rhythm wolf teardown: any questions?

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

Moderators: Kent, luketeaford, Joe.

Post Reply
User avatar
guest
Super Deluxe Wiggler
Posts: 5852
Joined: Mon Aug 19, 2013 11:49 am

Re: rhythm wolf teardown: any questions?

Post by guest » Thu Aug 13, 2020 6:57 pm

i wonder if an HC14 would be the smallest way to go. you could cut off all the legs you dont need, and feed it with a 10k resistor so the overvoltage doesnt matter. otherwise its 2 transistors, or an opamp. but both of those would require a bunch of passives.
openmusiclabs.com

User avatar
YashN
Wiggling with Experience
Posts: 414
Joined: Tue Jun 28, 2011 12:17 am

Re: rhythm wolf teardown: any questions?

Post by YashN » Fri Aug 14, 2020 9:08 am

guest wrote:
Thu Aug 13, 2020 6:57 pm
i wonder if an HC14 would be the smallest way to go. you could cut off all the legs you dont need, and feed it with a 10k resistor so the overvoltage doesnt matter.
I have 40106 at hand. Should work too even if less fast, right?
otherwise its 2 transistors, or an opamp. but both of those would require a bunch of passives.
For the transistors, long-tailed pair differential? Vref =2.5V on one input and the Trig on the other? For the lower resistor, can I connect that to GND too?

Yep, many questions...

User avatar
guest
Super Deluxe Wiggler
Posts: 5852
Joined: Mon Aug 19, 2013 11:49 am

Re: rhythm wolf teardown: any questions?

Post by guest » Fri Aug 14, 2020 12:32 pm

try the 40106 first. you can breadboard it and then run a few jumper wires to see if it works before figuring out how to squeeze it in. also, is there a 5V supply in there anywhere to use? if not, the transistors might be the lower part count way to go.
openmusiclabs.com

User avatar
YashN
Wiggling with Experience
Posts: 414
Joined: Tue Jun 28, 2011 12:17 am

Re: rhythm wolf teardown: any questions?

Post by YashN » Fri Aug 14, 2020 1:17 pm

guest wrote:
Fri Aug 14, 2020 12:32 pm
try the 40106 first. you can breadboard it and then run a few jumper wires to see if it works before figuring out how to squeeze it in. also, is there a 5V supply in there anywhere to use? if not, the transistors might be the lower part count way to go.
OK good to know, thanks. Just found an ST LM393N lying nearby too, so I might try that one first.

Not sure about the 5V supply, will check, else we might need a 5V Linear Reg or something.

User avatar
guest
Super Deluxe Wiggler
Posts: 5852
Joined: Mon Aug 19, 2013 11:49 am

Re: rhythm wolf teardown: any questions?

Post by guest » Fri Aug 14, 2020 1:26 pm

yeah, if you plan on doing a bunch of trig outs, or have use for 5V regulated inside for another reason, then a small linear regulator would be the way to go. otherwise you can do a voltage divider with resistors at the output of your 393.
openmusiclabs.com

User avatar
YashN
Wiggling with Experience
Posts: 414
Joined: Tue Jun 28, 2011 12:17 am

Re: rhythm wolf teardown: any questions?

Post by YashN » Fri Aug 14, 2020 2:09 pm

guest wrote:
Fri Aug 14, 2020 1:26 pm
yeah, if you plan on doing a bunch of trig outs,

otherwise you can do a voltage divider with resistors at the output of your 393.
I'd like just two triggers for now, I think that should be enough to get a little rig going well for some live jamming or minimal composition sessions.

Would a 5V Zener at output work as well?

User avatar
guest
Super Deluxe Wiggler
Posts: 5852
Joined: Mon Aug 19, 2013 11:49 am

Re: rhythm wolf teardown: any questions?

Post by guest » Fri Aug 14, 2020 3:20 pm

a 5V zener would work, although im not sure there is a lot of advantage to that over the resistors. its slightly better, but if you dont have them handy i wouldnt worry about it. you can do both triggers with your 393, so thats a bit of a space saver. they can also both share the voltage divider that sets the threshold (~2V). so its 2 resistors at the input, a 393, and 2 sets of 2 resistors at the output (or 2 sets of a resistor and zener). you could use a 4.7k and 3.3k for the output resistor combo, and that would get you pretty close to 5V (4.95V), and would give an output impedance of 1.9k, which seems like a reasonable tradeoff for power consumption.
openmusiclabs.com

User avatar
JimY
Wiggling with Experience
Posts: 397
Joined: Wed Nov 09, 2016 10:03 am
Location: Middle of Wales

Re: rhythm wolf teardown: any questions?

Post by JimY » Fri Aug 14, 2020 4:01 pm

If small size matters and you only need one CMOS inverter...
https://fscdn.rohm.com/en/products/data ... 69g2-e.pdf
I've looked in vain for Schmitt versions (apart from the HC14 type which is common in 1gate package).

User avatar
guest
Super Deluxe Wiggler
Posts: 5852
Joined: Mon Aug 19, 2013 11:49 am

Re: rhythm wolf teardown: any questions?

