Back to the future - UK Vintage Radio Repair and Restoration Discussion Forum

val33vo · 3rd Apr 2019, 7:13 pm

Has anyone on this forum tried building a modern version of Clive Sinclair's X10 D class audio amp using silicon transistors (not supposedly rumoured reject germanium ones like the original). I have decided to have a go just to see if I can get it to work. 40 kHz square wave generator, integrator and audio pre amp using BC549, output stage using TIP31 and TIP32 output tranies.

kalee20 · 3rd Apr 2019, 7:33 pm

No. But I'd be interested to hear of results!

The circuit looks as though it would work, but not work well. I like simple stuff, but this looks TOO simple for what it needs to do.

Craig Sawyers · 3rd Apr 2019, 7:59 pm

This was actually designed for uncle Clive by my old friend Gordon Edge. Actually Gordon's version was rather better than Sinclair eventually marketed. The final one that was sold had no output filter - it relied on the voice coil inductance of the speaker to do the filtering. Apparently caused mayhem with radio reception.

Unfortunately Gordon is no longer with us, so I can't ask him for any more background.

It was famed for lack of reliability, over-hyped power specs that it could not meet - so basically meat and two veg for Sinclair at that point.

Other Sinclair background. I bought a Sinclair Scientific calculator when it was first introduced. Suppose I must have been 17 or so. It had a wonderful quirk - if you asked it to do something like find the inverse sine of something greater than 1 (which has a complex solution) it gamely tried to do it, with the display flashing fitfully for a few minutes - and then gave a result, which was of course completely spurious.

And the QL had a similar quirk. The designers has put common constants and things that were done frequently by a programme writer in a look-up table. One of those was root 2. Except they had put in the wrong value into the ROM. So you got a tantalizing close answer, but subtly wrong. If you asked to find the root of 2.0001 it had to actually calculate the value - which it got right.

All wonderful in the world of Sinclair. The man who used tons of dud transistors as hard core underneath his drive. Allegedly.

Craig

G6Tanuki · 3rd Apr 2019, 8:33 pm

As noted, the original X10 with its lack of output-LPF would cause horrible interference to LW/MW radios.

(like many of Uncle Clive's offerings, there was probably more money spent on the advertising than on the technical design. I had a Sinclair "Black Watch" as a student; it went crazy every time I used one of the lab's 450MHz Pye PF70 walkie-talkie)]

Hartley118 · 3rd Apr 2019, 9:03 pm

I recall my X10 class D amplifier: in fact I'm sure that I still have it somewhere safely stored in a junk box. It worked tolerably well into a single 12-inch speaker, but quickly released its magic smoke when I connected it to a more sophisticated 2-way speaker with crossover: it just couldn't handle a complex impedance load.

Like so many Sinclair designs, it was a primitive premature application of an interesting innovative idea. It was way ahead of its time because of course, most consumer amplifiers are now class D. ISTR that I modified my X10 to have a much lower sample rate, and hence very restricted bandwidth. It was then little more than an illustration of the Class D principle, but interesting nevertheless.

Martin

Refugee · 3rd Apr 2019, 10:59 pm

Does anyone remember the early Sinclare basic calculator that used to count for ever if you divided 1 by zero?
They were in the shops in the mid 1970s.

Craig Sawyers · 3rd Apr 2019, 11:13 pm

The Scientific. Like I said in post #3

Craig

Refugee · 3rd Apr 2019, 11:16 pm

I am pretty sure it was a basic 4 function one.

Craig Sawyers · 3rd Apr 2019, 11:28 pm

I must admit I'm surprised that there were so many Sinclair calculators! Google being your friend....

http://www.vintagecalculators.com/html/sinclair1.html

Refugee · 3rd Apr 2019, 11:36 pm

I think it was a white one but not scientific.
It might have been a universal.
I was once given one with a broken case and the board used to do the same thing.

Radio Wrangler · 4th Apr 2019, 9:14 am

Martin had me laughing, and gave me the idea of making a jocular remark about Clive suffering from premature application, but it was his customers who did the suffering.

He missed out on making his C5 autonomous.

David

3rd Apr 2019, 7:13 pm	#1
val33vo Retired Dormant Member Join Date: Apr 2008 Location: Banffshire, Scotland, UK. Posts: 191	Back to the future Has anyone on this forum tried building a modern version of Clive Sinclair's X10 D class audio amp using silicon transistors (not supposedly rumoured reject germanium ones like the original). I have decided to have a go just to see if I can get it to work. 40 kHz square wave generator, integrator and audio pre amp using BC549, output stage using TIP31 and TIP32 output tranies.

3rd Apr 2019, 7:33 pm	#2
kalee20 Dekatron Join Date: Feb 2007 Location: Lynton, N. Devon, UK. Posts: 7,082	Re: Back to the future No. But I'd be interested to hear of results! The circuit looks as though it would work, but not work well. I like simple stuff, but this looks TOO simple for what it needs to do.

