humm, I answer to myself after some googling, I don not know if the 6np23 is nearer from the industrial E88CC/6922 or the "musical" but great dispersion ECC88, but no doubt the 6np23-EV this time is the lowest noise of the two with "fingers" mica inside.
I am still do not understand (but off topic) why a 6NP11 should be chosen over a 6NP23 for audio purpose. I wondr if the chineese kit is not made also by guys that rapidly had a look and took the same values mistaken 6nP1 with 6NP11 or even E88CC or even E88CC/6922 ? Maybe it is worthing to investigate the values of the parts and voltages involved ? - I mean before to make a tube choice in that kit in the dark...Aliwpress thinghy are not known for the last degree of serious seriously !-
Am I plain wrong or the 6Np11 is good enough to your ears ?
Thanks, yes the EV version is said to be 5000 h. Not sure the non EV has the mica thingies so more noiser than the EV or at least become harder in the treble after some rapid aging? Indeed the EV became harder to find and doesn't worth the 40 and more euros seen on Ebay. Not saying one has to find the guy with the reliable measurement.
Well the source is Ukrainia and Russia...so . No chineese good sounding equivalent if I understand it ?!
Well the source is Ukrainia and Russia...so . No chineese good sounding equivalent if I understand it ?!
There is no such thing as 6NP23. The 6N23P is equivalent to ECC88. The 6N23P-EV (6Н23П-ЕВ) is the military version with higher shock resistance (and probably longer life, I am not sure). The E88CC is the industrial version of the ECC88. I think there are bigger variation between individual tubes of the same type than between normal vs. industrial versions.
I have a lot of Tungsram, Mullard, etc. E88CC and many Russian 6N23P-EV tubes, so I could compare them. I measured the gain, S/N and THD in a line level SRPP amplifier stage. There was bigger variability between the Russian tubes than the European ones, but there were some examples with exceptional parameters, too.
I don't have any schematics, sorry. But it is very simple. All 3 SRPP stages are identical: Rk is 1.5k, lower Rk is not bypassed with any capacitor. It is described here:
https://www.diyaudio.com/community/threads/vishay-audio-resistors.119229/
Essentially, the passive R-C-R between the 1st and 2nd tube is responsible for the bass shelf (20dB attenuation of frequencies >500Hz, starting at 50Hz). The R-C between the 2nd and 3rd tube is responsible for the attenuation of frequencies >2.122kHz (and attenuation of noise of the whole preamplifier!)
Here you can find some useful information about the SRPP Anzai circuit:
https://www.diyaudio.com/community/threads/anzai-srpp-line-phono-and-eq-tube-preamplifier.319107/
What have members with Sonic Frontiers preamps been using in their units lately? I have gone through some of the Russian EV tubes, quite a few early Teslas, and dont want to be spending big $$ on NOS again, so interested in what current tubes people have used/using, even better if you have an SFL2 