YM/AY Soundcard with ZX True Tone (ZXTT) and AY-3-8910A, on the SAM Coupe

This video is showcasing several pieces of my new hardware - ZXTT and my 4 Slot RC2014 Bus Interface for the SAM Coupe, released in August 2021. For more information and to order please see my website: www.samcoupe.com

Two parts to the video, first is a live recording of a YM/AY Soundcard that's plugged into the SAM Coupe via the Bus Interface card, and it's using an AY-3-8910A with a date code of "8614', so manufactured in the 14th week of 1986, playing through an X-Mini Duo speaker. The second part of the video is the line out recording, sampled on a Zoom H1n Handy Recorder.

So taking a look at the hardware I build, the first is the ZX True Tone (or ZXTT for short). This is an add-on module for Ed Brindley's YM / AY soundcard for the RC2014 DIY computer (and compatibles, plus it can be used on the SAM Coupe as this video shows!) and its purpose is to give the sound chip in the soundcard the exact clock frequency to the sound chip to have the correct pitch matching the AY in the ZX Spectrum 128K onwards.

The tone of the YM and AY sound chips are all derived from the clock signal it receives. The ZX Spectrum's AY sound chip was fed with a 1.7734MHz clock which this module matches. There isn't much control of the clock on Ed's soundcard, as his circuit can provide a clock from either the main system clock divided by 2 or divided by 4, or on the Rev 6.1 card a separate oscillator module. If you are using the card to play ZX Spectrum tunes and the AY is fed a clock speed lower then the pitch of the tones will be lower, likewise if clocked higher then the pitch of the tone will be higher, so the tunes won't sound exactly right compared to a real ZX Spectrum.

My ZXTT module replaces one of the chips on the YM/AY interface and feeds the sound chip the exact 1.7734MHz clock speed so the tunes will be the exact same pitch as the ZX Spectrum. Essential for any serious demotune fans out there!

This module will fit both the Revision 5 of the YM/AY Soundcard boards (the version currently sold as a kit by RFC2795 Ltd on Tindie or z80kits.com and I'm using myself) and Revision 6.1 boards (gerbers & schematics for both 5 and 6.1 are available from Ed himself on Github: electrifiedrc2014-ym2149)

The soundcard is plugged into the SAM Coupe via my new 4 slot RC2014 Bus Interface, an expanded version of my original 2 slot interface originally launched back towards the end of 2019. This lets you connect 4 I/O based RC2014 peripherals (such as Ed's YM/AY Soundcard as shown playing here!) into the SAM.

The tune that's playing is 'Recollection' by MmcM. The code used to play it is a patched version of PTxPlay by Sergey Bulba. (Modified to output to the I/O port used by the YM/AY soundcard, not much of a patch - just one byte changed!) and I've the code running on the SAM Coupe via a small BASIC program.

I'll be looking at patching various ZX Spectrum music code to run on the SAM and this interface in a future issue of SAM Revival magazine.

Видео YM/AY Soundcard with ZX True Tone (ZXTT) and AY-3-8910A, on the SAM Coupe канала QuazarSamCoupe