Making footswitch for Blackstar amp... momentary? Normally open/closed?

TJT1979

I have a Blackstar Sonnet 120 acoustic amp. There is a footswitch available (FS-17 I think it was called), but where I live in S. America it's crazy expensive.

I actually have a homemade footswitch I made for my Boss DD-200 pedal. It's dual-momentary, normally closed if I remember correctly, but would be easy to switch to normally open.

Does anybody know what configuration Blackstar use for their footswitches?

Many thanks!!

Funkfingers

Footswitches for channel changing, reverb on/off or, say, chorus on/off are usually latching. 

The Blackstar FS-17, being a dual function footswitch, the cable needs to be two-conductor + shield via a TRS "stereo" jack plug.

TJT1979

Thanks for the reply.

I've got a few 3PDT switches lying round from pedal builds, which I could put in. Yes, it'll need a stereo cable. I've already got TRS connectors and a Hammond box.

How sure are you that they'll be latching? It makes sense now I think about it. 

Does anybody have a Blackstar footswitch and a multimeter?

TJT1979

Looking at pics, it has LEDs but no mention of batteries.  I'm guessing the LEDs are powered through the stereo cable. If I use a homemade switch without the the LEDs (and associated resistance/loading) could I damage something in the amp?

steamabacus

I'm not sure how they implement the power for the LEDs but I don't think you'll do any harm with a basic dual latching DIY switch. From the Sonnet 120 'Handbook' (manual) ....

39. Footswitch (Optional Purchase)
The optional FS-17 footswitch,    or any 2-way latching footswitch    can be connected
here. The first switch labelled ‘Mute’ will mute the whole amplifier, and the second
switch labelled ‘Reverb’ will defeat the reverb on both channels.

TJT1979

Aha, thanks! I didn't even THINK of looking in the manual.

Sounds like a basic dual-latching footswitch should work fine. I could even put an LED and a CLR in series with each switch and see if they light up...

Thanks peeps.

ICBM

If you want to add LEDs, there are two possible arrangements - either: the LED is in series with the switch, so the light is on when the switch is closed. With these, usually there’s no resistor in the pedal, so the only thing to determine is the polarity of the LED. (There will be current limiting in the amp.)

Or: the LED is in parallel with the switch, so the light is on when the switch is open, and the current drawn by the LED is too small to operate the switching circuit in the amp. These often do have a resistor, in which case you need to know the polarity and the resistor value.

Without experimenting or seeing the schematic, it’s impossible to say which it might be.

TJT1979

Thanks @ICBM ;

So I can choose... LED on with switch closed, or vice-versa.

It sounds like the first option will be easier without knowing anything about the amp... if I get the LED the wrong way round presumably the switch just won't turn on the Reverb or whatever, as the inverted LED will block the current which would usually signal ON to the amp.

Have I understood that right?

TJT1979

Actually, no... it sounds like it's either one or the other depending upon the configuration in the amp. If it's the first option (LED in series), then the amp will have CLR included. If it's the second, it won't.

So without seeing the schematic of the amp, I have no way of knowing.

ICBM

TJT1979 said:

So I can choose... LED on with switch closed, or vice-versa.

It sounds like the first option will be easier without knowing anything about the amp... if I get the LED the wrong way round presumably the switch just won't turn on the Reverb or whatever, as the inverted LED will block the current which would usually signal ON to the amp.

Have I understood that right?

No, you can’t choose - the way the amp has been designed dictates which it is.

You need to start by experimenting with an LED and a resistor and find out whether that alone operates the switching, or just lights up without doing.

TJT1979

ICBM said:

TJT1979 said:

So I can choose... LED on with switch closed, or vice-versa.

It sounds like the first option will be easier without knowing anything about the amp... if I get the LED the wrong way round presumably the switch just won't turn on the Reverb or whatever, as the inverted LED will block the current which would usually signal ON to the amp.

Have I understood that right?

No, you can’t choose - the way the amp has been designed dictates which it is.

You need to start by experimenting with an LED and a resistor and find out whether that alone operates the switching, or just lights up without doing.

Yep, understood. Thanks again for your help.