In the 1980's when I first got into electronics I built a few Maplin kits including 225/75/50 watt amplifiers, disco light controller and dual disco record decks.
I was studying for my City and Guilds in industrial electronics at the time which helped.
In recent years I have longed for those times again.
So I designed my own set of amplifiers which followed the Maplin designs but not too closely that I infringed on copyright.
I also designed 3 valve amplifiers 10 watt, 20 watt and 80 watt.
This was great fun and the amps worked well after a little tweaking.
I learned a lot about star ground with the valve amps.
I also designed a speaker protector circuit, a soft start circuit and a 2 way active crossover.
While I spent 20+ years in the electronics/software industry my time spent DIYing has been the most enjoyable. I can pick things up and drop them as I please with out any pressure to finish them.
I was studying for my City and Guilds in industrial electronics at the time which helped.
In recent years I have longed for those times again.
So I designed my own set of amplifiers which followed the Maplin designs but not too closely that I infringed on copyright.
I also designed 3 valve amplifiers 10 watt, 20 watt and 80 watt.
This was great fun and the amps worked well after a little tweaking.
I learned a lot about star ground with the valve amps.
I also designed a speaker protector circuit, a soft start circuit and a 2 way active crossover.
While I spent 20+ years in the electronics/software industry my time spent DIYing has been the most enjoyable. I can pick things up and drop them as I please with out any pressure to finish them.
Here are 3 of the 1980's Maplin amplifiers I have.
An externally hosted image should be here but it was not working when we last tested it.
I remember in the 70s Myself & friends blowing up a lot of Sinclair amp kits...
Then the ETI480 came along, I still have a pair powering my subs
Then the ETI480 came along, I still have a pair powering my subs
I got my start designing and scratch building small solid state amplifiers in the dawn of the 1980s.. Some of those amplifiers were still working just a few years ago so I guess I did something right..
The hallmark of my design philosophy at that time was simplicity, npn LTP with CCS, a pnp Vas with miller compensation CCS load, vbe multiplier with transistor on the heat sink, and fast delicate complementary output transistors (20W 15MHz silicon types made by Sylvania). Relatively low feedback margins, but open loop bandwidths in excess of 20kHz.
That amp ran for 30yrs without any issues and clipped at 15Wrms into 8 ohms, I imagine I exceeded the SOA doing so, but I mostly used this amp for driving AKG-140 headphones which it did extremely well. I was not feeling very sentimental during the last purge a couple years ago (I was very ill at the time) and it went right into the bin without further thought.
The hallmark of my design philosophy at that time was simplicity, npn LTP with CCS, a pnp Vas with miller compensation CCS load, vbe multiplier with transistor on the heat sink, and fast delicate complementary output transistors (20W 15MHz silicon types made by Sylvania). Relatively low feedback margins, but open loop bandwidths in excess of 20kHz.
That amp ran for 30yrs without any issues and clipped at 15Wrms into 8 ohms, I imagine I exceeded the SOA doing so, but I mostly used this amp for driving AKG-140 headphones which it did extremely well. I was not feeling very sentimental during the last purge a couple years ago (I was very ill at the time) and it went right into the bin without further thought.
Down under Electronics Australia magazine ruled the kit world, and I built a few Playmaster kits, the 116 guitar amplifier for my brother, http://www.retrovox.com.au/40WPM116.pdf, which he used for years playing in the venues in our town. For myself, the Playmaster 127, 128 preamp and power combo - could only find a pic of the amp,
I must be older then you guys. My first kit was an integrated Heathkit. Since I'm pretty colorblind, it didn't work. Took their tech 8 hours to make it work....
A couple years later, Dynaco PAT4 and stereo 120. Yeah, I measured every resistor.
All that stuff is long gone. I do miss my old Sony tts3000 turntable, though.
A couple years later, Dynaco PAT4 and stereo 120. Yeah, I measured every resistor.
All that stuff is long gone. I do miss my old Sony tts3000 turntable, though.
LOL, a company I worked for employed an inspector years ago, he didn't tell us he was colour blind...
Maplin 150W mosfet was one of my firsts.....
Heathkits, Dynakits, Southwest Technical Products Co. magazine articles by Dan Meyer and my Ace Audio preamp kit- definitely the good old days.
wiring up scores of Hafler kits for a local hi-fi dealer for me -not as far back as some of y'all, nor as purist in the DIY sense - but tons of fun trying to trim down assembly time
I never used any kits but built my audio amps from sratch. Starting with an EF86/EL84 guitar amp (my first an last tube amp) I followed the road of 2N3055/2N3773 quasi-complementary designs, MJ2955/MJ3055 true complementary designs followed by hitachi VMOS 2SK135/2SJ50. These where the best in their class imho and I built and sold several 5kW units, each containing 36 pairs of 2SK135/2SJ50 to achieve good overload margin at reactive loads. I built and used my guitar amps for a lifetime, never bought one since I was aged 20. In recent years I totally swapped to class-d-amps, battery driven and lightweight. The VOX AC30 is the one I really consider stylish, and you can see them often noadays on stage here. All in all I am happy with my light-weight amps and not nostalgic about these clumsy tube amps.
