[sdiy] Fet to short pedal input?

[el macaco]

Thanks everyone,

The portmento pedal is normally closed, push to open the terminals, and yes in my previous message I mentioned it is a mk I odyssey.

The pedal’s ground is not connected to the jack, sould I ground the velocity output jack to the ody? I assume so.

An optoisolator is also an option.

Good to know a bjt can do it theoretically.

Ed

Get Outlook for iOS<https://aka.ms/o0ukef>
________________________________
From: Synth-diy <synth-diy-bounces at synth-diy.org> on behalf of Michael E Caloroso via Synth-diy <synth-diy at synth-diy.org>
Sent: Friday, November 28, 2025 10:39:06 AM
To: Oren Leavitt <oleavitt at proton.me>
Cc: synth-diy at synth-diy.org <synth-diy at synth-diy.org>
Subject: Re: [sdiy] Fet to short pedal input?

The dark resistance of any LDR is always going to be in parallel with the 1M pot, which will reduce the max portamento rate.

You really need a control element with infinite resistance (open circuit).  That element needs to have open circuit and short circuit states and it's hard to beat a relay controlled by a Darlington BJT.

Routing MIDI note velocity to Portamento enable is a neat expression tool - it's a trick I use on choir patches on my Andromeda.  Pitch glides only at high velocity, and you don't need an extra hand to toggle it.

MC

On Fri, Nov 28, 2025 at 9:26 AM Oren Leavitt via Synth-diy <synth-diy at synth-diy.org<mailto:synth-diy at synth-diy.org>> wrote:
Looks to me like a simple LDR (LED/photocell) may do the trick here.
Given the LDR has sufficiently high "dark" resistance.

- Oren

On 11/28/25 5:47 AM, Tom Wiltshire wrote:
> I've checked the Arp Odyssey schematics (since it has one of these
> inputs). The relevant part is attached below.
>
> The Portamento input jack is a TRS jack connected across the ends of the
> 1M audio-taper portamento pot. So shorting the Tip and Ring connections
> disables the portamento. It's not a simple short-to-ground action as I
> had thought it might be, but any bidirectional switch should work in
> this position.
>
>
>
>> On 27 Nov 2025, at 20:34, el macaco via Synth-diy <synth-diy at synth-
>> diy.org<http://diy.org> <mailto:synth-diy at synth-diy.org<mailto:synth-diy at synth-diy.org>>> wrote:
>>
>> Hi all,
>>
>> The portamento pedal input on arps has me thinking of using my midi to
>> cv converter's velocity output (+5V) to activate a fet with the two
>> pedal contacts on the source and drain.
>>
>> Can it be this simple?  The only power coming from the velocity 5v?
>>
>> Thanks,
>>
>> Ed
>>
>> Get Outlook for iOS <https://aka.ms/o0ukef>
>> ________________________________________________________
>> This is the Synth-diy mailing list
>> Submit email to: Synth-diy at synth-diy.org<mailto:Synth-diy at synth-diy.org> <mailto:Synth-diy at synth-diy.org<mailto:Synth-diy at synth-diy.org>>
>> View archive at: https://synth-diy.org/pipermail/synth-diy/ <https://
>> synth-diy.org/pipermail/synth-diy/<http://synth-diy.org/pipermail/synth-diy/>>
>> Check your settings at: https://synth-diy.org/mailman/listinfo/synth-
>> diy <https://synth-diy.org/mailman/listinfo/synth-diy>
>> Selling or trading? Use marketplace at synth-diy.org<mailto:marketplace at synth-diy.org>
>> <mailto:marketplace at synth-diy.org<mailto:marketplace at synth-diy.org>>
>



________________________________________________________
This is the Synth-diy mailing list
Submit email to: Synth-diy at synth-diy.org<mailto:Synth-diy at synth-diy.org>
View archive at: https://synth-diy.org/pipermail/synth-diy/
Check your settings at: https://synth-diy.org/mailman/listinfo/synth-diy
Selling or trading? Use marketplace at synth-diy.org<mailto:marketplace at synth-diy.org>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://synth-diy.org/pipermail/synth-diy/attachments/20251128/879389db/attachment.htm>