Akai SS-1 Universal Synthesizer

[par4ken]

Agreed but the common bass signal typically cancelled out L-R so the rear speakers really did not need to be full range making the technique suitable to the satellite speaker concept. A good reason to make bass common in recordings is to get the benefit of 2 sets of drivers working together to push enoigh air to extend the bass, in addition to the wrong myth that bass is non directional below 150 Hz . Our tests showed that on sine wave pure tone bass is actually non directional to 800 Hz but on band limited pink noise was totally directional down to 35 Hz!! Explains why I can always point to where the subwoofer is for the first 30 seconds before my brain masks the position.

I recall years ago having either a woofer failure or a loose wire, I was amazed that I didn't notice it at all at first. One time I was toying with the idea of separate woofers and mid/tweeters mounted in separate enclosures. That experiment showed that the drivers had to be placed close together or they didn't sound right at all.

 

[par4ken]

I worked out a simple decoder using op-amps similar to the transistor based one that I built years ago. All you need is one quad op-amp, two dual pots and a bunch of equal value resistors.
I'll share the design once I have a chance to redraw it. Anyone know of an easy to use free CAD program for making schematics? Anyway all you need do is configure two op-amps as non-inverting summing amplifiers, the other two as differential amplifiers. You mix the say left with the right from the pot, and vice-versa. For a more complete project you could get fancy and add input buffering, input balance and maybe input level and output level controls if required/desired.

 

[Sonik Wiz]

I worked out a simple decoder using op-amps similar to the transistor based one that I built years ago. All you need is one quad op-amp, two dual pots and a bunch of equal value resistors.
I'll share the design once I have a chance to redraw it. Anyone know of an easy to use free CAD program for making schematics? Anyway all you need do is configure two op-amps as non-inverting summing amplifiers, the other two as differential amplifiers. You mix the say left with the right from the pot, and vice-versa. For a more complete project you could get fancy and add input buffering, input balance and maybe input level and output level controls if required/desired.

Mouser & Digikey offered free schematic drawing apps. There' quite a bit of difference between them so check both out.

 

[par4ken]

So hear is my proposed decoder /synthesizer. All resistors must be the same value, anything from 10K to 100K should be fine. The pot could be lets say 20K to 100K either log/audio or linear, dual ganged. The advantage of a linear pot would be that a mid setting would correspond to a mixing coefficient of 0.5, likewise other settings could be estimated by the position of the dial.

 

[Sonik Wiz]

So hear is my proposed decoder /synthesizer. All resistors must be the same value, anything from 10K to 100K should be fine. The pot could be lets say 20K to 100K either log/audio or linear, dual ganged. The advantage of a linear pot would be that a mid setting would correspond to a mixing coefficient of 0.5, likewise other settings could be estimated by the position of the dial.

Yup looks like decoder to me! Are any of those pots meant to be ganged?

What design app did you use? Looks great. You must be a quick learner as I had quite a bit of learning challenge when I tried that. I just don't remember if I used Mouser or Digikey...

 

[par4ken]

Yup looks like decoder to me! Are any of those pots meant to be ganged?

What design app did you use? Looks great. You must be a quick learner as I had quite a bit of learning challenge when I tried that. I just don't remember if I used Mouser or Digikey...

Yes as stated in the text the unit uses 2 dual ganged pots, I couldn't figure how to show that they were ganged in the CAD app. I used the one from Digi-key I couldn't find the one from Mouser. I tried to go to the Mouser.com site but it knew my IP was from Canada and kept sending me back to Mouser.ca, although I would think that it should be posted on both sites.
Anyway I'v always liked Digi-key, they are just across the border in Thief River Falls.

 

[MidiMagic]

That schematic from my UQ-44 is just the 90 degree phase shifter. You don't have the rest of the decoder.

 

[par4ken]

So here is the schematic of the Akai SS-1. The actual decoder/synthesizer circuit is very similar to the one that I built years ago. They include adjustment trimmers for the rear outputs to maximize rejection of common in phase signals (vocals), not sure that's necessary unless the parts tolerance are not very tight (likely the case). It includes a phono pre-amp, which might actually make it useful for some today that lack that feature. The unit also includes a mostly unnecessary output amplifier consisting of 3 transistors per output channel. I've uploaded the entire manual to hifiengine.com so check there in awhile if you want to download it.

 

[chucky3042]

So here is the schematic of the Akai SS-1. The actual decoder/synthesizer circuit is very similar to the one that I built years ago. They include adjustment trimmers for the rear outputs to maximize rejection of common in phase signals (vocals), not sure that's necessary unless the parts tolerance are not very tight (likely the case). It includes a phono pre-amp, which might actually make it useful for some today that lack that feature. The unit also includes a mostly unnecessary output amplifier consisting of 3 transistors per output channel. I've uploaded the entire manual to hifiengine.com so check there in awhile if you want to download it.

