PRE BX (EQ, Dist preamp) by FEEDBACK [NEW PRICES]

From circuitbending to homebrew stompboxes & synths, keep the DIY spirit alive!

Moderators: Kent, Joe., luketeaford, lisa

User avatar
strat-1
Veteran Wiggler
Posts: 515
Joined: Wed Jun 03, 2015 8:58 am
Location: Romania
Contact:

PRE BX (EQ, Dist preamp) by FEEDBACK [NEW PRICES]

Post by strat-1 » Tue Jun 14, 2016 6:36 am

UPDATE : I updated the prices for the majority of kits and modules. I found e better source for rare and common parts.

www.feedbackmodules.com

ImageImage
Image
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.

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

There are 3 type of kits available :

KIT1 : 20EUR (2PCBs+frontPanel)
KIT2 : 30EUR (Pcbs+FP, M5218L, Antilog POT 100KC)
KIT2 : 40EUR (Pcbs+FP, M5218L, Antilog POT 100KC, 2xminijacks, 3X50KA POTS, 2xboard connectors, 3xCream Knobs)

COMPLETE MODULE : 70eur

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

KIT1

Image

KIT2

Image

KIT3

Image
You do not have the required permissions to view the files attached to this post.
Last edited by strat-1 on Tue Sep 17, 2019 6:10 am, edited 13 times in total.

cupwise
Wiggling with Experience
Posts: 254
Joined: Fri Dec 02, 2011 2:51 am

Post by cupwise » Fri Jun 17, 2016 2:12 pm

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?

User avatar
strat-1
Veteran Wiggler
Posts: 515
Joined: Wed Jun 03, 2015 8:58 am
Location: Romania
Contact:

Post by strat-1 » Fri Jun 17, 2016 3:26 pm

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
Super Deluxe Wiggler
Posts: 2790
Joined: Mon Nov 15, 2010 6:34 am
Location: Rosmalen, NL

Post by Jarno » Fri Jun 17, 2016 4:06 pm

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
Wiggling with Experience
Posts: 254
Joined: Fri Dec 02, 2011 2:51 am

Post by cupwise » Fri Jun 17, 2016 6:26 pm

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.

User avatar
strat-1
Veteran Wiggler
Posts: 515
Joined: Wed Jun 03, 2015 8:58 am
Location: Romania
Contact:

Post by strat-1 » Fri Jun 17, 2016 9:34 pm

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

User avatar
Peake
I'm in ur DIY. Filling cases with Buchla
Posts: 7210
Joined: Fri Nov 07, 2008 10:00 pm
Location: Loss Angeles

Post by Peake » Fri Jun 17, 2016 11:46 pm

Rising and falling saws can sound a bit different when run into a highly resonant filter. Worth checking.
This is not the place I'd imagined it to be.

User avatar
Paradigm X
Super Deluxe Wiggler
Posts: 2056
Joined: Tue Nov 02, 2010 5:43 am

Post by Paradigm X » Wed Jun 29, 2016 5:29 am

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.

User avatar
maltemark
Ultra Wiggler
Posts: 783
Joined: Tue Dec 16, 2014 11:39 am
Location: Gothenburg

Post by maltemark » Mon Jul 11, 2016 10:47 am

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)

User avatar
strat-1
Veteran Wiggler
Posts: 515
Joined: Wed Jun 03, 2015 8:58 am
Location: Romania
Contact:

Post by strat-1 » Tue Jul 12, 2016 2:12 am

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.

User avatar
lintfresh
Veteran Wiggler
Posts: 529
Joined: Thu Aug 29, 2013 12:45 pm
Location: Seattle

Post by lintfresh » Tue Jul 12, 2016 2:46 am

Cool project.
Which mixers are these modules emulating exactly?

User avatar
mush
Veteran Wiggler
Posts: 597
Joined: Tue Sep 28, 2010 1:38 pm
Location: Copenhagen, Denmark

Post by mush » Tue Jul 12, 2016 3:18 am

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

;)

User avatar
synthetek
Wiggling with Experience
Posts: 497
Joined: Fri Jun 05, 2015 3:32 am
Location: Orange County, California
Contact:

Post by synthetek » Tue Jul 12, 2016 5:11 pm

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

;)
KM and BX are both Boss mixers

User avatar
strat-1
Veteran Wiggler
Posts: 515
Joined: Wed Jun 03, 2015 8:58 am
Location: Romania
Contact:

Post by strat-1 » Fri Jan 13, 2017 12:53 pm

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
Learning to Wiggle
Posts: 11
Joined: Tue May 01, 2012 3:05 pm
Location: London

Pre BXs and pre KMs

Post by gipsycat » Mon Feb 27, 2017 7:31 am

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.

