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6j6 tube preamp started
http://diyaudioprojects.com/Forum/viewtopic.php?f=9&t=427
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Author:  booangler [ 05 Feb 2009, 21:33 ]
Post subject:  Re: 6j6 tube preamp started

Way To Go Bill, :up:

I can hear your excitement in the post. Keep up the outstanding work!

Alan

Author:  billnchristy [ 05 Feb 2009, 22:13 ]
Post subject:  Re: 6j6 tube preamp started

Thank you!

I swapped the tubes and it is the tube that has the bright heater.

Author:  Gio [ 06 Feb 2009, 13:24 ]
Post subject:  Re: 6j6 tube preamp started

Hey Bill, that looks great. I like to use UF400x didoes. They are dirt cheap and work very well. They recover faster than what you used, but those look fine too.

What size resistor did you use as a bleeder? That will dictate how fast the caps drain.

Author:  billnchristy [ 06 Feb 2009, 13:47 ]
Post subject:  Re: 6j6 tube preamp started

I didnt thats the weird part.

Though I just looked and maybe it is the humbucking circuit that causes the drain? It comes off the 2nd triode's grid and is connected to B+ and ground via resistors. That will do it won't it as it is basically 2 resistors to ground.

Author:  billnchristy [ 06 Feb 2009, 15:54 ]
Post subject:  Re: 6j6 tube preamp started

Here is the final circuit with values.
Attachment:
6J6-Hum-Bucking-Common-Cathode-Preamp-Schematic.png

Author:  billnchristy [ 08 Feb 2009, 19:41 ]
Post subject:  Re: 6j6 tube preamp started

Another question:

While I am enjoying this preamp I have found that it is actually too critical with mp3 type material. Seeing as how it has a small form factor and is cheap to build I think its main role would be office and secondary system use.

Is there a good way to actually decrease this? Basically it really brings out the sound of compression. I am thinking a cap that is a little hazy on its own (like a Solen) might do the trick.

Any other suggestions?

Author:  Gio [ 08 Feb 2009, 21:57 ]
Post subject:  Re: 6j6 tube preamp started

Yes, less compression or go lossless! :)

How about noisy carbon comp resistors in the signal path?

Author:  billnchristy [ 08 Feb 2009, 22:26 ]
Post subject:  Re: 6j6 tube preamp started

That might be the way to go.

I will give that a try in Rev 2.

Rin seems like the best candidate.

Author:  Gio [ 08 Feb 2009, 23:01 ]
Post subject:  Re: 6j6 tube preamp started

billnchristy wrote:
That might be the way to go.

Yes, lossless. ;)
billnchristy wrote:
Rin seems like the best candidate.

You could also try the 1M and perhaps Ra too.

Here is a good summary of resistor noise: http://www.aikenamps.com/ResistorNoise.htm

Cheers

Author:  briansdad [ 21 Oct 2009, 21:44 ]
Post subject:  Re: 6j6 tube preamp started

I may have missed it, but what is the B+ on this preamp circuit, please? :xfingers:

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