Stone age stuff! But lots of fun

 

[Soundfield]

So hear is my proposed decoder /synthesizer. All resistors must be the same value, anything from 10K to 100K should be fine. The pot could be lets say 20K to 100K either log/audio or linear, dual ganged. The advantage of a linear pot would be that a mid setting would correspond to a mixing coefficient of 0.5, likewise other settings could be estimated by the position of the dial.

I'm often asked to make line level Hafler boxes for friends, and so next think I'll try using the rear channel half of your circuit - not sure I've any real need for the front half as the ability to reduce image width on purely stereo source material is of little value I suspect. I've a duff Sony SQD-2070 whose little case would be just the right size to house it and a power supply.

 

[chucky3042]

Dear All

This thread really has me going on old simple decoders (maybe we should start a new thread on this topic?)

Well, when I was a 14 year old kid (cute as a button) and not quite happy with my Halfer Dynaco connection surround, this came along in November 1972 Electronics Australia magazine written by the late editor Neville Williams. Great magazine, I have all the magazines back to 1969! It died and re emerges with Leo Simpson as the editor in the vastly inferior "Silicon Chip " magazine. I remember being at Leo's lovely house in North Sydney one afternoon chatting to his charming wife and it turned out that the only speaker that would ever sound good was if it had Dynaudio drivers, his wife said to me he never listens to LIVE music!!! Oh well, Leo has retired recently.

Neville makes some very observant points on surround in the article.

I digress - this was my second attempt at matrix surround, it leaves the fronts untreated and does a half arsed sorta QS decode of the rears and sorta does a 90 degree phase shift in the mid band whilst not cancelling the bass as with the Halfer approach. I built it to- was underwhelmed again!

If anyone wants a higher resolution picture just email me on [email protected] and I will send it.

Hey look how I put lines through the parts lists as I slowly got the parts! This is evidence that I was a sound / surround nutcase from a very early age, I was on a very low budget being the illegitimate son of a housemaid living as servants boy in rich peoples houses!

 

[Soundfield]

This thread really has me going on old simple decoders

You might have stopped when you were a teenager Chucky, but I still I love building simple decoders / synthesisers ! - and, as I said above, I’m next going to use par4ken’s modern variant of the Akai SS-1. Interesting that you should post the EA 1972 design as it’s also fundamentally the same thing. As I mentioned above, my slightly simplified version of par4ken’s circuit will dispense with the front channel mixing facility:

I’ve ripped the innards out of this old Sony SQD-2070 to use as the case:

I can’t remember how I came by the Sony, but I’ve had it for ages and it never worked. It was a Japanese 100V version and I think it must have got blown up by being connected to a higher (more sensible!) voltage mains at some time. I’m guessing that from the fact that someone had completely reworked the power supply at some stage in its life, but had made a complete mess of it. It wasn’t worth the effort to try and get going because the chances are that whatever fate befell it would have zapped those weird, delicate and unobtainable Sony decoder chips that they used briefly only in this and I think the SQD-2010.

 

[Sonik Wiz]

Dear All

This thread really has me going on old simple decoders (maybe we should start a new thread on this topic?)

Well, when I was a 14 year old kid (cute as a button) and not quite happy with my Halfer Dynaco connection surround, this came along in November 1972 Electronics Australia magazine written by the late editor Neville Williams. Great magazine, I have all the magazines back to 1969! It died and re emerges with Leo Simpson as the editor in the vastly inferior "Silicon Chip " magazine. I remember being at Leo's lovely house in North Sydney one afternoon chatting to his charming wife and it turned out that the only speaker that would ever sound good was if it had Dynaudio drivers, his wife said to me he never listens to LIVE music!!! Oh well, Leo has retired recently.

Neville makes some very observant points on surround in the article.

I digress - this was my second attempt at matrix surround, it leaves the fronts untreated and does a half arsed sorta QS decode of the rears and sorta does a 90 degree phase shift in the mid band whilst not cancelling the bass as with the Halfer approach. I built it to- was underwhelmed again!

If anyone wants a higher resolution picture just email me on [email protected] and I will send it.

Hey look how I put lines through the parts lists as I slowly got the parts! This is evidence that I was a sound / surround nutcase from a very early age, I was on a very low budget being the illegitimate son of a housemaid living as servants boy in rich peoples houses!


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I went to read this article & check out more from the whole issue at Radio Archives. Sadly I only found this:

https://worldradiohistory.com/Electronics_Australia_AU.htm
They are the only ones I know of that have taken this heavy handed approach.

