MB-808 first test

[sneakthief]

MB-808!!!

only one take.

all you hear is 808.

the tones are from self-oscillating congas.

(ghetto-ass distortion + compressor + reverb, all courtesy a roland m-16dx mixer)

mods:

- white noise level

- snare decay

- snare filter

- clap offset

- clap reverb amount

- maraca filter

- rimshot filter

- cowbell tuning x2

- open hat filter

- closed hat filter

- white & pink noise input jacks (not used in this demo)

- schmitt trigger input jacks (not used in this demo)

- self-oscillation of congas when the decay is set all the way

better pics coming soon...

[jojjelito]

Wow! Sounds real good

Care to share some of your mod details for others to follow?I could figure out how to do most of that out from your list, but I'm lazy You may already have written about those but the dedicated forum is down until further notice...

Cheers!

J

[sneakthief]

This list is mostly from http://xlargex.xl.funpic.de/

All resistors #'s refer to the original TR-808 schematic, not the MB-808.

1. Noise level:

22k(B) Potentiometer for TM4 (22kb)

2. SD: On LT decay: "Snappy" Decay

C51 (0,47µf) changed to 2,2µf

- in parallel a 250k (B) Potentiometer with a 22k Resistor in series

x3. "Snappy" Filter:

22k(A) Potentiometer + 1k in parallel for R201 (22k)

4. Clap offset 10kb

5. CP: On HT decay - clap reverb

replace r376 (47k) with 100k pot

6. MA Filter:

22K(A) Potentiometer for R339 (3,3k)

7. Rim/CL

Filter:

500k 22K(A) pot for R322 (10k)

+8. Cowbell Tune 1:

220k(B) Potentiometer for TM1 (220kb)

+9. Cowbell Tune 2:

220k(B) Potentiometer for TM2 (220kb)

10. CH Filter:

22K(B) Potentiometer for R153 (2,7k)

11. OH Filter:

22K(B) Potentiometer for R147 (2,7k)

For the noise inputs, I simply routed the white and pink noise out to a switched jack.

I wanted to do the clap timing mod but Erich Archer never replied to my request for info:

http://ericarcher.net/devices/clap-raca/

Upon close examination of his pics, I assume it's some pot between a 4.7k resistor going into what I think is pin 2 of the LM339 comparator. I don't have the energy or patience to explore this myself. I'm just happy it's done!

[jojjelito]

Burp!

Many thanks. I never saw the mods section at xlargex. Cool!

[Hawkeye]

Your 808 clone sounds really good, especially with these mods! :thumbsup:

Are there any schematics for the standalone (modded) drum modules (e.g. triggered via pulse from a MBSEQ) available?

No, it is not important, just pure interest, and surely not added to the build pipeline, da**it :-) :whistle:

Greets,

Peter

[Altitude]

Your 808 clone sounds really good, especially with these mods! :thumbsup:

Are there any schematics for the standalone (modded) drum modules (e.g. triggered via pulse from a MBSEQ) available?

No, it is not important, just pure interest, and surely not added to the build pipeline, da**it :-) :whistle:

Greets,

Peter

Yeah, http://xlargex.xl.funpic.de/ has them and board layouts as well for each of the voices.. I have built the kick

[sneakthief]

Background:

I got one of the second batch MB-808 pcb's and rare parts kits almost 4 years ago.

There are a few reasons why it took me so long to finally finish it, namely the desire to cut costs but also do a good job. It simply wasn't a high priority in my studio.

1. I waited patiently for someone to make a case for it but that never really materialized and I didn't feel like paying upwards of 200 or more euro for case machining and silk-screening.

Earlier this year I realized I could get a front panel for a good price from the same Dutch guy who did TK's, so I finally pulled the trigger:

http://www.frontplaten.net/#/content/FRONTPANELS/3_ACRYLAAT%20PANELEN/mb808-3.JPG/

2. Sourcing all the parts was a long process. I managed to find compatible switches for a good deal from the US a few years ago, but a big issue was the Mouser BOM. Every week some part would become obsolete or be out of stock! It took a while to find the proper substitutes for everything.

3. Incomplete documentation made this process very slow and tricky. The assembly manual ( http://www.eight-oh-eight.org/Assembly/ ) is either disogranized when it comes to the errata or simply missing a lot of little things:

- Cymbal decay http://m72.photobucket.com/albumview/albums/wholetone/MB-808/cymbaldecaymod.jpg.html?src=www&action=view¤t=cymbaldecaymod.jpg&newest=1

- The low tom is missing a resistor which makes it louder than the rest

- My congas self-oscillate but I decided I like using them as tones

- Some of the DOUT chips were NOT grounded on my pcb and that caused havoc!

- I had to cut some pots to make them all the same height because sourcing the proper height Alps pots became almost impossible

- There are no proper schematics for the MB-808, just some random pictures of the voice board component layout and a few incomplete signal flow schematics. This is intolerable for a project like this.

