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PRE BX (EQ, Dist preamp project by FEEDBACK - UPDATE rev1.1)
MUFF WIGGLER Forum Index -> Music Tech DIY  
Author PRE BX (EQ, Dist preamp project by FEEDBACK - UPDATE rev1.1)
strat-1
UPDATE : PRE BX is updated to rev 1.1 boards.
On the bottom of the post you will find new building files, including the manual 1.1 and photo zip with details of the construction.

what is new :
- the connectors are noted as in the schematic and a star shows pin 1 at each connector and IC
- Added an additional 2pin molex connector for output on the back, for a future mixer summer, or to link the module to another module without a jack cable.
- Added a filtering circuit for power, this doesn't affect in any way the circuit's sound, is just an extra protection for your power source.
- Added an extra NP cap print on top of the 0.22u EL cap so you will not have to bend the pins of the 220N cap.
- I enlarged the holes for the gain pot, so you will not have to drill them anymore.
- I moved the 5p cap closer to the opamp terminals.



Dear modular enthusiast.

A small and affordable mixer was always part of the electronic musicians setup.
Most of the times electronic musicians were using small and affordable mixers mostly
because they needed just a few channels, it had to be portable and relatively cheap.
In the last four decades there were tons of small and affordable mixers designed,
built and sold by various manufacturers but only a few became classics and long time
favourites for their sound in the electronic musician community.

There are three vintage small mixers that are highly regarded for their specific sound.
The oldest one was a product of a famous japanese guitar pedal maker and was used in
the late seventies and in the eighties by many electronic musicians (like Tangerine Dream
and others). It was a six channel stereo mixer with tone control on each channel.
A compact and sturdy little workhorse.

The second is also the product of the same company but a more modern one.
It was sold in two versions, eight and sixteen channel versions. It had a plastic case and
looked a bit like a toy but it didn't matter because it was used and loved by techno artists
since the early nineties and it is still used and loved for the sound.

The third one was a product of a US company and it was extremely popular in different fields
(small studios, rehearsal rooms, television, broadcast, etc ). It was a true winner because it
was affordable but at the same time it was very durable (sturdy metal case) and had tons of
features and connection possibilities. It existed in 12 and 16 channel versions. After this
successful series the company released "improved" versions but as a general consensus
between musicians only this old first generation mixer has "that sound".
It was extensively used with a very high gain setting to make a specific distorted TB303
sound. It was also used to mix some albums that became classics (like Biosphere Substrata).

Many years we saw people asking for modules that replicates the sounds of channel strips
from these small mixers. Ourselves being users of these mixers we thought it would be a
great idea to offer to the modular community the three classic sounds.
So we started breadboarding the circuits and tried to identify where the specific sound
comes from and how to reproduce this in the most convenient way. After a while we
identified which were the relevant aspects and made the prototypes.
Some more technical tests followed by listening tests and now we have three
eurorack modules, each one replicating the audio qualities of the vintage classics.

PRE KM - this module emulates the good old sound of the late seventies and eighties mixer
PRE BX - this modules emulates the sound of the mini plastic mixer used by the techno
artists from the nineties on.
PRE CR - this modules emulates the sound of the high gain TB303 distortion.

They all sound great and their sound can change from slghtly coloured to extreme distortion
and colour depending on gain and tone control. We encourage you to experiment with
different sounds from bass to drums and noises. You will have some pleasant surprises.


There are 3 type of kits available :

KIT 1 - PCB + PANEL = 20EUR
KIT 2 - PCB + PANEL + M5218L + CHIP SOCKET + ANTILOG POT 100KC = 30EUR
KIT 3 - PCB + PANEL + M5218L + Chip socket + 100KC POT +
3X50KA POTS, 2xMinijack Socket, Pin headers male+female, 3 Cream Knobs = 40EUR

Availability and prices :

KIT 1 - 20EUR (8pcs.)
KIT 2 - 30EUR (8pcs.)
KIT 3 - 40EUR (8pcs.)

Shipping to eu : 3eur, non eu : 5eur

FULLY BUILT MODULE - 70eur (5pcs.)

Shipping to eu : 10eur, non eu : 12eur

All the chips provided with the kits are tested and cleaned (many M5218L and HA1457 chips are coming with metal oxide between the pins)
For ordering write on the forum, but also pm me, it's hard of keeping track of ordering in two places. keep in mind that I will also
ask for 3% paypal fee from the total.
The project files are available for download at the end of the post. There are 3 archives : project files, photo archive and sound demos.

Here are the kits exemplified in pictures :

KIT1



KIT2 + 100KC ANTILOG POT (not in the picture)



KIT3




Sound Demos :
- all the modifications in the sound are made only with the PRE unit.
- all the demos respect the formula : 2-3 measures original sound, increasing hi freq, increasing low freq, increasing gain, increasing hi freq etc.

