I had a music habit that started when I was age 3 with a Bozo the Clown record player. Paper cone attached to steel needle, no amplifier. I loved Tchaikovsky Sleeping Beauty more than Teddy Bear Picnic. Then 1964 Mother bought a RCA stereo with 2" speakers and one 12AX7 per side. It sounded terrible compared to the live music I was playing in school band. Plus it ripped the highs off a new LP in one play. 5 gram ceramic cartridge. Got to college, they had dynaco ST35 in the library to listen to the records. A moving magnet 1 gram cartridge. Bliss, but sitting there with headphones wasted a lot of time. Bought a used dynakit PAS2 preamp + ST70 amp+AR turntable as a sophomore, okay but the macIntosh clinic salesman told me it was putting out 7 watts/channel at 7% Harmonic distortion. So I followed his instructions and put new electrolytic caps and a rectifier tube in. Much better. St70 was 300 watts, heated up the room in already hot Houston. I couldn't afford A/C a couple of years. I bought a dynaco ST120 transistor amp blown in 1985. When I did fix it, new output transistors drivers & semiconductors on the limiter board, it didn't sound as good as the ST70. Diyaudio forum became available to me and I discovered that sound improvements could be made for $20 in parts. Idle bias control from djoffe sounded nice, but it kept blowing a sense transistor for the control circuit and going to 200 ma idle current. A similar but low HD circuit (apex AX6) driver board could be built for <$20 in parts. There was a PCB, but it wouldn't fit in my chassis. So I built one point to point. Sounded great, used 60 W at idle instead of 300. Most of rest of music hobby is fixing things. I've put 177 capacitors in one Hammond organ that sounded like a wet kazoo when I bought it. I have built a pipe organ shade engine driver point to point, with some help from people on instruments & amps forum. 8 positions for the doors on the organ case, with closed loop sense of the positions on the actuator. I'm now building an electric shift for my 24 speed bicycle, since flicking the lever gives my thumb joint a cyst, and I'm not strong enough to twist the knob anymore. 24 vdc linear actuator, push button switches, dual fet actuator drivers, maybe a magnetic sense system to make the motor stop at the right 8 positions. Commercial electro-shifts (SRAM eagle $550) are limited to road bikes with drop handlebars (could crush my neck disk) 11 speeds in the back (wears out a chain every 1000 miles) and have a patented battery that lasts 2 years & costs $100, with $6 of cells inside.
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Hi. Thanks for responding. Is there a way I could get a copy of the schematic?
In the late 70’s what I could afford was horrible - “record players” with built in sub one watt IC amplifiers and 4” full range speakers in particleboard boxes. The kind with a ceramic cartridge that eats records for breakfast. Ended up with a Pickering V15AT2 (that’s right, the Stanton 500 clone) on that BSR - with an STK-module-based integrated amp kit driving radio shack and later McGee-sourced speakers. When I wanted more I needed to learn how to build the real thing. Speakers were easier - and far more critical to doing the music at the school dances. By then I could fix a dead amp (which could be purchased for a song). When we were all banned from doing the music because of the rivalry between the two big DJs - one black, one white - both of which I worked with, we had to take it off campus and we needed to fill bigger spaces which meant bigger speakers. And more watts. Since I wasnt doing this stuff all the time, of course I wanted to bring that music experience home.
About 25 years ago I gave up trying to merge my “big rig” and “home stereo” systems and treated them independently. I got my main home system to my satisfaction and have not seen a need to upgrade since. Built plenty of smaller stuff since. The PA continues to grow, regardless of whether I have an application for it at any given time. Just on and off - right now more “off” because of my new home build in progress. I’ve got bigger amplifiers for it that are still in design. Yes, I could drop 20 -30 grand and buy new Labgruppens, but that’s not the point. The idea is to make the whole damn thing. About one third powered by DIY, the rest store bought and the idea is eventually all DIY. And of course, you cant buy amplifiers like these anymore - they are too heavy to be commercially viable. Again, the idea is not to make a living - that is already taken care of.
5 or 6 years ago I rediscovered tubes. It started out I just wanted to build a giant bass guitar amp to use with an old 18” Pyle Driver left over from my early DJ days. I started with proper engineering analysis, and built the best 200 watter I reasonably could. My jaw dropped when I heard what it sounded like. Now a pair drive two double 15 3 ways in my shop - putting out the same levels we used to do at the dances/raves 35 years ago. Decommissioned from my PA because they are too small to do anything real with these days. Back where it all started, but blowing it away in the sound quality department. I learned a few things along the way.
