Hey, I built a Sinclair version of a cheap kit puter ("ZX81"). Programmed an assembler for it too as you did. All the source code for my assembler, though, had to be entered into REM statements at the beginning of a BASIC program and only opcode HEX words, constants, and some variable names could be used but not opcode mnemonics (so a kind of hack assembler).
Mee too. I bought a pair for $5 at a flea market in Massachusetts. All the guy selling could tell me about the unmarked cabinets (with an apparent quality to their build) was "they sound good". Whelp, the family I was part of then needed a dining room table / chairs, so out went the Tannoy fortune to help pay for that.
50 years ago my speaker cabinets came in two flavors. A big box with four 12 inch Utah guitar speakers, uh for playing the guitar loud. The other flavor had a single 15 inch woofer for the dance floor. Treble, who needs it? Miami had a large Spanish population and Latin / Cuban disco was already booming (literally) in the early 70's. I cloned nearly every Tiger that SWTPC made except for the Tigersaurus, but I shelled out well over $1K for their MC 6800 computer kit and terminal in 1975. I had it playing some real basic Chiptune music after about a year of tinkering with machine code. A $1 Pic Chip would crush it today.
Back in the day David Weems was some kind of Guru, same as SWTPC "Tigers" .
Not much information elsewhere.
Mainstays were the excellent Philips Netherland technical books, solid RCA Power Electronics, some from Motorola and excellent information from Wireless World, where the Gods used to write.
Built as much as possible from those sources.
Not much information elsewhere.
Mainstays were the excellent Philips Netherland technical books, solid RCA Power Electronics, some from Motorola and excellent information from Wireless World, where the Gods used to write.
Built as much as possible from those sources.
Not quite 50 years ago while a poor uni student I put together a kef concerto kit using the b139, b110 and t27 combo. My father helped me make sense of the crossover parts. A couple of years later after my cousin built a set, I bought the drivers and crossover for the Chris Roger’s pro9TL with the enclosure made from local chipboard etc. Only sold them a few years ago to pursue tube amps and smaller full range speakers, still TL.
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I stuffed some 8" fullrange speakers from radio shack in my first car
actually a truck. Woke up pretty good actually.
People thought I was crazy putting "ceiling" speakers in a car.
My dad taught me and I slightly understood sensitivity rating.
So I got the biggest speakers with highest sensitivity that would likely
fit in the door. Far as my knowledge went in those days.
Most my early projects were radio shack speakers.
First 3 way was 12", 5" with whizzer and soft dome tweeter.
And used the 3 way crossover from radio shack as well.
Big upgrade to the tiny shelf speakers I used since I was a kid.
The bass made the needle skip on my turntable.
Had to move the speakers off my dresser and hung them
on the wall, little higher than ear level
made even more bass. Was default party speakers
when I moved out.
Eventually added same soft domes to the truck
with radio shack 2 way crossover.
Vocal / drum cymbals clarity was actually impressive.
The 8" already installed made darn good bass.
actually a truck. Woke up pretty good actually.
People thought I was crazy putting "ceiling" speakers in a car.
My dad taught me and I slightly understood sensitivity rating.
So I got the biggest speakers with highest sensitivity that would likely
fit in the door. Far as my knowledge went in those days.
Most my early projects were radio shack speakers.
First 3 way was 12", 5" with whizzer and soft dome tweeter.
And used the 3 way crossover from radio shack as well.
Big upgrade to the tiny shelf speakers I used since I was a kid.
The bass made the needle skip on my turntable.
Had to move the speakers off my dresser and hung them
on the wall, little higher than ear level
made even more bass. Was default party speakers
when I moved out.
Eventually added same soft domes to the truck
with radio shack 2 way crossover.
Vocal / drum cymbals clarity was actually impressive.
The 8" already installed made darn good bass.
In '75 I built a pair of 12" 3 ways for a friend using Marsland drivers.
It was my first and last attempt to design and build a passive crossover, including winding the inductors.
Wasn't easy but eventually got them to sound OK. Driven by a pair of SWTPC plastic tigers and a Dynaco preamp kit.
Couldn't help but think the whole concept of a passive crossover was BS.
