OT: Alembic F-2B Tube Bass Preamp - Some Questions

Started by FrogBoy, July 19, 2005, 11:14:42 PM

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FrogBoy

Hi,

I am thinking about making the Alembic F-2B Tube Preamp as described in this link from geofex:  http://www.geofex.com/FX_images/alembpre.gif

I am planning on using a McTube style power supply for it.

The questions I have relate to the ratings of some of the components, and also the type of variable that are being used within the tone control section.

Do the capacitors within the tone control section (250pf, 0.1uf & 0.047uf) need to be able to handle the full plate voltage e.g. 240v?

The mid control on the schematic looks like a 10k rheostat (diagonal arrow) is this correct?

The Treble and Bass controls have some arrows on the diagram (poiting up on Treble, and Down on Bass) that I am not familiar with could anyone explain the meaning of these?

Any help would be greatly appreciated.

Thanks,

Chris.

markusw

For the tone control section I used some polyprops with IIRC 400V rating (they were available and quite cheap). To be sure I would use at leat 300V for 240V plate voltage. The mid and  bass control pots are wired as variables resistors with lugs 2+3 connected. IIRC bass and treble are both log, mid lin.

Good luck,

Markus

FrogBoy

Markus,

Thankyou very much, this is just the information I was after.

Are you happy with your build? Does it sound good?

Chris.

markusw

I'm more than happy with the sound.  :D

Markus

FrogBoy

Markus,

Did you use special high-voltage pots also, or just standard ones?

Thanks,

Chris.

markusw