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Decades-Old DIY Sampler Mystery Solved

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  Decades-Old DIY Sampler Mystery Solved Lawrence D’Oliveiro <ldo@nz.invalid> - 2025-11-10 00:58 +0000
    Re: Decades-Old DIY Sampler Mystery Solved Theo <theom+news@chiark.greenend.org.uk> - 2025-11-11 16:59 +0000
      Re: Decades-Old DIY Sampler Mystery Solved rbowman <bowman@montana.com> - 2025-11-11 18:24 +0000
        Re: Decades-Old DIY Sampler Mystery Solved Theo <theom+news@chiark.greenend.org.uk> - 2025-11-11 22:08 +0000
          Re: Decades-Old DIY Sampler Mystery Solved rbowman <bowman@montana.com> - 2025-11-12 02:51 +0000
            Re: Decades-Old DIY Sampler Mystery Solved "Carlos E.R." <robin_listas@es.invalid> - 2025-11-12 10:52 +0100
              Re: Decades-Old DIY Sampler Mystery Solved Theo <theom+news@chiark.greenend.org.uk> - 2025-11-12 13:14 +0000
                Re: Decades-Old DIY Sampler Mystery Solved "Carlos E.R." <robin_listas@es.invalid> - 2025-11-13 18:47 +0100
          Re: Decades-Old DIY Sampler Mystery Solved "Carlos E.R." <robin_listas@es.invalid> - 2025-11-12 10:45 +0100
            Re: Decades-Old DIY Sampler Mystery Solved rbowman <bowman@montana.com> - 2025-11-12 18:47 +0000
    Re: Decades-Old DIY Sampler Mystery Solved "Carlos E.R." <robin_listas@es.invalid> - 2025-11-12 10:46 +0100
      Re: Decades-Old DIY Sampler Mystery Solved rbowman <bowman@montana.com> - 2025-11-12 18:40 +0000
        Re: Decades-Old DIY Sampler Mystery Solved John Ames <commodorejohn@gmail.com> - 2025-11-12 11:00 -0800
          Re: Decades-Old DIY Sampler Mystery Solved scott@alfter.diespammersdie.us (Scott Alfter) - 2025-11-12 23:22 +0000
            Re: Decades-Old DIY Sampler Mystery Solved "Carlos E.R." <robin_listas@es.invalid> - 2025-11-13 19:03 +0100
        Re: Decades-Old DIY Sampler Mystery Solved "Carlos E.R." <robin_listas@es.invalid> - 2025-11-13 18:52 +0100
    Re: Decades-Old DIY Sampler Mystery Solved songbird <songbird@anthive.com> - 2025-11-14 23:43 -0500
      Re: Decades-Old DIY Sampler Mystery Solved "Carlos E.R." <robin_listas@es.invalid> - 2025-11-15 14:54 +0100

#232096 — Decades-Old DIY Sampler Mystery Solved

How’s this for a “cold case”
<https://www.tomshardware.com/pc-components/sound-cards/diy-amiga-sound-sampler-circuit-mystery-solved-32-years-later-magazine-instructions-had-key-component-spec-typos>:
an issue of “CU Amiga” magazine from 1993 had a project to let you
build your own audio sampler -- only it never worked.

One of those hackers who tried, and failed, to follow the project at
the time recently revisited it, and delved deeper into trying to
figure out why the completed project did nothing but crash his
machine. He found a couple of errors in capacitor values, particularly
one that threw a clock frequency way off -- instead of 30kHz, it was
putting out only 287Hz.

After fixing these problems, he finally had his working sampler!

Worth noting that one of those typos was pointed out in the subsequent
magazine issue, but it’s not clear that the other one was ever
corrected. Without that fix, it’s hard to see how anyone could have
successfully built the project. Did all those who failed simply chalk
it up to their own (assumed) lack of ability?

Imagine all those young, budding electronics engineers who were put
off that career for life, because they couldn’t figure out how to get
this thing working ...

