there was some days ago since I received that 5751 national tubes and too much job and less spare time, takes me out of the tube business. well after this time i tried that tubes.
So here I go: Well first of all i want to explain that 5751 tubes are perfectly exchange with 12ax7 due their datasheet curves are so close, so the bias point for a 12ax7 is quite similar for a 5751 and no cathode or anode resistors are needed to be replaced.
Mu factor ( amplificator or gain factor ) in 12ax7 are usually nearest to 100 and 5751 are closer to 70, so they are very similar.
Well I will try to avoid all the electronics slang and try to obtain my subjetives impressions. I think that it is better talking on the same language better than arguing in an electronics world where anybody could loose into the arguments.
The 5751 in my point of view are good enough on last preamp stages and they are wonderfull on phase inverters positions, all the amps I could test with that phase inverters becomes very very clean, with a higher headroom and all the notes becomes perfectly articulate. I also compare them with my favourites SED tubes and I was so annoyed when I discover that 5751 sounds a bit better than sed on phase inverter position.
I also tried the 5751 on first positions a la SRV and I don´t like them so much.
So my conclusion is that for phase inverter positions we have a new awarded citizen. The 5751 tubes :lol:
On the next weeks I will try to get another 5751 brands to compare and get the best brand for that kind of tube.
Stay on tune mr tarzan with the 5751 issue