pete millet low mu preamp

[tubo]

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

 

[dsavitsk]

hi, has anyone built or heard this low mu preamp?

Yes to both.

does the circuit invert phase?

Yes

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.

http://www.diyaudio.com/forums/tube...ine-stage-12b4-better-than-grounded-grid.html

http://www.diyaudio.com/forums/tubes-valves/141025-12b4-line-stage-amp.html

 

[TonyTecson]

the 6AS7 has a mu of about 2, it is an inverting type line amp.....

 

[TonyTecson]

and the 12b4 can be microphonic...be warned....

 

[radiostar]

My friend made it with 6AS7, works fine for my ears ...


Good luck!

 

[tubo]

thanks guys,

i think ill just convert the 6v6line amp to cathode follower and see what happens.

 

[Jeffrey Davison]

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

 

[radiostar]

Tidy job!

Congratulations!!!