Dreadbox Erebus DIY kit

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fwyar
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Post by fwyar » Thu Aug 16, 2018 7:21 am

Mmdm wrote:Finally mine works ok!! I was reversed two transistors.... I put new ones and works perfectly!!!

For those one with troubles double or triple check the soldering, the polarity of the components etc

I needed like 3 days of debbuging to find the error and it was so obvious...
Hey @Mmdm - do you know which transistor it was? I seem to be in the same spot with the noise.

aabbcc
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Post by aabbcc » Thu Aug 16, 2018 1:43 pm

fwyar wrote:
Mmdm wrote:Finally mine works ok!! I was reversed two transistors.... I put new ones and works perfectly!!!

For those one with troubles double or triple check the soldering, the polarity of the components etc

I needed like 3 days of debbuging to find the error and it was so obvious...
Hey @Mmdm - do you know which transistor it was? I seem to be in the same spot with the noise.
There are only like 6 transistors so just check if they line up with the silkscreen :p

fwyar
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Post by fwyar » Fri Aug 17, 2018 9:23 pm

aabbcc wrote:
fwyar wrote: Hey @Mmdm - do you know which transistor it was? I seem to be in the same spot with the noise.
There are only like 6 transistors so just check if they line up with the silkscreen :p
:) yeah
mine all line up so I thought I might have fried one of the transistors.
was hoping to narrow down the offender

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Muff McMuff
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Post by Muff McMuff » Sat Aug 18, 2018 11:21 pm

TaTechneta wrote:Quick update: re-flowing the LED resistors (R10, R11) and the sockets for IC 21 (after removing the chip) did the trick for the square LFO bleeding into VCO2‘s tuning! Although I can‘t say for sure, my best bet is on the LFO resistors not having grounded it fully, but I‘ll never know. Now VCO2 is stable as can be.

ALSO to anyone mildly interested in this synth, there is a summer sale on it right now. 110 bucks, that almost convinced me to get a second one :lol: .
That was a good offer, i would have bought one but it ended on 8th Aug. I wasn't aware of this kit until today.

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Supervillain
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Post by Supervillain » Sun Aug 19, 2018 9:07 pm

Hey !

Finished mine a few weeks back and i love it's sound.
Everything seems to work but i have some questions anyway...

-When fully closed (CCW) the filter frequency seems a bit high, i would say something near 40-50Hz
Is it normal? Is it moddable ?

-I also would like to mod the second VCO detune fader to have a smaller range but more precise setting.
Again, being a total noob idk how to do it ! :bang:

-Even with the smaller cap suggested on the pcb my lfo still pretty fast, i'll try some smaller value and see what's up.

adwer
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Post by adwer » Mon Sep 03, 2018 5:54 am

Hello people,
anyone here made a wood case for the desktop version? Is the supplied MIDI to minijack adapter the same pinout as the Korg SQ1's?

thanks

loresdef
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Post by loresdef » Tue Nov 06, 2018 8:05 am

HI There,

I have bought a build lil erebus a while back and enjoyed it so far, alltho i have a few things i was wondering about and hope someone here can clarify or answer:

1 : 2nd vco seems affected bij lfo2 in pitch, even with lfo fader down and nothing patched, does someone knows hows to fix this?

2 :The env is hardwired to the Cutoff, does someone here knows how to undo this, so for example: the env can be wired to vcf or vca and use a second ext. env. to control one or the other? I guess a trace should be cut somewhere?

Would have been nice if this was normalled(or hardwired) like it is now but when plugged into cutoff the env->vcf connection was broken some how.,
Thanks,

jakobprogsch
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VCA Mod

Post by jakobprogsch » Wed Nov 14, 2018 7:23 pm

I had two lil erebus modules for a while now and was always slightly irritated by the funky VCA behavior. It essentially does nothing between 0V and 3.5V an then exponentially ramps up to full amplitude between 3.5V and 5V. This makes it really hard to use with an envelope.

So I came up with the following modification to better suit my preferences:
Image
And here is the schematic of the VCA after the changes (there are two LM13700 attached at the Iabc node but I only drew one for simplicity):
Image

The result is that the VCAs are now more like regular linear VCAs. The changes I made are listed below. Attempt this at your own risk obviously. I'm no expert and these changes were not designed for "optimality" but rather minimum amount of required changes. Suggestions for improvement would be highly appreciated.