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#232111

Lawrence D’Oliveiro <ldo@nz.invalid> wrote:
> How’s this for a “cold case”
> <https://www.tomshardware.com/pc-components/sound-cards/diy-amiga-sound-sampler-circuit-mystery-solved-32-years-later-magazine-instructions-had-key-component-spec-typos>:
> an issue of “CU Amiga” magazine from 1993 had a project to let you
> build your own audio sampler -- only it never worked.
> 
> One of those hackers who tried, and failed, to follow the project at
> the time recently revisited it, and delved deeper into trying to
> figure out why the completed project did nothing but crash his
> machine. He found a couple of errors in capacitor values, particularly
> one that threw a clock frequency way off -- instead of 30kHz, it was
> putting out only 287Hz.
> 
> After fixing these problems, he finally had his working sampler!
> 
> Worth noting that one of those typos was pointed out in the subsequent
> magazine issue, but it’s not clear that the other one was ever
> corrected. Without that fix, it’s hard to see how anyone could have
> successfully built the project. Did all those who failed simply chalk
> it up to their own (assumed) lack of ability?

The first typo was pretty obvious - 7uF is not a common capacitor value.
Interestingly the datasheet has it (called Cref) as 4.7uF not 47uF as in the
correction.  I don't think it would have made a great difference - it's just
a decoupling cap.

For the clock, it appears to be set by C2 which looks like it should have
been 470pF not 470nF.

For C3 the datasheet says "[C1 it calls it] is chosen according
to the clock frequency so that droop of the capacitor voltage is
not significant during a conversion." but doesn't give any clues how to
calculate it.  At a guess 470nF is more likely than 470pF.

> Imagine all those young, budding electronics engineers who were put
> off that career for life, because they couldn’t figure out how to get
> this thing working ...

I suspect the number of people who made circuits out of computer magazines
was relatively small [I did!].  Probably more for dedicated electronics
magazines which were all about publishing projects.

Theo

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#232113

On 11 Nov 2025 16:59:41 +0000 (GMT), Theo wrote:

> I suspect the number of people who made circuits out of computer
> magazines was relatively small [I did!].  Probably more for dedicated
> electronics magazines which were all about publishing projects.

I think that's true for wood working, needle crafts, boat building, and so 
forth. It's sort of a vicarious feeling of satisfaction as people think 
'Yeah, I could do that!'.

I'm just as bad. i see MCU projects in Make magazine and websites that I 
could do. Sometimes I even have all the components on hand but soemhow I 
never get roundtoit.

Just as well. There were projects in 'The Anarchist Cookbook' and the like 
that could have led to loss of body parts or life had someone tried to 
replicate them.

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#232116

rbowman <bowman@montana.com> wrote:
> On 11 Nov 2025 16:59:41 +0000 (GMT), Theo wrote:
> 
> > I suspect the number of people who made circuits out of computer
> > magazines was relatively small [I did!].  Probably more for dedicated
> > electronics magazines which were all about publishing projects.
> 
> I think that's true for wood working, needle crafts, boat building, and so 
> forth. It's sort of a vicarious feeling of satisfaction as people think 
> 'Yeah, I could do that!'.

That and an interesting puzzle in the vein of 'C4 and R8 form a high pass
filter into the base of Q3, which is biased via R7 and R9.  Q5 ....'
It's nice to try to understand how a circuit works even if you'll never
build it, or have no use for the intended application.

(there were lots of projects like 'DIY electronic ignition for your car' and
I do wonder how many people actually built them in order to mod their cars)

> I'm just as bad. i see MCU projects in Make magazine and websites that I 
> could do. Sometimes I even have all the components on hand but soemhow I 
> never get roundtoit.

At that time I did build things just to build them, without actually having
much use for the end result.  I tend to be a bit more circumspect about
needing something nowadays.

Theo

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#232120

On 11 Nov 2025 22:08:41 +0000 (GMT), Theo wrote:

> (there were lots of projects like 'DIY electronic ignition for your car'
> and I do wonder how many people actually built them in order to mod
> their cars)

I did :)  The project specified a particular ferrite core that was 
unobtanium. A friend knew a guy who knew a guy...  At the time IBM spun 
off a lot of little cottage industries to handle stuff that they didn't 
want in house, in some cases because of paranoia about being a monopoly. 
Anyway the guy in question was operating his little ferrite business out 
of his garage. I drove down to his place in the outskirts of Kingston. As 
i recall he gave me the cores as a sample to avoid paperwork. And I was on 
my way to a CDI!