3rd Apr 2019, 8:33 pm	#4
G6Tanuki Dekatron Join Date: Apr 2012 Location: Wiltshire, UK. Posts: 13,998	Re: Back to the future As noted, the original X10 with its lack of output-LPF would cause horrible interference to LW/MW radios. (like many of Uncle Clive's offerings, there was probably more money spent on the advertising than on the technical design. I had a Sinclair "Black Watch" as a student; it went crazy every time I used one of the lab's 450MHz Pye PF70 walkie-talkie)]

3rd Apr 2019, 9:03 pm	#5
Hartley118 Nonode Join Date: Aug 2015 Location: Cambridge, Cambs. UK. Posts: 2,198	Re: Back to the future I recall my X10 class D amplifier: in fact I'm sure that I still have it somewhere safely stored in a junk box. It worked tolerably well into a single 12-inch speaker, but quickly released its magic smoke when I connected it to a more sophisticated 2-way speaker with crossover: it just couldn't handle a complex impedance load. Like so many Sinclair designs, it was a primitive premature application of an interesting innovative idea. It was way ahead of its time because of course, most consumer amplifiers are now class D. ISTR that I modified my X10 to have a much lower sample rate, and hence very restricted bandwidth. It was then little more than an illustration of the Class D principle, but interesting nevertheless. Martin __________________ BVWS Member

3rd Apr 2019, 10:59 pm	#6
Refugee Dekatron Join Date: Apr 2012 Location: Worksop, Nottinghamshire, UK. Posts: 5,553	Re: Back to the future Does anyone remember the early Sinclare basic calculator that used to count for ever if you divided 1 by zero? They were in the shops in the mid 1970s.

3rd Apr 2019, 7:59 pm	#3
Craig Sawyers Dekatron Join Date: Nov 2010 Location: Oxford, UK. Posts: 4,984	Re: Back to the future This was actually designed for uncle Clive by my old friend Gordon Edge. Actually Gordon's version was rather better than Sinclair eventually marketed. The final one that was sold had no output filter - it relied on the voice coil inductance of the speaker to do the filtering. Apparently caused mayhem with radio reception. Unfortunately Gordon is no longer with us, so I can't ask him for any more background. It was famed for lack of reliability, over-hyped power specs that it could not meet - so basically meat and two veg for Sinclair at that point. Other Sinclair background. I bought a Sinclair Scientific calculator when it was first introduced. Suppose I must have been 17 or so. It had a wonderful quirk - if you asked it to do something like find the inverse sine of something greater than 1 (which has a complex solution) it gamely tried to do it, with the display flashing fitfully for a few minutes - and then gave a result, which was of course completely spurious. And the QL had a similar quirk. The designers has put common constants and things that were done frequently by a programme writer in a look-up table. One of those was root 2. Except they had put in the wrong value into the ROM. So you got a tantalizing close answer, but subtly wrong. If you asked to find the root of 2.0001 it had to actually calculate the value - which it got right. All wonderful in the world of Sinclair. The man who used tons of dud transistors as hard core underneath his drive. Allegedly. Craig

3rd Apr 2019, 11:13 pm	#7
Craig Sawyers Dekatron Join Date: Nov 2010 Location: Oxford, UK. Posts: 4,984	Re: Back to the future The Scientific. Like I said in post #3 Craig

3rd Apr 2019, 11:16 pm	#8
Refugee Dekatron Join Date: Apr 2012 Location: Worksop, Nottinghamshire, UK. Posts: 5,553	Re: Back to the future I am pretty sure it was a basic 4 function one.

3rd Apr 2019, 11:28 pm	#9
Craig Sawyers Dekatron Join Date: Nov 2010 Location: Oxford, UK. Posts: 4,984	Re: Back to the future I must admit I'm surprised that there were so many Sinclair calculators! Google being your friend.... http://www.vintagecalculators.com/html/sinclair1.html Last edited by Craig Sawyers; 3rd Apr 2019 at 11:36 pm.

3rd Apr 2019, 11:36 pm	#10
Refugee Dekatron Join Date: Apr 2012 Location: Worksop, Nottinghamshire, UK. Posts: 5,553	Re: Back to the future I think it was a white one but not scientific. It might have been a universal. I was once given one with a broken case and the board used to do the same thing.

4th Apr 2019, 9:14 am	#11
Radio Wrangler Moderator Join Date: Mar 2012 Location: Fife, Scotland, UK. Posts: 22,877	Re: Back to the future Martin had me laughing, and gave me the idea of making a jocular remark about Clive suffering from premature application, but it was his customers who did the suffering. He missed out on making his C5 autonomous. David __________________ Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done