PT20 Tube Substitutions

M

MistaGuitah

Well-known member
OK, some questions about tubes in the PT20 (single 3- way switch version).
First, has anyone substituted the EL84s with 7189s? Second, would putting cleaner ecc83/12ax7 and a 5751 for the phase interver result in more clean headroom even when dimed? What tunes have you used in your PT20, pr does anyone know if Dave has ever chimed in on this?
 
7189's are a great choice, as are 6P14P's. These power tubes are spec'd for 400v operation as opposed to 300v with standard EL84's. That alone will extend your clean headroom a little bit when dimed.
 
its not a clean amp, have it modded with the simple clean otherwise forget it
 
Rex Rocker said:
Not really. It would just make the amp quieter at the same volume knob setting.
Click to expand...
I've used these tubes in other amps, and experimented with preamp tubes in the PT20 to an extent years ago before the 3-way switch was added, but noticed no real difference in overall volume. It might seem that way at lower volumes but past 12:00, the volume seems to be unaffected by those tubes. However, I take it by quieter, you mean less noise. Indeed, spme of these cleaner tubes do a great job of reducing hiss, crackle, feedback, etc. Even if these tubes caused marginal volume loss in the PT20, it's so loud and cutting that I don't think it would affect a band situation. Luckily, I'll just be practicing and recording with it.
LP Freak said:
How much clean headroom do you really expect to get out of a 20w amp?
Click to expand...
155 said:
its not a clean amp, have it modded with the simple clean otherwise forget it
Click to expand...
Well, don't make any assumptions about my expectation of this amp being "clean" in any sense of no breakup. I love how the PT20 delivers just past edge of breakup tones with low gain settings. My intention is to extend that same kind of breakup when the volume is between 6-7, that's all. Around 5-6 on the volume, it begins to distort just a little early. If I could get it to do the same thing just a little bit louder, it would be perfect.
155 said:
BackCrack said:
7189's are a great choice, as are 6P14P's. These power tubes are spec'd for 400v operation as opposed to 300v with standard EL84's. That alone will extend your clean headroom a little bit when dimed.
Click to expand...
Click to expand...
It would seem so but I don't know the operation specs of the PT20. I was hoping Friedman or someone here could shed some light on this issue. I've seen threads in other forums about the PT20 eating up power tubes, etc. I haven't had that experience, but among all the babble, there were a couple of specific things regarding power tube and preamp voltage/output in the PT20 design that I would like to know more about. Not that I'd be able to understand it beyond a rudimentary degree, but would be helpful to know some of the parameters before sticking various tubes in.

psychodave said:
I love the 6P14P from Russia. Years back they were super cheap since nobody really knew about them.
Click to expand...
I saw a matched pair of Russian 6p4p tubes for around $40 a couple of years ago. I imagine the process gave gone way past. I don't want to sink a bunch of money into NOS tubes or any of that, just experiment a little because the PT20 is so much fun to play. One of the tube websites sells a tube set for the PT20 specifically that's all Sovtek EL84 and 12ax7. That might be a pretty good deal for tested tubes. However, I think I read somewhere that Friedman kind of avoids Sovteks for some reason, but I don't want to misremember or misrepresent that so hopefully he can chime in.
 
Those should (in my amps at least) make the sound a bit less gainy, but not what I consider to be more headroom. 12BZ7’s are the pre’s with the most headroom. They’re supposedly higher gain too, but doesn’t come off that way to me that much. More like going from a 100w to a 150w aka headroom or efficiency of sound imo
 
MistaGuitah said:
I've used these tubes in other amps, and experimented with preamp tubes in the PT20 to an extent years ago before the 3-way switch was added, but noticed no real difference in overall volume. It might seem that way at lower volumes but past 12:00, the volume seems to be unaffected by those tubes. However, I take it by quieter, you mean less noise. Indeed, spme of these cleaner tubes do a great job of reducing hiss, crackle, feedback, etc. Even if these tubes caused marginal volume loss in the PT20, it's so loud and cutting that I don't think it would affect a band situation. Luckily, I'll just be practicing and recording with it.


Well, don't make any assumptions about my expectation of this amp being "clean" in any sense of no breakup. I love how the PT20 delivers just past edge of breakup tones with low gain settings. My intention is to extend that same kind of breakup when the volume is between 6-7, that's all. Around 5-6 on the volume, it begins to distort just a little early. If I could get it to do the same thing just a little bit louder, it would be perfect.

It would seem so but I don't know the operation specs of the PT20. I was hoping Friedman or someone here could shed some light on this issue. I've seen threads in other forums about the PT20 eating up power tubes, etc. I haven't had that experience, but among all the babble, there were a couple of specific things regarding power tube and preamp voltage/output in the PT20 design that I would like to know more about. Not that I'd be able to understand it beyond a rudimentary degree, but would be helpful to know some of the parameters before sticking various tubes in.


I saw a matched pair of Russian 6p4p tubes for around $40 a couple of years ago. I imagine the process gave gone way past. I don't want to sink a bunch of money into NOS tubes or any of that, just experiment a little because the PT20 is so much fun to play. One of the tube websites sells a tube set for the PT20 specifically that's all Sovtek EL84 and 12ax7. That might be a pretty good deal for tested tubes. However, I think I read somewhere that Friedman kind of avoids Sovteks for some reason, but I don't want to misremember or misrepresent that so hopefully he can chime in.
Click to expand...
My tech stopped using them too because he says recent Sovtek’s are way too unreliable, so maybe that’s why Friedman stopped too
 
IME the EL84 varieties with the most headroom are the E84L’s, but they’re very rare & expensive. The only brands I know of that made them were Siemens & Valvo
 
Sounds like you need a dial on each one of your preamp tubes.
You can dial in & find that frog hair of headroom you’re seeking.
 
You must log in or register to reply here.
Back
Top