I've looked at enough of those projects that when I see some strange 
component or parts with values that aren't common I realize those were 
whatever the author had laying on his workbench at the time rather than 
the result of careful design.

I still have a collection of ferrite toroids, air variable caps, and so 
forth from when I was messing around with radios. You can bet if I design 
something it will be using them. Good luck finding the exact part in 2025.

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#232123

On 2025-11-12 03:51, rbowman wrote:
> On 11 Nov 2025 22:08:41 +0000 (GMT), Theo wrote:
> 
>> (there were lots of projects like 'DIY electronic ignition for your car'
>> and I do wonder how many people actually built them in order to mod
>> their cars)
> 
> I did :)  The project specified a particular ferrite core that was
> unobtanium. A friend knew a guy who knew a guy...  At the time IBM spun
> off a lot of little cottage industries to handle stuff that they didn't
> want in house, in some cases because of paranoia about being a monopoly.
> Anyway the guy in question was operating his little ferrite business out
> of his garage. I drove down to his place in the outskirts of Kingston. As
> i recall he gave me the cores as a sample to avoid paperwork. And I was on
> my way to a CDI!
> 
> I've looked at enough of those projects that when I see some strange
> component or parts with values that aren't common I realize those were
> whatever the author had laying on his workbench at the time rather than
> the result of careful design.
> 
> I still have a collection of ferrite toroids, air variable caps, and so
> forth from when I was messing around with radios. You can bet if I design
> something it will be using them. Good luck finding the exact part in 2025.

Many coils and variable capacitors at the time were unobtanium :-(

Several projects I actually built did not have the exact pieces. Some 
worked some not. Like one amplifier that required a couple of matched 
push pull transistors. Each transistor I got was a different type of 
equivalent in different packaging. One plastic, the other metallic.

-- 
Cheers, Carlos.
ES🇪🇸, EU🇪🇺;

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#232124

Carlos E.R. <robin_listas@es.invalid> wrote:
> Many coils and variable capacitors at the time were unobtanium :-(
> 
> Several projects I actually built did not have the exact pieces. Some 
> worked some not. Like one amplifier that required a couple of matched 
> push pull transistors. Each transistor I got was a different type of 
> equivalent in different packaging. One plastic, the other metallic.

I used to avoid projects with inductors because they were much harder to get
hold of than resistors or capacitors.  Often the magazine would say 'we
arranged with XYZ supplier to stock the Coilcraft 1234-56789' but you just
knew that would be trouble, especially if it was a past issue and the
supplier had probably run out.  Winding your own was similarly risky - there
was usually a ferrite core that was similarly unobtainable.

It was very 'cargo cult' - you need XXXX-XXXX part number
inductor/core/transformer, instead of saying 'you need an inductor of XX uH
that supports YY amps up to ZZ kHz' at which point you might have been able
to find a replacement by specs locally.

Theo

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#232135

On 2025-11-12 14:14, Theo wrote:
> Carlos E.R. <robin_listas@es.invalid> wrote:
>> Many coils and variable capacitors at the time were unobtanium :-(
>>
>> Several projects I actually built did not have the exact pieces. Some
>> worked some not. Like one amplifier that required a couple of matched
>> push pull transistors. Each transistor I got was a different type of
>> equivalent in different packaging. One plastic, the other metallic.
> 
> I used to avoid projects with inductors because they were much harder to get
> hold of than resistors or capacitors.  Often the magazine would say 'we
> arranged with XYZ supplier to stock the Coilcraft 1234-56789' but you just
> knew that would be trouble, especially if it was a past issue and the
> supplier had probably run out.  Winding your own was similarly risky - there
> was usually a ferrite core that was similarly unobtainable.

Yes. There was a local shop that had the copper, but ferrite cores were 
almost impossible.


