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Old 17th September 2012, 07:04 AM   #81
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For 12AU7/ECC82, I found only three options:

PCB Experimenter's board

Tube buffer using 12AU7 Note: Take the 6N1P/6DJ8 schematic from post 1 and then modify that schematic to support 12AU7/ECC82 according to the directions in post 3.

Headphone amp (or hi-current preamp)
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Old 17th September 2012, 09:14 AM   #82
Gost22 is offline Gost22  Bolivia
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Quote:
Originally Posted by danielwritesbac View Post
For 12AU7/ECC82, I found only three options:

PCB Experimenter's board

Tube buffer using 12AU7 Note: Take the 6N1P/6DJ8 schematic from post 1 and then modify that schematic to support 12AU7/ECC82 according to the directions in post 3.

Headphone amp (or hi-current preamp)
thanks for your help!
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Old 17th March 2013, 07:10 AM   #83
Gost22 is offline Gost22  Bolivia
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Thumbs up Tube buffer with 6n3 for better sound !

Hi guys!
Instead of the proposed complete tube buffer schematic with 6n3 I would suggest this new improved schematic that provides better sound!
Yes Viewed schemtic so little comment if you have one.

Enjoy!!
Cheers!
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File Type: pdf 6N3 Tube Buffer Schematic.pdf (21.0 KB, 233 views)

Last edited by Gost22; 17th March 2013 at 07:14 AM.
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Old 24th May 2014, 09:38 AM   #84
AJT is offline AJT  Philippines
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Quote:
Originally Posted by danielwritesbac View Post
What is the optimal DC operating voltage?
This buffer project is very prone to clipping, thus the audio input has to be attenuated abnormally to prevent clipping. I'm looking for a way to get ordinary line level signal through this tube buffer, without either attenuating or clipping. Help?

i do not think clipping is an issue here.....
assuming 2 volts rms max input....
that is about 6 volts peak to peak,
the circuit is a cathode follower...
and 6 volts peak to peak is quite small
compared to the 60 volts peak to peak available...
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Old 16th August 2014, 11:01 PM   #85
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Default Has anyone noticed..?

On post #83 there was a schematic of a different tube based buffer presented.
Has anyone noticed that what is labeled as the earth ground on the voltage doubler is connected to the filament voltage?

I bought one of these and this is indeed how the board is laid out.

Anybody else think that this is a problem?
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Old 17th August 2014, 06:13 AM   #86
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Well, I noticed that it does run a bit warm (especially the piping hot filament regulator), and it is more problematic (albeit more fun) than a discrete solid state project. However, the filaments are lit to approximately the right amount, a dim yet fire color orange (not rusty red, not yellow), so it does appear that at least the filament portion is in the ballpark.
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Old 18th August 2014, 01:50 AM   #87
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Quote:
Anybody else think that this is a problem?
no problem, filaments can be grounded to the psu ground at either positive or negative end of the filament dc supply...
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Old 19th August 2014, 01:19 AM   #88
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Default Detailed of the Issue

Thank you for the responses, but I believe that I need to be clearer about the issue.

In the attached photo I am probing from pin 2 on the regulator (the output) to the ground pin on the right input.
Note that the meter is reading zero ohms meaning, and I followed the traces to be sure, that, as shown in the schematic, the regulator output is shorted to ground.
Hence, I am not surprised that there was a response that the regulator runs very hot.
It's likely pumping out large amounts of current trying to drive ground to the filament voltage, although I am not sure what resistance it's working against
In fact, I am surprised that the circuit works at all if people are connecting ground to the signal input and output ports!
Are people not making those connections?

I have identified some judicious cutting and pasting that could be done to elevate the short and allow connection to the input/output grounds.
However, before posting that I would be interested in knowing if there is anyone out there that has an assembled board that might be willing to make some voltage measurements and see where the doubler and PCB ground potentials sit with respect to earth ground.

Anyone game?
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Old 19th August 2014, 02:56 AM   #89
maton00 is online now maton00  Mexico
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Regulator 2nd pin is grounded because its a fixed one regulator not a 317
But if you detected a short circuit may cause alarm because it is not going to deliver the normal voltages spected here if using a 7805 at least put a 7806 in there so the tube could last a bit more
Look at the pic the regulator ground was elevated so that could deliver a more common voltage to the heaters (but I would triple check the PCB for security)
lm7805.png

A more acurate design but with 2 diodes instead of one, the upper pic also its miss calculated giving a lowish 5.6 -5.7 volts
reg ele.png

Last edited by maton00; 19th August 2014 at 03:15 AM.
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Old 20th August 2014, 01:39 AM   #90
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Default There really is a problem!

Thank you maton00 for the regulator and diode idea.
That is clever and I will have to try it.

However, the seller got back to me and admitted that the PCB is laid out incorrectly.
He suggested a three cut and three jumper correction.
The pictures he sent are attached, but I am only able to see two cuts and three jumpers.
Anybody see the third cut?
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File Type: jpg $_0.JPG (2.4 KB, 61 views)
File Type: jpg $_1.JPG (2.4 KB, 60 views)
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