I have been using a 6N30P on the output of a PCM1704 DAC for a while, and find that at low HT (70-90v) the sound is fine. As so many people claim that the 6N6P is superior I gave it a try and found the sound very unbalanced. It certainly gives more sense of space and air but lacked bass when biased for up to 20mA at 90-110v and with 10k-16k loads. Is this characteristic of the 6N6P?
I was rather disappointed because the fact that the 6N6P does not draw grid current until .5v makes it ideal for the output of a PCM1704 when using a small resistor for I/V conversion. It worked very well with zero bias voltage at about 15mA with an 11k load, apart from the lack of bass.
I was rather disappointed because the fact that the 6N6P does not draw grid current until .5v makes it ideal for the output of a PCM1704 when using a small resistor for I/V conversion. It worked very well with zero bias voltage at about 15mA with an 11k load, apart from the lack of bass.
The 6N30P-EV sounds very good to me but if you are offering me a DR variant to try, please do send me a PM.
I tried several variations of self-biased common cathode, but limited the current to around 22mA as I did not want to make a new power supply if this sound is just the nature of the valve. Various Rk values were bypassed with 1000µF BG - except for zero volts bias, of course. Note that I am only looking for 2v rms output here.
Nobody so far has said the 6N6P is good at bass, just that it likes current. Am I supposed to infer that it only does bass at high currents?
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That's what I thought too - so why am I being advised to raise the current?
No, it won't, but it's 11k and 15mA with 70-90v across the 6N30P. The 6N6P seems to like slightly higher volts.
Not at all. My 6N6P linestage isn't 'good' or 'bad' at bass; it's just correct. Like all other frequencies. That's why it would help if you could provide a schematic: you might have a topology issue that is causing your bass rolloff, if that's what it is.
My comments regarding current: I have found that in a given circuit, assuming proper design and construction, this tube (like most tubes operated within a reasonable range of their intended construction) sounds just fine from 6mA to 25mA, 70V plate to 150V plate. Bass is there, treble is there, etc. However, different operating points produce different sound qualities, some I prefer more than others. My generalized preference is that the higher in current I went, the better the sound quality. YMMV, of course.
FWIW, my applications with this tube are transformer coupled, so there is typically benefit to running at higher currents, where Rp is lower. The latest design where I have used this tube is found in a parallel thread inside a LTP with 22K plate loads. Each triode carries 6mA with plate voltage of about 110V. Wonderful sound, great bass (or should I say flat frequency response). Completely different application than transformer coupling.
Good Luck, and don't give up on the tube; it's probably not the tube's fault.
190V 22mA is within it's safe area, if I remember right.
Mine work about 4 years, did not need to replace yet.
I have a similar arrangement as well; in Pyramid-V I use 6N6P LTP driver, with 16K load resistors, 4K7 tail, about 120V from anodes to cathodes. But it is LTP, a very different arrangement, so 12 mA per triode is fine.
Zigzagflux - I don't know how to post a schematic here, and I'm not sure how it would help. It's just an ordinary self-biased common cathode circuit which works fine with the 6N30P. Because of the very small voltage swing in this application, I don't see any reason why the 6N6P should sound so different even when it is just plugged in place of the 6N30P without any component changes. As I say, my main interest was in running the 6N6P at zero volts bias, with the cathode grounded, and it sounded no worse used like this than it did when negatively biased. Perhaps I just have a faulty one, although it all looks OK. I will get some more and try again. Or perhaps it was oscillating at RF.
To bring...?
But I can display)))
Here 6N30P-DR
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Here even more rare Soviet tube 6N12C. Extremely dazzlingly sounding.
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Looking for a substitute for 12B4 in this headphones amplifier the 6N6P seems a candidate. Would doubling the triodes and Va=150V, Ia+Ia=36mA be a suitable operating point? The original circuit uses a 20:1 turns ratio OPT to obtain low output impedance. Would a standard 5K:8ohm OPT do?
Yes, a well known supplier 
In either topology the final stage output impedance is playing a large role on the amplifier bass roll off. John Broskie describes the effect on his pages. I learned 6N6P is a quit linear tube which makes a good choice for a (SR-)PP setup and low output impedance. Haven't descided on topology yet.
In either topology the final stage output impedance is playing a large role on the amplifier bass roll off. John Broskie describes the effect on his pages. I learned 6N6P is a quit linear tube which makes a good choice for a (SR-)PP setup and low output impedance. Haven't descided on topology yet.
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