About 25 years ago I gave up trying to merge my “big rig” and “home stereo” systems and treated them independently. I got my main home system to my satisfaction and have not seen a need to upgrade since. Built plenty of smaller stuff since. The PA continues to grow, regardless of whether I have an application for it at any given time. Just on and off - right now more “off” because of my new home build in progress. I’ve got bigger amplifiers for it that are still in design. Yes, I could drop 20 -30 grand and buy new Labgruppens, but that’s not the point. The idea is to make the whole damn thing. About one third powered by DIY, the rest store bought and the idea is eventually all DIY. And of course, you cant buy amplifiers like these anymore - they are too heavy to be commercially viable. Again, the idea is not to make a living - that is already taken care of.
5 or 6 years ago I rediscovered tubes. It started out I just wanted to build a giant bass guitar amp to use with an old 18” Pyle Driver left over from my early DJ days. I started with proper engineering analysis, and built the best 200 watter I reasonably could. My jaw dropped when I heard what it sounded like. Now a pair drive two double 15 3 ways in my shop - putting out the same levels we used to do at the dances/raves 35 years ago. Decommissioned from my PA because they are too small to do anything real with these days. Back where it all started, but blowing it away in the sound quality department. I learned a few things along the way.
Ha! Pretty much the same here back in school (43 years ago). My best mate at the time was handy in woodwork class and made me a pair of bookshelf size sealed cabinets, and I stuffed a pair of coaxial car speakers in them. They looked great (thanks to my mate's woodworking skills) and sounded very less than great (thanks to my lack of anything to do with proper design). But the point was they were my idea & creation, that's all that mattered.
Great days though.
I remember a pair of 6” car drivers I got from Poly-Paks of all places, thrown into random plywood boxes. The Radio Shack 8” blue cone full rangers were far better. But then there were the Varco 8’s from McGee that actually worked well in a moderate size sealed box. And only $6.95 each.
Poly-Paks! Now there is a name from the past! Bought a few things over the years. In the back pages of Radio Electronics magazine.
I bought speakers from surplus dealers, Radio Shack and scavenged from old TVs. Phonographs from my youth were mostly three tube afairs using a 50L6, 35Z3 and whatever signal tube, 6SL7 were common. Newer ones were 50C5, 35W4 and 12AX7. They sounded a lot better than the later transistor units.
I bought speakers from surplus dealers, Radio Shack and scavenged from old TVs. Phonographs from my youth were mostly three tube afairs using a 50L6, 35Z3 and whatever signal tube, 6SL7 were common. Newer ones were 50C5, 35W4 and 12AX7. They sounded a lot better than the later transistor units.
Transistor? No, things really went to s*** when they started using IC amplifiers in those things. The only decent ICs were the STK modules, which ran on enough voltage to do something with. When the STK439 amp died (they all did, remember?) it was replaced by one of those peanut pentode amps. The original LM377 was supposedly capable of more power than a pair of 50EH5, but it sure didn‘t sound like it to me.
Surplus dealers were where I got almost all of my transformers from. This actually continued up until I discovered Antek. But even today if I find a $15 500 VA toroid I’m going to buy it, even if it’s not needed right this minute (or even year). Those finds have been steadily decreasing over the last 3 decades.
Surplus dealers were where I got almost all of my transformers from. This actually continued up until I discovered Antek. But even today if I find a $15 500 VA toroid I’m going to buy it, even if it’s not needed right this minute (or even year). Those finds have been steadily decreasing over the last 3 decades.
I remember the STK439 well. That was all junk compared to decent discrete designs. STK0050 was another popular (output stage only), but those had manufacturing problems. STK products were an improvement over the common low-fi crappy circuits, but they were not that good, and could blow easily compared to normal discrete designs. Couple that with the fact they went obsolete relatively quickly (making the device unrepairable), the higher marks had sometimes different pin-outs or even number of connections, and if they didn't you had to re-compensate the circuit. Even newer manufacture of the current number could oscillate.
