DIY Pedal for boosting volume

[Kesh]

I thought I would get simple advice which pedal I should build. I guess I've started a topic which is far more complicated than I expected...

My reply, first reply, gave simple advice. It isn't that complicated.

[Rethfing]

Im going to build one of these pedals suggested and we'll see

[ashcat_lt]

This thread is riddled with folks using the term "gain" when they mean "distortion"!  It hurts my head and doesn't help the OP at all.  Gain =! Compression unless Gain x Input > the circuit's maximum output!  Then you get distortion.  Boosting before distortion adds gain, makes the input signal bigger and makes that Gain x Input thing hit the maximum output faster.  You get more distortion.  Boosting after distortion ALSO ADDS GAIN, makes the input to the next stage bigger.  Assuming that this next stage has a Max output which can handle the larger Gain x Input, you'll get more volume.  Otherwise you get more distortion.

Once a given stage is putting out all of the voltage that it can - whether restricted "naturally" by the power supply or "articially" via diodes clipping - you've got all the peak-to-peak voltage you will ever get from the thing.  From there increasing either Gain or Input voltage will increase RMS voltage and reduce crest factor.  This will appear to get louder for a while as the sound kind of fills out.  At a certain point you end up with square (rectangle or pulse) waves where RMS=Peak-to-Peak and then you've got nowhere to go.

The assumption is that the distorted channel of the amp is artificially restricting its Max output via diodes to some voltage which, when multiplied by the power amp's gain, does not exceed the PA's Max output.  If we can add gain to that signal before it hits the PA, we might be able to get more output from the PA. 

Of course, at some point this bigger input x PA gain will exceed the PA's maximum output.  A solid state power amplifier sounds disgusting when it clips, and does horrible things to speakers in the process.

[R.G.]

2) Yeah, rolling down volume might do the trick but... If I do that my amps distortion will sound thin + I will never be able to roll my volume the same amount every time I use it.

Actually, there is one commercial device that does exactly that - lets you hit closely the same volume changes.

[Jdansti]

To take RG's idea a step further and compensate for some of the effects of putting a volume control between the guitar and amp, place a Tillman preamp before the switch that selects lower or higher volume. The Tillman PA is a simple clean boost that should be able to compensate for the tonal degradation of the volume pot. My guitar just sounds better clean or dirty when I use my Tillman PA.

Here's a block diagram of what I'm thinking:



And here's a Tillman PA schematic:



PS-sorry about the low quality graphics. I did these on my iPhone.

[Ronan]

Nothing wrong with the graphics John, looks good.

I think whats going on here is that the guitarist uses the Marshall amp's preamp for distortion, and uses the TS for just a bit more cream when doing solo's. Therefore, no pedal on the input side of the amp is going to give a volume boost at the speaker, it will only drive the preamp harder (more dirt/more sustain/or different tone). There's a few guitarists around that will only use the guitar volume knob at 10, because anything less than that interferes with the desired sound. I am/was one of those guitarists. So the guy is running the guitar flat chat, into a Marshall preamp dialled up, and uses the master volume to get the required volume, the required volume being significantly lower than what the amp is capable of producing. (Hmmm, thats why they invented master volumes, to get some distortion without blowing your eardrums). For solo's, the guitarist likes the extra sustain by switching on the TS, but also wants a bit more volume from the amp to "cut through" a bit better, just for the solo. Basically if someone could just notch up the master volume control a bit for the solo, this is what he would want, no tonal changes, just a bit more volume.

When I was playing regularly, many years ago, I was in this exact same situation. I had a modified Fender silverface twin, and a tech responded to my situation with this - he put an LDR from the master volume pot wiper to ground. He rectified the heater voltages and drove an LED via a pot (the "boost" pot) which controlled the LDR. A jack was installed on the back of the amp and went to a footswitch to turn the LED on or off. When the LED was off, that was "lead" volume, when the LED was on, that was "rythm" volume. Sort of works back to front like RG stated in an earlier post. Anyway the mod worked fine for many years, just perfect.

Rethfing, have a look at madboy's and slackers posts, maybe those suggestions would do the required job a lot easier.

[GGBB]

As a few others have said in one way or another - some type of volume control in the effects loop will do what you want.  I use a Morley Little Alligator volume pedal (which has a minimum volume setting) in my effects loop for exactly this purpose: heel down - normal/rhythm volume, toe down - solo/lead volume.  You could put a volume pot and a bypass footswitch in a pedal to accomplish the same thing in a smaller package, and even make it fancy with some buffering if you really want, but I expect the differences to be inaudible.  How did this get so complicated?  Isn't this a pretty classic guitar issue that is normally solved easily with a volume pedal in the effects loop?