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Old 9th January 2008, 01:28 PM   #11
Sherman is offline Sherman  United States
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Quote:
Originally posted by Poindexter
Try this.

...

If interested, let me know, and I'll show you the power supply and stuff.

Hau'oli Makahiki Hou,

Poinz

I'd like to know more about this one as well. Just checked the price of 6T4 tubes.

What is the gain for this circuit?
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Old 9th January 2008, 03:13 PM   #12
SCD is offline SCD  Canada
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Default 6T4

I too am interested in the 6T4 circuit. What is the voltage swing and gain if you do not mind?
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Old 9th January 2008, 03:37 PM   #13
JimW is offline JimW  United States
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Another tube that works well in a low and hot srpp is the ECC99. I have one set up using 91r on cathodes, running 230 volts across the pair (115 per tube) at 17ma. Sounds pretty good, and should have an output z around 800 ohms if I calculated correctly. Don't forget to elevate heater voltage to avoid problems with the uper half or upper tube, as the case may be.
Jim
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Old 9th January 2008, 07:01 PM   #14
jduffy is offline jduffy  United States
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Default 12AU7

My first from scratch preamp was Bruce Rozenblit's 12AU7 Line Preamp from Glass Audio. Look it up online and you can find the schematic EZ. I built it for under $100 and it works very well. Great learning experience and I've passed it around to my friends to run in their systems, they love the thing.

I've used it with a tube amp, chip amp, SS amp and it never gets in the way of the music.

Good luck with your decision!
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Old 9th January 2008, 07:47 PM   #15
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Hold on, guys,

I'm having trouble with the FTP side of my site, so can't load the schem of the whole preamp.  I have a form off to my host, am awaiting reply.

Remedy soonest.  Until then, the numbers:

Voltage gain . . . . . . 5.1
Zout . . . . . . . . . . . . 200Ω
B/W (+0, -1db) . . . 6Hz - 240KHz

Aloha,

Poinz
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Old 9th January 2008, 07:51 PM   #16
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Oh, jduffy,

Bruce's mu-follower was my first preamp, too; in fact, my first scratch build.  The circuit I posted above is the fourth generation descendant of that project.

Aloha,

Poinz
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Old 9th January 2008, 08:11 PM   #17
JimW is offline JimW  United States
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Hey Poinz, what formula did you use to calculate your output z? BTW, was in your area couple of weeks ago - beautiful place, but the traffic sucks - rush hour never ends!
Jim
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Old 9th January 2008, 10:07 PM   #18
jduffy is offline jduffy  United States
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Default Nice!

Quote:
Originally posted by Poindexter
Oh, jduffy,

Bruce's mu-follower was my first preamp, too; in fact, my first scratch build.  The circuit I posted above is the fourth generation descendant of that project.

Aloha,

Poinz
Intriguing! Mahalo for the information.

Really curious to see what you've done.
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Old 10th January 2008, 12:36 AM   #19
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Hah, got it figured out.  Thank you Netfirms.

In the interests of file and image size, the parts information is a bit terse. If you have questions, ask. Everyt'ing stay bestest kine.

    Click the image to open in full size.

Yes, the power transformer is wired unconventionally. I'm burning about ¼ its VA rating, no winding is overvolted, it doesn't even get warm.

Aloha,

Poinz
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Old 10th January 2008, 01:05 AM   #20
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12B4 with a red LED string in the cathode. Gain is about 4 or 5.
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