Yamaha Guitars And Guitar Amplifiers 1968

Download the entire 12-page 1968 Yamaha Guitar/Amp Catalog (USA region):

DOWNLOAD: Yamaha_guitars_amps_1968_catalog

Models covered in this publication: Model 150, 120, 100, 80, and 60 Classical guitars.  Model FG-110, FG-150, FG-180, FG-230 steel-string acoustic guitars.  Model SA-50, SA-30, SA-70, SA-20, and AE-11 electric hollowbody guitars; and the TA-60 and TA-30 guitar amplifiers.

I have owned and used several of these instruments.  The electrics are really very cool, but keep in mind that most examples will need a neck reset and/or plane in order to play like a new guitar.  Dig that dark green finish on the bass though.  Killer.

It has often been noted that Jimmy Page toured with Yamaha acoustics in the early 70’s, which may be why Japanese Made ‘red-label’ Yamaha acoustics are currently in-demand.

Yamaha has used the term ‘natural sound’ for many decades to market a wide range of different audio gimmicks.  The only constant seems to be that ‘natural sound’ represents Yamaha’s willingness to try odd new things in a constant technological struggle to achieve more accurate sound-reproduction.  This early iteration of ‘natural sound’ seems to consist of these odd trapezoidal ‘happy-meal’ foam speakers.  We had one of these amps in our band back in the 90’s and it was heavy as a bastard and very dull-sounding.

Not sure if this was Yamaha’s own technology or if they licensed it from another firm.  In any event, these odd speakers made their way into an obscure Fender combo amp in 1969, the Bantam Bass.

(web source)

The Bantam Bass is essentially a Bassman 10 with one large foam speaker in place of four 10″ drivers.  It was a short-lived product.

Sears Silvertone Sound Systems 1940

Download a 17-page scan of the 1940 Sears Silvertone sound system catalog:

CLICK TO DOWNLOAD (10mb) : SearsSoundSystems1940

The PA, or Public-Address System, was still relatively new technology in 1940.

It’s hard for us to imagine any of the above scenarios without some sort of microphone/amplifier/speaker apparatus in play.  The human voice was not designed to clearly address dozens or hundreds of people who may or may not be paying attention.  Sure, we can yell pretty well; but the careful inflections of speech require an intimacy that cannot be accomplished on a mass scale.  Without some ‘reinforcement.’  Enter the Vacuum Tube.

I have owned quite a few of these antique units.  A few notable units have been restored; many more were gutted for parts, their chassis delivered to other uses.  One tip: beware the input transformers on these early PA units.  they are rarely magnetically shielded.  The physical orientation of the input transformer unit relative to the power transformer is crucial.   You can determine optimum positioning by placing your power transformer in the intended position.  Send 120V AC to the primary of the power transformer.   Then connect a low-impedance headphone (EG., a SONY 7506) to the primary or the secondary  of the input transformer (try both).  Now move the input transformer around relative to the power transformer.  If the transformer is unshielded, you will clearly hear an optimum (less hum audible) position.  This trick also works great for determining optimum output transformer position for hi-fi amps and guitar amps btw.

Polyfusion Modular Synthesizers

Polyfusion is an electronics firm in the Buffalo, NY area which began in the mid-1970s.  According to their very outdated website, their sole standard product these days is a frequency-shifting device intended as a feedback-reducer in (presumably voice-only) PA systems.   I do not know anything about these devices beyond what I have seen online, but I did recently come across a large folio of promo materials from the 1970s.  It seems that Polyfusion got their start making modular synths which were used by such folks as Vince Clarke, Ken Hemsley, Scott Humphrey, Masterworks, Steve Porcaro and Tangerine Dream.”

Anyhow.  Here is the 1977 Polyfusion catalog and pricelist.  Enjoy.  If anyone is interested: I also have another 24 pages of detailed specs on each one of the modules, so drop me a line if you want to see those too.

DOWNLOAD THE 6-PAGE SERIES 2000 CATALOG: Polyfusion_1977_catalog

RCA microphones catalog circa 1965

Click the link below to download the entire circa 1965 RCA microphone catalog.

DOWNLOAD: RCA_Circa1965_Catalog

A lot of interesting pieces here.  I personally love the BK5.