> It was very 'cargo cult' - you need XXXX-XXXX part number
> inductor/core/transformer, instead of saying 'you need an inductor of XX uH
> that supports YY amps up to ZZ kHz' at which point you might have been able
> to find a replacement by specs locally.

Maybe they did not know the specs themselves.

-- 
Cheers, Carlos.
ES🇪🇸, EU🇪🇺;

[toc] | [prev] | [next] | [standalone]

#232121

On 2025-11-11 23:08, Theo wrote:
> rbowman <bowman@montana.com> wrote:
>> On 11 Nov 2025 16:59:41 +0000 (GMT), Theo wrote:
>>
>>> I suspect the number of people who made circuits out of computer
>>> magazines was relatively small [I did!].  Probably more for dedicated
>>> electronics magazines which were all about publishing projects.
>>
>> I think that's true for wood working, needle crafts, boat building, and so
>> forth. It's sort of a vicarious feeling of satisfaction as people think
>> 'Yeah, I could do that!'.
> 
> That and an interesting puzzle in the vein of 'C4 and R8 form a high pass
> filter into the base of Q3, which is biased via R7 and R9.  Q5 ....'
> It's nice to try to understand how a circuit works even if you'll never
> build it, or have no use for the intended application.
> 
> (there were lots of projects like 'DIY electronic ignition for your car' and
> I do wonder how many people actually built them in order to mod their cars)

I did, I built one such. It lasted something like 60 Km. But it was 
designed so that it was easy to remove and have the car as originally, 
so I just did that on the road and continued the trip. I supposed the 
back EMF from the car coil burned the electronics.

I was very curious to find how modern cars solved the problem. A low 
voltage electronics, and one little coil per cylinder.

> 
>> I'm just as bad. i see MCU projects in Make magazine and websites that I
>> could do. Sometimes I even have all the components on hand but soemhow I
>> never get roundtoit.
> 
> At that time I did build things just to build them, without actually having
> much use for the end result.  I tend to be a bit more circumspect about
> needing something nowadays.
> 
> Theo


-- 
Cheers, Carlos.
ES🇪🇸, EU🇪🇺;

[toc] | [prev] | [next] | [standalone]

#232126

On Wed, 12 Nov 2025 10:45:48 +0100, Carlos E.R. wrote:


> I was very curious to find how modern cars solved the problem. A low
> voltage electronics, and one little coil per cylinder.

When buying a car I check out the engine compartment for filter placement 
and other things that might make maintenance difficult. With the first 
Toyota I bought I assumes the ignition wires were neatly concealed behind 
an easily removable plastic panel. I was partially right. You can get to 
the spark plugs easily, each with their coil, although you probably will 
never need to. 

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#232122

On 2025-11-10 01:58, Lawrence D’Oliveiro wrote:
> How’s this for a “cold case”
> <https://www.tomshardware.com/pc-components/sound-cards/diy-amiga-sound-sampler-circuit-mystery-solved-32-years-later-magazine-instructions-had-key-component-spec-typos>:
> an issue of “CU Amiga” magazine from 1993 had a project to let you
> build your own audio sampler -- only it never worked.
> 
> One of those hackers who tried, and failed, to follow the project at
> the time recently revisited it, and delved deeper into trying to
> figure out why the completed project did nothing but crash his
> machine. He found a couple of errors in capacitor values, particularly
> one that threw a clock frequency way off -- instead of 30kHz, it was
> putting out only 287Hz.
> 
> After fixing these problems, he finally had his working sampler!
> 
> Worth noting that one of those typos was pointed out in the subsequent
> magazine issue, but it’s not clear that the other one was ever
> corrected. Without that fix, it’s hard to see how anyone could have
> successfully built the project. Did all those who failed simply chalk
> it up to their own (assumed) lack of ability?
> 
> Imagine all those young, budding electronics engineers who were put
> off that career for life, because they couldn’t figure out how to get
> this thing working ...