I buy E-I transformers (for good reason). I have some toroid types, but I don't buy them unless I have to. I buy new transformers, normally from Hammond. Those are simply better and that is worthwhile to me. I have some Chinese ones, purely for prototypes once I get past the bench power supply stage.
I don't need the low profile a toroid offers either. That reduces heat sink height and takes up way more horizontal room. Added, the high inrush current and wide band response are solidly negative aspects in my view. I use inrush limiting for large transformers of every type, but with a toroid it is really required even at lower V-A ratings..
I buy E-I transformers (for good reason). I have some toroid types, but I don't buy them unless I have to. I buy new transformers, normally from Hammond. Those are simply better and that is worthwhile to me. I have some Chinese ones, purely for prototypes once I get past the bench power supply stage.
I don't need the low profile a toroid offers either. That reduces heat sink height and takes up way more horizontal room. Added, the high inrush current and wide band response are solidly negative aspects in my view. I use inrush limiting for large transformers of every type, but with a toroid it is really required even at lower V-A ratings..
I remember going to a Parma OH Amateur Radio Club "Hamfest", early 1960's, in which they had an afternoon devoted to explaining transistors and some applications from code oscillators, mixers, QRP transmitters, regen receivers etc. If I look hard, I can probably find the mimeographed notes from that first meeting.
I built most of my ham stuff either from scratch, from military surplus (ARC5, BC348) or from Knight and Heath kits. Salvaged a lot of TVs for their transformers etc. A high school bud and I discovered a TV-Repair shop which saved the old sets just for ham radio ops and experimenters. At that time defense electronics was still pretty big in OH, so we got a lot of castoffs (sorry, no more UHF acorn tubes).
Those STK439’s were just such an improvement over the two watt 14 pin DIPs and 10 pin SIPs they were putting in cheap stereos. Of course, a real discrete design or even tubes are generally better but I hadn’t learned to build those yet. Finding PNPs good for more than 40 volts was a challenge given my resources, and you can’t build an amp that’s worth a **** without at least one. I had made a few 20, 40, 50 watters with varying levels of success, but the first “real” home brew one wasn’t till the end of my freshmen year in college. Found some 80VCT/6A EIs for $15 a pop and built a nice pair of amps similar in capability to the DC300A. Heat sinks from Skycraft, caps from a ham fest, the 2SD424/B554 banks from MCM. Ran them bridged into 2 pair of PA speakers for years.
lol!
The DC300 is an awful thing, but better (sadly) than many others! Those transformers were an excellent buy! Really useful in fact. The 2SD424/2SB554 pairs were fantastic. I stocked those as preferred output types, and 2SD555/2SB600 along with JEDEC numbers 2N15024/2N15025. I grabbed MJ15003/MJ15004 and a few others also. They each had their best application. Running a large service shop you don't have time for service returns or issues, or the ability to stock a wide range of types in the quantities needed to get matches. So you stocked the best and protected your reputation.
You are absolutely right on the STK modules. They greatly improved the performance of the cheaper products. The problem was that at the time the industry dropped performance and reliability and was going for profits - trading on their previous solid reputations. What Philips did to Marantz was a crime, people thought they were buying one thing and actually got something entirely different. I dropped doing Marantz warranty at that point.
I really liked early DIY. People built circuits from magazines and also from the RCA databook. You really had to think back then.
The DC300 is an awful thing, but better (sadly) than many others! Those transformers were an excellent buy! Really useful in fact. The 2SD424/2SB554 pairs were fantastic. I stocked those as preferred output types, and 2SD555/2SB600 along with JEDEC numbers 2N15024/2N15025. I grabbed MJ15003/MJ15004 and a few others also. They each had their best application. Running a large service shop you don't have time for service returns or issues, or the ability to stock a wide range of types in the quantities needed to get matches. So you stocked the best and protected your reputation.
You are absolutely right on the STK modules. They greatly improved the performance of the cheaper products. The problem was that at the time the industry dropped performance and reliability and was going for profits - trading on their previous solid reputations. What Philips did to Marantz was a crime, people thought they were buying one thing and actually got something entirely different. I dropped doing Marantz warranty at that point.
I really liked early DIY. People built circuits from magazines and also from the RCA databook. You really had to think back then.
