That is correct way. Here are sometimes stories about tube comparison where for example 12AX7 and 12AU7 are directly swapped with same circuit and "results analyzed".
I have used both 6N6P and 6N6P-I in preamp and as output tube of 6W PP (AB2) amplifier (schematic attached). Both give similar THD numbers.
Attachments
Last edited:
Just stumbled upon this topic.. here my 5 cents..
Depending on circuit design and biasing, at least in my headphone amp, 6N6P sounds excellent, 6N6P-I sounds a tiny little bit too bright, but also excellent (matter of taste, right ?)
- whereas heating is also stronger (more current at same raw 6.3V AC) on the I version. (Since then I went to DC heating so can't try again but remember well).
Overall tube life is shorter on the 6N6P-I... Of course if you drive them by intention within corridors, e.g. biased around sweet spot and on a more forgiving heating (lower voltage, e.g. 5.7-5.9V, to be closer to normal 6N6P-equivalent heater power consumption), I think they perform just as well and long like normal versions. I tried it and sounded similarly good (tiny little bit bright, still).
They also differ in size, the 6N6P-I-s are a little shorter than the taller 6N6P-s.
Heaters are glowing significantly stronger on the 6N6P-I-s, than on the normal ones. After living with 6N6P-I-s for some months in my headphone amp, when I switched back to normal 6N6P-s I almost wanted to measure my heater voltage if everything's okay due to less glowing of the heaters Of course everything was okay.
The "I" versions were originally designed for impulse based operation mainly in rocket driving electronics hence lifetime was not a design criteria for them in general, a rocket flight is quite quick actually.. couple of seconds, maybe half a minute (already long).. and also think about quicker heating when launched or at least just before launching, they of course can't keep the tubes warm all the time days, weeks, months long, on the other hand if the soldier is pulling the magic trigger, they should launch instantly - hence the increased heater power, they might need to heat up maybe within some 10-30 seconds during targeting or so, imagine winter in the tundra, harsh conditions, whatever.. just guessing..
I stick to the normal 6N6P-s, 'burned' all my 6N6P-I-s actually (used up 2 pairs only) and I was happy to be able to get my hands on NOS 6N6P-s in great condition, matched pairs from my not-so-long-ago-attacked neighbouring country via eBay. Together with my 6N1P-s on the input, the 6N6P-s deliver ultra-high quality in my headphone amp (output stage, OTL).
(And now have the 6N2P-ER-s in my living room OTL, can't wait to hear them in action).
My next move will be to 1:1 swap them to JJ ECC99 tubes and see/hear the difference. Just for fun. The JJ-s are told to be strong contenders.. we'll see. These small-signal Russian tubes tend to sound a little better (doubt if this is real or psychological effect) than western ones, I think it's up to the circuit and finding the sweet spots for them.. however, the manufacturing spread is bigger due to looser quality control processes, slightly different material (same, but I can imagine palladium, metal, etc... purity differences), assembly technology, etc. Anyway, I use Russian tubes with pleasure but only buy from sellers who have tons of positive feedbacks AND advertise them as matched pairs, matched quads, and/or even tell about the testing method, so I can be sure it's really good stuff I'm buying. Sure, there's always some risk they don't get matched or so, or the seller is just doing bullshitting, but I've never experienced such, luckily: tubes were close to eachother as promised, always good and at least in pairs quite identical. Lots of positive feedbacks and/or 0-1 negatives are the ones to aim for. At least on eBay.. western online tube shops do a (seemingly) more-promising tube matching for us, but for a recognizable extra price for sure. If money is not an issue, go with them, otherwise eBay is a great place to find great tubes for bargains, with a lot of money I would request not pieces, but kilogramms of tubes from some sellers who have access to NOS military sellouts.)
Anyway, reading the comments of first page here, I agree with Lampizator's finding: for me, the 6N6P-s sounded the best. This doesn't mean the "I"-s can't sound good but I'm pretty sure they need some adjustment from electronics side, using them 1:1 as a replacement for 6N6P-s works but not really ideal let's put it that way, at least in my circuit design.
Depending on circuit design and biasing, at least in my headphone amp, 6N6P sounds excellent, 6N6P-I sounds a tiny little bit too bright, but also excellent (matter of taste, right ?)
- whereas heating is also stronger (more current at same raw 6.3V AC) on the I version. (Since then I went to DC heating so can't try again but remember well). Overall tube life is shorter on the 6N6P-I... Of course if you drive them by intention within corridors, e.g. biased around sweet spot and on a more forgiving heating (lower voltage, e.g. 5.7-5.9V, to be closer to normal 6N6P-equivalent heater power consumption), I think they perform just as well and long like normal versions. I tried it and sounded similarly good (tiny little bit bright, still).
They also differ in size, the 6N6P-I-s are a little shorter than the taller 6N6P-s.
Heaters are glowing significantly stronger on the 6N6P-I-s, than on the normal ones. After living with 6N6P-I-s for some months in my headphone amp, when I switched back to normal 6N6P-s I almost wanted to measure my heater voltage if everything's okay due to less glowing of the heaters
Of course everything was okay.The "I" versions were originally designed for impulse based operation mainly in rocket driving electronics hence lifetime was not a design criteria for them in general, a rocket flight is quite quick actually.. couple of seconds, maybe half a minute (already long).. and also think about quicker heating when launched or at least just before launching, they of course can't keep the tubes warm all the time days, weeks, months long, on the other hand if the soldier is pulling the magic trigger, they should launch instantly - hence the increased heater power, they might need to heat up maybe within some 10-30 seconds during targeting or so, imagine winter in the tundra, harsh conditions, whatever.. just guessing..
I stick to the normal 6N6P-s, 'burned' all my 6N6P-I-s actually (used up 2 pairs only) and I was happy to be able to get my hands on NOS 6N6P-s in great condition, matched pairs from my not-so-long-ago-attacked neighbouring country via eBay. Together with my 6N1P-s on the input, the 6N6P-s deliver ultra-high quality in my headphone amp (output stage, OTL).
(And now have the 6N2P-ER-s in my living room OTL, can't wait to hear them in action).
My next move will be to 1:1 swap them to JJ ECC99 tubes and see/hear the difference. Just for fun. The JJ-s are told to be strong contenders.. we'll see. These small-signal Russian tubes tend to sound a little better (doubt if this is real or psychological effect) than western ones, I think it's up to the circuit and finding the sweet spots for them.. however, the manufacturing spread is bigger due to looser quality control processes, slightly different material (same, but I can imagine palladium, metal, etc... purity differences), assembly technology, etc. Anyway, I use Russian tubes with pleasure but only buy from sellers who have tons of positive feedbacks AND advertise them as matched pairs, matched quads, and/or even tell about the testing method, so I can be sure it's really good stuff I'm buying. Sure, there's always some risk they don't get matched or so, or the seller is just doing bullshitting, but I've never experienced such, luckily: tubes were close to eachother as promised, always good and at least in pairs quite identical. Lots of positive feedbacks and/or 0-1 negatives are the ones to aim for. At least on eBay.. western online tube shops do a (seemingly) more-promising tube matching for us, but for a recognizable extra price for sure. If money is not an issue, go with them, otherwise eBay is a great place to find great tubes for bargains, with a lot of money I would request not pieces, but kilogramms of tubes from some sellers who have access to NOS military sellouts.
) Anyway, reading the comments of first page here, I agree with Lampizator's finding: for me, the 6N6P-s sounded the best. This doesn't mean the "I"-s can't sound good but I'm pretty sure they need some adjustment from electronics side, using them 1:1 as a replacement for 6N6P-s works but not really ideal let's put it that way, at least in my circuit design.