Members Ron Burgandy Posted March 23, 2012 Members Share Posted March 23, 2012 This dude definitely doesn't either. Very nice guy. Almost makes me wonder what's up Link to comment Share on other sites More sharing options...
Members knucklefux Posted March 23, 2012 Members Share Posted March 23, 2012 12AT7's are cool tubes. Lower gain but they produce more voltage. So in the PI they work well as they're a bit more dynamic. At least that's the theory and it's been my experience. It's mostly a feel thing. tubes don't produce any voltage... Link to comment Share on other sites More sharing options...
Members ej Posted March 23, 2012 Members Share Posted March 23, 2012 tubes don't produce any voltage... And the mighty Zach, bearing the mark they call SIN, did swing his might hammer of wisdom and smote all those without knowledge. Link to comment Share on other sites More sharing options...
Members Dolf Posted March 23, 2012 Author Members Share Posted March 23, 2012 And the den ran violently with the blood of the heathen Link to comment Share on other sites More sharing options...
Members ej Posted March 23, 2012 Members Share Posted March 23, 2012 and all was laid to waste. Link to comment Share on other sites More sharing options...
Members eyeball987 Posted March 23, 2012 Members Share Posted March 23, 2012 I use a JAN GE 5751 in the PI spot of the Randall RM's I have had. In my experience, it adds some clarity and more usable range on the gain with the preamp's. The 5751 had this effect when using 6550's, 6L6's, EL34's, and any combination of those tubes in the 100 watt power sections of the RM's I have played. I believe that many Fender amps come stock with the AT7 in the PI. I remember reading somewhere that the AT7 also works well in Rivera's. I have had a few of those as well but don't remember trying that out. Link to comment Share on other sites More sharing options...
Members knucklefux Posted March 23, 2012 Members Share Posted March 23, 2012 so i'm laying {censored} to waste now? {censored} yeah. Link to comment Share on other sites More sharing options...
Members madryan Posted March 23, 2012 Members Share Posted March 23, 2012 depends on the components in the PI circuit. in mine, the result is a larger signal swing than with a 12ax7.tubes don't produce any voltage... I coulda swore I read that {censored} on Aiken amps site... hmmm... Link to comment Share on other sites More sharing options...
Members knucklefux Posted March 23, 2012 Members Share Posted March 23, 2012 I coulda swore I read that {censored} on Aiken amps site... hmmm... if RA said that tubes produce voltage, i'll eat {censored}. Link to comment Share on other sites More sharing options...
Members NaturalBornBoy Posted March 23, 2012 Members Share Posted March 23, 2012 depends on the components in the PI circuit. in mine, the result is a larger signal swing than with a 12ax7. Signal swing Is that when signals share partners with other signals? What about a DSL 100? Would a AT7 in the PI do any good? Link to comment Share on other sites More sharing options...
Members madryan Posted March 23, 2012 Members Share Posted March 23, 2012 if RA said that tubes produce voltage, i'll eat {censored}. Nope... he didn't. I just skimmed his site again. Great site. Somewhere I read something about the relationship of gain vs. voltage as it relates to 12AX7's vs. 12AT7's. I need to do more reading anyway. Link to comment Share on other sites More sharing options...
Members knucklefux Posted March 23, 2012 Members Share Posted March 23, 2012 by signal swing, i mean the total voltage of the signal peak to peak (like a sine wave, positive peak to negative peak). a 12at7 will certainly sound different in the PI than a 12ax7. if it's good or bad is up to you Link to comment Share on other sites More sharing options...
Members knucklefux Posted March 23, 2012 Members Share Posted March 23, 2012 Nope... he didn't. I just skimmed his site again. Great site. Somewhere I read something about the relationship of gain vs. voltage as it relates to 12AX7's vs. 12AT7's. I need to do more reading anyway. what you probably read is that a 12at7 conducts about 10 times the current of a 12ax7. in the case of a long tail pair PI, that translates into a 12AT7 having a greater voltage gain than a 12AX7. you can verify what i'm saying using the PI calculator on the pentode press site. bottom line is that in most amps, a 12at7 PI hits the power tubes harder than a 12ax7. whether that's good or bad depends on the user. Link to comment Share on other sites More sharing options...
Members madryan Posted March 23, 2012 Members Share Posted March 23, 2012 what you probably read is that a 12at7 conducts about 10 times the current of a 12ax7. in the case of a long tail pair PI, that translates into a 12AT7 having a greater voltage gain than a 12AX7. you can verify what i'm saying using the PI calculator on the pentode press site.bottom line is that in most amps, a 12at7 PI hits the power tubes harder than a 12ax7. whether that's good or bad depends on the user. That's exactly it lol... It's finals week mang... between my toddler and that my brain is barely working right now. I've got a local dude about to order one of your amps tho lol. He's scrambling for the cash after I told him about you and had him look at your site. Link to comment Share on other sites More sharing options...
Members knucklefux Posted March 23, 2012 Members Share Posted March 23, 2012 right on Link to comment Share on other sites More sharing options...
Members Dolf Posted March 24, 2012 Author Members Share Posted March 24, 2012 So, in short, the PI controls how quickly you lose power amp headroom/start power amp clipping, affects overall volume? In layman's, of course. Link to comment Share on other sites More sharing options...
Members knucklefux Posted March 24, 2012 Members Share Posted March 24, 2012 yeah, sorta. the larger the signal swing out of the PI, the more overdriven the power tubes can be. there's also some distortion to the signal caused by overdriving the PI. Link to comment Share on other sites More sharing options...
Members paul88lx Posted March 24, 2012 Members Share Posted March 24, 2012 yeah, sorta. the larger the signal swing out of the PI, the more overdriven the power tubes can be. there's also some distortion to the signal caused by overdriving the PI. So, this is why a 12AT7 in the PI spot of my JCM makes for killer clean tones? Like unbelievable sparkly clean tones? Because it can handle more heat pretty much? Simpleton asking here. But it did make a stunning difference in my Marshall. Link to comment Share on other sites More sharing options...
Members madryan Posted March 24, 2012 Members Share Posted March 24, 2012 Lol... I just spent the day un-{censored}ing an amp I built (2203) that the guy took to a local "amp guru" to have converted to run 6550's. What a mess. Dude didn't have a clue what he was doing. He just sort of randomly swapped stuff around in the bias supply circuit till it sort of worked. He even went so far as to install a bias trim pot where one of the 15k resistors should have been rather than just calculate or look up the appropriate value. lulz... Sounds killer now. Link to comment Share on other sites More sharing options...
Members knucklefux Posted March 24, 2012 Members Share Posted March 24, 2012 So, this is why a 12AT7 in the PI spot of my JCM makes for killer clean tones? Like unbelievable sparkly clean tones? Because it can handle more heat pretty much?Simpleton asking here. But it did make a stunning difference in my Marshall. yes, but not for the reasons you think. in most long tail pair phase inverters (which your marshall has), using a 12AT7 results in a larger signal going to the power tubes. this increases harmonic distortion, which makes stuff sound better. what you hear as clean really isn't clean at all, you see. edit: here's a link to a calculator that will show you what i'm talking about: http://www.ampbooks.com/home/amplifier-calculators/long-tailed-pair/ to get an accurate number, change the "tail resistor" value to 10K. hit calculate with 12ax7 selected and look at the numbers it spits out. then, change the tube type to 12at7 and see what the numbers go to. Link to comment Share on other sites More sharing options...
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