User avatar
strat-1
Veteran Wiggler
Posts: 515
Joined: Wed Jun 03, 2015 8:58 am
Location: Romania
Contact:

Re: Pre BXs and pre KMs

Post by strat-1 » Mon Feb 27, 2017 2:58 pm

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

User avatar
aswefallintostatic
Common Wiggler
Posts: 136
Joined: Tue Nov 11, 2014 5:58 pm
Contact:

Post by aswefallintostatic » Fri Oct 06, 2017 5:54 am

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...

User avatar
bradpickapiper
Common Wiggler
Posts: 203
Joined: Sun Oct 11, 2015 11:59 am
Location: Toronto, Canada

Post by bradpickapiper » Mon Sep 17, 2018 8:43 pm

aswefallintostatic wrote: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...
would also like to know this if anyone has any insight?

User avatar
uniquepersonno2
Super Deluxe Wiggler
Posts: 1032
Joined: Sun Mar 05, 2017 7:11 pm
Location: LA

Post by uniquepersonno2 » Tue Oct 02, 2018 10:32 pm

Curious if anybody is using these, they look really cool. I was looking for some EQ modules that weren't gigantic and I always like something that can add a little character. Would love to hear other people's thoughts!
It's done!
...probably! Ahhh, who am I kidding...

User avatar
secrethero303
Common Wiggler
Posts: 127
Joined: Tue Oct 25, 2016 5:23 pm
Location: WI, USA

Post by secrethero303 » Wed Oct 03, 2018 8:32 am

I'm using this one and the Pre-CR. Both add some really good character to the sound, and also work as an input from external instruments. I'm using them as an input/overdrive for a TB-303 and it sounds great.

User avatar
uniquepersonno2
Super Deluxe Wiggler
Posts: 1032
Joined: Sun Mar 05, 2017 7:11 pm
Location: LA

Post by uniquepersonno2 » Wed Oct 03, 2018 6:14 pm

secrethero303 wrote:I'm using this one and the Pre-CR. Both add some really good character to the sound, and also work as an input from external instruments. I'm using them as an input/overdrive for a TB-303 and it sounds great.
Ah, that's very good to know. Thanks!
It's done!
...probably! Ahhh, who am I kidding...

User avatar
strat-1
Veteran Wiggler
Posts: 515
Joined: Wed Jun 03, 2015 8:58 am
Location: Romania
Contact:

Post by strat-1 » Thu Oct 25, 2018 6:49 am

aswefallintostatic wrote: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...
UPDATE :
I attached a pdf file in main post with output readings of each PRE type using a 1Vpp source at input.
1Vpp is lower than a laptop, phone or any sampler output.
You can see in the pdf output Vpp at different gain, volume settings.

stevelate
1-Post Wiggler
Posts: 1
Joined: Sun Aug 13, 2017 5:53 pm
Location: vienna

Anybody selling theirs

Post by stevelate » Sat Mar 09, 2019 2:49 am

I need second one of those and they are sold out.
So if anybody is selling theirs -
send me a quick message!

steve at stevelate.com


:yay:

User avatar
strat-1
Veteran Wiggler
Posts: 515
Joined: Wed Jun 03, 2015 8:58 am
Location: Romania
Contact:

Re: Anybody selling theirs

Post by strat-1 » Sat Mar 09, 2019 9:02 am

stevelate wrote:I need second one of those and they are sold out.
So if anybody is selling theirs -
send me a quick message!

steve at stevelate.com


:yay:
It will be available again in 10days :)

User avatar
strat-1
Veteran Wiggler
Posts: 515
Joined: Wed Jun 03, 2015 8:58 am
Location: Romania
Contact:

Post by strat-1 » Mon Mar 18, 2019 10:02 am

[UPDATE] PRE BX and PRE CR kits and modules are back in stock.

Post Reply

Return to “Music Tech DIY”