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Old 3rd September 2009, 10:33 AM   #1
Ardee is offline Ardee  England
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Default 6N6P Unbalanced Sound?

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.
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Old 3rd September 2009, 10:53 AM   #2
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Try 30mA. These like current.

Cheers!
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Old 3rd September 2009, 12:51 PM   #3
Vlauga is offline Vlauga  Russian Federation
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6N6P and its up-to-date replacement 6N30P it is the bad tubes for a sound.

One of the best Soviet tubes (the double triode) for a sound it 6N30P-DR. Unfortunately, it was made only in the Soviet time in small circulation. Also it is very major rarity now.

VU
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Old 3rd September 2009, 02:12 PM   #4
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Might be your circuit implementation; those operating points aren't bad, though I agree this tube likes current. Could you share the schematic?
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Old 3rd September 2009, 05:54 PM   #5
Ardee is offline Ardee  England
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Quote:
Originally Posted by Vlauga View Post
6N6P and its up-to-date replacement 6N30P it is the bad tubes for a sound.
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.

Quote:
Might be your circuit implementation; those operating points aren't bad, though I agree this tube likes current. Could you share the schematic?
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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Old 3rd September 2009, 06:06 PM   #6
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What bass?
It is frequency independent on low frequencies, like any other tube. Bass has higher power in a music, so will be distorted heavier if the tube works out of it's sweet spot.
15K 11 MA means 165V drop on the resistor. If your B+ is 70-90V it won't work.
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Old 3rd September 2009, 06:18 PM   #7
Ardee is offline Ardee  England
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Quote:
Originally Posted by Wavebourn View Post
What bass?
It is frequency independent on low frequencies, like any other tube. Bass has higher power in a music, so will be distorted heavier if the tube works out of it's sweet spot.
That's what I thought too - so why am I being advised to raise the current?

Quote:
15K 11 MA means 165V drop on the resistor. If your B+ is 70-90V it won't work.
No, it won't, but it's 11k and 15mA with 70-90v across the 6N30P. The 6N6P seems to like slightly higher volts.
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Old 3rd September 2009, 07:36 PM   #8
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Try 7K5 in anode, 200 Ohm in cathode, for 360V B+
You should see about 190V on anode. It was a sweet spot for 6N6P in my Pyramid amp.
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Old 3rd September 2009, 09:16 PM   #9
Ardee is offline Ardee  England
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Thanks Wavebourn, I will give that a try as a driver stage. Isn't 360v exceeding the 6N6P maximum voltage rating, though, and do they last at >4W?
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Old 3rd September 2009, 09:21 PM   #10
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Quote:
Originally Posted by Ardee View Post
Thanks Wavebourn, I will give that a try as a driver stage. Isn't 360v exceeding the 6N6P maximum voltage rating, though, and do they last at >4W?
Quote:
...You should see about 190V on anode.
360V anode when cold is OK for a short time.

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