Wasp Filter for Shruthi in works


Hello, I was pretty curious what a Wasp Filter for the Shruthi sounds like.
So I built a prototype. This has 2 filter modes, LP and BP as well as an adjustable distortion and can be switched to a ‘bad’ mode.
A fast soundexample here . I play a little with distortion ,Q and LP,BP

All in all, the filter can work gently on the sound or with a really powerful punch and proper sounding distortions - almost down to 0 hz.
Think this will be another new filter board for Shruthi. At the same time the motherboard will be reworked. Men, let us surprise you .
PS: yes, the de-generator is still in work …


I’m curious what news you will bring to the shurthi motherboard!


Very cool! Im a huge fan of the Wasp filter and often wondered why it hadn’t happened for the Shruthi already (Besides not being smart enough to do it myself!)

Somewhat related… I admit my only Wasp experience is from my Doepfer Wasp Eurocrack filter, which are not known for the their reliability (Has an appetite for 4069’s), is that an issue you are familiar with? I only ask as there has been multiple threads on Muffwiggler about the issue and naturally I wonder if this is common to all Wasp filter clones, including yours?
That said, im pretty sure I worked out that some brands of 4069 are hardier than others. In my own (not very scientific!) experience, the originally supplied TI (Texas Instruments) 4069 only lasted a couple of months, I replaced it with an ST (SGS Thomson) 4069 and that has lasted about 3 years so far.


Hi Luap , well, then I hope my filter design isn’t so 4069 hungry.
If can go then so a IC broken ?
1:) when switching on - undefined input states, the input signal U_in is greater than the operating voltage.
2:) by static charge
3:) through continuous operation outside specifications
In my Wasp filter I only use 3 of the 6 gates. Also the power supply is +/- 2,5 Volt. Then it was easier with the log converter. You can imagine that you do not handle a prototype squeamishly. There is already missing a voltage or it happens a short circuit. But - so far everything runs perfectly, and I haven’t slaughtered an IC yet.
Your objection is but nevertheless good . I will run times with maximum distortion and resonance the box times a day . Let’s see what happens .



No big changings - a few things i miss .


Hi Luap , the filter sounds now since 6 hours with heavy distortions and maximum Q .
No Problems with the 4069 and BTW , this IC costs 20…40 Eurocent by Reichelt … so no big deal .
Actual i work on the PCB …


I might have to make up another Shruthi-1, just for this…


I doubt it’s something like this that can damage the chip. It’s more likely to be something happening at startup.


I think also it is on startup. But my WASP works . Maybe because the input can’t get higher than 5 Volt.
OK , it is also not a Doepfer WASP, it is a TubeOhm Wasp. I think i have another Filter design


Apologies for the slight thread diversion there! It’s just an interesting subject for me as a fan of this filter & Shruthis :+1:


Hi Luap, no apologies. It seems that it is a fact that on some Wasp there is a problem with the 4069 and this is good to know for me .
So i design and test it it in this way , that the filter works in the Shruth/Phoenix.


Hi all ,
new infos about Wasp and the new Motherboard is HERE :slight_smile:



Ok , first - now you can use new switches . Second , i add a MCP6004 , now it is possible to use the 4 analouge inputs. OK the rate isn’t very high , but it is usefull for a distance sensor,
or other Sensors like a capacitiv sensor …


FWIW the issue with the 4069 is not Herr Doeofer or anyone else’s fault-it’s because a chip designed to only sink internal power during transition stages is being forced into linear mode (ie imitating an op-amp), which means that the gates inside the chip sink power continually, so the chip has a shortened lifespan. There used to be a white paper from one of the semiconductor companies on the net about this, but I can’t find it now. Using a -UB suffix part minimises this (it has fewer output stages so minimises heat buildup). You can always stick a mini heat sink on the chip if you’re still worried :wink: