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New (Old) Amp Day- Magnatone Varsity 108


Chris Loeffler

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There has definitely been more modified than the power cable and speaker swap...

 

The second instrument input jack was replaced with a knob that seems to work as a pre-volume control, and their is an added switch next to the Switch/Tone knob that I'm not quite sure what it does.

 

I only demoed it for a minute or two, so I'll have to sit down and figure out what's actually happening with those two mods.

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Hmmm... I noticed on the badge it's signed by Dan Torres and dated 2/13/83. I also noticed that two of the tubes listed have replacement tubes handwritten in by Torres... 7025 below the 12ax7 and 5AR4 above the 5Y3.

 

I know a 7025 is supposedly a lower noise 12ax7 (basically the same thing), but to my knowledge a 5AR4 has quite a bit more plate voltage than a 5Y3. I'm not an amp tech, but it seems like it'd be pushing the 6V6 on the verge, if not beyond, specs.

 

The amp came to me with a JAN Philips/Sylvania 5Y3WGT, so it looks like a previous owner/tech swapped it back.

 

I wonder if the circuit was at all modified to accommodate Torres' rectifier swap or if he just swapped it for personal tone reasons. Ugh... I think my curiosity is is going to result in some circuit tracing compared to the official schematic.

 

Based on pure specs, I would assume the 5AR4 would have less sag then a 5Y3?

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7025 is the industrial version of a Hi Fi tube. Its was simply more durable then a 12AX7. There was less noise because the elements wouldn't fall apart and become microphonic. Just about all 12AX7's went up in quality and today they match the 7025 standards.

 

The rectifier tubes have the same pin outs so that can be safely swapped in many amps. The 5AR4/GZ34 has a total plate resistance of approximately 80 Ohms when used as a full wave rectifier (two plates in parallel). The 5Y3 has a resistance is around 400 Ohms so the voltage drop across a 5Y3is going to be greater then a 5AR4. This will result in lower plate voltage and lower total output power and its why a 5AR4 would works better with low AC Mains voltages. The major difference between them is the 5AR4 has to heat the plates before it fully applies power to the B+. The 5Y3 is an instant on tube and the power/current hits the B+ supply with a surge. This is fine so long as you have good caps but the 5AR4 is more forgiving to older components duse to its softer start when you hit the power switch.

 

The amp does have a new 22uf power cap, I suspect the amp had a catastrophic failue due to age at some point. That power transformer looks bran new. No signs or rust of corrosion, and much larger then an amp of its size normally needs. If it is a replacement, its likely a beefier transformer, liiks like a Hammond which are pretty good.

 

It looks to have a 3 wire AC cord installed, the green wire soldered to ground is fresh (poorly done by the way, they had an under powered iron and the solder joint my be cold)

 

The mystery switch looks to be a ground switch. Single ended amps with a 2 prong plug has to be plugged in properly or the chassis was hot and could zap you good. A cap was used to prevent the full current of AC from killing you (often called a death cap which is a misnomer, its actually a life saver cap) The switch might have originally ben a polarity reversal switch. It looks like a spst switch now with the safety cap repurposed when the AC cord was switched to a 3 prong plug. Cant see where the other cap lead off the switch goes but it may be to the rectifier tube ground and is there to minimize hum without a dead short to the tube.

 

Other then the tone cap, Most of the other components look original.

 

Good find. Magnatone amps are pretty rare. Too bad it wasn't a higher end version that had true vibrato. Those are the amps that are in high demand and very expensive now but at least you get the tone of the brand. You may want to find an alnico Jensen or Utah speaker from that era for an even richer vintage tone. It will increase the value of the amp too.

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7025 is the industrial version of a Hi Fi tube. Its was simply more durable then a 12AX7. There was less noise because the elements wouldn't fall apart and become microphonic. Just about all 12AX7's went up in quality and today they match the 7025 standards.

 

The rectifier tubes have the same pin outs so that can be safely swapped in many amps. The 5AR4/GZ34 has a total plate resistance of approximately 80 Ohms when used as a full wave rectifier (two plates in parallel). The 5Y3 has a resistance is around 400 Ohms so the voltage drop across a 5Y3is going to be greater then a 5AR4. This will result in lower plate voltage and lower total output power and its why a 5AR4 would works better with low AC Mains voltages. The major difference between them is the 5AR4 has to heat the plates before it fully applies power to the B+. The 5Y3 is an instant on tube and the power/current hits the B+ supply with a surge. This is fine so long as you have good caps but the 5AR4 is more forgiving to older components duse to its softer start when you hit the power switch.

