DIY Airbrake...

[sliberty]

YMMV, but here's my take on the Airbrake.

The first 3 notches on the attenuation switch sound great. After that, and especially in bedroom mode, the tone gets a bit buzzy. No major loss of highs like some other attenuators that I have used (Weber MiniMass for example), butthe buziness is annoying to me.

I use it mostly when I am using my UniWreck at a band practice. A few db of attenuation makes keeps my bass player from cranking his 400 watt GK, and in those low settings I don't find any loss of tone.

[KGW]

Apex Jr has heatsinks... poke around on his misc and new additions page...

Thanks. The gold one looks like it may work it it were cut down a bit.
Of course L x W = 9" x 2" would fit that Hammond box exactly.

[Munga]

I am also wondering where I can find a layout of this.


Thanks

[pjl]

Not exactly an L-Pad. It is a fixed shunt, variable series resistance attenuator. It doesn't do proper impedance matching, but apparently that's not a big problem.

The reason for not using an impedance matched L-Pad? Well, because that's not how Ken Fisher did it...

Dont think. Just clone...

(I'm using a variable 100W hifi L-Pad built into a speaker cabinet. It works OK for minor attenuation, but there is definately major tone-loss once the attenuation goes below -6dB or so. Perhaps the Airbrake works better.)

Maybe it is the mismatch that makes the power amp behave in a different way or something.

This just kind of takes the edge of the legend that pluggin your speaker cab to the wrong impedance input will destroy your OT... Funny, since Wrecks seem to have 6k primaries. Exactly the case of pluggin 8ohm cab to 4 ohm input of your 50W Marshall

Pekka

[populartsl]

I wonder if you can help a little bit. I've recieved my parts for the airbrake and the lorlin rotary switch the numbers go up anti-clockwise where on the layout there clockwise do i still attach to the numbers as in layout. And the clips for the 25ohm adjustible do i measure resistance across clip and contact to position them correctly.

Many thanks

Ben

[hairyandy]

I wonder if you can help a little bit. I've recieved my parts for the airbrake and the lorlin rotary switch the numbers go up anti-clockwise where on the layout there clockwise do i still attach to the numbers as in layout. And the clips for the 25ohm adjustible do i measure resistance across clip and contact to position them correctly.

Many thanks

Ben

Ben,

Don't worry about the orientation of the Lorlin switch, just make sure the numbers are connected correctly as per the layout. I had problems with my Lorlin switch. I'm not sure if I heated it up too much, I don't think so as I'm pretty damn good at soldering if I do say so myself, but I was getting continuity across ground and hot and it ended up being in the switch. I wired up a cheap Radio Shack switch and it worked like a champ first time.

As for the adjustible clips on the 25-ohm resistor, orient them as they look on the layout and measure the resistance from each clip to the end of the resistor closest to the first clip (that's the right side as you're looking down at it). Sometimes the clips can be touchy, you have to make sure you get them positioned right in between two ridges or they don't conduct correctly.

Hope that helps,

Andy

[populartsl]

Cheers Andy

Your helps very much appreciated

Thanks Ben

[Analog Assassin]

I have understood that the Airbrake is an L-pad attenuator with one fixed resistor and one tapped at convinient locations. Question: why not use two tapped resistors to get better impedance match? Calculating the values is easy: http://www.lalena.com/Audio/Calculator/LPad/

Pekka

Not exactly an L-Pad. It is a fixed shunt, variable series resistance attenuator. It doesn't do proper impedance matching, but apparently that's not a big problem.

The reason for not using an impedance matched L-Pad? Well, because that's not how Ken Fisher did it...

(I'm using a variable 100W hifi L-Pad built into a speaker cabinet. It works OK for minor attenuation, but there is definately major tone-loss once the attenuation goes below -6dB or so. Perhaps the Airbrake works better.)

Airbrakes are not recommended for 2-ohm output amps, according to the Trainwreck forum. What values should I use so I can use with with a Super Reverb and Bassman?

[hairyandy]

I've done a search of the forum but couldn't find anything so I thought I'd ask a question in this thread. How would/could you go about adding a line out to an Airbrake? The front end of my Express really doesn't like delays or reverbs when it's cookin' so I figured you could take a line out from the Airbrake and send it to a power amp and cab to add a "wet" signal.

Thanks for any ideas,

Andy

[Rick]

This http://www.tkk.fi/Misc/Electronics/circ ... _line.html will link to a simple voltage divider type line level circuit you could add on, but... I've found straight, unconditioned line level signals don't sound very good. One easy way around this is to use something like the Behringer Ultra G100 direct box with 4-12 cab simulation built in, it doesn't work that bad for the money...

[hairyandy]

Thanks for the link Rick. Rather than buy the Behringer unit maybe it would be cooler to build the ROG Condor Cab Sim into the line out circuit. Here's a link to the ROG Condor page:

http://runoffgroove.com/condor.html

This could be pretty cool and not too hard to implement.

Andy

[rhubarb9999]

Was a layout for this project ever done??

[BBQLS1]

I'm going to have to do this one.

[BBQLS1]

Is there a layout or schematic? I seem to find that everyone was emailed one?

(Thanks guys! I got it)

[nickt]

Could I get a copy of the schemo/layout as well?

email: thurni AT mail DOT tpg DOT com DOT au

thanks