permanantly fixed to the top of the cabinet. Except for the the speakers and the preamp unit, the M35 and M32 was identical to a PS300 powered speaker cabinet (see "public address").

The M32/M35/PS300 cabinet was fitted with two 15" speakers. The M35 was fitted with a high frequency horn as well. The M32 used special bass response 15" speakers while the M35 and PS300 used mid-range response 15" speakers. Standard speakers were ceramics (maybe CTS?) but a JBL-D140F 15" was available for added cost.

The M32 was called "Big Henry". It had a two channel preamp with treble, bass and volume controls for each preamp. The M32 and M35's preamps were identical (see "Preamp" section below).

The reverb PCB made use of six transistors and used a 25-0002 reverb tank (1.2KΩ input, 2KΩ output). The vibrato used two PCB boards, a primary board that included the signal vibrato circuit and the oscillator circuit and an auxillary board that included another signal vibrato circuit. Both signal vibrato circuits ran off the same oscillator and used a total of four LDR's to recreate Bonham's F.M. Vibrato in solid state.

The M32 and M35 came with twin 4Ω 15" speakers and the M35 added a pair of 16Ω high frequency horns. The schematic indicates that the M35 was initially released to production November 27 1967.

All power amps in the bottom of the cabinets had a power-amp input. The PS300 (or PS150 or PAS150's) could be daisy chained to a M32/M25 to all power.

 

left: Here's an M35 lurking in a storage area in Michigan. center: although it looks like a detachable head unit, the preamp deck was permanently affixed to the cabinet. right: A Billings, Montana classified ad for a M35 built into some odd-ball cabinets.

M30 "Fang" and M27 "Bad Boy"

The M27 and M30 were advertised as 150 Watt amplifiers for bass and guitar/organ. The cabinet mounted two 15" speakers. One was a passive radiator and other driven by a power amplifier mounted in the bottom of the cabinet. The cabinet and power amp for the M27 and M30 were identical and were also shared with the PS150 power speaker cabinet (see public address below).

Both the M27 and M30's preamp PCBs were mounted in a "preamp deck" that was permanently mounted to the top of the cabinet (see "Preamp" section below). The M30 had reverb (same reverb circuit fitted to the M35) and vibrato (one of the two vibrato PCBs that was fitted to the M35).

The M27 was fitted with a special bass response speaker and the M35 and PS150 used a mid-range 15" speaker. The M35 was fitted with a high frequency horn (like the M35).

The M27 and M30 were released in November 1967 and the PS150 was released in March 1968.

Preamp for M27 M30 M32 and M35

The preamp used in the M27 M30 M32 and M35 amplifiers all used the same basic preamp. The M27 being a single channel amp used 1 PCB board and the others used two boards. Each board (partno. 35-0059) was a basic one channel circuit with volume, treble, and bass controls plus a "normal", "mellow", "brite" tone switch. These were mounted along with three transistors to a single PCB.

On the M30 and M35 there was also a "MILA" or Magnatone Instrument Level Adjustment control knob near the input jack that was 1MΩ pot attenuator between the jack and the first transistor gain stage.

Public Address PA: MC100 PAS150 PS150 and PS300

The MC100 was a six channel mixing console. Each channel had a microphone input, volume and tone control. There was an onboard spring reverb unit and each channel had a toggle switch to send that channel to the reverb unit. The MC100 did not have it's own power supply. It required a power cable from a PS150/PAS150 or a PS300 power amplifier unit. The MC100 was designed and released in early 1968.

The PS150 was a ?? 2x15" powered speaker cabinet with the power amp in the bottom of the cabinet. It shared a cabinet with the M27 and M30. The M27 and M30 amps were actually PS150's with a preamp section in a head unit called a "preamp deck" that was permanently mounted to the top of the speaker cabinet.

The PS300 was a 2x15" power speaker cabinet with two power amps, once for each 15" speaker. The PS300 shared a cabinet with the M32 and M35. The PS300 weighed nearly 90 pounds and stood 39" tall.

Magnatone put these same power amplifiers into a power tower column PA speaker cabinet called the PAS150. The PAS150 used four 12" speakers and the same amplifier used in the PA150, M27, and M30.

These PA systems appeared in the spring of 1968. They were developed soon after the M27/M30/M32/M35 amps were released. At some point a PAS300 was released as well.

Power Amplifiers for M27/M30/PS150 and M32/M35/PS300

As discussed above, the power amplifier assemblies for all of the Brute Power series amps and PA systems were the same units. The 150 watt M27/M30/PS150 (and PAS150) used a TPA50 power amp and the 300 watt amps used a TPA100 unit (at some point these names were changed to TPA150 and TPA300). The TPA100 was two TPA50's together. The TPA100 used a bigger power transformer (and fuse!), but otherwise the two designs were the same.

