Alembic filter preamp PF-6

Pickups, wiring schemes, switch techniques and onboard active electronics for guitars and basses
Post Reply
User avatar
Jarno
Resistor Ronker
Information
Posts: 348
Joined: 12 Nov 2008, 10:18
my favorite amplifier: Something nice
Completed builds: Alembic-like state-variable and sallen-key filter preamps
Lovepedal Eternity
Phase 100
Brown source
Fuzz Face
Flipster
Alembic F2B (tube preamp)
Opamp and FET buffers
Loads of speakercabinets and ampracks
Busy building a modular synth (ssm2044 vcfs, preamps, ADSR's, VCO's, VCA's)
Tables
Bookshelves
Basses
So many things! :D
Location: Rosmalen, NL
Has thanked: 27 times
Been thanked: 77 times

Post by Jarno »

Like the F1x, was browsing and recalled that I actually bought the schematic for the Alembic onboard dual filter preamp (older version of the "series" onboard electronics, I think).
I'll post it here for posterity.
Quite elaborate, these basses have two pickups and a dummy coil, which needs to be carefully adjusted. They also have a second order low pass filter per pickup, with either a switch or a pot for "Q". In the old days, they used a separate outboard power supply, not sure if that is still the case.

The (dual) fet is probably unobtainium by now, as is the weird opamp (Harris HA-911), but that opamp is not great apparently. (well, as can be expected, there has been some progress in the performance of IC's in 45 years :) )
51621.jpg
51620.jpg
25013.jpg
25013.jpg (108.93 KiB) Viewed 1505 times
Attachments
Alembic PF-6 Preamp Service Schematic.pdf
(195.94 KiB) Downloaded 178 times
"It crackles....., but that's ok"

User avatar
bow_and_error
Breadboard Brother
Information
Posts: 56
Joined: 13 Jun 2019, 23:13
Has thanked: 93 times
Been thanked: 41 times
Contact:

Post by bow_and_error »

Interesting use of what looks like RG316 coaxial cable in place of a standard shielded one. I never thought to just terminate both directly to the board. We have a bunch of this at work, so I may have to give it a shot next time I wire up a guitar.

User avatar
Jarno
Resistor Ronker
Information
Posts: 348
Joined: 12 Nov 2008, 10:18
my favorite amplifier: Something nice
Completed builds: Alembic-like state-variable and sallen-key filter preamps
Lovepedal Eternity
Phase 100
Brown source
Fuzz Face
Flipster
Alembic F2B (tube preamp)
Opamp and FET buffers
Loads of speakercabinets and ampracks
Busy building a modular synth (ssm2044 vcfs, preamps, ADSR's, VCO's, VCA's)
Tables
Bookshelves
Basses
So many things! :D
Location: Rosmalen, NL
Has thanked: 27 times
Been thanked: 77 times

Post by Jarno »

We have that stuff as well, stripping it is a real PITA, at least the stuff that we have here. Those inline connectors are interesting as well, but knowing Alembic, probably heinously expensive (and I wonder if these are meant for this type of cable and thus lend themselves to proper crimping).
Also, I bought a bass with Alembic pickups, and that has the simpler preamp, will reverse engineer that as well, that does not have the JFET buffers, no dummy coil for noise cancelling, and switchable Q rather than continously variable Q.
"It crackles....., but that's ok"

Post Reply