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6N6P Operating Points
6N6P Operating Points
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Old 30th September 2006, 11:51 PM   #1
Ruach is offline Ruach  Singapore
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Default 6N6P Operating Points

Hi guys,

I have bought a bunch of the 6N6P tubes and I plan to use the 6N6P in a tube line preamp project.

If anyone has used this tube in a similar application, I would appreciate if you can advise what s a good operating point for this tube - plate voltage, biasing current etc...

The electrical parameters of the 6N6P is very similar to that of the 5687 except for different pinouts.

Thanks in advance.


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Old 1st October 2006, 12:20 AM   #2
Wavebourn is offline Wavebourn  United States
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6N6P Operating Points
I used it long-long time ago to drive GU-50 PP amp. If I remember right, the point was with 120V on plates, plate load resistors were 10 KOhm connected to +400V, common cathodes with 100 Ohm potentiometer tail. I needed 100V of clean swing and I got it.

However, today I would use CCS and 170-180V only instead of 10K and 400V.
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Old 5th October 2006, 07:48 AM   #3
Ruach is offline Ruach  Singapore
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I found the website below which documents a 6N6P-based preamp design.

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Old 5th October 2006, 11:59 AM   #4
ErikdeBest is offline ErikdeBest  Switzerland
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6N6P Operating Points
Hi Ruach

The traditional question when thinking about an preamp is the amount of gain needed.

The preamp is quite a heavy beast...it's dragging about 80ma per channel (My power amp produces 15W from the same current, but slightly higher voltage). The gain will be aprox half the gain of the 6N6P. Paralleling tubes will lower the output impedance, what is better for driving long cables. But paralleling also seems to 'kill' the sound (there was a recent thread on this). Other options to lower output impedance is the use of CF or variations... so, what do you need?

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Old 5th October 2006, 03:31 PM   #5
Brian Beck is offline Brian Beck  United States
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I have my doubts that paralleling tubes will always “kill” the sound (it doesn’t have to), but I do think that the low plate load resistance (~ equal to rp) in this design will make it a second-harmonic generator. This may please some, but it won’t be true to the music passing through it. If someone is hellbent on using these triodes (times 4), then the plate either needs a beefy CCS, a beefy choke, or bigger power resistors connected to a higher B+, wasting a lot of heat.
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Old 11th October 2006, 08:43 AM   #6
Ruach is offline Ruach  Singapore
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I have managed to modify my existing 5687 preamp to accept a 6N6P tube. It is based on a simple anode follower design, using a single piece of 5687 tube (see attached photo).

I had some help from James D. Thanks James.

The 6N6P is the most natural sounding tube that my 5687 preamp has ever worked with.

I have tried 6900, 7119, 7044, E182CC and a whole lot of various makes/brand of 5687 and the 6N6P (IMHO) has the nicest balance throughout the audio spectrum, and it does not have the aggression/thin sound of the 5687.

I am running it at Rp=10K, Vg= -5.5V to -6V, Va=160V, Ia=18mA

I tried running it at Rp=10K, Vg= -6V, Va=140V, Ia= 9 mA and there was a mid bass/lower mids bloatedness.

James suggested giving the 6N6P more juice and the 6N6P really sang after that.

Thanks to all who helped
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