Pentode/Triode switch
- Thread starter Mugician
- Start date
well... you cant "really" get it into triod
But, you'll get roughly 2.5 times the hum, half the wattage dissipation, half or less tube life, about 3x the distortion at some frequencies, and a hole in your amp for the switch. Done right, you'll need to trim the bias for each set of tubes you put in there - that is - two bias circuits, one for "pseudo-triode" and one for pentode (or more likely, beam power tube).
Pentodes are pentodes because they have five elements - cathode, control grid, screen grid, suppressor grid, and plate. The screen and suppressor grid control some of the intra-tube capacitance as well (effectively halving it), so when you switch the screens, you'll knock the highs into the trash.
A better mod, imho, is altering the negative feedback circuit from "none" to stock (or maybe a bit more than stock too), via a three or four way rotary switch. This will act as a presence control - sort of - not exactly, but will dramatically shape your high end, and breakup grit. Doesn't shorten tube life, or require a bias mumbo jumbo feature, but you'll still have a hole in your amp for the switch.
But, you'll get roughly 2.5 times the hum, half the wattage dissipation, half or less tube life, about 3x the distortion at some frequencies, and a hole in your amp for the switch. Done right, you'll need to trim the bias for each set of tubes you put in there - that is - two bias circuits, one for "pseudo-triode" and one for pentode (or more likely, beam power tube).
Pentodes are pentodes because they have five elements - cathode, control grid, screen grid, suppressor grid, and plate. The screen and suppressor grid control some of the intra-tube capacitance as well (effectively halving it), so when you switch the screens, you'll knock the highs into the trash.
A better mod, imho, is altering the negative feedback circuit from "none" to stock (or maybe a bit more than stock too), via a three or four way rotary switch. This will act as a presence control - sort of - not exactly, but will dramatically shape your high end, and breakup grit. Doesn't shorten tube life, or require a bias mumbo jumbo feature, but you'll still have a hole in your amp for the switch.
Since I don't know anything about this stuff, please forgive my ignorance.
What I was thinking of was a switch to half the power (or even a three way for full, half, and a quarter power) so I can get earlier break up. I'm playing through a 50 watt amp that really needs to be cranked to get natural break up, and I'm currently out of a band and doing a helluva job annoying my brothers who have to listen to me tear it up.
I'm really into minimalism, and love the idea of amps like this: http://www.ampmaker.com/ak03x.asp, but then again, amps like this: http://www.mesaboogie.com/Product_Info/Lonestar/LonestarSpecial.htm really get me going too. I love the idea of an amp that can switch between a high wattage and a low wattage, and would love a simple, sexy amp that I can carry with one hand (my current amp takes two, and a lot of effort).
Problem is, I don't have the money to be buying things left and right and trying them out, and therefore, decisions on gear purchases are becoming major investments. So, instead of worrying about what I'd like different about my amp, I figure I'd just make the changes myself.
I've built a couple effect pedals for myself, and love working with a soldering iron, and really want to tackle one of those Ceriatone amps one day. I know I don't know much of anything having to do with the science behind amps, but you gotta start somewhere right? And I figure starting with modding your own amp is a good place...
Okay, back to the point. I want to be able to take the power rating down on my 50 watt amp. Not just take it down, but be able to switch between say, 5, 25, and 50 watts. Possible?
What I was thinking of was a switch to half the power (or even a three way for full, half, and a quarter power) so I can get earlier break up. I'm playing through a 50 watt amp that really needs to be cranked to get natural break up, and I'm currently out of a band and doing a helluva job annoying my brothers who have to listen to me tear it up.
I'm really into minimalism, and love the idea of amps like this: http://www.ampmaker.com/ak03x.asp, but then again, amps like this: http://www.mesaboogie.com/Product_Info/Lonestar/LonestarSpecial.htm really get me going too. I love the idea of an amp that can switch between a high wattage and a low wattage, and would love a simple, sexy amp that I can carry with one hand (my current amp takes two, and a lot of effort).
Problem is, I don't have the money to be buying things left and right and trying them out, and therefore, decisions on gear purchases are becoming major investments. So, instead of worrying about what I'd like different about my amp, I figure I'd just make the changes myself.
I've built a couple effect pedals for myself, and love working with a soldering iron, and really want to tackle one of those Ceriatone amps one day. I know I don't know much of anything having to do with the science behind amps, but you gotta start somewhere right? And I figure starting with modding your own amp is a good place...
Okay, back to the point. I want to be able to take the power rating down on my 50 watt amp. Not just take it down, but be able to switch between say, 5, 25, and 50 watts. Possible?
mayfly
Epic Member
- Messages
- 8,746
Well, my experiments in 'triode' switches convinced me that it won't do what you are looking for.
In my experience (in a fender deluxe reverb), it did NOT make the amp appreciably quieter, and changed the overall character of the amp so it had significantly slower transient attack. Translation - it sounded like crap.
I managed to get what you are looking for using a Tom Sholtz power soak and a big boost pedal out front. You can get the power soak cheap these days, as it's been a bit outclassed with modern attenuators. Still sounded fine IMHO. Oh - and I ran it in pentode mode as it was designed to be run.
In my experience (in a fender deluxe reverb), it did NOT make the amp appreciably quieter, and changed the overall character of the amp so it had significantly slower transient attack. Translation - it sounded like crap.
I managed to get what you are looking for using a Tom Sholtz power soak and a big boost pedal out front. You can get the power soak cheap these days, as it's been a bit outclassed with modern attenuators. Still sounded fine IMHO. Oh - and I ran it in pentode mode as it was designed to be run.
jackthehack
Epic Member
- Messages
- 5,630
What kind of an amp do you have? Where do you play?
