Volume boost installing

[cornel moldovan]

Hi everybody..i feel the need to install a simple footswich for simple volume boost on my Dumble .. Can any body give me some suggestions about the best stage that can host this function ?... I want to keep the classic 1979 schematic , that seems to me best sounding.. Will it be good if i'll tweak the bias voltage, for this? Or to use a j FET to modify the value of the volume pot (grid resistor) , without affecting the Anode and Cathode resistor values . Keep in mind ,that i want the boost , effective both for clean and drive tones,and I do not agree the mid boost , or external booster pedal. It should be good if to replace the PRESENCE , with a BOOST RANGE potentiometer , that you could preset the lead level , a little bit over the normal riff level. My English is very bad..

[Bob-I]

I've thought about this myself and ran a test. I put a volume pedal in the loop. I set the amp so that the pedal on the floor was the boost volume I wanted, then backed it off a tad for lower volumes with the same amount of drive. Works well and no mods to the amp at all.

The mods you mention would change the amps tone too much. If you don't want to use the volume pedal, I'd put a 1M pot just before the PI and a relay to switch it out of the circuit. Set the amp for the boost volume you want, the extra pot for reduced volume.

In my opinion, you'd want to lower the volume of the amp from your max setting, not raise it. Boosting the volume will change the amp too much.

[mlp-mx6]

Brandon's footswitchable FET may fit the bill.

[sound mind]

Hi,
I am sorry but you cannot do any of the things in the way you have suggested without changing the sound of the amp. The best of your ideas is the one where you add a resistance (variable and switched in or out by relay) from the volume pot wiper to ground but this will tend to reduce bass, depending on how high your volume pot needs to be set. The higher you have to set it, the more bass you will lose when you add the resistance. It may work well enough if you don't mind some amount of bass loss when playing quieter.

LC uses a volume pedal with a built in FET interface to achieve the result you want.

The only other thing I can think of is to motorize the volume pot with radio control like Neil Young, which will be expensive and difficult to do. Or maybe do it more cheaply by devising a mechanical arrangement with maybe a cable and using a pedal to control some of the range of your original pot. I once used a photographer's bulb shutter release to control a string bender installed on my headstock by air pressure. It worked well actually, until the bulb rubber deteriorated.

[Bob-I]

Hi,
I am sorry but you cannot do any of the things in the way you have suggested without changing the sound of the amp. The best of your ideas is the one where you add a resistance (variable and switched in or out by relay) from the volume pot wiper to ground but this will tend to reduce bass, depending on how high your volume pot needs to be set.

That wasn't my experience at all. The volume pedal was in parallel with the master volume making it a 500K pot instead of a 1M. If you want to be really picky you could go with 2M pots. I found it worked great with 1M pots with no drop in bottom or top.

[llemtt]

I personnally use a footswitchable pot inside the (active) loop, no appreciable tone change and it works.

But since I like much more keeping my amp volume constant and add a little boost at p.a. for solos I am now changing my setup like this:

amp -> palmer speaker sim D.I. (goes also to speaker) -> boost footswitch -> p.a.

cheers
teo

[sound mind]

Hi,
I am sorry but you cannot do any of the things in the way you have suggested without changing the sound of the amp. The best of your ideas is the one where you add a resistance (variable and switched in or out by relay) from the volume pot wiper to ground but this will tend to reduce bass, depending on how high your volume pot needs to be set.

That wasn't my experience at all. The volume pedal was in parallel with the master volume making it a 500K pot instead of a 1M. If you want to be really picky you could go with 2M pots. I found it worked great with 1M pots with no drop in bottom or top.

So going by the #124 schematic I am looking at, which has a 1M master, I guess you mean the volume pedal was in parallel with the wiper to ground of the master volume pot and no dlator used, that would be good enough with the master backed off as the impedance sent to the pedal would be lower than 1M. With the cable runs and the 1M value of the pedal, did you perceive any loss of highs when backing off the pedal? Or did you have a bright cap in the pedal too? I am going to try it if it worked well.

[Structo]

How about using a clean boost pedal in front of the amp?

I think the PAB was Dumbles idea of a cheap boost but it is dependent on where the tone controls are set for how much boost you get.

That Dr. Ika has a mod for his amp I'll see if I can dig it up.
I didn't do it because it requires another hole in the face plate.
But he uses the FET jack hole.

I'm not sure because I haven't studied it but I think it is only for the overdrive channel.

[Structo]

This is his whole Ceriatone layout that he modded.

[greenbottle]

Tom
I think you will find that the particulal mod you are refering to is an addittional pot in series with the normal volume pot. The second pot (in the FET hole) is short circuited by the PAB relay.

Thus you would operate the PAB relay and adjust the normal volume control to establish where you wanted be "out of the mix" release the PAB relay and adjust the second pot for where you want to be "within the mix". The beauty is the right amount of boost for all occasions.

Alan

[Bob-I]

With the cable runs and the 1M value of the pedal, did you perceive any loss of highs when backing off the pedal? Or did you have a bright cap in the pedal too? I am going to try it if it worked well.

I ran very short cables from the D-ulator and there was no real difference in treble. One of the beauties was the highs didn't roll off when I backed off the pedal. A better implementation IMHO would be a relay switched pot in the amp. I found the pedal a bit sensitive to slight changes with my foot.