6N3 SRPP + 6N5P Cathode Follower HPA Testing

siliconray · 26th February 2012, 01:22 PM

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.

Koifarm · 26th February 2012, 02:22 PM

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

siliconray · 26th February 2012, 02:32 PM

6n3 can't drive low impedance headphones well by cathode output. the gain was just Radom set by the volum pot.

Koifarm · 02:45 PM

Try this,

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

siliconray · 27th February 2012, 12:27 AM

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

siliconray · 27th February 2012, 07:22 AM

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%.

Doz · 27th February 2012, 10:08 AM

What is your +B?

siliconray · 27th February 2012, 10:33 AM

120V for 6N5P, 150V for 6N3

Koifarm · 01:08 PM

Try to use 200mv input, your gain is to much.

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

siliconray · 28th February 2012, 08:12 AM

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.

26th February 2012, 02:32 PM	#3
siliconray diyAudio Member Join Date: Sep 2011	6n3 can't drive low impedance headphones well by cathode output. the gain was just Radom set by the volum pot. __________________ www.siliconray.com High Quality Audio Enclosures, Amp Kits, Amplifiers, PCB Fab Services Chat with me

26th February 2012, 02:32 PM	#4
Koifarm diyAudio Member Join Date: Aug 2005	Try this, 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.

27th February 2012, 07:22 AM	#6
siliconray diyAudio Member Join Date: Sep 2011	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%. __________________ www.siliconray.com High Quality Audio Enclosures, Amp Kits, Amplifiers, PCB Fab Services Chat with me

27th February 2012, 10:08 AM	#7
Doz diyAudio Member Join Date: Jul 2010 Location: Sat Down	What is your +B? __________________ "To err is human.. to make a real balls-up requires a computer"

27th February 2012, 10:33 AM	#8
siliconray diyAudio Member Join Date: Sep 2011	120V for 6N5P, 150V for 6N3 __________________ www.siliconray.com High Quality Audio Enclosures, Amp Kits, Amplifiers, PCB Fab Services Chat with me


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26th February 2012, 02:22 PM	#2
Koifarm diyAudio Member Join Date: Aug 2005	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

27th February 2012, 01:05 PM	#9
Koifarm diyAudio Member Join Date: Aug 2005	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.

28th February 2012, 08:12 AM	#10
siliconray diyAudio Member Join Date: Sep 2011	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. __________________ www.siliconray.com High Quality Audio Enclosures, Amp Kits, Amplifiers, PCB Fab Services Chat with me

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