Categories
Technical

Add Vibrato (?) To Any Tube Amp! (1962)

Download a short article from 1962 by one F.H. Calvert on the subject of adding a vibrato circuit to any vacuum-tube audio amplifier:

DOWNLOAD: Vibrato

Above, the schematics.  These are not plans for a stand-alone device: rather this circuit (the schem on the left) is intended to be added to any resistance-coupled voltage amplification stage (for instance, the circuit on the right).  It requires an extra single hi-mu triode section.  The author suggests 1/2 a 6SC7 or 1/2 a 6SL7, but it would presumably work just as well with 1/2 a 12AY7 or 1/2 a 12AT7, with maybe just a slight change to the 2.2K cathode bias resistor (can anyone tell me what the single-triode sub-miniature equivalent of the 12AY7 and the 12AT7 are?  Do they even exist?)  I have not built this circuit yet so no promises.   A few observations tho:  I find it hard to believe that this is actually a vibrato device; it seems like it’s likely a tremolo circuit.  It looks very similar, in fact, to the trem circuit in the ole 18watt Marshall combo. Also: if it’s worth building, it’s certainly worth adding the speed variation pot.  Contrary to what the author suggests, my best guess would be to replace the left-most 2M resistor with a 2M pot PLUS a fixed 470K resistor in series. Def gonna try adding this to the next Recycled Champ that I turn out.

Categories
Concert Sound Guitar Equipment Publications

Out-of-print Book Report: “Professional Rock And Roll” (1967)

Download a six-page excerpt regarding ‘the sound system’ from “Professional Rock And Roll” (Ed. Herbert Wise, Collier, 1967):

DOWNLOAD: Professional_Rock_And_Roll_Excerpt

Very much along the lines of “Electric Rock” (1971)  and “Starting Your Own Band” (1980), “Professional Rock And Roll” (h.f. “PRR”) is especially interesting in that it was published a mere three years after The Beatles appeared on Ed Sullivan, an event which is widely considered to have marked the beginning of The Sixties Rock Era.  In such a short span of time, enough of an industry and codified set of working-practices seems to have formed around young teen-oriented electric-guitar-based groups to have resulted in the large paperback that I now hold in my hand.

“PRR” parses the idea of what it takes to be a ‘professional rock and roll band’ in some interesting ways.  There is the chapter on PA equipment, with the various above-illustrated items discussed (BTW, I still regularly find most of these items at the estates+fleas, so points to the author for accuracy), as well as a chapter each on Electric Guitars and Keyboards.

Above: the three types of Electric guitar: ‘Early,’ ‘Solid Body,’ and ‘With Accessories.’

Above: The Rock Organ Player

We also get chapters on putting a band together, chords, songwriting, lead-singing, hitting-the-road, and managers/agents/publishers.  Somewhat more surprising is the in-depth chapter on how to locate and buy stage-clothing and the chapter on light-shows.

I think it’s somewhat interesting to learn how important the idea of visual-accompaniment-to-music was in those early years of the Rock industry.  We’ve been told so often how MTV changed the visual/sonic balance of musical-signification so drastically, to such varied effect as manufacturers’ increasing the size of their logos on equipment (E.G., Zildjian Cymbals) and even the barring of rock-stardom to homely female performers (I.E., the Janis-Joplin-wouldn’t-have-made-it-today assertion).   I can’t really say that this changes the argument, but it’s worth consideration.

“PRR” also has a number of charming anachronisms, such as the diagram above.  The authors felt it necessary to explain how a group should properly stage their gear on BOTH of the common types of stages: the theatre-type stage (band faces the audience) and, of course, the round stage.  Wow.  Were rock-shows on round-stages really that common in 1967?  I’ve performed probably a thousand shows since the early 1990s, in venues as small as basements and as big as 10,000+ festivals, and never once on a round stage with the audience on all sides.  Crazy.

Perhaps the most interesting thing about “PRR” is the subject that it totally omits: there is nothing offered on the subject of recording.  Not demo recording, not studio recording.  No mention.  Also lacking is a chapter on promotion and publicity.  To most musical groups today, these seem to be the central issues that occupy most of their energy:  thanks to all of the incredible, affordable audio-recording equipment and software we have now, recording and composing music have effectively become the same task; they are inseperble activities.  Likewise, the public promotion, marketing, and branding of a musical project can now begin as soon as the first track is mixed down.

