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6N3 Tube Preamp with DC-DC converter
6N3 Tube Preamp with DC-DC converter
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Old 25th September 2017, 11:24 PM   #131
Pygmy is offline Pygmy  Netherlands
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Quote:
Originally Posted by Listen View Post
That's what I did and it worked for me. Also bolted a small heat sink onto the regulator and upgraded the caps. Been a long while, but I think I made a few other minor changes as well. Have a look at the schematic for ideas. As I recall I had quite a bit of fun with this project, tried some other tubes and so on...
I replaced the caps with some Nichicon Muse caps I had laying around, but they're specced to 85 degrees. Which made me worry about the heat generated by the 7805

Which 7806 did you use?
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Old 30th September 2017, 11:10 PM   #132
danielwritesbac is offline danielwritesbac  United States
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One ordinary diode drop to middle pin makes up the difference without swapping the part. You'd have 5.57v then. Upping the voltage on the heater did not improve the audio quality. Might as well spare the tube unnecessary wear.
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Old 16th October 2017, 06:29 AM   #133
LSOJ is offline LSOJ
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Hey, why not... Use an L7812 and then cut down the voltage with a resistor for the filament supply?
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Old 28th October 2017, 12:24 AM   #134
MJL112 is offline MJL112
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Originally Posted by PALUSE View Post

Hi People.

Finally I finish the prototype tests for the "Phase 2" and "Phase 3" of 6N3 buffer.

Phase 2 consists in a CCS implementation with 2SK30A FET or a dedicated CCS diode.


Phase 2 already with a higher plate voltage PSU transformer. The Heater power line is separate now with a dedicated secondary voltage.
6N3 Tube Preamp with DC-DC converter


Phase 3 with the same CCS theme based on the 2SK30A.
About 3.8mA cathode current rise the HD to high.
Now the new voltage regulators circuit are implemented and working well with a higher plate voltage, around 85,5V, and a good"Buffer input voltage" for the regulators do their job "well".
Smoother sound is noticed at the "start-up" of this toy.
6N3 Tube Preamp with DC-DC converter


Final Phase 3 implementation.
Diode CCS is preferred since HD is around -50db (0,32%) at 3,5V RMS input (9.9V PP) 20Hz to 20kHz.A much lower HD value than obtained with the 2SK30 CCS; but its a matter of current since the FETs drain about 3,8mA and the diodes are configured to deliver a smaller current. The PCB space is small so this solution is "better".
6N3 Tube Preamp with DC-DC converter


Signal attenuation is very low, around -0,4db, stereo separation is about 40db at 20kHz and frequency response is flat from 10Hz to 100kHZ.
6N3 Tube Preamp with DC-DC converter


Poor specs for digital age but the sound is very gutsy...

...so I donīt give a "bit" about the poor HD and stereo separation.
For 2V RMS digital output HD is even better, and the output holds a 10kOhms load.

The tube is a 6N3 with a "M" grade mark. A "J" military grade is even better, specially at HD values. The GL-5670 works also very well or even better than the "J" grade 6n3.


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CAN YOU PLEASE WROTE YOUR MODIFICATIONS ON THE ORIGINAL SCHEMATIC AND UPLOAD TO BE ABLE TO MAKE A EXACT COPY OF YOUR DESING? IT WILL BE GREAT FOR ME!!!
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Old 28th October 2017, 01:25 AM   #135
kevinkr is offline kevinkr  United States
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6N3 Tube Preamp with DC-DC converter
Please don't post all caps, it's a violation of forum rules. Thanks!
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Old 28th October 2017, 12:34 PM   #136
MJL112 is offline MJL112
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Originally Posted by MJL112 View Post
CAN YOU PLEASE WROTE YOUR MODIFICATIONS ON THE ORIGINAL SCHEMATIC AND UPLOAD TO BE ABLE TO MAKE A EXACT COPY OF YOUR DESING? IT WILL BE GREAT FOR ME!!!
OK, sorry for my caps... cab you please..?
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Old 9th November 2018, 01:35 PM   #137
Hugh Jazz is offline Hugh Jazz  Taiwan
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Has anyone tried the Zerozone version which claims to have fixed the voltage issues? I noticed that some of the caps are 63V suggesting they have boosted the voltages from the first design on this thread many years ago. PCB looks single sided - rubbish?
Click the image to open in full size.
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Last edited by Hugh Jazz; 9th November 2018 at 01:40 PM.
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Old 9th November 2018, 06:37 PM   #138
Henkjan is offline Henkjan  Netherlands
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I also have a 6N3 board laying around (see photos), waiting for some time to be married to a 41Hz Amp6 and a USB DAC to make a nice PC amp.

"Ah!buis", our local (dutch dyi audio forum) tube guru came with 2 simple modifications to improve the performance. The first is to use a 12-0-12 transformer, the second will increase the voltage on the tube to 48V (will require cap upgrade as well)

I have not tested it, but with my new reading glasses I should be able to see the print well enough to do the soldering I hope te find some more spare time at the end of the year to actually continue with this project
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Old 9th November 2018, 08:19 PM   #139
6A3sUMMER is offline 6A3sUMMER  United States
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12VAC is about 17V peak. There are 2 voltage doublers (a + and a -) with the diode drops There should be about +33V and -33V, and there are 2 voltage regulators that give about +30V and -30V out. The triodes are wired as cathode followers, so the gain is less than Unity (less than 1). The voltage across the triodes are [60V - (the drop in the self bias resistor + the drop in the cathode load resistor)].

Oops, I just saw that this was not a new posting, just a new comment on one that already has over 130 posts.

Last edited by 6A3sUMMER; 9th November 2018 at 08:22 PM.
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Old 9th November 2018, 11:24 PM   #140
Hugh Jazz is offline Hugh Jazz  Taiwan
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Quote:
Originally Posted by Henkjan View Post
I also have a 6N3 board laying around (see photos), waiting for some time to be married to a 41Hz Amp6 and a USB DAC to make a nice PC amp.

"Ah!buis", our local (dutch dyi audio forum) tube guru came with 2 simple modifications to improve the performance. The first is to use a 12-0-12 transformer, the second will increase the voltage on the tube to 48V (will require cap upgrade as well)

I have not tested it, but with my new reading glasses I should be able to see the print well enough to do the soldering I hope te find some more spare time at the end of the year to actually continue with this project
I'm at that need-stronger-glasses time of life too :-)

Thanks for posting the pics. I've ordered two of these out of curiosity (apparently channel separation is poor so each one will be mono). AFAICS the only difference on the ones I'm getting is that the 1n4007 diodes are now FR207 fast recovery types. The rest seems to be the same. I'll post pics when they arrive.
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