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First amp I built was the (original) JLH, I then really wanted one of the Hart JLH mosfet kits, but couldn't afford one, boohoo.
I was fascinated by the Maplin valve kits, but again, couldn't afford any of them.
The original JLH amp is a great starting point for anyone, I think, you can get a working amp for next to nothing.
I was fascinated by the Maplin valve kits, but again, couldn't afford any of them.
The original JLH amp is a great starting point for anyone, I think, you can get a working amp for next to nothing.
Years ago,
I built turntables with AL60's in the Plinth and controls on the front..😀
And played records for hours. Aged 14..pic attached
The AL60 was an intrest recently and I spent some time tracing out the circuit if you do a search its on DIY audio.
Then I built my own circuit board with two AL60 amps into a tape deck the transport was sourced from Monolith magnetics..Aged 16..LOL
And the PW oscilloscope project. (fly back suppression was a problem)
Then a practical wireless clock at 17..Pic below. Found in the back of my Dads garage recently..😀 build date 1976 Photo etch boards..
NB it still works the Supply cap was changed about 5 years ago..because they were still using it..🙂
Regards
M. Gregg
I built turntables with AL60's in the Plinth and controls on the front..😀
And played records for hours. Aged 14..pic attached
The AL60 was an intrest recently and I spent some time tracing out the circuit if you do a search its on DIY audio.
Then I built my own circuit board with two AL60 amps into a tape deck the transport was sourced from Monolith magnetics..Aged 16..LOL
And the PW oscilloscope project. (fly back suppression was a problem)
Then a practical wireless clock at 17..Pic below. Found in the back of my Dads garage recently..😀 build date 1976 Photo etch boards..
NB it still works the Supply cap was changed about 5 years ago..because they were still using it..🙂
Regards
M. Gregg
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I built,
two maplin mosfet amps and a bridging module for a project. However I got interested in something else 1970's. I still have the built modules if I can find them I will post a picture they were never even powered up to test.
So guess they are still virgin in the box.
Way back my first transistor build was a transmitter using OC71 and OC45 transitors. It was used to transmit my CD player around the house.
Think I was about 12-13 at the time..
I built so many amps using modules...and one even had the maplin bar driver circuit for power output it was discreet transistors..I don't think they had a module then it was to long ago.
I also built the Dolby maplin module as well..😀
Most of it as I started my apprenticeship..that's where kind people took pity on a DIY electronics kid and let me use the photo etch equipment..😀
Its a long time ago now!
Regards
M. Gregg
two maplin mosfet amps and a bridging module for a project. However I got interested in something else 1970's. I still have the built modules if I can find them I will post a picture they were never even powered up to test.
So guess they are still virgin in the box.
Way back my first transistor build was a transmitter using OC71 and OC45 transitors. It was used to transmit my CD player around the house.
Think I was about 12-13 at the time..
I built so many amps using modules...and one even had the maplin bar driver circuit for power output it was discreet transistors..I don't think they had a module then it was to long ago.
I also built the Dolby maplin module as well..😀
Most of it as I started my apprenticeship..that's where kind people took pity on a DIY electronics kid and let me use the photo etch equipment..😀
Its a long time ago now!
Regards
M. Gregg
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I was just thinking,
The very early transmitter I made when I was 13 could have been in the transistor circuits manual No.2 clive sinclair 163.
However its not in PDF on line so I can't see..😀
I guess nobody has a copy they could post the circuit...just for interest.
I remember something like this:
I remember the never ending problem of AF117...LMAO
Give them a bash and they started working again for about 10 seconds..I think we used AF127 as a replacement but its been a long time ago..
Regards
M. Gregg
The very early transmitter I made when I was 13 could have been in the transistor circuits manual No.2 clive sinclair 163.
However its not in PDF on line so I can't see..😀
I guess nobody has a copy they could post the circuit...just for interest.
I remember something like this:
I remember the never ending problem of AF117...LMAO
Give them a bash and they started working again for about 10 seconds..I think we used AF127 as a replacement but its been a long time ago..
Regards
M. Gregg
Attachments
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😀
Just found it the PW clock..post 13#
Regards
M. Gregg
Ah yes, the magazines on the newsstand. As a child I was very active building kits (non-audio) but drifted away. In my late teens (early 80s) I noticed the large quantity of DIY electronics magazines and rediscovered my earlier interest. I was amazed at the scope of projects they covered. They actually drew me back to electronics but this time my focus was on audio.
Yes, those plus Allied Radio and Lafayette (sp?). And, the CK722 transistor for hobbyist.
-Richard Marsh
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Where I worked we got Wireless World every month.
I enjoyed the readers circuits.
I picked up a circuit for emulating valve distortion.
It was a soft limiter which rounded off the top of the waveform.
My next project is a solid state guitar amplifier with the soft limiter incorporated into it.
I enjoyed the readers circuits.
I picked up a circuit for emulating valve distortion.
It was a soft limiter which rounded off the top of the waveform.
My next project is a solid state guitar amplifier with the soft limiter incorporated into it.
An externally hosted image should be here but it was not working when we last tested it.
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