Most famous mods with the V2.0 extra space

Re: Most famous mods with the V2.0 extra space

Postby gihaume » Mar 13th, '19, 06:57

Sorry but what is PN ?

Also, I have this crazy idea that I will NOT build the "NOISE" section of the PCB. Instead, I will make an third board with the same exact circuit and connect to the main board using JST connectors. The benefit is that, in the external board, I will plug two 3.5MM STEREO jacks (one for WN and one for PN). So, with that, if I want I can "replace" the circuits WN or PN with some external source... What do you think?

Not sure to understand fully as it seems irrelevant. You could just cut traces which feed noise to sections on the Yocto PCB and connect them to a switching jack..?
gihaume
 
Posts: 237
Joined: May 12th, '14, 14:48

Re: Most famous mods with the V2.0 extra space

Postby bsas » Mar 13th, '19, 21:16

gihaume wrote:Sorry but what is PN ?


So, if you check the "NOISE" section on the Yocto diagram, it is responsible to generate the WN (white noise) used by SNARE, CLAP/MARACA and the PN (pink noise) used by all the TOMS/CONGAS. There is a famous quote from the 808 documentary about how critical this circuit section is to the overall sound of the unit, and it is the part responsible for driving and filtering the famous Q35 transistor. You can check here about it:

http://secretlifeofsynthesizers.com/the-strange-heart-of-the-roland-tr-808/
http://secretlifeofsynthesizers.com/roland-tr-808-noise-transistor-update/

As you can see in this article, there is multiple ways to try to get closer to the original noise sound. Sometimes changing the circuit, the transitor or tuning it. That is why the Yocto added a trim pot according to the "Roland TR-808 Service Manual" (http://www.dinsync.info/2010/02/roland-tr-808-service-manual.html).

So, my logic goes like this:

The 808 circuit has basically 3 distinct NOISE generation circuits for the multiple voices:
- The "METAL" noise section is partially responsible for the COWBELL through the TP6 and TP7 output, it is fully responsible for the CYMBAL sound and partially responsible for the HATS sound thought the TO_HH output.
- The "NOISE" section is responsible for the SNARE, CLAP/MARACA through the WN output
- The "NOISE" section takes the WN output and filters to a PN (you can see that over the R133), and that is responsible for the TOMS/CONGAS

So, my first idea was quite simple. In the HATS switches I would first change the noise input from TO_HH (stock) to a WN from the NOISE section. Then, I thought that the other switch could flip WN to PN and feed the first switch, allowing me to choose between 3 possible noise sources for the HATS.

But then, I read this cool paragraph in this classic TR-808 mod page: "Cymbal / Hi Hat Alternative Noise Input" (http://www.firstpr.com.au/rwi/tr-808/)

Basically he feeds an external input to the CYMBAL and HATS noise source and get multiple sound variations. It is a very cool idea.

But then, when I though about the infamous "NOISE" section that is so different between all 808s, it occurred me that instead of changing the noise source of CYMBAL and HATS (and I don't want too since that needs a lot of circuit changes specifically on the CYMBAL) and I was already doing a mod on the HATS to change it's noise source, what if I could completely change the WN and PN on the NOISE section with an external source? That would affect far more voices and you can use all sorts of noises, from synths to recorded sounds (like a snare recording on your phone).

Then, when I looked at the NOISE section, it is not too hard to isolate it from the circuit. Check this picture (I didn't soldered it yet, I was just test fitting): Noise section isolation picture.

Basically with those 3 JST-XH 2 pin connectors I can make a separate board for the noise source. I actually just need 5 pins: +B4 (get that from U24 pin 8), -B4 (get that from U24 pin 4), GND (get that from R131 S*), WN (get that from R130 S*) and PN (get that from U24 pin 7). I am wiring U24 pin 3 there just to hold the connector better, but that is not used for anything, so it will be NC.

Than, the idea is simple:
1) First, build an external board identical to the Yocto schematic, so, it will be "stock";
2) Second, build an external board with different features. For example, different noise sources or 3.5MM STEREO jacks to "override" the circuit WN and PN.

If everything works fine I can just offer the circuit files for anyone to print if they want. Maybe the Yocto community could get together to order a bunch of PCBs so the cost of each board goes down.

The possibilities are quite interesting... what do you think? :D

gihaume wrote:Not sure to understand fully as it seems irrelevant. You could just cut traces which feed noise to sections on the Yocto PCB and connect them to a switching jack..?


My personal goal is to not cut traces on the board. I want to keep the Yocto boards "stock". I know it is harder to do that way but I feel more comfortable about it :D
bsas
 
Posts: 21
Joined: Jan 2nd, '19, 20:44

Re: Most famous mods with the V2.0 extra space

Postby gihaume » Mar 13th, '19, 23:43

Or just give value to your work and cut traces ;)
gihaume
 
Posts: 237
Joined: May 12th, '14, 14:48

Re: Most famous mods with the V2.0 extra space

Postby bsas » Mar 14th, '19, 16:00

gihaume wrote:Or just give value to your work and cut traces ;)


I just cannot cut traces on this beautiful black PCB board :D... it hurts me...

Anyway, the other benefit of my "complicated" design is that I can create different noise modules in the future. For example, I can make a 909 noise module, or a Delptronics noise module, etc. The board is quite simple:

3 power inputs: +15V, -15V and GND
2 audio outputs: WN and PN

I can play with a lot of different noise generation boards and fine tune them. And using simple JST-XH connectors is very easy to switch the boards.

I think I am settle in trying that, it sounds too cool to not try and... because I am not cutting any trace (hehehe :D)... it is very easy to revert back.
bsas
 
Posts: 21
Joined: Jan 2nd, '19, 20:44

Re: Most famous mods with the V2.0 extra space

Postby bsas » Mar 14th, '19, 20:43

By the way gihaume, before I order the extra pots and switches, do you think that my selection of mods make sense?
I just really like to hear your feedback if the ones I selected are the most "useful" or "versatile" or "good sounding" ones from the Cocteau board! :D

Again, thanks a lot for your feedback!!! :D
bsas
 
Posts: 21
Joined: Jan 2nd, '19, 20:44

Re: Most famous mods with the V2.0 extra space

Postby gihaume » Mar 16th, '19, 13:59

You shouldn't replace OH/CH Filter Cutoff by Filter Resonance... you only add Resonance if you have Cutoff. If you only have room for one then get Cutoff.

About the LT/MT/HT Noise Amount and Reverb, not sure how they're related but Noise Amount is not the most interesting. I think you wrote that you wouldn't like Decay as it's unusable on the Congas... I can understand but on the Cocteau there is not this problem anymore as Effegee found a way to get rid of it. Then there's also a new way to get lower range here and it's so nice to have little picky toms sometimes.

For the noise sources, I prefer a switched jack allowing to insert another noise, those boards seem a lot of work for little effect...
gihaume
 
Posts: 237
Joined: May 12th, '14, 14:48

Previous

Return to Yocto² Mods

Who is online

Users browsing this forum: No registered users and 1 guest