Only built speakers with full range drivers before and after that until recently getting into active XOs.
It was my first and last attempt to design and build a passive crossover, including winding the inductors.
Wasn't easy but eventually got them to sound OK. Driven by a pair of SWTPC plastic tigers and a Dynaco preamp kit.
Couldn't help but think the whole concept of a passive crossover was BS.
Only built speakers with full range drivers before and after that until recently getting into active XOs.
1972 starting point a Tesla turntable+ Philips widerange in 15 mm chipboard enclosure from re-purposed miniature railway table,driven by 6+6 watt module of obscure Japanse origin.
1973 Goodmans DIN 20 kit: some 15 Pound Stirling a set, plus BSR Turntable with Goldring cartridge. After the umpteenth blow up of the Elektor Ekwa, Bi-Pak 12 Watt RMS modules proved to be undestructable. The BSR was replaced by an ERA 444 with Shure M95 that same year. Then came Thorens.
From 1976 the Pro9 TL (B139/KO40MRF/HD25)ruled for some time, driven by Crimson CE608.
Between 1978 and 1982 I built quite a few ca 45 liter 3 ways using either the KEF DN 12 or the IMF TLS 80 x/o with Philips 10100W8 Woofer/various Audax 13 cm mids (bextrene or paper plus various 25mm domes. Those systems sounded surprisingly good.
1973 Goodmans DIN 20 kit: some 15 Pound Stirling a set, plus BSR Turntable with Goldring cartridge. After the umpteenth blow up of the Elektor Ekwa, Bi-Pak 12 Watt RMS modules proved to be undestructable. The BSR was replaced by an ERA 444 with Shure M95 that same year. Then came Thorens.
From 1976 the Pro9 TL (B139/KO40MRF/HD25)ruled for some time, driven by Crimson CE608.
Between 1978 and 1982 I built quite a few ca 45 liter 3 ways using either the KEF DN 12 or the IMF TLS 80 x/o with Philips 10100W8 Woofer/various Audax 13 cm mids (bextrene or paper plus various 25mm domes. Those systems sounded surprisingly good.
The picture on the front of the Weems book reminded me of some other "dawn of disco" era speakers that I made. What do you make when you have a bunch of plywood offcuts from a guy who re-roofed houses, some odd colored Naugahyde and Crushed Velvet from waterbed and bean-bag chair factory. You also work in an Olson Electronics store where you can get car stereo speakers cheap. I made several sets of these over a two year period from whatever material I could scrounge. They were scientifically designed to be the biggest box pair possible from a given pile of plywood. No other design criteria was used. The pair seen here were part of a set of 4 identical cabinets, but someone actually stole the pair that I would set on top of my 1965 Dodge Dart when we had parties at Dania Beach. These were found when I cleaned out my warehouse before moving north in 2014. Would they still play? I hooked them up to a guitar amp and they got to eat some of my lousy guitar playing for a few minutes at moderate volume. Failure of the blue foam surround was obvious, so I plugged in a bass guitar, dimed the volume knob and covered my driveway in blue confetti, then threw them in the trash.
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50 years ago the idea of portable entertainment was a dream for many of us, who liked to party in remote areas. All my stuff ran on 117 VAC. At 17, I didnt know how to make a switching converter that would pump up +12 into the higher voltages needed by a power amplifier.
My father had a small box that he'd use to run his electric shaver in his Volkswagon Beetle; apparently he was in a hurry some mornings. I remembered it made this buzzing sound, from its mechanical actuator, which switched the +12V input back and forth between a center tapped primary. I remember the contacts would arc, like the brushes on an AC/DC motor. I found it stashed in the basement and wondered if I could replace the buzzing element with transistors?
A schematic of a transistor "multivibrator" circuit looked about right, with the cross-coupling resistors and all. I knew Radio Shack sold such a thing for about $50. So I got some big transistors my father brought home from work, put them on heatsinks and wired it up. Just the transformer, the transistors and a couple resistors. Turning it on, it actually multivibrated and at about 60 Hz too. What luck!!