For reference the original schematic and layout can be found on the dreadbox site here.
  • desolder transitors T5 and Q7 and replace them with a 2N3906 (or similar PNP) as shown
  • desolder resistor R107 on the side closer to the IC and instead connect it to the transistors emitter as shown. Alternatively completely remove the resistor and simply connect the emitter on the far side from the IC. This should work the same but only occurred to me later so I didn't test it.
  • (optional) remove capacitor C28. The capacitor limits attack and release slope. This sounds better when using a gate as "envelope" as per lil erebus normaling but gets in the way of controlling them from an external EG.
  • swap R83 and R58 with 100K resistors
  • swap R57 and R65 with 1M resistors
It works without the last two steps, but the output levels of the VCA and therefore the master volume will approximately be halved.

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zoompig
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VCA Click null dependence on resonance setting

Post by zoompig » Sat Dec 08, 2018 3:45 pm

Just put mine together and tuned it up.

I am finding that the correct null positions for trimpots R92 and R94 on the input of the LM13700 OTAs depend on the resonance control position in the VCF section.
Is this normal behavior? Has anybody else noticed this?

Thanks,

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oppositaer
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Post by oppositaer » Sun Dec 09, 2018 1:15 pm

at a quick view the relation costs/quality is great if compared to other companies releasing diy kits.. specialy when kits come together with front panel! i'd set it to the "things to build" list for sure..

big up to dreadbox as far as they don't mess up with components values and/or wrong building instruction..
I build DIY kits and projects in South Europe.. PM me if you need help!

Some sounds:
https://www.mixcloud.com/oppositaer/
https://soundcloud.com/arinev

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undress
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Post by undress » Sun Jan 13, 2019 12:06 pm

Hello,

I would like to report my first module ever and my first successful build. I did manage to invert a 4k7 with a 47k resistor at some point, but caught the error before finishing. I still have some fine tuning to do but so far so good.

Thanks for the detailed tuning instructions.

audiocommand
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Erebus jacks?

Post by audiocommand » Sun Feb 03, 2019 10:31 am

hey

anyone knows a part number from the jacks?

one from me erebus was killd by a bad patchkable and it need
to replace!

Thanks for help

Dominic

wicked_experimenter
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mcp4922 voltage

Post by wicked_experimenter » Wed Feb 20, 2019 10:50 am

HELP, PLEASE!

my tlo74's get the +12/ -12 voltages, but my mcp4922 gets +11V on pin 1 instead of 5.

any ideas what might be wrong?

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Rob Kam
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Re: Erebus jacks?

Post by Rob Kam » Thu Feb 28, 2019 1:40 pm

audiocommand wrote: anyone knows a part number from the jacks?
Possibly WQP-PJ3420

brainctrl
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Post by brainctrl » Sun Mar 10, 2019 1:31 pm

The transistor on the bottom is upside down.
aabbcc wrote:Ugh so Dreadbox apparently can't release schematics for this one.

Anyone have a good idea where to start?

Problem being I have continuity between +12v and ground pins. Have gone through everything with a magnyfiyng glass and can't find any small piece of solder or similiar shorting anything.

Follow link for a bit more detailed photos or just zoom on this one. (And I'm aware of the two pins sticking out slightly above the "D" in "Dreadbox :) )


Image
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lilakmonoke
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Post by lilakmonoke » Wed Mar 20, 2019 8:24 pm

ive just inherited a finished lilerebus that doesnt work at all, no sound. apparently midi is working and it made some incoherent weak tones at which point the collegue decided that ic no2 (fet opamp) wasnt working and replaced it with a new one. after that no more sounds. he thinks he messed up the pcb during desoldering the ic.

i know almost nothing about circuits but i can solder and i have a multimeter. im also determined to make this thing work. where do i start?
.

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Troubleshooter
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Post by Troubleshooter » Thu Apr 11, 2019 9:04 am

To what I can see the Midi cirquit is family of the MidiSizer Midi2CV Mk2. At least the same D/A convertor is used and the pinout is almost the same. Maby we can tweak the MidiSizer code and provide an more open source alternative firmware.

aabbcc
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Post by aabbcc » Mon Apr 15, 2019 4:29 pm

brainctrl wrote:The transistor on the bottom is upside down.
aabbcc wrote:Ugh so Dreadbox apparently can't release schematics for this one.