*Is there a similar book to “PRR” published for the modern musical era?

*If a high-school age band were today to study and implement the ideas in “PRR,” could they generate a 1968-type garage-rock group?

*Did anyone reading this purchase “PRR” as a young musician?  Did you find it helpful?

Next up in this series: “Making Four Track Music,” John Peel, 1987.

Categories
Guitar Equipment

Martin Electric Guitars of the late 1970s

Download the four-page c. 1979 Martin Electric Guitars catalog:

DOWNLOAD: MartinElectricGuitars1979

Models covered, with text, specs, and photos, include: Martin E-18 electric guitar, EM-18 electric w/upgraded electronics, and EB-18 electric bass.

The 1979 Martin EM-18

With their entry in the ‘Hippie Sandwich’ runoff of the late 1970s (see: here, here, and here, to name a few), Martin got into the solidbody electric guitar fray for a few years.  I have never played one of these; anyone?

One example currently on GBase for $1.5k.

Categories
Guitar Equipment Technical

Magnasync Moviola URS as a guitar amp – UPDATE

Magnasync/Moviola was a Los-Angeles based manufacturer of film editing equipment.  They did make a few audio products designed to support the large upright and flatbed Moviola film-editing machines which were their main products.   The most common of these audio-products is the URS 5-watt tube amplifier with built in 4″ AlNiCo speaker.  The URS apparently debuted sometime around 1955.

I recently purchased a pair of these things for a few bucks.  Aside from needing new pilot bulbs and some contact cleaner in the volume pot, they seemed to be working alright.

The rear of the unit (not shown) has a 1/4″ speaker jack (labeled ‘Headphones” which mutes the built in speaker when a cable is inserted.  Other than that, though, there was no obvious input jack.  There is a 4-pin amphenol jack with DC present on 3 of the pins.  the 4th pin is the audio input. Ahh Ok.    There is a also a single-pin DC power connector/takeoff?  Not sure.

Anyhow, kinda irrelevant.  Since no one is going to be using these things with an actual Moviola sound-head, figured I would just make em into lil guitar amps. OK it’s gonna get a little technical here, so pls skip the next paragraph if you wanna just get to the sounds…

Since the tube compliment is 7025 (aka 12AX7) – into 6AQ5 power tube (aka basically lower-voltage rated, small-bottle 6V6) with a single volume pot between the two 7025 stages, this thing is basically…. a tweed fender champ.  Yes, there are some important differences – different plate resistor values, no cathode bypass caps on the preamp stages, and i think some frequency compensation in a the feedback loop?  But basically a tweed champ.  ANYhow…  Following the advice offered here, i put a 1/4″ guitar jack where the single-pin power socket had been.    Then i simply added the other basic components of a Fender guitar-input-stage:  a 1m resistor to ground, and a 68k resistor between the input and the grid of the input tube stage.  Replaced the 2-wire AC cable with a 3-wire grounded cable, and done.

There is plenty of talk on the web about these things…  lotsa folks have converted these to guitar amps in the same manner that i discussed… and people seem to be very happy with them.    Check out this fellow’s work. He did an especially thorough job.  I was personally kinda shocked with the sound that it makes.  Never in my life have i heard so much distortion and fuzz out of an amp.  It really is, pardon my language, fucking insane. Here’s 3 sound clips.  (Gibson Firebird gtr.   SM57 3″ in front of the speaker, into MBox.  ‘Clean’ and ‘Overdrive’ examples have analog echo pedal between the guitar and the amp.  Fuzz is just the amp.  No other eq or processing applied).  Check it…

Clean: Magnasync_URS_clean

Overdrive, fingerpicked: Magnasync_URS_overdriven

Fuzzed out (max volume): Magnasync_URS_fuzz

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UPDATE:  One of the two URS conversions that I built was purchased by producer P.K.  for use on an album project with a new band out of London.  When the record comes out (assuming the URS tracks make the final mix), I’ll post links to the cuts here so that y’all can hear the sound of these fantastic little amps in-context.

Oh and about that other URS conversion that I built: as of today, it is still on-sale at Main Drag Music in Brooklyn NY for a mere $250.  Call or email them if yr interested.