How to boost volume level in Express for lead playing

[Jackie Treehorn]

The trouble with completely bypassing the airbrake is all the extra speaker cable and interrupting the speaker connection with a switch. I've posted previously about making the an footswitchable but got alukewarm response. The way I do it is to make a loop from the airbrake output to the second lug of the series resistor with a relay in the loop. Put a 9 volt in a footswitch and when you activate the relay you go from click 4 or 3 to 2. Big boost. You can choose whichever lugs you like or add a dedicated boost lug. Another way would be to break the parallel resistor into 2 resistances and jump one of them. Then the boost would work on all the settings.

[mane]

Hello Glen.
Thanks for the information.
I love your Youtube videos. Great tone and playing.

Hello Rimy.
I don't know if I understood what you wrote.
Did you mod an Airbrake so you can footswitch between bypass and the
first attenuated setting?
If so, how is it done?
Thank you.

Hi Harryk.
I have never built an amp, only FX pedals and I have very limited
electronics knowledge. I am just a musician so don't trust me too much in the technical side.
But if you use the unused half of the second triode for a boost and the output section is already compressing you would get a more
distorted sound but not an increase in perceived volume.

Riding the guitar volume knob seems to be more than enough to go from
clean to super distorted with a Trainwreck and at the same time without
huge volume changes from the clips I've heard. That's great when playing live.
Some bands and styles of music require you to have very limited dynamics and your dirty sounds should be
only a little louder or the same as your cleans. I've found this to be true specially when there are many musicians in a band.
When soloing in this situation you need some kind of volume boost.
In a trio it's easier for the drums and bass to track a guitarist dynamics.
Hendrix's Experience had a broad dynamic range playing live, dynamic changes could happen gradually which to me gives music an organic quality.
Live sound engineers can have a nightmare mixing large bands with unknown equipment or bad acoustics in the room.
If it's the first time they work with you they may not know the song structures,
or when they have to push the fader for your solo to be heard or which parts of the show require a special treatment.
It's advisable to take care of volume changes yourself. I always do.
They'll thank you for it. You will feel safer.

Mané

[harryk]

:DHi Mane! I have been playing in different bands over 30 yeras (I am 52 years now) and been building tube amps since I was 14 years old. To me this question of boosting sound level is not an critical issue. When my friend rised this topic, I tought that it would be a nice question to handle in this forum of talented tube amp hobbyists. Mr. Fisher was a genius, but being a Finnish guy and thinking how to do things in different ways, I am tempted to try to use that unused triode half to boost sound level for leads in my amp. Harry

[Ron Worley]

Riding the guitar volume knob seems to be more than enough to go from
clean to super distorted with a Trainwreck and at the same time without
huge volume changes from the clips I've heard. That's great when playing live.


Mané

I think that you have hit on what makes this amp so special- granted it's not a foot switch action- but then you get all that tonal palate in between a rhythm setting on the guitar's Volume knob and all out... plus, this amp allows you to use picking attack to vary apparent gain and level by dint of it's superior touch sensitivity. Just my 2 pesos....

Ron

[kindred]

switchable speaker cabs! one with greenies, one with h30's . impractical but it could work... actually with a 412 you might be able to go from one half of the 412 to using the full thing, impedence mismatch might be a bit to much for the ot though.

[JimiB]

why dont you just build him a pedal that has a 500K pot in it with a footswitch to turn it on and off. When its on turn it down and set the rhythm level so that when the pedal gets turned off the volume jumps up.

[j-po]

Harryk, I think you might be better off forgetting the unused triode. No trick in the pre-amp will give you more output power.

The switchable VVR sounds the best alternative to me.

Since you would be switching between just two volume levels, you don't even need full vvr - a switchable high-power zener in the power supply will do. Or a zener for B and a zener or resistor for controlling bias. Could be done with a single dpdt relay.

[harryk]

That is a good idea. The only problem that I see, is capacitors charging time when switching from one B+ voltage to another. I may try this mod when I have time within next weeks. Harry

[villems]

Hi Harry,

you could try the new DC power scaling kit from london power with two PS pots. It says on the london power site that "DC operation affords high stability and extreme responsiveness - power output changes as quickly as you can sweep the PS pot or switch between two different PS pots."

All you need (probably) is super budget kit with additional PS pot and relay to switch between different PS settings.

[Buschman]

I have seen these Marshall JCM 900s with 2 master volumes and always wondered "what the hell is that for". Now I know. A boost pedal might help some but it will overdrive things more if he is cranked up.

[Rimy]

hi mane,
you got me right, allmost.
i mod my airbrake with a footswitch so it is possible to switch between the full signal, when the footswitch is on, and the level you set on the airbrake.
whether 3, or 4 or bedroom level. you just put the footswitch in the signal path. the signal will allways take the path with the less resistance. and the question about the cable length? i've got about 5 meters of speaker cable to the footswitch and honestly, i can't hear a difference, with or without the footswitch.

ralph

[Jackie Treehorn]

The trouble with completely bypassing the airbrake is all the extra speaker cable and interrupting the speaker connection with a switch. I've posted previously about making the an footswitchable but got alukewarm response. The way I do it is to make a loop from the airbrake output to the second lug of the series resistor with a relay in the loop. Put a 9 volt in a footswitch and when you activate the relay you go from click 4 or 3 to 2. Big boost. You can choose whichever lugs you like or add a dedicated boost lug. Another way would be to break the parallel resistor into 2 resistances and jump one of them. Then the boost would work on all the settings.

Some pictures...


[img:640:480]http://www.theinside.net/misc/ab1.JPG[/img]
[img:640:480]http://www.theinside.net/misc/ab2.JPG[/img]

[/img]

[Ron Worley]

Hey Jackie- it's not really clear what you've done here, could you whip up a quick schematic???

Many thanks in advance...

Ron

[Jackie Treehorn]

Hey Jackie- it's not really clear what you've done here, could you whip up a quick schematic???

Many thanks in advance...

Ron

I went a little nuts on the "schematics." I've got three. I'd appreciate it if someone could check them, as I did them pretty quick. The black is the stock design and the modifications are in red.


Here's what I did to my airbrake, very simple and fits in the enclosure, which is tight. The relay I used is from radio shack, btw.

[img1700]http://www.theinside.net/misc/ABModSimpleBoost.jpg[/img]

Here's the same concept with a 1 pole 4 position switch added so that you can select the boost. Set the stock switch on a higher setting (BR to 2 )and the new switch on a lower (4 to 1) and switch between them.

[img1700]http://www.theinside.net/misc/ABModSelectBoost.jpg[/img]

Here's one I haven't tried, but could be interesting. It uses the rheostat as a variable boost, putting it in front of the series resistor. So, this one doesn't retain the "stock" circuit. I'm not sure of the wattage rating of the rheostat, but it would probably lower the rating of the whole attenuator with this configuration. One could also substitute another 100 watt variable wirewound resistor and be safer.

[img1700]http://www.theinside.net/misc/ABModRheoBoost.jpg[/img]


I hope these are useful!