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Vintage Computers Any vintage computer systems, calculators, video games etc., but with an emphasis on 1980s and earlier equipment.

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Old 20th May 2024, 10:26 pm   #1
ScottishColin
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Default PET KL-4M DAC Card

I have managed to acquire a KL-4M DAC sound card for my PETs which I haven't tested yet. Once I manage to find some time I'll test it out. There seem to be schematics and a program to use it on Zimmers (Visible Music Monitor).

There's a short review here and a google search shows me that it pops in in a few early PET magazines too.

https://www.atarimagazines.com/compu..._COMPUTERS.php

Colin.
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Old 20th May 2024, 11:18 pm   #2
SiriusHardware
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Default Re: PET KL-4M DAC Card

Sounds great, the closest thing to that that I ever used on any computer was Activision's 'The Music Studio' which came in a big software bundle of mostly games with my Atari ST - I spent far more time, for longer, playing with TMS than with anything else which came with the machine.

What you have there sounds like an approximately similar setup for the PET, if so you're going to have great fun with that.
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Old 21st May 2024, 4:43 am   #3
TonyDuell
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Default Re: PET KL-4M DAC Card

Closest thing I have is Orchestra-90 for the TRS-80 Color Computer. This is a plug-in cartridge containg a ROM and a couple of 8-bit DACs feeding phono sockets on the end of the unit. You link those to the aux inputs on a stereo amplifier and can compose/play music using it.
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Old 21st May 2024, 11:26 am   #4
Phil__G
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Default Re: PET KL-4M DAC Card

There are an awful lot of resistors, its not a ladder DAC is it?
What are the two chips Colin?
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Old 21st May 2024, 11:35 am   #5
TonyDuell
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Default Re: PET KL-4M DAC Card

The resistors could well be 1k8 and 3k6 which would make an R-2R ladder very likely.

I am pretty sure the Orchestra-90 I mentioned uses discrete resistors.

I assume this KL-4M plugs into the user port (for the data lines) and a cassette port (for power)
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Old 21st May 2024, 1:37 pm   #6
ScottishColin
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Default Re: PET KL-4M DAC Card

LM358P and LM386N.

Reverse engineered schematics are here:

https://www.zimmers.net/anonftp/pub/...t/petsound.gif

Colin.

Quote:
Originally Posted by Phil__G View Post
There are an awful lot of resistors, its not a ladder DAC is it?
What are the two chips Colin?
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Old 21st May 2024, 1:38 pm   #7
ScottishColin
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Default Re: PET KL-4M DAC Card

The schematics here seem to agree with you:

https://www.zimmers.net/anonftp/pub/...t/petsound.gif

It does plug into the user port and as far as I can see from the schematics only uses the 5V pin from the cassette port.

Both the user port and cassette port are extended out to allow for other devices to also be plugged into those ports.

Colin.

Quote:
Originally Posted by TonyDuell View Post
The resistors could well be 1k8 and 3k6 which would make an R-2R ladder very likely.

I am pretty sure the Orchestra-90 I mentioned uses discrete resistors.

I assume this KL-4M plugs into the user port (for the data lines) and a cassette port (for power)
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Old 21st May 2024, 2:10 pm   #8
SiriusHardware
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Default Re: PET KL-4M DAC Card

The LM386 (+Speaker) are a loudspeaker amplifier and I notice it has an audio 'mixer' which passes the 'normal' PET audio output (from 'M') to the amplifier as well. So even when you are not using it as a DAC, you can still use it as an audio-out-to-speaker device.
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Old 3rd Jun 2024, 8:22 pm   #9
ScottishColin
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Default Re: PET KL-4M DAC Card

The inspiration bit me (along with my fear of having a bare pcb at the back of my PET) so I designed/printed a case for the KL-4M.

In the extremely unlikely event that anyone else may ever want one, it's here.

https://www.thingiverse.com/thing:6648248

Colin.
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Old 3rd Jun 2024, 8:52 pm   #10
ScottishColin
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Default Re: PET KL-4M DAC Card

And here's a Youtube video showing it in action:

https://www.youtube.com/watch?v=kukqYKvgH3A

Colin.
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Old 3rd Jun 2024, 9:27 pm   #11
Phil__G
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Default Re: PET KL-4M DAC Card

I sounds very much like Richard Russell's music compiler for CP/M
https://youtu.be/TI4b-tdONdk?si=kpNkTdPt8FKq8sB0&t=41
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