I put it in a wood box with a meter that read the AC voltage, two binding posts for the +12V connection. Its debut was in a Ford Van, running my AC powered Teac tape deck and an AC powered EV receiver, into I cant remember which pair of speakers. It presented an amusing anomaly; when the van was driving uphill the music would play a little flat or slower, going downhill it would play sharp or a little faster. At least that's what I thought I heard - who knows what we were all "on", on that drive -
Arriving at an outdoor park where the party was set to take place, I discovered AC already provided - so my contraption wasnt needed. At some point, someone in charge of the place decided that they'd cut the AC powering the music at these teenagers party. A few minutes later, the music was playing again. Not as loud as via the main AC, but still came back on again. Ha!
I never did fix the frequency shift with input voltage issue. The little device even operating at all was quite a gift, which I squandered instead of developing through my upcoming 4 years at University as a power conversion electronics focus.
My father had a small box that he'd use to run his electric shaver in his Volkswagon Beetle; apparently he was in a hurry some mornings. I remembered it made this buzzing sound, from its mechanical actuator, which switched the +12V input back and forth between a center tapped primary. I remember the contacts would arc, like the brushes on an AC/DC motor. I found it stashed in the basement and wondered if I could replace the buzzing element with transistors?
A schematic of a transistor "multivibrator" circuit looked about right, with the cross-coupling resistors and all. I knew Radio Shack sold such a thing for about $50. So I got some big transistors my father brought home from work, put them on heatsinks and wired it up. Just the transformer, the transistors and a couple resistors. Turning it on, it actually multivibrated and at about 60 Hz too. What luck!!
I put it in a wood box with a meter that read the AC voltage, two binding posts for the +12V connection. Its debut was in a Ford Van, running my AC powered Teac tape deck and an AC powered EV receiver, into I cant remember which pair of speakers. It presented an amusing anomaly; when the van was driving uphill the music would play a little flat or slower, going downhill it would play sharp or a little faster. At least that's what I thought I heard - who knows what we were all "on", on that drive -
Arriving at an outdoor park where the party was set to take place, I discovered AC already provided - so my contraption wasnt needed. At some point, someone in charge of the place decided that they'd cut the AC powering the music at these teenagers party. A few minutes later, the music was playing again. Not as loud as via the main AC, but still came back on again. Ha!
I never did fix the frequency shift with input voltage issue. The little device even operating at all was quite a gift, which I squandered instead of developing through my upcoming 4 years at University as a power conversion electronics focus.
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Back in the dark ages people wanted illegal booster amps for their CB radios. Lots of pricey but poorly designed junk stepped in to fill the void. The Fantom 500 was one of the biggest examples. Why would you use 4 big 24LQ6 sweep tubes to boost the 4 watt input to a sufficient level to drive 6 more of the same tube to 500 watts? Because you had no clue how to match the RF impedances, and no way to measure anything if you actually understood what you were doing. The Fantom and all those like it ATE sweep tubes like a big hungry dog with a stolen steak. This is why there are two kinds of sweep tubes, those that were used in these amps (rare and expensive) and those that weren't (plentiful and cheap). Those choices seem to have been made based on what the original "designer" had available to him at the time. If someone who understood RF created such a beast, he would have used a single 6146A to drive a 4-400 to about 1 KW of RF power on 3700 volts.
Once there was a suitable quantity of one and two tube amps to copy that actually worked, the next step was to create a mobile power supply. The "designers" that had two working brain cells had the intuition to simply clone the power supply from a marine or ham radio that used one or two sweep tubes in its transmitter. Around the same time (mid 70's) a local marine radio company was revamping their product line and the old HF vacuum tube marine radio was discontinued and the power supply parts hit their dumpster and the surplus market. It was a simple matter to rip the HV winding off of the toroid and wind a secondary to make me +/- 40 VDC. That's when the 73 Chevy van started rocking. It had 8 X Plastic Tiger clones, one for each speaker and a Universal Tiger feeding the 15 inch sub under the bed. The van also featured a "Concord" (Olson house brand, made by Nakamichi) home cassette deck mounted upside down in the overhead console.
The power supplies robbed from these mobile radios and CB amps operated in the audio frequency range (about 2 KHz) to avoid melting the slow germanium transistors that were used for their low VceSAT. The best solution I found was to mount a pair of these switchers in front of the radiator under the hood with LPF's at the source, and more at the power entry point into the van.