Post by guest » Fri Aug 14, 2020 4:44 pm

the 4s584 is a single schmitt trigger that can run to 20V (if thats the reason the HC14 doesnt work).
openmusiclabs.com

User avatar
YashN
Wiggling with Experience
Posts: 414
Joined: Tue Jun 28, 2011 12:17 am

Re: rhythm wolf teardown: any questions?

Post by YashN » Sun Aug 16, 2020 11:26 am

guest wrote:
Fri Aug 14, 2020 3:20 pm
they can also both share the voltage divider that sets the threshold (~2V). so its 2 resistors at the input, a 393, and 2 sets of 2 resistors at the output (or 2 sets of a resistor and zener). you could use a 4.7k and 3.3k for the output resistor combo, and that would get you pretty close to 5V (4.95V), and would give an output impedance of 1.9k, which seems like a reasonable tradeoff for power consumption.
Sounds good to me, thanks. I think that's the way to go as well, especially after doing some testing yesterday and today with a voltage divider prior to powering the LM393 since it can also work on low power - couldn't quite get it like I wanted, output always too much below 5V.

Rewired a simple straight +12V supply and now I get a lot more output to play with, so I'm going to re-design that little circuit.

User avatar
YashN
Wiggling with Experience
Posts: 414
Joined: Tue Jun 28, 2011 12:17 am

Re: rhythm wolf teardown: any questions?

Post by YashN » Sun Aug 16, 2020 11:28 am

JimY wrote:
Fri Aug 14, 2020 4:01 pm
If small size matters and you only need one CMOS inverter...
Shouldn't invert in that case if you want to sync properly.

And yes, the box is quite compact as it is, now if you count adding, say 4 individual outs, one or two pots, there's little space for additional PCBs, so anything added has to be added carefully in a compact manner.

The alternative, of course, is to make a breakout box and install a suitable connector, but I'd rather have everything in the box.

User avatar
YashN
Wiggling with Experience
Posts: 414
Joined: Tue Jun 28, 2011 12:17 am

Re: rhythm wolf teardown: any questions?

Post by YashN » Sun Aug 16, 2020 11:35 am

I might have been doing something wrong, but can anyone tell me if the output of the LM393 does swing completely to the +V rail?

I thought I saw a drop of around 1.25V this morning.

EDIT: Found it:

From the datasheet:

Input Common Voltage Range: V CC+ -1.5 V | V CC+ -2, depending on temperature.

Edit 2 Hmmm, I'm thinking I'd need to revisit my low powering the LM393 again, taking this into account. A bit more work if it still doesn't work properly, but there are advantages having this in the box somewhere near the main supply and dropping leads from the output further away.

User avatar
guest
Super Deluxe Wiggler
Posts: 5852
Joined: Mon Aug 19, 2013 11:49 am

Re: rhythm wolf teardown: any questions?

Post by guest » Sun Aug 16, 2020 4:57 pm

the output of the lm393 is open collector, which means it needs a resistor to +12V for the output to go high. without a resistor to a higher voltage, the output will just be 0V. youll want to run the lm393 off of 12V because the accenet signal can go as high as 10V, so youll need the headroom.
openmusiclabs.com

User avatar
YashN
Wiggling with Experience
Posts: 414
Joined: Tue Jun 28, 2011 12:17 am

Re: rhythm wolf teardown: any questions?

Post by YashN » Sun Aug 16, 2020 5:06 pm

guest wrote:
Sun Aug 16, 2020 4:57 pm
the output of the lm393 is open collector, which means it needs a resistor to +12V for the output to go high. without a resistor to a higher voltage, the output will just be 0V. youll want to run the lm393 off of 12V because the accenet signal can go as high as 10V, so youll need the headroom.
I had a 10K pull-up going to a bit less than 5V as V+. The Trig out doesn't need to go higher than +5V for the target gear though (maybe shouldn't even go higher).

Will that work?

User avatar
guest
Super Deluxe Wiggler
Posts: 5852
Joined: Mon Aug 19, 2013 11:49 am

Re: rhythm wolf teardown: any questions?

Post by guest » Sun Aug 16, 2020 5:39 pm

that should work.
openmusiclabs.com

User avatar
YashN
Wiggling with Experience
Posts: 414
Joined: Tue Jun 28, 2011 12:17 am

Re: rhythm wolf teardown: any questions?

Post by YashN » Sun Aug 16, 2020 5:41 pm

Notwithstanding the output levels which weren't good enough, it did seem to work when I tested with the highest velocities on the Kick this morning.

Will re-test my circuit, after having re-checked necessary values and voltages talking into account the LM393 V drop this time.

We should be good. Will probably update tomorrow.

User avatar
YashN
Wiggling with Experience
Posts: 414
Joined: Tue Jun 28, 2011 12:17 am

Re: rhythm wolf teardown: any questions?