The BK5 is an unusually bright and aggresssive ribbon mic.  Highly recommended for…  pretty much any spot-mic task.  Hands-down better than the Royer R121.  And about 1/2 the price.  Not so reliable tho…  mine has broken twice in as many years.  but good god what a sound.  and the pattern is super-tight.

Where do you find all those old tubes?

When folks learn that I build and service vacuum-tube based audio equipment, some of the first questions they ask are: Is it hard to find those old tubes?  Where do you find them?  As it turns out, lots of different places.

The RelaxAcizor was, depending on who you ask, either a quack-medical/exercise device or a sex toy that was marketed clandestinely to women in the 1950s.  It consists of a voltage amplifier in a chassis with a series of electrodes that attach to the (female) body on numerous pads.

Looks fairly horrifying.  Anyhow, using dials on the amplifier-unit, the user can vary the amount of voltage that the various muscles experience.  The result?  The manufacturer claimed that it would lead to ‘effortless weight loss.’  But as Peggy Olson experienced in episode 1.11 of MADMEN, it is more likely to lead to orgasm.

(Peggy Olson, noted audiophile.  WEB SOURCE)

Anyways… I bought a partially-disassembled RelaxAcizor for a few dollars at the flea market yesterday.  It was oddly missing its case, so the rear of the chassis was exposed.  This is a crucial point.  Because the innards of the unit were visible, I was able to see that it contained a VT-52 tube.

The VT-52 is a very valuable and useful audio tube.  It’s basically (BASICALLY..) a 2A3 designed for 6.3v through 7v filament voltage rather than 2.5 volts.    This tube has a huge cult following.  Check out this deep website dedicated solely to the VT52. I love the sound of the 2A3.  My main home-music listening amplifier for the past 5 years is a stereo 6SL7/2A3 amp that I built based on a schematic from Angela dot com.  There are a ton of great, simple schematics for Single-Ended high-fi amps that use the VT52 as the output tube; and unlike the 2A3, which requires an unusual filament voltage and requires an unusually low output transformer primary, it appears that the Vt52 will work fine with normal ‘guitar-amp’ type 5K Output transformer.  Directly-heated Fender Champ?  Yes I think so.  I am inclined to recommend this schematic over the others.  The 2A3 likes to be fed by a low-impedance signal and I would bet that the VT52 is similar in this regard.

Carving up the RelaxAcizor also resulted in this nice wrinkle-finish chassis, which will find a good home someday in a a future project.  E commented that perhaps I cut up the unit because I felt threatened by it.  Well, either that, or the fact that VT52 tubes go for upwards of $100 on eBay.  $300 if they are W.E. branded.

Alright so what’s the point?  Search web forums and you will be told that the VT-52 is a very rare, mysterious tube.  OK.  But consider that over 400,000 RelaxAcizors were sold in the US.  That’s a lot of expensive directly-heated triodes sitting, hidden, in junk piles throughout this country.  So get digging folks.

One warning:  you might have a hard time prying the R/Z from the hands of this lady.

Scully 280 tape machines. Not Preserved.

Scully was one of the main US makers of professional multi-track tape machines through the 1970s.  Scully was based in our fair city of Bridgeport CT.  Wikipedia has no information on this classic manufacturer; in fact, they incorrectly identify it being from ‘bridgewater connecticut.’  I’ve been slowly accumulating archival material on this company and hope to have a comprehensive treatment together at some point.

Earlier this week I bought a full truck load of old Scully and Ampex tape machines for a few bucks (no joke).  I think that there were about four Scully 280 2-track machines, several Ampex 351s and PR10s, a 16-track scully 2″ machine, and a few other odds and ends.  My truck is currently out-of-commission awaiting some parts, so I was limited to taking just the stuff that would fit in my VW.  This meant leaving the transports behind and just taking the electronics portions of a few of the machines.

The most exciting piece is this Ampex 3761.  It needs a complete restoration (nearly every part and connector is rotten), but the chassis/faceplate and UTC transformers are intact, so I think I will give it another life.  The 3761 is not a particularly useful device, but it does have an incredible pedigree.   It is a four-into-one microphone level mixer which uses the excellent 5879 pentode tube, and some of the best input transformers that UTC (or anyone else) ever made.  The 3761 was used in order to mix four microphones onto one track of an Ampex tape machine (in fact, it gets its power from the tape machine).  And what recordings were made using these devices?  How about most of the classic STAX recordings.  Good God.

