#1
Hi. So I've built my amp from a kit. And I want to mod it. I want a bit more of distortion. The amp I have is the s5a from ampmaker. However I want to add another tube before the tone stack.
Silly question. The B+ in the last stages has to have a bigger voltage than the 1st two? I ask because every schematic I see, that is the case.
If so..why?
Thanks!!
#2
You may want to just build a booster pedal to push the tubes harder, rather than creating a new tube stage, just incorporate a MosFET booster before the preamp. Makes the tubes distort more and offers little distortion itself.
#3
Quote by blandguitar
You may want to just build a booster pedal to push the tubes harder, rather than creating a new tube stage, just incorporate a MosFET booster before the preamp. Makes the tubes distort more and offers little distortion itself.


I have a pedal that works fine for it....but :
1. I wanted to know,
2. It's fun
3. Wanted a pure amp distortion (maybe just...because)
4 . The MosFET option was thought as well.

What I wanted in the end, was to make a on/off switch-able extra stage It's not a big fuss. Just need an extra tube, the biasing and that's it. But if it's recommendable to have higher voltage in the last tube to have more distortion maybe, i'll have change some wiring in the tube already in the circuit.
#4
It would be pure amp distortion, that's the beauty of it. You use a clean booster to merely drive the tubes harder. If you wanted more distortion, you lower the voltage to decrease the headroom. Adding a tube sounds all and well, however, if the power transformer isn't designed to handle the additional load for the filaments, it's more complicated. Whereas a MosFET stage can use hardly any current and your PT won't even know.
#6
It would help if you have a schematic o the amp, and a picture of the build that shows how much room you have in there. Some amps are luxurious in terms of room than others.


Yes, you can add a tube. I would personally add the new tube after the preamp, not before. Then add an input volume control, gain control, and a master for the new stages. Sort of what dumble did with the blackface fender circuits. It really depends on what you want to do, the tools available, budget, etc. I understand that you want to keep it all tube.
Call me "Shot".

ShotRod Guitar Works

Custom Hand-wired Amplifiers and Effect Pedals.

Est. 2007


Source to everything I say about Guitars, Pedals, and Amplifiers: I make them.


UG's Best DIY PedalBoard
#7
I have built the SE-5A myself, so I know what you are talking about. Personally, I went on to build another amp with a bigger output stage and four cascading gain stages in the preamp, but there is no reason you can't add another tube to your amp.. The PT should hold up fine, and there is plenty of room, though you may want to buy another blank turret board and start the board from scratch, to keep things tidy.

Your best bet is probably adding a gain stage then a cathode follower, between the second existing gain stage and the tone stack. This is a pretty common layout, and should give you lots more gain to play with! I am not an expert, but as I understand it, the B+ doesn't have to be bigger in the latter stages, but it usually is, because you generally need a bit more power supply filtering between every couple of preamp stages to keep the noise down, and the usual way to do this is a resistor in the B+ line and a big capacitor to ground. This resistor is what causes the drop in B+ as you get closer to the input. Good luck!
#8
Pre amp tubes don't draw all that much current so I think you'll be alright running another tube off the PT. You definitely can do it. And I second what EC says about adding a master volume after the pre amp so if you want you can crank up the pre amp and resist it down for a lower volume with overdriven sounds (although no power tube distortion in that case).
#9
Quote by LeviMan_2001
I like the mosfet idea. But lets consider first what tubes you've got. If they're something like 12au7s you can just swap them for 12ax7s for more gain!

I have one 12ax7s.

I already ordered the stuff. I'm adding an extra 12ax7 with cathode follower, which will be optionally bypassed . to have clean and "lead" sound. Lets see what will be the sound after the modding.
#10
Quote by the_lowlifer
I have built the SE-5A myself, so I know what you are talking about. Personally, I went on to build another amp with a bigger output stage and four cascading gain stages in the preamp, but there is no reason you can't add another tube to your amp.. The PT should hold up fine, and there is plenty of room, though you may want to buy another blank turret board and start the board from scratch, to keep things tidy.

I ordered another board (not turret the perforated ones) and I'll add the mods to it while connecting the points to the old turret. Like this I can go back really fast if the sound doesn't please me.

QUOTE=the_lowlifer]
Your best bet is probably adding a gain stage then a cathode follower,

That's what I'm doing.



between the second existing gain stage and the tone stack. This is a pretty common layout, and should give you lots more gain to play with! I am not an expert, but as I understand it, the B+ doesn't have to be bigger in the latter stages, but it usually is, because you generally need a bit more power supply filtering between every couple of preamp stages to keep the noise down, and the usual way to do this is a resistor in the B+ line and a big capacitor to ground. This resistor is what causes the drop in B+ as you get closer to the input. Good luck!