[sdiy] MIDI cable impedance and MIDI In ESD protection?

[Oren Leavitt]

The ferrites are nice to have - particularly if you're near a 61,000 
watt FM radio station.

- Oren

On 6/26/24 5:49 PM, grant musictechnologiesgroup.com wrote:
> The latest MIDI electrical spec CA33 shows "optional ferrite beads to 
>  improve EMI/EMC performance (FBx 1K @100MHz)"as well as "optional 
> small capacitor (0.1 μF typical) to improve RF grounding", along with 
> diagrams.
>
> GB
>
> ------ Original Message ------
> From "Mattias Rickardsson" <mr at analogue.org>
> To "modular at go2.pl" <modular at go2.pl>
> Cc "synth-diy at synth-diy.org" <synth-diy at synth-diy.org>
> Date 6/26/2024 1:57:09 PM
> Subject Re: [sdiy] MIDI cable impedance and MIDI In ESD protection?
>
>> Thanks all for the discussion and advice.
>> Also a good idea to peek in commercial schematics, I see Kurzweil's 
>> 1nF caps now. :-) A bit larger than the 330pF ESD caps I was 
>> simulating, and a bit smaller than the 3nF of the wurst-case MIDI 
>> cable in Roman's example - which barely passes the MIDI pulses with 
>> style.
>>
>> /mr
>>
>>
>> Den ons 26 juni 2024 17:21Roman Sowa via Synth-diy 
>> <synth-diy at synth-diy.org> skrev:
>>
>>     yes, before the resistor, otherwise it made no sense - LED or
>>     resistor
>>     would go poof before TVS start to conduct
>>
>>     Roman
>>
>>     W dniu 2024-06-26 o 17:00, Ingo Debus via Synth-diy pisze:
>>     >
>>     >
>>     >> Am 26.06.2024 um 15:51 schrieb Roman Sowa via Synth-diy
>>     >> <synth-diy at synth-diy.org <mailto:synth-diy at synth-diy.org>>:
>>     >>
>>     >> Maybe better to use TVS across the LED
>>     >
>>     > Hmm, usually there’s already a standard silicon diode (1N914 etc)
>>     > anti-parallel to the LED, for reverse-voltage protection. Would an
>>     > additional TVS do any good here? The LED or the silicon diode
>>     would
>>     > conduct at a much lower voltage than the TVS.
>>     > If there’s a really nasty spike, the 220-ohms-resistor would
>>     have to
>>     > absorb most of its energy, no matter which of the diodes/TVS
>>     conduct. Or
>>     > do you mean to connect the TVS _before_ that resistor?
>>     >
>>     > Ingo (remembering endless discussions with colleagues on the
>>     use of TVS
>>     > diodes and varistors…)
>>     >
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