 

[Sonik Wiz]

You might have stopped when you were a teenager Chucky, but I still I love building simple decoders / synthesisers ! - and, as I said above, I’m next going to use par4ken’s modern variant of the Akai SS-1. Interesting that you should post the EA 1972 design as it’s also fundamentally the same thing. As I mentioned above, my slightly simplified version of par4ken’s circuit will dispense with the front channel mixing facility:

View attachment 56706

I’ve ripped the innards out of this old Sony SQD-2070 to use as the case:

View attachment 56707

I can’t remember how I came by the Sony, but I’ve had it for ages and it never worked. It was a Japanese 100V version and I think it must have got blown up by being connected to a higher (more sensible!) voltage mains at some time. I’m guessing that from the fact that someone had completely reworked the power supply at some stage in its life, but had made a complete mess of it. It wasn’t worth the effort to try and get going because the chances are that whatever fate befell it would have zapped those weird, delicate and unobtainable Sony decoder chips that they used briefly only in this and I think the SQD-2010.

And if you were to take that circuits output & feed it to the input of a Surround Master or other QS decoder you would have an excellent variable pre-synthesizer for surround.

When I honeymooned in the UK I had the wonderful chance to meet with another quad fan by the name of Alan Turner. He lived in Romsey & he took me & my new wife on the same tour Princess Diana did after her wedding.

Anyways his soul surround sound gear was a Hafler speaker set up which he called cheap & cheerful. It was a great evening with good music. It is good to see the simple surround approach is still appreciated by others today!

 

[Soundfield]

And if you were to take that circuits output & feed it to the input of a Surround Master or other QS decoder you would have an excellent variable pre-synthesizer for surround.

I had I feeling you might say that! I'll certainly give it a try.

 

[par4ken]

You might have stopped when you were a teenager Chucky, but I still I love building simple decoders / synthesisers ! - and, as I said above, I’m next going to use par4ken’s modern variant of the Akai SS-1. Interesting that you should post the EA 1972 design as it’s also fundamentally the same thing. As I mentioned above, my slightly simplified version of par4ken’s circuit will dispense with the front channel mixing facility:

View attachment 56706

I’ve ripped the innards out of this old Sony SQD-2070 to use as the case:

View attachment 56707

I can’t remember how I came by the Sony, but I’ve had it for ages and it never worked. It was a Japanese 100V version and I think it must have got blown up by being connected to a higher (more sensible!) voltage mains at some time. I’m guessing that from the fact that someone had completely reworked the power supply at some stage in its life, but had made a complete mess of it. It wasn’t worth the effort to try and get going because the chances are that whatever fate befell it would have zapped those weird, delicate and unobtainable Sony decoder chips that they used briefly only in this and I think the SQD-2010.

I just bought one on eBay for a measly $35.00. I'm actually quite impressed with it. It sounds better than the SQD-2010 due to less analog circuitry in the signal path. The chips are available on eBay but not really worth the effort to attempt repairs to a dead one. I didn't need another decoder but it's still fun to listen to these vintage units to see what they had to offer, especially when you find them at bargain basement prices.

 

[chucky3042]

I went to read this article & check out more from the whole issue at Radio Archives. Sadly I only found this:

https://worldradiohistory.com/Electronics_Australia_AU.htm
They are the only ones I know of that have taken this heavy handed approach.

Hi Sonic

Here is a list of all EA projects (I will have them somewhere!)- just ask
http://www.siliconchip.com.au/Static/EA Projects
Also
https://electronicsluckydip.com/2019/Electronics_Australia_File_Archive/

 

[par4ken]

In Canada we had in addition to the American Magazines "Electronics Today International". ETI also had an Australian, UK and a Dutch edition I think. The Canadian edition started in 1977, I used to build several projects from almost every issue for awhile. Like all good things the quality of the issues deteriorated over time and it eventually ceased publishing.

 

[chucky3042]

In Canada we had in addition to the American Magazines "Electronics Today International". ETI also had an Australian, UK and a Dutch edition I think. The Canadian edition started in 1977, I used to build several projects from almost every issue for awhile. Like all good things the quality of the issues deteriorated over time and it eventually ceased publishing.

I have most of them to!!!! And another one AEM (Australia electronics monthly.... Really good mag, now also gone)

 

[Soundfield]

In Canada we had in addition to the American Magazines "Electronics Today International". ETI also had an Australian, UK and a Dutch edition I think. The Canadian edition started in 1977, I used to build several projects from almost every issue for awhile. Like all good things the quality of the issues deteriorated over time and it eventually ceased publishing.

Yes, agreed. ETI was a terrific magazine in its early days. My avavtar is taken from the cover of July 1972 issue. It was a great inspiration to a young lad, as I explained a couple of years ago-

ETI Magazine & Quad