Anyhow, seems like this thing deserves another chance.

How about the rest of that stuff though?  It all dates to around 1965-1970.  None of it seems to have been maintained since 1990, and everything was generally filled with dog hair, dead bugs, and bits of food that (presumably) mice secreted away in there.  Yes it was really that nasty. So i was not about to risk a major biohazzard restoring this stuff.  The only other option:  Chop it up.

Each of the 280 chassis contain a number of excellent hermetically-sealed transformers: a UTC A18, UTC A39, and a very large Freed 600:600 (split) transformer. I have yet to find a UTC A-series transformer that did not work, so I am reasonably optimistic.

Three of the 280s also had a UTC 0-1 500:50K input transformer.  Many of the 280s also had clean XLR jacks, lamp holders, and API VU meters.  So it was a good harvest in general.

I do feel a little guilty about chopping up these classic units, made with care here in BPT; but I have a plan to earn back the audio karma.  Once I can track down the schematic for the 280, I will clone the mic pre-amp circuit, and build a few stand-alone 280 clone pre-amps using the original transformers, meters, and whatever other cosmetic parts that I salvaged.  I have been waiting for the right solid-state pro-audio project to present itself, and I think it found me.

It was a little painful to dumpster the carcasses; I felt a little better after K told me that someone shortly thereafter pulled them from the dumpster, shouting excitedly that they were brass, and therefore valuable for salvage.  One person’s junk…

Premier 88: ready to go.

After probably 14 hours of work and $200 of parts, my Premier 88 is working 100%.

As I described in an earlier post, the Premier 88 is a rare and highly unusual instrument amplifier from the 1950s.  It consists of an amplifier unit and a speaker unit; but rather than the amplifier unit sitting atop the speaker, like most every other 2-piece amp, the 88’s amplifier sits beside the speaker cabinet.  The two sections clasp together with luggage latches.  It moves as one (very large and heavy) piece.

This odd side-by-side form-factor is not the only unique feature of the 88.  Check out the control panel.  Rather than conventional bass/middle/treble knobs, the ‘instrument’ channel of the 88 has 5 organ-stop-type levers that can be switched in or out.  Each lever is a bandpass filter.  IE., if you depress all 5 levers, you get the full tonal spectrum.  If you depress none of the levers, you get silence.   The ‘Microphone’ channel also has a pair of unusual tone control switches; they seem to be hi-cut filters.

Here are some examples of the sounds that the 88 produces.  Right channel is an SM-57 close to the speaker; Left channel is a 414 in omni approx 10 feet away.

LISTEN:  Low_and_High

Listen: Mid_only

The trem is super weird and extreme. Here are a couple of examples:

Listen: Trem_low_settings

Listen: Trem_HighSpeed





In all honesty, this amp was a pain in the ass to service.  When I first brought it into the shop, it did turn on and pass signal; the tremolo sort-of worked, as did all of the tone controls.  It just sounded terrible and it had no output.  The longer it ran, though, more and more parts seemed to fail, starting with B+ resistors and then moving on to the 50 year-old tubes.  So eventually I ended up replacing most of the components in the amplifier.

When I first opened it up, I saw tha someone had added a Pilotuner mono FM receiver to the speaker cabinet.  I removed the tuner, and I then had to fabricate cover-plates for where the tuner face and tuner knobs had been.  I used aluminum plate stock.  That was the first piece of work.  And then:

*replaced the 15″ Jensen Alnico speaker with a new Jensen 15″ ceramic (there was a weird rattle in original speaker)

*replaced all electrolytic capacitors in amp (approx. 20)

*replaced all B+ and plate-mixing resistors in upper preamp chassis (approx 15)

*replaced all caps in tremolo circuit (some needed to be replaced twice in order to get the right response)

*clean all tube sockets and replace 3x 12ax7 in pre-amp.

*add grounded AC line to power amp chassis

*replaced 6L6 and 5U4 and 12au7 tubes in power amp chassis

Good lord.  Was it worth is?  Who knows.  Once you start a restoration like this, you kinda just need to push on through until it’s done done done.  This is possibly the only working example of this amp in the world, so I felt like it deserved a chance.

The repair was difficult owing to 2 conditions:

*There is no schematic available for this particular iteration of the Premier 88, and the pre-amp is extremely complex owing to the bandpass filter arrangement.

