Cassette Interface Assistance

dwight dkelvey at
Wed Mar 1 11:56:49 CST 2017

I'm not sure how something as simple as a cassette interface could be causing so much issues.

Can you post a schematic of what you have now and what the signal amplitude is?


From: cctalk <cctalk-bounces at> on behalf of allison via cctalk <cctalk at>
Sent: Wednesday, March 1, 2017 3:10:50 AM
To: cctalk at
Subject: Re: Cassette Interface Assistance

On 03/01/2017 01:40 AM, Jim Brain via cctalk wrote:
> On 2/28/2017 2:34 PM, Brent Hilpert wrote:
> Obviously, given the LM339 issues, this is unworkable in the end, but
> it did get me to realizing some outputs on the LM339, so thanks to
> both of you.
> I can plainly see the oscillation on the comparator transitions, so it
> is obvious I need a better comparator.  I'll have to source a few
> different comparator options from Digikey to fill my parts box.
> Suggestions are welcome.
OR  a bit of positive feedback.

>> Using the internal AVR comparator sounds like a better final solution
>> (fewer components), but in devising an
>> input circuit for the AVR you may be running into the same issue of
>> loading a high-impedance source.
> Though it plays into Tonly's notes about my analog understanding (or
> lack thereof), I was so disillusioned by the analog uncertainties that
> I initial focused on the AVR comparator.  By correctly biasing the
> comparator, I was able to get much better results tonight, but the
> lack of any ability to add hysteresis into the design hindered my
> success.  At transition, the signal simply bounces badly.  I tried to
> construct a low pass filter (22pF and 5K6), and some variations, but I
> was not able to overcome.  I then tried to deal with it in SW, but I
> have not yet been successful.  I'll try again, but lack of hysteresis
> is a big issue.
Single transistor audio amp before it.


> Jim

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