Switchable Volume on Airbrake

[murky69nz]

Hi ya'll

Just wondering whether it's possible and/or relatively easy to incorporate two footswitchable volumes into a DIY airbrake - switched with either a simple on/off footswitch, or a relay out like you find on many modern effects units?

The issue I have is that once the amp is dimed and attenuated, there's nowhere to go in terms of volume for solos etc.

Anyone got any ideas?

[ckpop]

Question Do you use any effects in front of the amp ?

If you do anything with a level control might give you the boost for solo's. You can use the level control and turn down the effect level. The best results is for the effect to have a true bypass. You may have to experiment to see what works the best in front of the amp and how far down you crank the airbrake.

Yes I understand many purist don't believe in anything in front of the Trainwreck but it is not wrong. Playing live is a different sitiuation than recording with the amp. Give this a try first and see if it works for you

[Tone_Chaser]

I was in the same boat, this is how I did it. I am running a Plexi dimed with a PPIMV used to set my lead volume and the attenuator to get my rhythm vlolume (no boost or volume pedal would do any good with it dimed).

I couldn't find a DPDT relay around so I used two SPDT relays (7-9V relay $4.50 ea from Radio Shack). You power the relays through a footswitch. Either put a battery in the footswitch or power it with a 9V power supply. Remove the wire from the input to the first lug and wire it to both inputs on the relays. Use either the NC or NO from one of the relays and hook it to to the first lug (where the input wire was) and then use the NC or NO from the 2nd relay (which ever one you didn't use on the first relay) and hook it directly to the output. It only makes a difference how you hook it up if you put an LED in the footswitch.

In one position you go through the Airbrake at whatever you have the switch set to, the other position bypasses the Airbrake. If you need attenuation for both settings then hook one to what ever lug you need instead of the output.

I hope this makes sense with the picture.

[murky69nz]

Awesome, that makes perfect sense.....

I've done a lot of tinkering and building over the years, but have never had occasion to tinker with relays.....so I'll do a little homework on the practicallities of how they work before I dive in.

Napkin diagram would be great if you can be bothered, but please don't put yourself out, I'm happy to do the ground work myself....

One Q though, is the footswitch a simple matter of your standard on/on footswitch turning a 9v on and off? Any other circuitry required in the footswitch to regulate current etc or is that done in the relay itself? How long will the battery last if you leave it "on"?

Thanks

[Tone_Chaser]

There are dozens of guys here who could explain it better than I can, but this is the long and the short of it.

A relay has a contact or set of contacts that are either closed (or shorted) or open with no voltage applied. When you energize the relay it will change states (open if closed and closed if open). The normal state is whatever the state of the contacts is when no power is applied. So a normally open relay (NO) will close with power applied.

You can use just a basic on/off footswitch to kill or apply power to the relays. I use a power supply so I don't know how long a battery will last. If you only use it for leads I would think it would last a while, there is very little current draw from the relays.

You can also add an LED to show you what state you are in (power or no power). I have mine wired to the NC contact which engages the attenuator and when I hit the lead switch that contact opens and the NO contact closes sending the signal from the input straight to the output, bypassing the airbrake.

I hope this and the associated drawing helps. There really isn't much to relays and this is a really simple thing to add to your airbrake.

And it's no trouble, just paying it forward from all of the help I have received here. There are a bunch of great, knowledgeable people here who are very willing to help.

[Ron Worley]

Barry, I'd like to see how you have the LED wired into this circuit. I'm assuming that you just have it switched with the 9V power with a dropping resistor then to ground?

I get the relay part and found a nice 24VDC DPDT relay in my parts bin... so I am defintely going to give this a go.

[Tone_Chaser]

Ron-

I'm going to have to look at my pedal (it's on my pedal board in the trailor). I had to futz with it a little bit to get it to work the way I wanted so I don't remember for sure how I did it. I'll look when we play Saturday night and let you know.

I'm sure it's something like what you said. Basically across the battery with a resistor and the switch opens the circuit which removes the battery from the LED and the relays.

Give it a try, it's really easy. Once I built it I plugged in a cable and put a 9V battery across the tip & sleeve to test the relays. I heard them clicking away so I plugged it in hit a cord & put the battery across it again and the volume jumped up.

This really helped me out, it's the only thing I could find that would give me enough boost.

[Ron Worley]

The other question I have is the rating of the relay- given the relatively high current of a speaker output, what rating is required with a safety margin?

[Ron Worley]

Bump, anybody have an idea on the current rating required for the relay?

[Tone_Chaser]

Ron-

That's a good question. I'm not sure how to figure that, but this is the relay I am using:

http://www.radioshack.com/product/index ... Id=2049716

I've been using this setup for close to a year with no issues so I would think it won't be an issue.

[Tone_Chaser]

Here is the diaram of my footswitch. There may have been a better way to do it, but this works for me so I just left it and didn't search for a better way.

[murky69nz]

Barry, just wondering, are those relays you're using on/on or on/off ? I'm assuming on/off as you've used two. If they were on/on you could get away with using just one right?

[Tone_Chaser]

I am trying to remember why we decided to go with the DPDT (in this case two SPDT) relay instead of the single SPDT. The other guitar player in my band is an electrician and he helped me with the idea.

Here are a couple of pictures of my Airbrake & footswitch. The gut shot of the pedal isn't very pretty because I had to wire it two or three different times to get it to work how I wanted it. But it will give you an idea.

[Tone_Chaser]

The pedal shot was taken with my phone, so......

Basically the red wire on the right goes from the positive terminal of the power jack to the footswitch. The other contact of the footswitch has two red wires coming off of it. One goes to the tip of the jack to turn the relay on and off and the other wire goes to the LED. The 2nd leg of the LED goes to a resistor and then to the sleeve lug of the footswitch jack. Then there is a black wire from the same sleeve lug to the negative terminal of the power jack.


Whew!

[Ron Worley]

Thanks Barry, I understand it perfectly now. I am going with a 10 amp rated relay, that should be plenty..