There are more things that I'm blocking from my memory because of the trauma :P

4. The Mods... what can I say? I only planned a few but then as I started testing them it became evident that it would take this machine into whole new sonic territory. It takes a lot of time to decide which mods are worthwhile and to cross-reference the original 808 schematics with the MB-808 pcb to find the location of each mod. I also had to take spend time experimenting with the clap reverb mod to find out what sounded good.

Also, I didn't want to deface the front panel with all sorts of random pots and besides there wasn't room for all 11 so I decided to put them on the very front, minimizing the negative aesthetic impact of ugly mods lol.

5. Machining the case. Coincidentally, I had this steel Hammond case for eleven years already and it's the perfect size for the MB-808 pcb. Laying out all the holes takes time, not to mention all the drilling and sawing. I shouldn't mention this, but my lcd was a bit too large and I actually CUT THE MB-808 PCB for it to fit :S Embarrassing, but nobody will ever see it.

All in all, this was one of the most difficult DIY projects I've ever done. Maybe not as complex as my ASM-2 modular, but probably more frustrating because of sourcing the parts, front panel difficulties and documentation issues.

Total cost: 360 euro

Edited August 2, 2011 by sneakthief

[Altitude]

Man, I have to talk to you about the cymbal decay, mine is still super short. I have some TR-808s come in for service and that was the first thing I noticed when I A/B them to the MB808. with the 808 forums completely wiped out now, I dont have any reference for fixing it. I went with the Hammond case as well, it is a perfect fit and you cant beat it for the price

I also have a neat solution for dealing with the heat from the 7805, I'll post something abut this later today

Edited August 2, 2011 by Altitude

[sneakthief]

Altitude - I've got a fat heatsink on my 7805 so all is well on that front.

The original cymbal decay pot is 2M while the one that came with the MB-808 batch 1 & 2 is 1M.

So, just connect two pins of the cymbal decay pot - and make sure the first pin goes to ground:

http://m72.photobucket.com/albumview/albums/wholetone/MB-808/cymbaldecaymod.jpg.html?src=www&action=view%C2%A4t=cymbaldecaymod.jpg&newest=1

If this doesn't solve your problem, then I suggest you check your capacitor and resistor values.

[the19thbear]

That soundcloud track is WAY cool! coolness that you can make a whole song with just a drum machine. the osc drums is a great idea!

[sneakthief]

[Hawkeye]

That is one great looking unit! Congratulations! The yellow LCD looks fantastic on the black plexiglass.

[jojjelito]

Yowza yowza yowza! Looks very nice! Nice to see a case solution in pictures.

Side note - lots of persons seem to have the FS1r. Interesting... We should team up against the world with those superior modules.

[gtxdude]

WOW! What a beautiful piece of equipment! I love it. You should be very proud, Congrats!

[sneakthief]

Thanks for all the nice compliments! Couldn't have done it without TK's great work.

The orange lcd is super cheap ($6.64 USD including free shipping to most places) and looks good:

http://cgi.ebay.com/16x2-LCD-Orange-Characters-Black-backlight-HD44780-New-/120748772099?pt=LH_DefaultDomain_0&hash=item1c1d300b03

However since the LCD cable passes over all the analog circuits I was getting high-pitched whine interference! Luckily I had disassembled some DB-9 cable that had foil shielding which I then used to wrap around the entire length of the LCD's ribbon cable.

I connected one end of the shielding to ground and that solved everything. I wonder if anyone else building MIDIboxes had this issue?

Re. FS1r - I've had it since 1998 and wouldn't ever sell it. Despite the quirky user interface, Iit's all the FM I need (no offense to SammsichFM or MIDIbox FM)

[bilderbuchi]

ha, so I'm not the only one using these "cases". :thumbsup:

[sneakthief]

@bilderbuchi - yes! good idea, and cheap too :)

I was looking for a little case that would be easy to modify for this oscilloscope:

http://www.gabotronics.com/development-boards/xmega-xprotolab.htm

[bilderbuchi]

ha that scope looks awesome :D

[moogah]

What a fantastic build! And very good sound too! It always surprises me how each new MB808 has a slightly different personality, none sound quite identical.

It is a shame that the eight-oh-eight forum is still down, I think I'm going to look into getting back up and running since it's such a good resource for information about both the MB808 and the original 808 as well.

Regarding build documentation, specifically schematics and layout documents: it's a bit tricky for me to make these avilable to the public at large, but I hope everyone with a MB808 kit knows that they can contact me anytime at my gmail address (moogah,gmail,com) and I'm very happy to help you and provide documents you need :thumbsup:

[vortura]

Nothing to add, but I just wanted to join the chorus and say your box looks and sounds fantastic. Something to aspire to.