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[Build Thread] Jasper, an EDP Wasp Clone
MUFF WIGGLER Forum Index -> Music Tech DIY Goto page Previous  1, 2, 3, 4 ... 30, 31, 32  Next [all]
Author [Build Thread] Jasper, an EDP Wasp Clone
Macc29
Is there a way to shut the keyboard off? I am going to use it with Midi anyway. Of course I can set the keyboard trigger sensitivity to "very unsensitive" but does it eradicate random triggerings?
jasonl
Not received any update notifications to the thread - I'll read back more carefully and respond later.

Anyway, I finally completed an illustrated build guide - attached to the first post in this thread. This shows how I made up the PCB.
jasonl
Macc29 wrote:
Is there a way to shut the keyboard off? I am going to use it with Midi anyway. Of course I can set the keyboard trigger sensitivity to "very unsensitive" but does it eradicate random triggerings?


I've not done this, but from looking at the schematic, simply removing R137 and/or R138 should disable the keyboard completely.

I've not had any problems with random keyboard randomly triggering, and have had my prototypes running for hours.... thought the sensing circuit was fairly robust - as I've used several different power supplies, and plugged it into various bits of equipment.... Perhaps I'm just fortunate to be blessed with decent mains power...

I did alter the Jasper from the original for the new TI 4069 ICs used. Changed R137 from 33K to 22K, to increase the gain on the amplifier that follows it in order to get it to trigger using the modern TI chips. Might be worth experimenting with increasing this to 27K. If you're not using a TI CD4069 for IC35, then increase R137 to 33K, the Wasp's original value.

Another trick to prevent spurious triggering if you're using the keyboard is to use an anti-static wrist-strap to reference yourself to the circuit. The GND pads on the right hand side of the PCB near the keyboard are for a PCB mounted banana socket... The top-right panel screw/hex spacer is also connected to GND, so you could experiment by touching this while using the keyboard with your other hand...
jasonl
LektroiD wrote:

4046's appear to be used for the glide circuit on this, so no real correlation between these oscillators and the TH/Fonik 4046. Now to continue looking for a way to tap a sync into this baby...! Jason?


As I understand it the 4046 PLL ICs turn the narrow pulse of the generated by the oscillator divider (output of the 40103) into a useful square wave sent to the waveform shapers.... Haven't quite got my head around PLLs, and the glide circuit is only part of it....

As regards external syncing, I've prototyped a simple CV/Gate interface that can be used to trigger Jasper. Need to sort out the firmware, but the little PCB I made seems to work OK.

VCA noise - yep, there is a bit. I think it's a limitation of the circuit.

Certainly, try tuning the VCA trimmer. That adjusts the DC offset, so mainly deals with an audible click or thump when the VCA is opened.

I also think noise also comes from the filter - especially when resonance is turned up...
jasonl
kluberrrrr wrote:

I'm not sure about the noise filter mod behavior as well. If selected it adds noise into the filter but it doesn't look like modulated.

Small tip: as I forgot to buy the Stereo 1M pot for the glide which gives the same amount of "glide" to both VCO I only wired one and bypassed the other= FUN! nanners


Thanks Kluberrrr! Great videos - it's good to see and hear it's working!

I agree about the noise modulation in the filter being superfluous - it's as it was in the Wasp - it just sends noise into the filter CV, which bleeds though into the filter audio. I notice this option was removed from the Gnat.

When using the RND LFO waveform, there is some clicking as the random voltage changes. I'm thinking of seeing if it's feasible to put a capacitor somewhere to smooth the harsh transitions - but as it stands the RND LFO sounds pretty cool as it is.

Good idea about using one pot for the glide. I experimented using two separate pots - you can get some interesting results with those!
jasonl
biosynth wrote:
What is BEAD at the right of the pcb please?


A ferrite bead. It's aim is to help suppress noise on the power rail... If you don't have one, you can get away with just jumpering the pads, or use a 10ohm resistor.
kluberrrrr
LektroiD wrote:


Yes, the same happens with mine, when I touch my macbook, take it out of sleep mode, etc. Strange though, as it should be well grounded with the synth being sat on the antistatic mat on my bench.

Maybe better if I can get some kind of base for it. I was thinking of buying a blank PCB panel the size of the main PCB and mounting it on standoffs, or maybe an aluminium panel would be better...


I'm going to build my own case with some aluminium panel definitely!

