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PRE KM (EQ, Dist preamp) by FEEDBACK
MUFF WIGGLER Forum Index -> Music Tech DIY  
Author PRE KM (EQ, Dist preamp) by FEEDBACK
UPDATE : I uploaded the last version of the building manual 1.3
I made a pdf file with output readings of each PRE type using a 1Vpp source at input.

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.

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.


There are 3 type of kits available :

KIT1 : 20EUR (2PCBs+frontPanel)
KIT2 : 30EUR (Pcbs+FP, + 2xHA1457)
KIT3 : 40EUR (Pcbs+FP, + 2xHA1457 + 20KB POT + 2X50KB POTS + 2xMinijacks + 2xboard connectors + 3XCream Knobs)


All the chips provided with the kits are tested and cleaned (many M5218L and HA1457 chips are coming with metal oxide between the pins)




UPDATE : PRE KM is updated to rev 1.1 boards.

On the bottom of the main 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
- corrected some parts names
- I 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.
- I added a filtering power circuit, this doesn't affect in any way the circuit's sound, is just an extra protection for your power source.
- I added an extra NP cap print on top of the 0.47u EL cap so you will not have to bend the pins of the 470N cap.
Hi, i have been trying to work out which mixers these are from, is the BX the Boss BX-800? Which are the others?

Look cool either ways smile

UPDATE : There was a missing cap in the manual. I corrected that.

I updated the post look and I attached a pdf file in the main post with output readings of each PRE type using a 1Vpp source at input.

I uploaded the last version of the building manual 1.3
A new demo for the PRE series by Color My Sound :

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