*The amplifier is split into 2 sections: The top half is the pre-amp and trem circuit, and the bottom half is the phase inverter, power amp, and power supply.  These two sections are joined by two cables: a shielded RCA line (audio signal) as well as an octal snake that carries B+, ground, heater lines, and tremolo defeat control.  Owing to the extremely short length of these two cables and the manner in which they pass through the tight trapezoidal enclosure,  the preamp cannot be operated unless the unit is fully assembled.  So… the preamp circuit cannot be operated while its circuit is accessible.

Now that all is said and done, it is clear that I would have benefited from making an octal extender cable so that the preamp circuit could be accessible while active.  Hindsight is of course 20/20.

A few things other repair tips that this repair has illustrated:

*If you are missing a schematic:  don’t assume that the plate resistors for 12A_7s are 100k ohm.  The 88 had 270k ohm plate resistors.  Generally speaking, when i get an old, noisy amp, I just replace all the 100k resistors, assuming that these are the plate resistors.  Bad carbon-comp plate resistors are often the source of weird intermittent noise in guitar amps.  But not in this case!  Premier used 270k ohm.

*Alnico speakers definitely sound better than ceramics for old guitar amps.  I always suspected this, and now I am convinced.  Wish I had sprung for the extra $100 for the Alnico Jensen.

*Don’t assume that working tubes can’t be causing weird intermittent problems.  I am generally pretty trusting of working preamp and rectifier tubes, and  I am often quick to assume that B+ resistors are bad, when i fact, it COULD also be the tube…



Weekend Update With(out) Dennis Miller

Damn that dude was funny.  Heard he became/was-always a major reactionary.  Anyhow, PS was not updated this weekend because…  this weekend was ‘open studios’ in scenic Bridgeport CT.  My shop is located in an Arts-Space building, and we opened the doors to all comers this weekend. As always, met some real characters, and got to know the other folks in the bldg a little better.    If you came by and rapped with me…  thank you.  Hope you enjoyed the event.

E and I like to ‘work-through’ these open-studio events; keep it productive while taking the time to speak to anyone interested in our arcane activities.  You likely know that I am involved in the creation and servicing of tube-based audio equipment; E is a letterpress printer.  During these open-studio working-sessions, E refers to our spot as ‘Sturbridge Village‘, and I find this hilariously accurate.

(This is from Sturbridge Village, not our shop.  But u get the idea)

ANYhow… point is…  I actually got a lot done this weekend due to the fact that I was forced to be in the shop for two entire days straight.  This week, we will look in-depth at…

..the Premier 88. Which is finally F’ING DONE!  and oh my god does it sound killer.  Also….

…Repaired/Restored a Magnecord PT-6 all-tube pro reel-to-reel recorder (circa 1950).  This was a great find that turned out really well.  It is up and running 100% after a little attention and…  114db mic pre amp?  What the F?  But it sounds great.  Also….

…the Mic PreAmp saga continues.  Completed my 3-stage Pentode pre-amp.  This is the culmination of years of experimenting with various ancient broadcast preamp ideas, and… so far, so good.  It works well. Next step…  frequency sweep tests.

I hope to cover all of this (and more…) this week.

ICON: Marshall Amplification

What greater visual icon for the mythic virility and power of the circa-1970 Rock-Star than the “Marshall Stack?”

(web source)

(web source)

(web source)

Jim Marshall was a drum-shop keeper in London in the mid-60’s who began cloning the 1959 Fender Bassman amplifier in order to give British Musicians the popular American-Amplifer sound they wanted at a lower price made possible by domestic UK manufacture.

By around 1968 he had arrived at the classic Marshall formula of a simple Fender-derived circuit using 4x EL34 output tubes, Drake transformers, and a head unit sitting atop 2 large sealed cabinets each holding four 12-inch speakers.  It is the use of the EL34 tubes (rather than Fender’s 6L6s) , with their greater power and gain, along with the ‘tight’ bass response afforded by the large speakers in the sealed boxes, that are most responsible for the ‘Marshall’ sound.

It is said that Pete Townsend was the impetus for the large human-height ‘stack’ aspect of the amplifier.  The form of these things certainly suggests the huge volumes of sound/noise that they can produce.    A great many bands used the ‘Marshall Stack’ in the 1970’s.

Nowadays, the ‘Marshall Stack’ is generally only used by true hard-rock and Metal bands, as well as the occasional ironic user.  Well, maybe ironic.  Who knows.

