AirBrake with remote bypass?

[The_Nuge]

Hi!
I recently built an AirBrake for a friend of mine, using the plans from here and parts from Mouser. It works very well, and my friend (who's a pro guitarist) uses it a lot to tame his Plexi Marshalls. So far so good!
He asked me if there was a way remotely bypass it, so that he can knock down the volume some for rhythm, and bypass it for leads. I was thinking of fitting a relay to either bypass the signal path, or to put it throught the AirBrake circuit. I'd then switch the relay via a standard guitar amp switch and a apropriate power supply... would that work? Anyone done it? And what kind/size of relay would I need?

Cheers

Es

[RJ Guitars]

Nuge,

You should be able to do that with just a DPDT footswitch. However, it can be fraught with Peril if you create an open circuit momentarily as you make the switch.

It might be wiser to simply add a short across the airbrake that essentially works the same but doesn't have that risk. A short in parallel with a load will allow the signal to take the path of least resistance and life is good... well sorta. Open up the short and the signal is attenuated, however, some funky stuff is happening with your output impedance in this case and you might add changes in the behavior of the amp and no telling what complexities might occur. Just don't let it go to an open circuit no matter what else happens.

As option 2 you could build him an Express and let get used to doing the same thing with the volume control on his guitar.

YMMV,

rj

[The_Nuge]

Thanks rj,

The idea with the short is good!
My friend wants the AirBrake to sit back where the amp is, and switch it from the front of the stage, which is why I think I need a relay.
If just used a simple footswitch, I'd be running the speaker signal out to the footswitch and back to the AirBrake again in bypass-mode, no?
I'm a bit worried about the impedance as well...

What kind of voltage does an amp like a Plexi put out under load?

Cheers

[vibratoking]

To be honest, I can't figure out why a pro guitarist needs to reduce volume for rhythm by switching an Airbrake? The human, or the pro in this case, in the loop should be able to accomplish this very easily. It's part and parcel of playing the guitar IMO. If I were you, I'd tell him to get more pro. J/K...kinda.

[pdf64]

Not sure that an Air Brake is a good match for a Plexi; what's it's VB+?
F***ing around with the load on a screaming amp is asking for potentially damaging levels of flyback to frolic around the OT / power tubes; not destined for a long service life.

[RJ Guitars]

The build featured in the thread listed below might also give you some ideas... I much prefer the sound of this to any of the master volume or power scaling efforts I've attempted. It might give you an idea of how you can do this with a simplified version of an airbrake built into your amp... that might make it easier to switch between the attenuated and non-attenuated states.

https://tubeamparchive.com/viewtopic.php?t=25510

This is something that I refer to as "The Power Broker"

[The_Nuge]

To be honest, I can't figure out why a pro guitarist needs to reduce volume for rhythm by switching an Airbrake? The human, or the pro in this case, in the loop should be able to accomplish this very easily. It's part and parcel of playing the guitar IMO. If I were you, I'd tell him to get more pro. J/K...kinda.

He's pro enough, don't worry about that.
The thing is, he doesn't want to knock down the volume using the guitar, as that changes the sound a lot, he just wants two different levels of volume of the same sound!

[The_Nuge]

Not sure that an Air Brake is a good match for a Plexi; what's it's VB+?
F***ing around with the load on a screaming amp is asking for potentially damaging levels of flyback to frolic around the OT / power tubes; not destined for a long service life.

The AirBrake certainly sounds stellar - much better than the other attenuators he has (Marshall and something else I forget the name of).

I am also a bit worried about the OT and power tubes. If I figure out how to do the bypass, I'll want it tried out on a non-collectable amp

[The_Nuge]

The build featured in the thread listed below might also give you some ideas... I much prefer the sound of this to any of the master volume or power scaling efforts I've attempted. It might give you an idea of how you can do this with a simplified version of an airbrake built into your amp... that might make it easier to switch between the attenuated and non-attenuated states.

https://tubeamparchive.com/viewtopic.php?t=25510

This is something that I refer to as "The Power Broker"

Thanks! Will have look at that!

[LeeMo]

Show him this:
http://www.badcatamps.com/unleash-v2/

[RJ Guitars]

That is way cool... but of course for $549.00 you might consider an A/B switch and a 2nd amp?

[M Fowler]

To be honest, I can't figure out why a pro guitarist needs to reduce volume for rhythm by switching an Airbrake? The human, or the pro in this case, in the loop should be able to accomplish this very easily. It's part and parcel of playing the guitar IMO. If I were you, I'd tell him to get more pro. J/K...kinda.

He's pro enough, don't worry about that.
The thing is, he doesn't want to knock down the volume using the guitar, as that changes the sound a lot, he just wants two different levels of volume of the same sound!

Well that is an easy fix just build him a box like this to knock the volume down as needed.

[Littlewyan]

I have an attenuator with two L Pads inside which I can switch between using a footswitch. There is a little relay inside which does the switching and a battery in the footswitch. Works great for when I need a solo boost.

[RJ Guitars]

...Well that is an easy fix just build him a box like this to knock the volume down as needed.

That was the same circuit I created for the first DIY guitar amp box I ever made for myself - 1974. I didn't know much at the time and I wasn't happy with it because I didn't know to add a bright cap and it sucked the top off of my guitar sound along with the volume. I still have that box around here somewhere.

This is essentially a volume control if I have it figured correctly and I'm still inclined to think that is where the true solution is... use the volume control on your guitar and make sure your guitar has a type of control circuit that doesn't tone suck as you dial down the volume. Even with stomp boxes the volume control is one of the best tools you can make use of to vary your sounds... I will admit I really didn't appreciate that fact until I built my first TW Express and I became a believer.

[vibratoking]

Everything starts to look like a nail when you have a hammer.

Sorry, but the Airbrake idea is a bad one. Every volume change will have some effect on tone. It's inescapable.