PDA

View Full Version : Commodore PC 40-III AUDIO connector



Xacalite
March 11th, 2017, 05:25 AM
Recently I saw a Commodore PC 40-III, unfortunately without opportunity to explore it deeper.
What caught my attention was the "AUDIO" connector at the rear.
I can't find any evidence of 40-III having any special sound chip, which probably means it's an output of the PC Speaker circuitry.
Can anybody confirm this?
It's a rare feature to have PC Speaker sound available on an external connector, isn't it?

krebizfan
March 11th, 2017, 07:14 AM
The service manual is out there and it shows the audio port is attached to the FE3010 which typically handles the speaker so that looks correct. I think it is there only because the earlier XT clone versions of the case had a hole in the same place for composite video and it looks like Commodore used an audio connector instead of leaving a hole to nowhere.

A-ko
March 12th, 2017, 06:54 PM
i wish more PCs came with an output, or at least a volume control! got me in trouble running games on our library's card catalog computer one time...

Scali
March 13th, 2017, 12:00 AM
Yes, I remember one clone, I think it was an Olivetti, which had a headphone jack and volume knob. As far as I know, it only had a PC speaker, no extra onboard audio.
I agree, more builders should have thought of that, because PC speakers can be LOUD, especially the ones with actual cone speakers (piezos tend to be loud only at specific resonant frequencies... still very annoying).

KC9UDX
March 13th, 2017, 12:56 AM
I built such a thing for the first AT clone I had. I made a panel that fit into an unused 3.5" drive bay, and it had a volume knob and (proper 1/4") headphone jack. It was easy enough to do. I always wondered why no one else did, and why such a thing wasn't for sale anywhere.

Xacalite
March 13th, 2017, 11:49 AM
Volume knobs seem to be more popular, they are present in Amstrad PC1512, PC1640, maybe also others of that series.
And I saw at least one PC with PC Speaker volume control in BIOS setup.

pcdata76
March 13th, 2017, 09:49 PM
And I saw at least one PC with PC Speaker volume control in BIOS setup.

Olivetti in my signature has that feature in BIOS setup. It is not so practical as the mechanical knob, but good enough if you don't need to change the setting often.

I usually route PC speaker signal over the sound card if the PC has a sound card with PC speaker input, but this time you hear nothing until the initialization of the sound card (POST beeps etc.).

Flamin Joe
March 13th, 2017, 10:55 PM
I built such a thing for the first AT clone I had. I made a panel that fit into an unused 3.5" drive bay, and it had a volume knob and (proper 1/4") headphone jack. It was easy enough to do. I always wondered why no one else did, and why such a thing wasn't for sale anywhere.

With one of the Atari PC3 8088's I have in my collection, the previous owner did a hack like this for the PC speaker (minus the volume knob) but on the side of the case. Quite cleverly they drilled a perfectly sized hole into the thick plastic trim on the left hand side exactly where the PC speaker sits internally and slotted in a headphone jack. It was very well done and you'd almost think it was factory fitted if you didn't know any better.