Have done quite a lot of loadlines of popular pentodes for triode-strapping. I´m not impressed.
Typical tubes are EL34 and 6L6, have also checked E130L and 807/1625(close to 6L6). Probably they would do in PP but as SE they don´t impress me much.
The reason I ask is that I want a tube with enough linearity to be on par with 2A3 but with higher senstivity.
Any suggestions?
Typical tubes are EL34 and 6L6, have also checked E130L and 807/1625(close to 6L6). Probably they would do in PP but as SE they don´t impress me much.
The reason I ask is that I want a tube with enough linearity to be on par with 2A3 but with higher senstivity.
Any suggestions?
A pure pentode with plate to grid feedback 😉
Running a pentode in triode mode is like sticking a towel in the intake of an engine!
Running a pentode in triode mode is like sticking a towel in the intake of an engine!
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6p15p
6p1p
12l6gt, 25l6gt, 50l6gt
Right. But the question was exactly about best running engine with a towel in the intake.
6p1p
12l6gt, 25l6gt, 50l6gt
Right. But the question was exactly about best running engine with a towel in the intake.
The short reply is that triodes are not linier, none of them. And there is no such thing as a load line. That is why we like triodes.
That line we draw on the graph paper assumes that the load is purely resistive. Plus that directly heated 2A3 is not as linier as we think. The plate curves on the 2A3 data sheet resemble the shape of the French curve laid on the page in 1943 more that performance of that NOS tube in hand.
Turn up the voltage, turn up the current, never mind the maximum rating of the tube until the plate glows red and the smoke comes out. Turn the next one down 10%. That is how to maximize the linearity.
Pentodes with feedback or triode strapped start to behave like triodes. They are not linier either. That is why we like them too.
Since this for fun trace the plate curves for that 2A3 as installed in your preferred amplifier circuit and you will not recognize it.
Try an 837 they are fun.
That line we draw on the graph paper assumes that the load is purely resistive. Plus that directly heated 2A3 is not as linier as we think. The plate curves on the 2A3 data sheet resemble the shape of the French curve laid on the page in 1943 more that performance of that NOS tube in hand.
Turn up the voltage, turn up the current, never mind the maximum rating of the tube until the plate glows red and the smoke comes out. Turn the next one down 10%. That is how to maximize the linearity.
Pentodes with feedback or triode strapped start to behave like triodes. They are not linier either. That is why we like them too.
Since this for fun trace the plate curves for that 2A3 as installed in your preferred amplifier circuit and you will not recognize it.
Try an 837 they are fun.
I 2nd the 6V6 family motion. Look at the curves (page 8). The highly revered 6SN7 doesn't do better.
Inexpensive NOS is available. Buy 14C5s. NOS 12V6s still carry "rational" price tags. Want miniature types? Use 6AQ5, 12AQ5, 12AB5, and 6005. Want current production? New Sensor's Saratov, Russia, plant makes 2 nice varieties: the EH and the "reissue" TungSol.
Inexpensive NOS is available. Buy 14C5s. NOS 12V6s still carry "rational" price tags. Want miniature types? Use 6AQ5, 12AQ5, 12AB5, and 6005. Want current production? New Sensor's Saratov, Russia, plant makes 2 nice varieties: the EH and the "reissue" TungSol.
D.T.N Williamson wrote that triode-connected KT-66 was nearly the same as a PX-4. So why not? A $200 tube for a $500 tube.
John
John
That concept sounds vaguely familiar. I have heard that somewhere before. Some tubes respond to this, and some dont. The EH KT88's triode wired sound best at the edge of a dull red glow. The previously mentioned 307A is rated for something like 15 watts of dissipation. It will take about 35 watts to provoke glow, but they sound best at about 25 watts or so. Mine run at 360 volts and 70 mA into a 5K load for about 7 watts of power. More current does nothing for the sound, or the power output. Interestingly these tubes really don't like being wired for UL. Power doesn't go up, but the distortion does.
6V6 in triode is another good one too. Run them at about 325 volts and about 30 ma (maybe a wee bit more) into a 5K load. The best sounding 2 watts that you gan get without a 45.
I've found the 8417 to be an excellent triode. Too bad they're obsolete and expensive when you can find them.
The 8417 Tube
The 8417 Tube
revintage,
I may have missed your point. Are you looking to maximize power output? Are you looking to minimize Total Harmonic Distortion? Are looking to sculpt the distortion spectrum? Are you looking to get the sound of a 2A3 with a less expensive triode strapped pentode?
None of the above?
I may have missed your point. Are you looking to maximize power output? Are you looking to minimize Total Harmonic Distortion? Are looking to sculpt the distortion spectrum? Are you looking to get the sound of a 2A3 with a less expensive triode strapped pentode?
None of the above?
How about a 6P31S, EL36, PL36 Tube? Strapped as a triode it resembles a poor man´s 2A3 ( needs a stronger preampstage too ).
If you are just calculating this on paper you may not be making decisions about how these tubes actually sound. The 807 in triode, for example, is a superb sound. I've only used these in PP but in that context they have a well-deserved reputation for good sound. Why not try some directly heated tubes? The 2E22 is very good, and the 1624 should be pretty good too and has useful gain. The 46 is superb in triode but probably too wimpy for your needs - if you have very sensitive speakers it's really worth trying out. Not a pentode as such, but since we're using it in triode who cares!
Andy
Andy
Hey guys,
Sorry, think I forgot to tell you that the purpose was to get good triode-characteristics with high sensitivity.
It has to be something like 60Vptp to work. Otherwise I had gone for 6B4G which I have plenty of and also like.
A 1:1,5 stepup could be a solution but that would be suboptimal.
Someone mentioned 6E5P and that one might do the trick if parallelled. I checked 807 and sensitivity is a little on the low side but a good tube.
Sorry, think I forgot to tell you that the purpose was to get good triode-characteristics with high sensitivity.
It has to be something like 60Vptp to work. Otherwise I had gone for 6B4G which I have plenty of and also like.
A 1:1,5 stepup could be a solution but that would be suboptimal.
Someone mentioned 6E5P and that one might do the trick if parallelled. I checked 807 and sensitivity is a little on the low side but a good tube.
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