https://github.com/mdouchement/alembic-f2b
Alembic F2b tube preamp schematic
https://github.com/mdouchement/alembic-f2b
12ax7 alembic ecc83 preamp preamplifier tube valve
Last synced: 4 months ago
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Alembic F2b tube preamp schematic
- Host: GitHub
- URL: https://github.com/mdouchement/alembic-f2b
- Owner: mdouchement
- Created: 2021-01-27T18:21:46.000Z (over 5 years ago)
- Default Branch: main
- Last Pushed: 2021-01-27T18:25:53.000Z (over 5 years ago)
- Last Synced: 2025-07-11T15:32:43.229Z (11 months ago)
- Topics: 12ax7, alembic, ecc83, preamp, preamplifier, tube, valve
- Homepage:
- Size: 771 KB
- Stars: 6
- Watchers: 4
- Forks: 2
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
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README
# Alembic F2b
This repository contains schematic and layout for the Alembic F2b preamp.
This project took its inspiration from:
- https://the7line.clan.su/publ/diystompbox/alembic_f2b/2-1-0-58
- https://the7line.clan.su/publ/diystompbox/bass_tube_preamp_alembik_bassman/2-1-0-38.
## Details
All the following section is based on the [Alembic_F2b_bass_preamp_schema.pdf](Alembic_F2b_bass_preamp_schema.pdf) schematic.
Input:
- 12VDC @ ~310mA
- ~150mA is used for 12AX7/ECC83 heater
### True bypass
True by using `SW1` footswitch.
R200 and C200 are used to smooth the switch.
### Grid-stopper
`R5` is the grid-stopper along with `C0` the Miller capacitance (R5+C0 forms a low-pass filter that atenuate frequencies greater than ~34KHz).
Resource: http://www.valvewizard.co.uk/gridstopper.html
### Gain stages
First stage is composed `R1`, `C1`, `R3` and `C3`.
Second stage is composed `R2`, `C2`, `R4` and `C9` that can saturate when the Gain's pot is at its maximum.
Resources:
- http://www.valvewizard.co.uk/gainstage.html
- https://www.ampbooks.com/mobile/amplifier-calculators/cathode-capacitor/ for `C1` and `C2`
- http://www.learningaboutelectronics.com/Articles/What-is-a-coupling-capacitor for `C3`, `C9` and `C10`
### Tone stack
Fender like tone stack: `C5`, `C6`, `C7`, `Bass`, `Midrange` and `Treble`.
`C8` is used as bright mod.
`Sweep` is used to move the mid freqs but it also changes the behaviour of bass and treble pots, default is 0% (100KΩ).
Resource: http://www.guitarscience.net/tsc/fender.htm
### Impedance adaptor
#### Input
`R200` is the input impedance for instrument.
`R7` is the grid leak.
#### Output
This part of the schema is juste used to reduce the output impedance.
`R9` and `R10` divides the HT voltage by 2 and put the AC signal provided by `C9` oscillating around 110VDC.
`Q1` is just used as a cathode folower, no amplification is done, we just use the low impedance property of the transistor.
### Heater filtering
`C100`, `L1` and `C101` are used to filter the voltage and current in order to minimize the hum provided by the heater.
If your power supply has a good quality, this part is not needed.
Resource: http://www.valvewizard.co.uk/heater.html
## Tools
- [KiCAD](https://kicad.org)
- https://gitlab.com/kicad/code/kicad
- https://github.com/KiCad
- [DIYLC](http://diy-fever.com/software/diylc)
- https://github.com/bancika/diy-layout-creator
- [LiveSPICE](https://github.com/dsharlet/LiveSPICE)
## Resources
- http://www.valvewizard.co.uk/index.html
- https://www.ampbooks.com/mobile/amplifier-calculators
- http://www.guitarscience.net/tsc/info.htm (tonestack calculator)