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Old 8th January 2012, 08:00 AM   #1
tubo is offline tubo  Philippines
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Default pete millet low mu preamp

hi,

has anyone built or heard this low mu preamp? does the circuit invert phase? i don't need to much gain in my amps that's why im interested in building this.any input please.thanks

Low-mu preamp
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Old 8th January 2012, 08:53 AM   #2
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Quote:
Originally Posted by tubo View Post
hi, has anyone built or heard this low mu preamp?
Yes to both.

Quote:
Originally Posted by tubo View Post
does the circuit invert phase?
Yes

Quote:
Originally Posted by tubo View Post
i don't need to much gain in my amps that's why im interested in building this.any input please.
The 6AS7 can be a very noisy tube. Look around for the 12B4 threads -- you can build much the same design with that tube, but it is quieter and more linear.

Yet another 12B4 line stage, or is the 12B4 better than the Grounded Grid.....

12B4 Line Stage Amp
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Old 8th January 2012, 08:54 AM   #3
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the 6AS7 has a mu of about 2, it is an inverting type line amp.....
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Old 8th January 2012, 08:55 AM   #4
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and the 12b4 can be microphonic...be warned....
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Old 8th January 2012, 09:54 AM   #5
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My friend made it with 6AS7, works fine for my ears ...


Good luck!
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Old 8th January 2012, 10:14 PM   #6
tubo is offline tubo  Philippines
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thanks guys,

i think ill just convert the 6v6line amp to cathode follower and see what happens.
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Old 9th January 2012, 05:53 AM   #7
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Built one about a year and a half ago. Went with a single transfomer but dual power supplies, one for each channel. Went with a grid choke instead of a grid leak resistor. Geartz hybrid with the rectifiers. Need a touch of gain so went with a 421a. Just a little hum, but not intrusive enough to distract from the music. Just last week I went with DC on the 421a filament with a vccs rectifier/regulator. Also upgraded to Clarity Cap MR on the 10uf output caps, not that the Obligatos were bad, just want a bit more out of this piece. The pics were taken after I finished building it. Rectifier tubes are now a pair of EML 274B mesh plates and went with Shuguang Treasure series 6Ca7 as the old KT77's I had were a tad noisy as a CCS. Treasures were much quiter. VERY happy with the sonics.

JD
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Last edited by Jeffrey Davison; 9th January 2012 at 06:05 AM.
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Old 9th January 2012, 02:15 PM   #8
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Tidy job!

Congratulations!!!
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