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Old 8th June 2013, 03:59 PM   #1
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Default 6N1P

I want to use a 6N1P valve as a line input and a concertina phase splitter, having
280 volts on the B side of the HT could any one suggest the resistors for the plate and cathode voltages so as to obtain the least distortion.

llan
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Old 8th June 2013, 04:44 PM   #2
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Take a look at improved Williamson Amplifier, it uses DC coupled 6SN7 input and concertina. You can replace 6SN7 with 6N1P.
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Old 9th June 2013, 05:42 AM   #3
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How much drive voltage you need from 6N1P concertina ?
Which output tubes ? 280 V as +Ub is quite low.
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Old 9th June 2013, 05:58 AM   #4
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Quote:
Originally Posted by artosalo View Post
280 V as +Ub is quite low.
and I thought 6N1P would want it even lower ?
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Old 9th June 2013, 06:48 AM   #5
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With higher +Ub the output can be higher as well. Isn't this obvious ?

Click the image to open in full size.

EDIT: When R2 = 1k8, max. output is some 28 V.

Last edited by artosalo; 9th June 2013 at 07:13 AM.
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Old 10th June 2013, 01:21 PM   #6
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Default 6N1P

Thanks for your input, my line input stage as a 47K on the plate and a 1K on the cathode the other half used as a phase splitter as two 33K resistors one for the
plate and one for the cathode to drive a couple of 6L6 valves, is there any way to improve this concertina phase splitter or do you have to use a better type phase splitter for lower distortion and a better top response, the Radford 25 watt amp used a ECF82 as a phase splitter I believe this was done to improve the high frequency response.

Llan
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Old 10th June 2013, 02:09 PM   #7
tinitus is offline tinitus  Europe
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how about using 6n6p/ecc99 instead ?

Quote:
Originally Posted by llan View Post
....is there any way to improve this concertina phase splitter....
Llan
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Old 10th June 2013, 07:34 PM   #8
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Quote:
Originally Posted by llan View Post
...my line input stage as a 47K on the plate and a 1K on the cathode the other half used as a phase splitter as two 33K resistors one for the plate and one for the cathode to drive a couple of 6L6 valves, is there any way to improve this concertina phase splitter or do you have to use a better type phase splitter for lower distortion and a better top response...
Llan
I understand that your 6N1P amplifier stage is direct connected to cathodyne.
If this is correct, this is the reason for high distortion.
To make well designed and well performing amplifier/phase splitter you should use a capacitor between the stages and bias both to optimum.
I already gave you a schematic of such cathodyne.
The frequency response of cathodyne stage is beyond 100 kHz, so should not be a problem.

You told in the first post that the supply voltage is 280 V. What is the supply voltage for the 6L6 output tubes ?
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Old 11th June 2013, 03:13 PM   #9
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Default 6N1P

Sorry, I made a mistake, I have two amps one both using the concertina phase splitters, the one with the 280 B plus volts uses EL84s as push pull output the other uses two 6L6s in the out put this amp as 365 volts on the plates of the 6L6s and the B plus is 350.

Yes there are both DC coupled, I have seen this being used in other valve amps why is it important to use a coupling cap instead of it being dc coupled how does this lower the distortion.

I take your point about the 6N6P/ECC99 would this be a better valve for this position.

Llan
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Old 11th June 2013, 05:15 PM   #10
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Quote:
Originally Posted by llan View Post
...Yes there are both DC coupled, I have seen this being used in other valve amps why is it important to use a coupling cap instead of it being dc coupled how does this lower the distortion....
I take your point about the 6N6P/ECC99 would this be a better valve for this position.

Llan
When the voltage amplifier stage is operating at minimum distortion point, its anode voltage is, say 150 V for example.
The optimum bias voltage of a concertina at 280 V +Ub is much smaller, say 80...90 V.
If you direct connect this 150 V to concertina, its output voltage is highly limited. On the other hand, if you bias the voltage amplifier so that its anode voltage is 90 V, the result is distorted output signal at the voltage amplifier.
Therefore individual biasing is necessary in most cases.
Direct connection works well with some pentodes as voltage amplifiers because these operate at low anode voltage.
Also 12AX7 is good with direct connection if small driving voltage is required.

There is basically no difference if 6N1P or 6N6P is used as a concertina, because it has full negative feedback that minimizes the differences between used tubes/types.
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