6N3 SRPP + 6N5P Cathode Follower HPA Testing - diyAudio
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Old 26th February 2012, 01:22 PM   #1
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Default 6N3 SRPP + 6N5P Cathode Follower HPA Testing

This is a very simple and low cost headphone amplifier which can also be used as preamplifier. The total cost of the 3 tubes used in this design is less than $10.

2 troids in one 6N3P forms SRPP voltage amplificier. A 6N5P cathode follower is used as driving stage. It can drive headphones from 32 Ohm to 600 Ohm very well. I'm happy with the sound quality when used on my HD600

Here're some of the testing results.
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Old 26th February 2012, 02:22 PM   #2
Koifarm is offline Koifarm  Netherlands
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Hai siliconray,

why using a 6n5 tube when 6n3 can also do a better job in the output stage.
The 6n5 is a slow tube with a lot of heatercurrent. If you like the sound oke that is personal. But using 1 tube for both channels is always a compromise. I think it is better to use a 6n3 parallel triode cathode folower in the output like shanling does.

And why all that gain? We do all have equipment with 1Vrms or more output voltage.

Ronny
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Old 26th February 2012, 02:32 PM   #3
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6n3 can't drive low impedance headphones well by cathode output. the gain was just Radom set by the volum pot.
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Old 26th February 2012, 02:32 PM   #4
Koifarm is offline Koifarm  Netherlands
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Try this,

Click the image to open in full size.

This drives also 8 or 16 ohm headphone with very low distorsion.
And it will even sound better with a 6n6p. Also this tube is very cheap.

Ronny

Last edited by Koifarm; 26th February 2012 at 02:45 PM.
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Old 27th February 2012, 12:27 AM   #5
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Hi Koifarm

Thanks for posting the schematic, I will try it later. I found 6N5P can even drive speaker very well, I'm sure the power is more than 2W, amazing.

BTW, do you think a NFB to the input state will improve the performance?

Have a look at our work in a long version RE1506 enclosure
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File Type: jpg DSCN9336.JPG (71.0 KB, 77 views)
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Old 27th February 2012, 07:22 AM   #6
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Tested with 7723A just now. The distortion is 0.54%, 1KHz, 470 Ohm load, 1Vp-p. Is it good enough for a tube headphone amplifier? My JLH is only 0.008%.
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Old 27th February 2012, 10:08 AM   #7
Doz is offline Doz  United Kingdom
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What is your +B?
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Old 27th February 2012, 10:33 AM   #8
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120V for 6N5P, 150V for 6N3
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Old 27th February 2012, 01:05 PM   #9
Koifarm is offline Koifarm  Netherlands
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Try to use 200mv input, your gain is to much.

Output power is 90mW you need only 20mW.
Or change inputvoltage devider.

Last edited by Koifarm; 27th February 2012 at 01:08 PM.
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Old 28th February 2012, 08:12 AM   #10
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I think the distortion shouldn't be that much even at 90mW. The THD is 0.3% when lower the voltage down to 0.5V.

The 6N5P is a junk tube. Some said this circuit has amazing performance when replace 6N5P with Raython 6080. I will try it tomorrow.
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