 

The amp does have a new 22uf power cap, I suspect the amp had a catastrophic failue due to age at some point. That power transformer looks bran new. No signs or rust of corrosion, and much larger then an amp of its size normally needs. If it is a replacement, its likely a beefier transformer, liiks like a Hammond which are pretty good.

 

It looks to have a 3 wire AC cord installed, the green wire soldered to ground is fresh (poorly done by the way, they had an under powered iron and the solder joint my be cold)

 

The mystery switch looks to be a ground switch. Single ended amps with a 2 prong plug has to be plugged in properly or the chassis was hot and could zap you good. A cap was used to prevent the full current of AC from killing you (often called a death cap which is a misnomer, its actually a life saver cap) The switch might have originally ben a polarity reversal switch. It looks like a spst switch now with the safety cap repurposed when the AC cord was switched to a 3 prong plug. Cant see where the other cap lead off the switch goes but it may be to the rectifier tube ground and is there to minimize hum without a dead short to the tube.

 

Other then the tone cap, Most of the other components look original.

 

Good find. Magnatone amps are pretty rare. Too bad it wasn't a higher end version that had true vibrato. Those are the amps that are in high demand and very expensive now but at least you get the tone of the brand. You may want to find an alnico Jensen or Utah speaker from that era for an even richer vintage tone. It will increase the value of the amp too.

 

You just saved me a weekend of tracing the circuit! Thank you (I know my family will)!

 

Power transformer is definitely replaced (doesn't look like any stock model I could find).

 

I noticed the solder on the ground wire and planned on reflowing this weekend. Agreed, it seemed sloppy (if I can do a better job, I KNOW there's a problem!).

 

Great speaker recommendations... and thanks again for the info!

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I'm not sure what the old Varsity sounds like, but Magnatone is back in biz. I was looking at their amps last year.

 

Chris Wood of the Wood Brother was using an old one the last time I saw them live.

 

The new ones are scary amazing sweet sounding and they should be, as they are not inexpensive amps.

 

Hope your new old amp sound killer.

 

 

 

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The new Magnatone, like the new Supro amps, are in name only and have no direct relationship to the venerable manufacturers.

 

Originally these were Dickersons [every now and then original Dickerson lap steels show up on Reverb.com], Dickerson sold the company around 1941, but they changed the company name to Magna Electronics when it was sold a second time around 1946.

 

These little low watt amps were often paired to Magnatone's line of lap steels. Dating the manufacture of these instruments and amps is virtually impossible, to the best of my knowledge, even though they are serialized, as no one seems to have the records on them anymore. I currently still have a working pre-'Starlet', circa 1948, that I picked up through Reverb.com a few years back, as well as a lap steel from approximately the same era that I found in a pawn shop in NM back in 1990; it is the oldest instrument in my collection. The guy who used to service my amps was a collector back then and 'schooled' me on the Magnatone story, so I'd been looking for an amp to match my lap for decades. Thanks to the internet, I did. These were considered extremely rare and highly collectible [as pairs in good condition] back in the pre-internet era. Now it seems there are far more still in working condition [or modified/upgraded condition like yours] than anyone was aware of...still, they are great little units. The amps have a very 'sweet' nature until you push them past about half way, then they start to growl...with an interesting breakup at peak volume... great amp to record a blistering solo with...

 

Magnatone, like many music manufacturers [i.e. Valco, Harmony, etc.] of the post-WWII era had limited advertising resources, and the bulk of their income was in building unbranded units and applying logos for other companies. But they built their reputation across a solid base, making student /introductory models and professional level models. The tremolo models, called F.M. Vibrato, [i believe for frequency modulation] that WRGKMC referred to came later in the mid 1950s, and that sound is nothing like the vibrato circuits of Fenders or other manufacturers of the era. Good luck finding those in working condition, unmodified, at a reasonable price...I have been looking for decades. Neil Young has one, Lonnie Mack had one...and apparently Young's amp tech was involved in the designs of the new Magnatone amps. Around 1955 Paul Bigsby [yes, that Bigsby] designed some electric guitars for Magna, the earliest example that I have seen is the Mark V [circa 1957], which looks remarkably similar to the early 1960s Gibson Melody Maker Double Cutaway model...

 

The MOTS look of these was also used on the radios, portable phonograph players and extension speakers built in the same factory here in Los Angeles.