I wonder how many projects I made failed because of printing typos :-/

-- 
Cheers, Carlos.
ES🇪🇸, EU🇪🇺;

[toc] | [prev] | [next] | [standalone]

#232125

On Wed, 12 Nov 2025 10:46:47 +0100, Carlos E.R. wrote:

> I wonder how many projects I made failed because of printing typos :-/

Those BASIC programs printed in magazines that required PUSHing half a 
page of hex values must have been fun. Years ago I had a TracFone where 
actuation required entering 24, iirc, hex values. Great fun. 

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#232127

On 12 Nov 2025 18:40:09 GMT
rbowman <bowman@montana.com> wrote:

> > I wonder how many projects I made failed because of printing typos
> > :-/  
> 
> Those BASIC programs printed in magazines that required PUSHing half
> a page of hex values must have been fun. Years ago I had a TracFone
> where actuation required entering 24, iirc, hex values. Great fun. 

Compute's Gazette actually developed a checksum system for those pages
upon pages of DATA statements so's readers could catch and correct
typing errors on a line-by-line basis o_O

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#232131

In article <20251112110002.00004ddd@gmail.com>,
John Ames  <commodorejohn@gmail.com> wrote:
>On 12 Nov 2025 18:40:09 GMT
>rbowman <bowman@montana.com> wrote:
>
>> > I wonder how many projects I made failed because of printing typos
>> > :-/  
>> 
>> Those BASIC programs printed in magazines that required PUSHing half
>> a page of hex values must have been fun. Years ago I had a TracFone
>> where actuation required entering 24, iirc, hex values. Great fun. 
>
>Compute's Gazette actually developed a checksum system for those pages
>upon pages of DATA statements so's readers could catch and correct
>typing errors on a line-by-line basis o_O

Nibble had a couple of checksum systems to cover both BASIC programs and
binary blobs.  They sold their first one, but the second one was offered as
both a paid program that would dump checksums for a program and a free
version, small enough to include in every issue, that would check each line
as you typed it in.

I took that free version and hacked it into something that would dump
checksums for a program you'd already typed in.  If I remember right, I
tried submitting that back to them as a suggested improvement, but they
weren't interested for some reason. :) 

Fun fact: a dump of checksums from the older of these systems shows up in
The Terminator as part of the T-800's HUD-like display:

https://www.youtube.com/watch?v=v0vbTHd04gE

I found this explanation, which tracked down the particular issues of Nibble
with code featured in the movie:

https://www.theterminatorfans.com/the-terminator-vision-hud-source-code-explained/

-- 
  _/_
 / v \ Scott Alfter (remove the obvious to send mail)
(IIGS( https://alfter.us/         Top-posting!
 \_^_/                            >What's the most annoying thing on Usenet?

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#232137

On 2025-11-13 00:22, Scott Alfter wrote:
> In article <20251112110002.00004ddd@gmail.com>,
> John Ames  <commodorejohn@gmail.com> wrote:
>> On 12 Nov 2025 18:40:09 GMT
>> rbowman <bowman@montana.com> wrote:
>>
>>>> I wonder how many projects I made failed because of printing typos
>>>> :-/
>>>
>>> Those BASIC programs printed in magazines that required PUSHing half
>>> a page of hex values must have been fun. Years ago I had a TracFone
>>> where actuation required entering 24, iirc, hex values. Great fun.
>>
>> Compute's Gazette actually developed a checksum system for those pages
>> upon pages of DATA statements so's readers could catch and correct
>> typing errors on a line-by-line basis o_O
> 
> Nibble had a couple of checksum systems to cover both BASIC programs and
> binary blobs.  They sold their first one, but the second one was offered as
> both a paid program that would dump checksums for a program and a free
> version, small enough to include in every issue, that would check each line
> as you typed it in.
> 
> I took that free version and hacked it into something that would dump
> checksums for a program you'd already typed in.  If I remember right, I
> tried submitting that back to them as a suggested improvement, but they
> weren't interested for some reason. :)
> 
> Fun fact: a dump of checksums from the older of these systems shows up in
> The Terminator as part of the T-800's HUD-like display:
> 
> https://www.youtube.com/watch?v=v0vbTHd04gE
> 
> I found this explanation, which tracked down the particular issues of Nibble
> with code featured in the movie:
> 
> https://www.theterminatorfans.com/the-terminator-vision-hud-source-code-explained/
> 

Cute.