Once there was a suitable quantity of one and two tube amps to copy that actually worked, the next step was to create a mobile power supply. The "designers" that had two working brain cells had the intuition to simply clone the power supply from a marine or ham radio that used one or two sweep tubes in its transmitter. Around the same time (mid 70's) a local marine radio company was revamping their product line and the old HF vacuum tube marine radio was discontinued and the power supply parts hit their dumpster and the surplus market. It was a simple matter to rip the HV winding off of the toroid and wind a secondary to make me +/- 40 VDC. That's when the 73 Chevy van started rocking. It had 8 X Plastic Tiger clones, one for each speaker and a Universal Tiger feeding the 15 inch sub under the bed. The van also featured a "Concord" (Olson house brand, made by Nakamichi) home cassette deck mounted upside down in the overhead console.
The power supplies robbed from these mobile radios and CB amps operated in the audio frequency range (about 2 KHz) to avoid melting the slow germanium transistors that were used for their low VceSAT. The best solution I found was to mount a pair of these switchers in front of the radiator under the hood with LPF's at the source, and more at the power entry point into the van.
Modifying - as long as it was 50 years ago - counts.
Snooping inside my Teac cassette deck, I noticed the belt could ride on one of two pulleys on the motor. The bigger diameter was for 50 hz, Having the basic knowledge that 7-1/2 records better than 3-3/4, I swapped the pulley position, running the 50Hz diameter on 60Hz - making all my recorded cassette tapes incompatible with every other player. In my teenage strife, to get a little bit better, in my audio sound.
I bought Olson's Concord in-dash FM cassette player with the dolby and separate bass/treble controls when I worked there. Loved that player. I think it only had 15W total. Two RS 12" guitar speakers mounted on the cardboard rear cargo cover of a VW Scirocco, with a couple Motorola Piezos thrown on top, from the blue Olsons vacuum package. I took the one with the bent phase plug...
Snooping inside my Teac cassette deck, I noticed the belt could ride on one of two pulleys on the motor. The bigger diameter was for 50 hz, Having the basic knowledge that 7-1/2 records better than 3-3/4, I swapped the pulley position, running the 50Hz diameter on 60Hz - making all my recorded cassette tapes incompatible with every other player. In my teenage strife, to get a little bit better, in my audio sound.
Wow - I_bow_to. That must've been quite a ride, sound wise.
I bought Olson's Concord in-dash FM cassette player with the dolby and separate bass/treble controls when I worked there. Loved that player. I think it only had 15W total. Two RS 12" guitar speakers mounted on the cardboard rear cargo cover of a VW Scirocco, with a couple Motorola Piezos thrown on top, from the blue Olsons vacuum package. I took the one with the bent phase plug...
Built a lot of horn PA cabinets in high school shop 1973 and 1974.
Used Steve Hall's "Hyppo" design for many of them:
I didn't know "Hyppo" was a play on the hyperbolic/ exponential horn flare until later
Here is a two way 1975 "line array" assembled using 18", 15" and 12" Hyppo cabinets, topped off by Recchi and EV 8HD horns, and a University H-600 with an RCA driver scavenged from under the Met Sports center bleachers (before it was replaced by the Mall of America):
Recchi Engineering built lots of fiberglass horns and "Hog Troughs":
The black horns did not have the Heil name on them, but there were a lot of them bootlegged out Recchi's back door that needed boxes around them, I probably built a dozen in that era.
Lots of 19" racks too..
Art
Used Steve Hall's "Hyppo" design for many of them:
I didn't know "Hyppo" was a play on the hyperbolic/ exponential horn flare until later
Here is a two way 1975 "line array" assembled using 18", 15" and 12" Hyppo cabinets, topped off by Recchi and EV 8HD horns, and a University H-600 with an RCA driver scavenged from under the Met Sports center bleachers (before it was replaced by the Mall of America):
Recchi Engineering built lots of fiberglass horns and "Hog Troughs":
The black horns did not have the Heil name on them, but there were a lot of them bootlegged out Recchi's back door that needed boxes around them, I probably built a dozen in that era.
Lots of 19" racks too..
Art