 

BTW, the handle on your amp is a modern replacement, as is the grille cloth. The original handles were actually drawer handles for kitchen cabinets...a major cost saving, no doubt. Later ones were custom made; I have seen a number of variants in my research.

 

These are my 'Maggies'....

 

 

[ATTACH=CONFIG]n31887473[/ATTACH]

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BTW, the handle on your amp is a modern replacement, as is the grille cloth. The original handles were actually drawer handles for kitchen cabinets...a major cost saving, no doubt. Later ones were custom made; I have seen a number of variants in my research.

 

 

 

I suspected such... any vintage gear I've had in the past has been "straight"... maybe a recap or solder touch up. This is my first Frankenstein'ed vintage piece. Made in the mid-50's, modded in the early 80's, rocking strong in the mid 10's!

 

 

These are my 'Maggies'....

 

 

Beautiful!

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The mods done shouldn't affect the tone of the amp. They were necessary mods that made the amp safe to use. The PT is likely the correct voltage and that's all that matters. The output transformer looks original and that's when the amp gets its unique tone in conjunction with the power tube.

 

The circuit isn't much different then many old table top radios back in the day and the components used were stock parts you could buy at any electronics parts outlet like Allied Radio, Lafayette, and most radio TV shops. The fact that newer parts were used is unavoidable. There are some netter makers of power caps then the one used but I wouldn't bother with it unless you develop some AC hum.

 

The speaker will be the key component in getting a better vintage sound. The rest is mostly cosmetic so I wouldn't even worry too much.

 

If you can find one of these alnicos at a good price it should help giving you better saturated tones then a ceramic.. The new Jensens are very well made, better then many vintage Jensens I've owned. I have four of the 10" alnico's like this in a 4X10" I run with my Fender Bassman head and it definitely gives me those classic tones.

 

Theres a couple of the 8" seconds here for around $60 https://www.amazon.com/gp/offer-list...JV86E0FNYAWYF9 You just want to check the impedance.

 

[ATTACH=CONFIG]n31887604[/ATTACH]

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By the way, these are the ones that came to mind when I hear Magnatone. 1957 model being sold one EBay for around $2k

http://www.ebay.com/itm/1957-Magnato...3D162196066485

 

I read up on the circuitry awhile ago and the Vibrato is a very cool circuit design called Resistance-Reactance Bridge Vibrato Technique. It uses varistors to change the note pitch using frequency modulation.

 

 

[ATTACH=CONFIG]n31887634[/ATTACH]

 

[ATTACH=CONFIG]n31887635[/ATTACH]

 

[ATTACH=CONFIG]n31887636[/ATTACH]

 

 

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Yeah... that is a super cool amp. Of course, it is almost 10x what I traded for the 108. :-)

 

I know Phil checked out a pedal from Bigtone called the Maggie that was supposed to be based on the Magnatone vibrato in stereo... http://www.harmonycentral.com/expert-reviews/big-tone-music-brewery-maggie-sv280

 

Maybe it's time to check schematics!

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Nice little amp. That looks like it's the same design used on a number of low-watters - perhaps it was a Valco or some other OEM amp? Fender, Gretch and Gibson have recently released modern versions of theirs:

 

481209000136000-00-500x500.jpg

 

1951-Fender-Champ-600-Amp-Big.jpg

 

gretsch-g5222-electromatic-amp-79581.jpg

 

Of course yours is PTP, not PCB like the newer versions, making mods much easier to do on the originals.

 

The new Magnatones are designed by Obeid Khan, the same fellow who designed Crate's V series and Reason [http://www.guitarplayer.com/miscellaneous/1139/reason-bambino/12558] amps. I met him the year they launched the Magnatone reissues at NAMM and he really impressed me with how anal he was in getting as close to the original circuit as possible, notwithstanding the fact that some of the component's were no longer available. His amps sound so lush, warm and wonderful I can almost justify the huge price-tag they carry.

 

Supro's are Bruce Zinky amps that may or may not resemble the original Supro circuits. They're PCB, country of origin unknown, so they balance new with old.

 

Back in the day Supro's were low-cost mass manufactured department story fare. The fact they actually sounded good has more to do with how few components they put between the guitar and the speaker than any ingenious design. Mangatone, OTOH, were into some pretty advanced stuff with their unique take on their vibrato circuit, which is what makes them so lush.

 

Vintage Supro's can be had all day for under $600 and, because they're PTP, for another $200 you can replace most of the components and get a near new amp. Vintage Magnatones are very rare and command huge dollars from what I've seen.

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