Mine had about 4X the heat sinking of the DC300A, and EF3 full comp outputs. I also learned along the way that high speed DRIVERS were absolutely critical to getting that “high end Japanese receiver” sound. So I went for the gusto - 2SC2564/A1094 (80 MHz). They weren’t even prohibitively expensive at the time (but the Sanken types were). It’s too bad you can’t get those anymore, not even in TO-3P, or I’d still be using them. As drivers - for output banks that tend to be on the “beefy” side. It goes without saying, it didn’t sound anything like a DC300A, just put out the same power and would take as many speakers in parallel as you could find.
What Philips did to EVERYTHING was a crime. About the time I built those amps we started up with the “Philips isn’t worth a $***”, which continues to this day.
I've realised that my post about making my own speakers didn't actually answer the OP's question - ' what inspired me to do it?'.
The fact that I managed to blow the loudspeakers of my parents' Sanyo G3001 Music Centre was the inspiration. I remember clearly my dad saying 'that's coming out of your pocket/birthday/christmas money', so when I showed him the fruits of my diy audio labour he laughed, and seemed genuinely impressed by my initiative. He let me off the cost of any new speakers, and we used my diy replacements until he could bear them no more.
A side note, out of interest I just looked on ebay for that same G3001 music centre - seems they go for silly amounts now!
The fact that I managed to blow the loudspeakers of my parents' Sanyo G3001 Music Centre was the inspiration. I remember clearly my dad saying 'that's coming out of your pocket/birthday/christmas money', so when I showed him the fruits of my diy audio labour he laughed, and seemed genuinely impressed by my initiative. He let me off the cost of any new speakers, and we used my diy replacements until he could bear them no more.
A side note, out of interest I just looked on ebay for that same G3001 music centre - seems they go for silly amounts now!
I had to look up the history of Marantz - I never knew which companies owned which brands so many decades ago. But I do remember a full-page Marantz ad in some hifi magazine, circa early 70s, featuring Elton John. What I found "remarkable" was the frequency response claim in that ad, 20 Hz (though it surely said cps instead of Hz back then) to 20,000 kHz.
Marantz actually understated their performance. Superscope bought Marantz early on. Things were fine and they produced some excellent products. Coming up to the sale for North American distribution to Philps things became less well engineered some times. The circuits were fine but construction wasn't kind to service people. Once Philips bought the distribution everything immediately hit rock bottom, the equipment was pure junk. They didn't support parts, manuals or service staff (TC Electronics became the Canadian distributor after BSR - I dropped them then). Superscope was excellent to work with and supported the best quality service, I got most of my raining there.
Marantz equipment before 1980 would go through ridiculous abuse and keep working. That's what the ad campaigns were all about. I did see a couple that went through fires and still worked. Cosmetically they were totalled though! Saw them dropped from reasonable heights and all kinds of silliness. They really were tough. They cost more new than others, and they were more than worth the difference when you look at the circuit design, performance and construction.
I've worked on these since probably 1979 and still do. I've serviced 1960's equipment and also their tube grear. Today it's more about reversing damage that idiots do when servicing, and updating circuits and generally reversing age and aligning them. I love restoring to better than original performance and one in good cosmetic condition is a joy. I do own some old Marantz along with other excellent brands of equipment, and I love using the Marantz equipment. Besides, it looks fantastic! It is really important to maintain the original look, and most LED lamp kits fail totally in that regard. I use LEDs, but many times I do things differently especially with the black-out style (2325 types). I do not use lamp kits. I also use real vellum.
-Chris
Marantz equipment before 1980 would go through ridiculous abuse and keep working. That's what the ad campaigns were all about. I did see a couple that went through fires and still worked. Cosmetically they were totalled though! Saw them dropped from reasonable heights and all kinds of silliness. They really were tough. They cost more new than others, and they were more than worth the difference when you look at the circuit design, performance and construction.
I've worked on these since probably 1979 and still do. I've serviced 1960's equipment and also their tube grear. Today it's more about reversing damage that idiots do when servicing, and updating circuits and generally reversing age and aligning them. I love restoring to better than original performance and one in good cosmetic condition is a joy. I do own some old Marantz along with other excellent brands of equipment, and I love using the Marantz equipment. Besides, it looks fantastic! It is really important to maintain the original look, and most LED lamp kits fail totally in that regard. I use LEDs, but many times I do things differently especially with the black-out style (2325 types). I do not use lamp kits. I also use real vellum.
-Chris