[s]https://soundcloud.com/strat1/pre-bx-3vco-arp[/s]
[s]https://soundcloud.com/strat1/pre-bx-tb303[/s]
 [s]https://soundcloud.com/strat1/pre-bx-kick909[/s]
[s]https://soundcloud.com/strat1/pre-bx-snare909[/s]
 [s]https://soundcloud.com/strat1/pre-bx-synthlead[/s]











Other FEEDBACK projects you can build :

CP3+ Mixer :
https://www.muffwiggler.com/forum/viewtopic.php?t=158439
SmArTT verter :
https://www.muffwiggler.com/forum/viewtopic.php?t=158691
106 Chorus :
https://www.muffwiggler.com/forum/viewtopic.php?t=158257
PRE CR :
https://www.muffwiggler.com/forum/viewtopic.php?t=163228
PRE KM :
https://www.muffwiggler.com/forum/viewtopic.php?t=163227
106 Chorus Slim :
https://www.muffwiggler.com/forum/viewtopic.php?t=166892
TWO59 Complex VCO :
https://www.muffwiggler.com/forum/viewtopic.php?t=169990


cupwise
so these things can be used to get signals into the modular? do they still have a decent signal to noise ratio after raising a signal that much? are all 3 using the same circuitry for the eq portion, with only the preamp part itself being different between them, or is the eq section unique in each one also?
strat-1
cupwise wrote:
so these things can be used to get signals into the modular? do they still have a decent signal to noise ratio after raising a signal that much? are all 3 using the same circuitry for the eq portion, with only the preamp part itself being different between them, or is the eq section unique in each one also?


They are not used only to get signals into modular, but also to shape sound from oscillators or any module you want, from soft clean sound, to extreme distortion with fat bass.
Each module have different circuitry and different eq.

PRE KM - You can obtain the sound of the 70's electronica, like Tangerine Dream leads and arps.
PRE BX - Originally used to distort the kick of the 808 in the techno house od the 80's
PRE CR - It's "that 303" distorted sound

I personally use them to add harmonics and boost eq of different
oscillators.
Jarno
Was looking at the schematic out of interest, but this inverts, right? First stage is inverting, second one isn't. Can you tack on extra inputs?
cupwise
ok nice, yeah i get that theyre mainly intended as tone modules and i think that's already cool and i might want to grab a few just for that purpose. i was just wondering how good they would be for bringing external inputs into modular.
strat-1
Jarno wrote:
Was looking at the schematic out of interest, but this inverts, right? First stage is inverting, second one isn't. Can you tack on extra inputs?


Yes. PRE BX and PRE KM inverts the signal, but an inverted saw or ramp will sound the same for ears. I preserved the original schematic, without adding extra parts to invert the signal again.
PRE CR is non inverting
Peake
Rising and falling saws can sound a bit different when run into a highly resonant filter. Worth checking.
Paradigm X
hey many thanks for sharing the schematics. i build in 5u so the panel combo is a bit ott, so may have a go at stripboarding it.

cheers.
maltemark
Package with some mixer channels kit 2 arrived safely. Nicely packed, thanks!

I just wanted to report an error in the BOM -
100KC (ANTI-LOG)
is listed as
1 ALPHA POT RD901F-40-15R1-A50K
(same as 50KA (LOG) 9MM)
strat-1
maltemark wrote:
Package with some mixer channels kit 2 arrived safely. Nicely packed, thanks!

I just wanted to report an error in the BOM -
100KC (ANTI-LOG)
is listed as
1 ALPHA POT RD901F-40-15R1-A50K
(same as 50KA (LOG) 9MM)


Thank you. I will correct that.
lintfresh
Cool project.
Which mixers are these modules emulating exactly?
mush
lintfresh wrote:
Cool project.
Which mixers are these modules emulating exactly?


Wild guess...
KM - Korg KM series
BX - Boss BX series
CR - Mackie CR series

wink
synthetek
mush wrote:
lintfresh wrote:
Cool project.
Which mixers are these modules emulating exactly?


Wild guess...
KM - Korg KM series
BX - Boss BX series
CR - Mackie CR series

wink


KM and BX are both Boss mixers
strat-1
UPDATE : PRE BX is updated to rev 1.1 boards.
On the bottom of the post you will find new building files, including the manual 1.1 and photo zip with details of the construction.

what is new :
- the connectors are noted as in the schematic and a star shows pin 1 at each connector and IC
- Added an additional 2pin molex connector for output on the back, for a future mixer summer, or to link the module to another module without a jack cable.
- Added a filtering circuit for power, this doesn't affect in any way the circuit's sound, is just an extra protection for your power source.
- Added an extra NP cap print on top of the 0.22u EL cap so you will not have to bend the pins of the 220N cap.
- I enlarged the holes for the gain pot, so you will not have to drill them anymore.
- I moved the 5p cap closer to the opamp terminals.
gipsycat
Hi,

Are you still making the PCBs for these? I would like to buy the PCBs only if that is possible as I want to do my own MU panels for them...

2 x PCBs pre BX
2 x PCBs pre MK
Thanks a lot.
strat-1
gipsycat wrote:
Hi,

Are you still making the PCBs for these? I would like to buy the PCBs only if that is possible as I want to do my own MU panels for them...

2 x PCBs pre BX
2 x PCBs pre MK
Thanks a lot.


I don't sell PCBs only. You buy the project, not only the pcbs.
(time invested in pcb making, testing, writing the manual etc.)
Consider the panels are a bonus, you are free not to use them, I will include them in the package anyway.

You can find all the kits at www.feedbackmodules.com
aswefallintostatic
Hey, do these have enough gain to amplify external audio to modular level?

Am wondering if i could use it as a nice colour module to connect an external synth to the modular world...
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