LektroiD wrote:

Not a bad idea, especially if we can find a way to tap in and activate oscillator sync! I think I'll look at the Fonik 4046 oscillators and compare notes, see where sync taps in to the circuit and if it's doable on here. It would work really nicely with your config.

*EDIT*
4046's appear to be used for the glide circuit on this, so no real correlation between these oscillators and the TH/Fonik 4046. Now to continue looking for a way to tap a sync into this baby...! Jason?


My two cents really... I don't understand electronic. But look at the schematics here (Page 6), at some point there is a separation of the two oscs from the master osc. I guess if you "jump" over the pot called "pitch" of the osc2, both oscs should be "synchronized". You could mount a switch before the "pitch mod". One way would go through the pitch pot, the other way would be just like the osc1. Keep in mind R16 and R142 which have different values. Again I don't understand electronic. Maybe someone could check this first to confirm it.

LektroiD
jasonl wrote:
VCA noise - yep, there is a bit. I think it's a limitation of the circuit.

Certainly, try tuning the VCA trimmer. That adjusts the DC offset, so mainly deals with an audible click or thump when the VCA is opened.


Where's the best point to probe with a scope to balance the DC offset accurately?
kluberrrrr
jasonl wrote:


I agree about the noise modulation in the filter being superfluous - it's as it was in the Wasp - it just sends noise into the filter CV, which bleeds though into the filter audio. I notice this option was removed from the Gnat.

When using the RND LFO waveform, there is some clicking as the random voltage changes. I'm thinking of seeing if it's feasible to put a capacitor somewhere to smooth the harsh transitions - but as it stands the RND LFO sounds pretty cool as it is.

It really does and it is one of the options among others which make this synth special and experimental!

jasonl wrote:
Good idea about using one pot for the glide. I experimented using two separate pots - you can get some interesting results with those!


Yeah 2 different gildes would be awesome and a lot of fun!

The enhanced mod is great as well kind of discreet tho. I wonder if there is a way to add a pot to change the modulation speed for one of the osc. My guess would be R8 since you advised to put a carbon resistor here.

Also I REALLY like the repeat mod of the filter ENV. It's too bad is not synchronized. I would love suc a feature like that. Any idea in mind? Like bypassing the "mini LFO" and add a trig input to sync it with a drum machine or something? As I'm writing I'm thinking about something even simpler. What about an input to trig the enveloppe i would do the same result.

EDIT= [i]I sort of found it! I connected the hot tip of gate wire coming from the beat step pro to the pin 8 or 12 of IC35 and you play along on the keyboard to change the pitch. I works but with an offset...
LektroiD
On the Thomas Henry 555 VCO, the sync circuit goes into pin 4 (reset) of the 555...
So maybe if I lift pin 4 of one of the the 555's and tap in using a SPDT to switch between sync'd and non sync'd... May need to change the value of the pull up resistor for use with 9V

jasonl
LektroiD wrote:
jasonl wrote:
VCA noise - yep, there is a bit. I think it's a limitation of the circuit.

Certainly, try tuning the VCA trimmer. That adjusts the DC offset, so mainly deals with an audible click or thump when the VCA is opened.


Where's the best point to probe with a scope to balance the DC offset accurately?


I'm not sure about scoping it - PR2 feeds into the network before pins 13 & 14 of IC6... I only ever set PR2 by ear listening for clicks when operating the keyboard with oscillators off.

From the Wasp` service manual - this assumes Attack and Decay are both set fully anti-clockwise:
Step 72: Turn both oscillators off. Set SUSLEV to "repeat" mode and turn the volume on full. Press any key. The residual buzz that can be heard is due to an offset in IC6. Adjust the VCA BAL control (PR2) for minimum buzz.
jasonl
kluberrrrr wrote:

The enhanced mod is great as well kind of discreet tho. I wonder if there is a way to add a pot to change the modulation speed for one of the osc. My guess would be R8 since you advised to put a carbon resistor here.

I wanted to keep it simple. hihi It's a really simple LFO, you could put a 1M pot in series with R8 to make it variable. R8 and C3 determine the oscillation speed. Maybe increase C3 to 1uF or 2uF with a smaller R8 to get a more useful range from a 1M pot.

kluberrrrr wrote:

Also I REALLY like the repeat mod of the filter ENV. It's too bad is not synchronized. I would love suc a feature like that. Any idea in mind? Like bypassing the "mini LFO" and add a trig input to sync it with a drum machine or something? As I'm writing I'm thinking about something even simpler. What about an input to trig the enveloppe i would do the same result.


