The card shown looks very professionally done, I think.
It uses classic components, heatsinks, good capacitors, ground planes (not the aerial, hi) , and phono plugs.
If it would use BNC, it would be lab grade. Maybe. ;)
PS: I'd use a small AF tube in my design..
Edit: The TL074 are modern substitutes for the 741 op-amp. Interesting!
Edit: Do they form a push-pull output stage, for the headphones?
Edit: About that card.. Could it be that this one was made as a tone generator?
Not as a melodic card, but as a frequency generator? Sine wave, sawtooth etc ?
It would have been useful in music class or a school's computer lab.
Edit: Are the two phono plugs in parallel? Maybe for use with a stereo system?
Edit: Ok, just read page 1.. Makes sense.
A card as simple as the AdLib was likely to be invented earlier, by another group.
For simple designs, there's often just one way or two ways to approach a situation.
In this case, it is a rudimentary addess decoder and a pair of i/o ports.
Personally, I like the less conventional op-amp design in favor of an 386 amp IC.
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