I should not read these things, though, they ruin the magic :-D

-- 
Cheers, Carlos.
ES🇪🇸, EU🇪🇺;

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#232136

On 2025-11-12 19:40, rbowman wrote:
> On Wed, 12 Nov 2025 10:46:47 +0100, Carlos E.R. wrote:
> 
>> I wonder how many projects I made failed because of printing typos :-/
> 
> Those BASIC programs printed in magazines that required PUSHing half a
> page of hex values must have been fun. Years ago I had a TracFone where
> actuation required entering 24, iirc, hex values. Great fun.

I think I did two of those, but they also came in ASM and I used that 
instead. I created some typo of my own. The one I remember was ted.com, 
a tiny text editor of 3 KB that would fit easily in floppies.

-- 
Cheers, Carlos.
ES🇪🇸, EU🇪🇺;

[toc] | [prev] | [next] | [standalone]

#232157

Lawrence D’Oliveiro wrote:
...
> Worth noting that one of those typos was pointed out in the subsequent
> magazine issue, but it’s not clear that the other one was ever
> corrected. Without that fix, it’s hard to see how anyone could have
> successfully built the project. Did all those who failed simply chalk
> it up to their own (assumed) lack of ability?
>
> Imagine all those young, budding electronics engineers who were put
> off that career for life, because they couldn’t figure out how to get
> this thing working ...

  amazingly i built a model railroad control system back in the
mid-to later '70s from a series of articles in a magazine and it
worked.

  there were step-by-step instructions and measurements you took
at certain points to verify things worked.  i had it up and
running before i went away to college but the house it was all
set up in was sold when i was away at college so i ended up with
boxes of model railroad, parts for the engines, all the electronics
and things all packed together in a rather jumbled mess.  i don't
know if the guy i sold it all to ever used it and some years later
after he passed away his wife asked me to sell it for her and i
had my brother do it so i never set it all up again.

  as a description is that it was a fixed voltage on the rails so
you did not need to break the circuit into different parts and the
computer imposed a signal on that voltage that was picked up by
receivers in each engine you had going.  so you needed a controller
for each engine.  at most i had three engines running at once but
i think the overall capacity was more than that (enough that i
doubt i'd have been able to run them all due to current limitations.


  songbird

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#232162

On 2025-11-15 05:43, songbird wrote:
> Lawrence D’Oliveiro wrote:
> ...
>> Worth noting that one of those typos was pointed out in the subsequent
>> magazine issue, but it’s not clear that the other one was ever
>> corrected. Without that fix, it’s hard to see how anyone could have
>> successfully built the project. Did all those who failed simply chalk
>> it up to their own (assumed) lack of ability?
>>
>> Imagine all those young, budding electronics engineers who were put
>> off that career for life, because they couldn’t figure out how to get
>> this thing working ...
> 
>    amazingly i built a model railroad control system back in the
> mid-to later '70s from a series of articles in a magazine and it
> worked.
> 
>    there were step-by-step instructions and measurements you took
> at certain points to verify things worked.  i had it up and
> running before i went away to college but the house it was all
> set up in was sold when i was away at college so i ended up with
> boxes of model railroad, parts for the engines, all the electronics
> and things all packed together in a rather jumbled mess.  i don't
> know if the guy i sold it all to ever used it and some years later
> after he passed away his wife asked me to sell it for her and i
> had my brother do it so i never set it all up again.
> 
>    as a description is that it was a fixed voltage on the rails so
> you did not need to break the circuit into different parts and the
> computer imposed a signal on that voltage that was picked up by
> receivers in each engine you had going.  so you needed a controller
> for each engine.  at most i had three engines running at once but
> i think the overall capacity was more than that (enough that i
> doubt i'd have been able to run them all due to current limitations.

Nice!


-- 
Cheers, Carlos.
ES🇪🇸, EU🇪🇺;

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