I think it is synchronised to the VCA EG - Pin13 of IC20 triggers the attack of the VCA EG, and the VCF EG at pin 3..... a logical pulse there should trigger the VCF EG - but you'd probably need a diode to stop it affecting the VCA EG...
kluberrrrr
jasonl wrote:
kluberrrrr wrote:

The enhanced mod is great as well kind of discreet tho. I wonder if there is a way to add a pot to change the modulation speed for one of the osc. My guess would be R8 since you advised to put a carbon resistor here.

I wanted to keep it simple. hihi It's a really simple LFO, you could put a 1M pot in series with R8 to make it variable. R8 and C3 determine the oscillation speed. Maybe increase C3 to 1uF or 2uF with a smaller R8 to get a more useful range from a 1M pot.


Oh great! Thanks a lot! I'm definitely gonna try this! thumbs up

jasonl wrote:
kluberrrrr wrote:

Also I REALLY like the repeat mod of the filter ENV. It's too bad is not synchronized. I would love suc a feature like that. Any idea in mind? Like bypassing the "mini LFO" and add a trig input to sync it with a drum machine or something? As I'm writing I'm thinking about something even simpler. What about an input to trig the enveloppe i would do the same result.


I think it is synchronised to the VCA EG - Pin13 of IC20 triggers the attack of the VCA EG, and the VCF EG at pin 3..... a logical pulse there should trigger the VCF EG - but you'd probably need a diode to stop it affecting the VCA EG...


See my previous post I edited it.

@LektroiD About the random notes triggering, do you have by any chance the speaker connected? Because I just disconnected it and now it looks like it's gone.
Arnoid
kluberrrrr wrote:


[video]https://youtu.be/wrYmrcpUDhk[/video]

[video]https://www.youtube.com/watch?v=SllZtq_LvtU[/video]


Wow sounds great the first video espacially very liquid smile
BugBrand
1M+100K gives 90.9090909etc k.

Haven't seen where that actual resistor is though!
masterofstuff124
when he batted the hand away in the video i rofled. sounds amazing.
jasonl
biosynth wrote:
BugBrand wrote:
1M+100K gives 90.9090909etc k.

Haven't seen where that actual resistor is though!

we're not worthy
with 1% tolerance that's ok wink


Congrats on your build! thumbs up

The resistor in the Enhanced mode PCB circuit.

You can just use a 100K resistor. When tested, 91K (a standard E24 series resistor) gets a slightly wider modulation of the pulse width without pushing the pulse 'off the end'...

If you separate them, the enhanced PCBs will just about fit under the panel, stuck with adhesive foam pads or velcro - along the top edge, near the left hand stand-off. Be careful not to short any of the components on the main PCB below.

Otherwise, when you make a case/enclosure, make some space behind the main PCB for mounting the enhanced PCBs. If you're planning on putting in a MIDI board or internal speaker, then you'd need to do this anyway.
jasonl
biosynth wrote:
where do you put 'enhanced pcbs' please? There are m3 holes... hmmm.....


The M3 holes are for fixing in the case, when you make it. cool

Or as I said previously, just use sticky-fix foam pads to affix to the panel.

Piccie:
AonFLuX
Amazing work with the build instructions as-well, Jason!
No the loooong wait for the possible second run smile
kluberrrrr
Talking about led. I would love to add led for the LFO and the repeat options!
Could be great! w00t
LektroiD
biosynth wrote:
where to put enhanced pcbs?


I used 22mm heat shrink to prevent shorting, and just placed them inside the synth upside down. There's plenty of space.

mangros
Lektroid: Are those rotaries the break-before-make rotaries from Tayda? And if so do they create clicks when switching?

I've got six of those ready to solder but I'm a bit dubious about installing them as everyone else seems to be getting the MBB type.
jasonl
biosynth wrote:
is there a way to slow down the LFO ?


Increase C36 - you can get film 1.5uf or 2uf caps, or use an electrolytic. You will shift the range downwards, losing the higher speed.

Don't forget, you can use the Control Envelope on repeat as a nice slow LFO.
kluberrrrr
what about enlarging the whole range? Or even 2 different speed ranges Slow and Fast
jhulk
if its in audio path they need to be shorting

if they are not then none shorting will do as they are cheaper but if you have shorting use them

as it says either
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