[Coco] Coco Cassette interface help

Dave Philipsen dave at davebiz.com
Tue Feb 28 17:26:05 EST 2017

> On Feb 28, 2017, at 1:25 PM, RETRO Innovations <go4retro at go4retro.com> wrote:
>> On 2/28/2017 1:05 PM, Dave Philipsen wrote:
>> All you want to do is amplify the signal that is coming from the CoCo cassette out. Use a capacitor to de-couple it from the comparator circuit. It won't matter if there's DC bias on the output of the op amp because you will effectively remove it with the cap.
> True, and I will give it a shot, but I'll continue to search for a way to make the comparator idea work alone.  Amplifying the source only to get it "over the bias" of the comparator just seems wrong to me :-)

If you think about it, in essence, that's exactly what the cassette deck is doing by amplifying the signal into the range of amplitude that is usable by an 8-ohm speaker which is slightly higher than line level.  The whole problem here is that the cassette out is line level and cassette in is speaker level. If you want to use the exact same comparator circuit used on the cassette input of the CoCo then you have to amplify your signal up to speaker level.  Alternatively, you can tweak the comparator to work with line level.


> Still, I already was thinking of your idea, in the context of using an LM386 to amp the signal brute force to get it to work.  So, I agree it's a workable solution.  Thanks for the suggestion.
> I am also going to see if I can feed some known signals into the comparator to see if I have messed up the design.
> Jim
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