(web source)




Today we will look at some early 70’s Marshall promotional material from the PS pile/archive.

Click on the link to download the entire 20-page 1971 full-line catalog: Marshall_1971_cat

Some circa 1970 Marshall oddities.  I have never come across any of these for sale anywhere.  Anyone?

20-channel Marshall ‘festival’ mixer.

400-watt Marshall PA rig circa 1971.  The Mixer unit actually had some pretty intelligent features for the day, like a 2-watt headphone amp with a simple single  knob to cue any individual channel or the mix buss.

And who used this stuff?  Joe Cocker, apparently.

Marshall even marketed a Microphone at the time. The Model 3700.  Looks shitty. It is nearly impossible to research this unit due to the fact that an entire line of Marshall (no relation) Mics is currently being made.  Killer mic box, tho.

….And don’t forget the Marshal Super-Sound T-shirt.  Wow.  What can you say about this ad.  Note that only small and medium are on offer.

The Marshall Artist does turn up from time to time.  I could get into one of these.  Seems to be like a BluesBreaker plus reverb.

We’ll close this out with a couple of original pricelists:  USA 1972 and Germany 1974.   A reality check:  the ‘stack’ of a 100-watt head plus 2 4×12 cabs was listed at $1600 in 1972. This equals $8629.69 in current US currency.  Even allowing for usual 40% retail price deduction, that was still a $5000 amp.  Good lord.

DESIGN ICON: MXR audio effects in the 1970s

MXR Innovations began making their first product, the Phase 90 phase-shift pedal, in the early 1970s.

(web source)

Phase-shift is an audio effect which adds a gentle ‘swirl-y’ motion to a sound.   The sound of a clean electric guitar picking through a chord progression with a phase-shift effect is one of the truly definitive sounds of 70’s rock music.  Listen to the rhythm guitar part in this long-haired chestnut and you will hear what I am talking about.

MXR did not invent the phase-shift effect, but their Phase-90 did more to popularize it than any of its predecessors.  MXR’s real ‘innovation’ was the high-quality, small physical size and indestructible nature of the device.  In contrast, previous phase-shift pedals tended to be bulky, noisy, and not especially durable.

BTW, the MXR phase 90 is still made today, 40 years later; and it is still in wide use.  MXR Innovations no longer exists as a corporate entity; the brand-name and trademark were sold in the 1980s to the Jim Dunlop Corp, who now manufacture Phase 90 pedals in various subtle varieties.

A book could be written on the history of MXR, and it is not my intent here to share that long and fascinating story.  If you are interested in the details, I highly recommend Tom Hughes’ excellent book “Analogman’s Guide to Vintage Effects,” which features candid long-form interviews with a few of MXR’s founders.  This book is a must-read for anyone who uses audio-effect processors in their work.  Thorough and essential.

Anyhow, let’s just take a moment to celebrate the incredible and powerful industrial design and graphic design of the iconic MXR brand.  In a previous post, I included a scan of one of the early MXR ads.  It still looks beautiful and evocative today, 35 years later.  Everything that these guys did in the 70’s was done with care and attention to detail. Consider these c.1980 MXR dealer-support materials, including a full scan of the circa 1980 full-line catalog (16pp).


From the Hughes book, in the words of MXR founder and Phase 90 creator Keith Barr (later, founder of Alesis (!)):

“I mean, to me, MXR was an art project.  Yeah, it was a business, and yeah there was the little game to see how cheap we could make a unit, but still make it reliable…Richard was the guy who was really into the sound, I was the guy who was into clever design, Tony was the guy who was into digital circuitry, and all of us were into…that’s why they ended up calling there company ART, A-R-T.  We had this idea collectively that what we were doing was an artistic expression; it was the way this thing was packaged, the way it looked, the way it felt- all these little things made up what it is” (Hughes, 234).

Oh yeah… in case you were wondering… not only did Barr go on to create Alesis (the company that literally changed the world of home-recording forever with it’s ADAT digital 8-track),  the other MXR designers Richard Neatour and Tony Gambacurta created ART, arguably the most innovative guitar effects company of the 1980s and 1990s; and Mike Laiacona, MXR’s first salesman, created Whirlwind, which is still one of the major forces in meat-and-potatoes basic pro-audio hardware.  Incredible.