Post by YashN » Sun Aug 16, 2020 6:27 pm

Quick update after re-testing just now:

It definitely doesn't work properly if I power from 6.xV with a resistive divider at the start. I get a big voltage drop when the comparator pull-up resistor is connected as well as the VRef is connected. Therefore, output dwindles to less than 5V like I found in my initial tests.

So, @guest's solution is the best one: power from the +12, then only tailor the output to get the +5V trigger.

Rather good-looking +5.xV at output, tested with Highest Vel first, then Lowest:
Kick Trigger Out
Kick Trigger Out
Lovely.

Thanks @guest. :sb:

User avatar
elriqui
Learning to Wiggle
Posts: 2
Joined: Sun Oct 25, 2020 2:49 pm
Location: Bolivia
Contact:

Re: rhythm wolf teardown: any questions?

Post by elriqui » Sun Oct 25, 2020 3:07 pm

Hi you all. Thanks for the good info you share here.
I'm so into aplying the 'Open hat closure' mod stated on this site
http://wiki.openmusiclabs.com/wiki/RWhihat
but i wasn't able to find C104 :/ I've look on the entire board with any luck. Could anybody share some light about it?
Many thanks.

User avatar
guest
Super Deluxe Wiggler
Posts: 5852
Joined: Mon Aug 19, 2013 11:49 am

Re: rhythm wolf teardown: any questions?

Post by guest » Sun Oct 25, 2020 9:54 pm

unfortunately i buttoned mine back up. but, if i recall correctly, U36 is on the backside of the board, a little SOIC-8 device. i think i ran the resistor on the backside of the board as well. C104 is an electrolytic cap, so you can solder to the pin that pokes through the board to the backside. look near Q32, i think it was towards the bottom where all the trigger signals run below the last row of pots.
openmusiclabs.com

User avatar
elriqui
Learning to Wiggle
Posts: 2
Joined: Sun Oct 25, 2020 2:49 pm
Location: Bolivia
Contact:

Re: rhythm wolf teardown: any questions?

Post by elriqui » Mon Oct 26, 2020 12:12 pm

Got it! made it, 33k works like a charm. Thanks for your help, i've never even thougth about looking at the back side of the board :confused:

Tr909
Learning to Wiggle
Posts: 8
Joined: Sun Apr 04, 2021 10:40 am

Re: rhythm wolf teardown: any questions?

Post by Tr909 » Sun Apr 04, 2021 10:47 am

Hello everyone! I'm Salvador from Spain and I just modified the wolf with the independent outputs mod and they work perfectly for me. The problem is that
now through the general output (the Main out) only the bass, HH and percussion can be heard ... the kick drum and the snare have mysteriously disappeared! And they are not muted from the pads or anything like that. I have tested it with patterns that I have made with all parts of the wolf and nothing. I have also updated the firmware in case the output circuit had been crashed and idem of the same ... Has someone something similar happened to him? ... Greetings!

User avatar
guest
Super Deluxe Wiggler
Posts: 5852
Joined: Mon Aug 19, 2013 11:49 am

Re: rhythm wolf teardown: any questions?

Post by guest » Sun Apr 04, 2021 7:32 pm

can you explain what your mod was for the kick and snare outputs? do you hear signal at the individual kick and snare outputs, but they are not in the main mix?
openmusiclabs.com

Tr909
Learning to Wiggle
Posts: 8
Joined: Sun Apr 04, 2021 10:40 am

Re: rhythm wolf teardown: any questions?

Post by Tr909 » Mon Apr 05, 2021 6:01 am

guest wrote:
Sun Apr 04, 2021 7:32 pm
can you explain what your mod was for the kick and snare outputs? do you hear signal at the individual kick and snare outputs, but they are not in the main mix?
I have made the modification from the output resistors that are marked on the board :




All the assembly I have taken from this tutorial:https://cavisynth.com/akai-rhythmwolf-s ... tputs-mod/ After mounting it and testing the individual outputs (they all work correctly ..) The problem is that only percussion, bass and hh are heard through the mainout.
Attachments
akai mod.jpg

User avatar
guest
Super Deluxe Wiggler
Posts: 5852
Joined: Mon Aug 19, 2013 11:49 am

Re: rhythm wolf teardown: any questions?

Post by guest » Mon Apr 05, 2021 7:15 am

snare and kick are right next to each other, so maybe there is a short someplace? can you post a picture? turn the power off, and measure the resistance to ground from those points.
openmusiclabs.com

Tr909
Learning to Wiggle
Posts: 8
Joined: Sun Apr 04, 2021 10:40 am

Re: rhythm wolf teardown: any questions?

Post by Tr909 » Mon Apr 05, 2021 9:33 am

guest wrote:
Mon Apr 05, 2021 7:15 am
snare and kick are right next to each other, so maybe there is a short someplace? can you post a picture? turn the power off, and measure the resistance to ground from those points.
Does anyone have the service manual for the rythm wolf or some schematic of the mainboard or something similar?
Attachments
WhatsApp Image 2021-04-05 at 15.53.02.jpeg

Post Reply

Return to “Music Tech DIY”