Anyone have a good idea where to start?

Problem being I have continuity between +12v and ground pins. Have gone through everything with a magnyfiyng glass and can't find any small piece of solder or similiar shorting anything.

Follow link for a bit more detailed photos or just zoom on this one. (And I'm aware of the two pins sticking out slightly above the "D" in "Dreadbox :) )


Image
Oh, thats a bc something something transistors that I can't remember now with flipped pinout, thus it being "backwards" :)

Rupert the not so great
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Post by Rupert the not so great » Wed May 01, 2019 8:04 am

Hello, looking for some help with the voltage check on the lil erebus -

Never done this part before so i'm not sure I understand it, would someone be able to explain to a total newbie?

Is it AC or DC I use on the multimeter? Where does the black lead go and where does the red lead go? I know the manual explains this but wheres pin 4 and pin 11 on the TL074 IC and where is pin 1 on the MCP4922 IC?

SOOO confused!

Cheers

Rupert the not so great
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Post by Rupert the not so great » Wed May 01, 2019 8:43 am

Update - Just done a wee search online and although i'm not convinced it's the correct way I thought i'd try it anyway.

Every bloody chip was a different voltage. Could someone tell me how I go about measuring Pin 4 -> +12V +/- 0,5V
Pin 11 -> -12V +/- 0,5V

and MCP4922 IC, Pin 1 -> +5V +/- 0,2V

Im so sure i've done it wrong or at least i've messed up something while building..

Rupert the not so great
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Post by Rupert the not so great » Sat May 04, 2019 1:43 pm

Hi again,

*sorry to post another* - finally got to the bottom on testing the voltages and everything has turned out with testing voltage.

Just wondering - Theres no echo and just a click with VCO 1 ( no oscillation) - does anyone have any ideas as to why it's not working and how I can troubleshoot?

I have a few pictures of my board here - Image
Image


Please if someone could point me in the right direction that would be great :help:

The LED was missing the casing or whatever you want to call it so I just soldered it on without - could that be the problem?

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jdaddyaz
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Post by jdaddyaz » Fri Jul 26, 2019 1:51 pm

Finished reading through this discussion and didnt see my problem already listed. I finished building, tuned it, everything working. Wake up next day turn it in, and now none of the OSCs work. The lfo and echos work, as I get the gate triggers when trying to trigger the osc. Any ideas? This is my forth build so I'm still using training wheels. Might be worth to note that my EXOS also doesnt make a sound and was powered by the same uzeus.
Be good to yourself, and be good to others.

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jdaddyaz
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Post by jdaddyaz » Mon Aug 05, 2019 12:01 am

:help:
Be good to yourself, and be good to others.

jakobprogsch
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Post by jakobprogsch » Mon Aug 05, 2019 7:54 am

That's hard to debug from afar. Considering another module doesn't work I'd guess maybe there is a power related issue? Check if all rails are on and at the expected voltage and that there is no short or disconnect. The echo chip only runs off the positive supply. So I guess that could be working with a screwed up negative supply. Not sure why the lfo would work in that situation though.

fivebodysword
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Post by fivebodysword » Thu Aug 15, 2019 12:37 pm

UPDATE - I fixed it! One of the CoolAudio chips must have been damaged somehow, replaced it and now I'm back in dubverb heaven.


Hi friends, I recently picked up a pre-built DIY Lil Erebus, which I have been eyeing for quite awhile. When I got it, everything worked as generally expected, great tones, no problem for the first day or so, except the oscillators were out of tune. I got them both in tune following the video guide via CV/gate from my M32 via a tuner module, could hear everything, no VCA problems, etc - ready to go!

However, when I re-connected the module back into its spot in the case, I ended up with the "everything but what appears to be the VCA" working - gate is hitting, echo works on the gate-clicking, both LFOs and OSCs, LFO LED goes. No audio-through in the audio input. I very slowly went back through the VCA clean trim, no luck. Checked voltages on a TL074 and the MCP4922, all matched the build guide.

I also tried the "stuck in polychain" on-offing the dip4, no luck. I had looked at these switches and switched them a bit in looking to configure the mono/duo -so this may be part of the problem, however if it is, I cannot get the on/off thing to work no matter how fast or slow I do it in the 5 seconds. Is there another way for the board to "forget" this mode?

Thanks for thinking this over!

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