Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: garyboy on December 18, 2012, 10:20:00 pm

Title: PAB how does it work?
Post by: garyboy on December 18, 2012, 10:20:00 pm

I was tossing around the idea of installing a PAB on a Marshall JTM45 circuit and was wondering if someone could shed some light on how it works in the circuit and what its doing to get the boost effect. I can't wrap my brain around it right now. "My tiny pea brain needs electro-lyteh"~TROPIC THUNDER. Nah just need more coffee.

Title: Re: PAB how does it work?
Post by: tubenit on December 19, 2012, 01:30:32 am

http://ampgarage.com/forum/viewtopic.php?t=15229&highlight=pab+comparison (http://ampgarage.com/forum/viewtopic.php?t=15229&highlight=pab+comparison)

with respect, Tubenit

Title: Re: PAB how does it work?
Post by: jerrydyer on December 19, 2012, 10:32:31 am

easiest mod in the world. install switch (break) between mid pot ground lug and actual ground

Title: Re: PAB how does it work?
Post by: garyboy on December 20, 2012, 09:52:53 am

Thanks for the link Tubenit. Installing a switch between mid pot ground lug and ground I heard something like that before. I think someone on this board called it a "LICK LIFTER" but i think they had it wired so that you could switch a 5k-10k resistor between the pot's ground and actual ground.

Title: Re: PAB how does it work?
Post by: guitardude57 on December 21, 2012, 10:08:14 am

As Tubenit and Geezer explained in a previous post, you can share a ground switch with the bass and mid pot grounds,
adding a resistor from switch to ground.  Anywhere from a 5K or more resistor, to taste.

Title: Re: PAB how does it work?
Post by: jojokeo on December 22, 2012, 02:28:52 pm

It's basically a "ground" lift not a lick lifter. That's just some kind of gimmick name to what it actually is and does. BY lifting the tone stack you are effectively ungrounding it, hence "lifting" it from ground. What this does is it keeps your signal from being loaded or "dragged" down which increases the signal voltage level/strength to what it would otherwise be without having a tone stack. This effect is more of what gives a Tweed amp their sound with the signal then having all of the mids that a normal tone stack tends to remove or "notch" out. End result is a full broad spectrum signal and at a higher voltage level which sounds much louder and fuller.