 

Brute Series Cabinets

The cabinet design was similar to what was going on for the organ side of the house. Construction design more closely ressembled Estey organs which looked like home furniture.

Production was limited to a couple years, and production figures were not very high. They were not cheaply built but they were somewhat unconventional in appearance (Although, Gibson released a solid state series about the same time with a similar top "control panel" look). There were also some unfortunate cabinet design issues that caused a lot of warranty work, and the series might have suffered a bad reputation at music stores because of it.

Right: These giant column speakers are PAS-150 powered speaker systems that were sold with PA systems.

 

240SV Stereo-Vibrato Magna-chordion

The 240SV was released in late 1968 and was given the name Magna-chordion in Sales literature. Accordion distributors preferred the conventional styling of the 400 series amplifiers, so much so that Estey continued to produce those style amps with names like Tonemaster and Da Vinci even though they no longer sold them under the Magnatone brand. The 240SV not only set out to recreate the aesthetics of the old amps, the controls and vibrato were near duplicates in solid-state as well.

The control panel was slanted and rear facing just like the 460 The 240SV came with two 12" 4Ω speakers, and two 2" tweeters. Two input channels with a stereo vibrato (hence the "SV") and spring reverb produced 240 Watts output. The vibrato was given the name "Swinging Sound", and like an M15, you could switch between stereo and monaural vibrato. The 240SV also came with a feature called "MILA" or Magnatone Instrument Level Adjustment.

the 240SV had 28 transistors, on seven printed circuit boards. The retail price in 1970 was $620. It was initially released for production in November 1968. A service manual dated November 1970 indicate it was available for a few years.

There were 1/4" output jacks on the bottom rear that allowed the 240SV to power PS150, PAS150, or PS300 powered speaker cabinets.

 

130V

The 130V was a small two channel combo with vibrato labeled an accordion amplifier in the service manual. This amp was designed to be the little brother to the 240SV in aesthetics as well as circuit and power. While the 240SV had two vibrato units, the 130V had a single vibrato unit. The 130V likely first appeared in 1968 or 1969 and was available through 1971.

 

 

150R Firestar

The 150R Firestar was a big 72 pound combo amp with 4 10" speakers. It used a similar power amp that was used in the M27/M30 and PS150. Channel One had bass, treble and volume controls and Channel Two had bass, treble and volume controls plus a bright boost switch, reverb and vibrato. If 4x10"s weren't enough, PS150 or PS300 power speakers could be connected. Retail price in 1968 was $450.00 These are not common amps these days, but they were good quality and sounded good.

120R 120B MC120

The 120 was a small single channel combo amplifier. The bass amplifier version was branded the CU120B/120B "Cougar" and appeared in late 1968. A guitar version was introduced soon after with spring reverb, vibrato and integrated "E tuner". The "E tuner" was a simple oscillator calibrated to produce a 329.5Hz sine wave. A two channel PA version was also produced called the MC120.

The pre-amp circuit board and all of it's components are the same for all three versions. All versions of this have the same power amplifier section that expects to see a 4Ω load.

This is the MC120 version together with two SC3 speaker cabinets fitted with lightweight Jensen Alnico speakers.

 

30B and 30R

The 30R and 30B models were released in late 1968. These were smaller combo's with 12" speakers. The 30R featured reverb and tremolo. Unlike the LDR based vibrato on the premium models like the 240SV, the tremolo on the 30R varied the bias of the first transistor. The 30B was a basic version of the 30R sans tremolo and reverb.

 

Neil Young's famous giant speaker cabinet.

Pictured at right is Neil Young's big Magnatone cabinet. These were built as promotional items for guitar shows and some of the big stores. They were never offered for retail.

At the July 1968 NAMM show, Magnatone displayed this cabinet as part of a 1000 watt amplifier (EIA rating no doubt) display called "The Monster". It was also called "Tiny Tim". In this 500 pound eight foot high cabinet, Estey installed two 15" woofers, two 15" mid-range speakers, two 15" passive radiators, four 10" high-frequency speakers and eight high-frequency horns! Only a handful (10) were made and Estey ordered all of them to be returned to Harmony. All but this one were returned and destroyed. Somehow Neil managed to get ahold of one and keep it. The others ended up in the dump in Harmony.

This is a promo picture. The "models" might have been a son of Estey President Stan Green and his pal. A couple of these might have been sent on tour with the Estey sponsored group Orpheus when they opened for the Who. (rumor?).

 

Schematics

See schematics.

 

Need more info

If you have more information about these solid state amps, please contact me.

DA/MagnatoneAmps.com

 

 

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