Adding balanced input to 6N1P tube.

tripathdude · 7th July 2011, 01:42 PM

I have a Promitheus Tube Buffer that I wish to use as a tube stage for a AK4395 DAC. I wish to take the differential output from the dac directly into the 6N1P tube. Is this possible? I don't know how to draw up schematics for tubes, so I took pictures of the inside of the unit. This will be outputted to a TK2050 amp.

The specs of the unit can be found on this page except it doesn't have XLR inputs, but XLR outputs (weird huh) and no TVC. Apollo preamp

Here are some pictures of the buffer.

tripathdude · 7th July 2011, 01:50 PM

I forgot to mention that the last close up picture is the 6N1P tube circuit. The red wire is the incoming signal wire. White and Pink are ground. Orange is wire to output transformer. Black and brown are power supply I believe.

tripathdude · 7th July 2011, 01:54 PM

Resistor values are 100 ohms from signal. 100 ohms and 32K to ground.

Fenris · 7th July 2011, 03:05 PM

The cross-wiring on the 6N1P means that both internal triodes have been combined to form on large triode. It's probably used as a standard single ended common cathode amplifier. The 100 ohm from signal is a grid stopper. The other 100 ohm sets the cathode bias, 100 ohms is a good value, depending on the B+. 32K probably sets the input impedance. It's easy to get balanced outs from a transformer - they can easily be wired that way. There's no easy way to get a balanced in. Theoretically, you could turn it into a differential amp and maybe wire the transformer between the anodes, but I doubt is would work as well. The transformer has an air gap to operate in SE mode and that works against it as a push-pull transformer. It could be done, but I'm not sure it would be an improvement.

tripathdude · 7th July 2011, 03:25 PM

If the transformer is made for SE mode then it wouldn't be worth it. Is there that much sound improvement in going balanced input from DAC? I paid 500 dollars for this unit and love the way it sounds, but could I have done better with making a tube output stage?Thanks for your input!

Pyka · 20th July 2011, 11:58 PM

Quote:

Originally Posted by tripathdude

I forgot to mention that the last close up picture is the 6N1P tube circuit. The red wire is the incoming signal wire. White and Pink are ground. Orange is wire to output transformer. Black and brown are power supply I believe.

B+=?,Ia=?Thank you！

7th July 2011, 03:05 PM	#4
Fenris diyAudio Member Join Date: Jun 2004 Location: The last frontier	The cross-wiring on the 6N1P means that both internal triodes have been combined to form on large triode. It's probably used as a standard single ended common cathode amplifier. The 100 ohm from signal is a grid stopper. The other 100 ohm sets the cathode bias, 100 ohms is a good value, depending on the B+. 32K probably sets the input impedance. It's easy to get balanced outs from a transformer - they can easily be wired that way. There's no easy way to get a balanced in. Theoretically, you could turn it into a differential amp and maybe wire the transformer between the anodes, but I doubt is would work as well. The transformer has an air gap to operate in SE mode and that works against it as a push-pull transformer. It could be done, but I'm not sure it would be an improvement. __________________ Listen to the music through the stereo, not the stereo through the music.

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7th July 2011, 01:50 PM	#2
tripathdude diyAudio Member Join Date: Mar 2007	I forgot to mention that the last close up picture is the 6N1P tube circuit. The red wire is the incoming signal wire. White and Pink are ground. Orange is wire to output transformer. Black and brown are power supply I believe.

7th July 2011, 01:54 PM	#3
tripathdude diyAudio Member Join Date: Mar 2007	Resistor values are 100 ohms from signal. 100 ohms and 32K to ground.

7th July 2011, 03:25 PM	#5
tripathdude diyAudio Member Join Date: Mar 2007	If the transformer is made for SE mode then it wouldn't be worth it. Is there that much sound improvement in going balanced input from DAC? I paid 500 dollars for this unit and love the way it sounds, but could I have done better with making a tube output stage?Thanks for your input!

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