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Do it yourself crew in the house?


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 Thanks! Yeah, it’s a fantastic device. Also like the min and, especially, max outputs: you can get really interesting sound structures with those.

After completing the Rampage I put together the first module I designed myself, on the first PCB I’ve ver designed myself. Surprisingly enough everything fit (except for the power connector, because I placed two capacitors a little too close, so it’s now a little bent) and ... it works! So proud of myself 😁

But ... if you have PCBs made the minimum number they will ship you is 5. So now I have 4 additional PCBs for the “rhmilo extremely sloppy dual VCA” available. It’s not a fantastically useful or even very good module, but I guess if someone wants one and is willing to pay the shipping costs, they can have it. PM me, I guess.

It’s a 4HP dual VCA. BOM is 6 Thonkiconn jacks,  4 100k resistors, 2 1k resistors, 2 100nF ceramic caps, 2 1m logarithmic pots (Panel mount, 16mm), 2 TL072 op amps, 2 2n222 npn transistors and a power connector.

Panel you’ll have to make yourself (I used cardboard). Utility of the pots is not clear: you could possibly replace them with fixed resistors.

You’ll get a simple VCA where CV and audio go in and audio of which the volume level is modulated by the CV comes in. Linear or logarithmic? Who knows ...

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  • 2 months later...

I've been having trouble with getting my Phonic Taxidermist (https://www.circuitbenders.co.uk/forsale/phonictaxi/ptaxi.html) not be incredibly noisy. I've asked for help in a thread dedicated to the pt over at MW but it seems to be pretty much dead so I thought I'd come to the friendly watmm diy crowd in hope of guidance or ridicule. Realize it's slightly pointless asking for help on such a specific build in a general thread like this but I'm more or less desperate so trying this before either doing an entire rebuild or archiving the hot noisy mess in the hopes of one day being able to figure it out.   

 In essence the module seems to be working as intended but the amount of additional noise seems to be beyond specification.

I'm using ram and delay chips ordered from circuitbenders after concluding that the aliexpress chips I got were probably all duds/blacktops.
Things I've tried:
Triple checked the grounding on the pots
Reflowed suspect joints, twice
Verified R31
Improvised shielding
Reseated the ics
Different powersupply

Things I haven't tried yet:
replacing the feedback pot, although readings with my multimeter indicate no issues
used a 630v film cap for c19, rest is 100v, but as far as my limited knowledge goes, this shouldn't be an issue.

All more or less to no avail. Here are some pictures of the build. I've also included a short audio clip (phone held next to headphones, but it's enough to hear what's going on). !!!Please turn down your volume before playing the audio file, lots of nasty frequencies.!!!

 

PTbuild-1.jpg.44124a8064602e71368ccb578e0ac1e4.jpgPTbuild-2.jpg.d6c5bc8236bb1d8697acd6132957ded6.jpgPTbuild-3.jpg.fbb6017e2346c62ea27619062973a318.jpg        

!!!Please turn down your volume before playing the audio file, lots of nasty frequencies.!!!

Phonic Taxi Noise.mp3        

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Since the ICs are socketed, would it make sense to pull them out one at a time and see if the noise disappears? Probably not helpful (since it'd remove large chunks of the circuit) but I have no idea. Those switches look weird to me but I guess I'm just accustomed to board-mounted designs that don't utilize wires, and I don't think they'd be a source of noise unless they're shorting something.

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Thanks for the response.

The noise might disappear but that wouldn't necessarily mean that that ic is the direct cause of the noise. The delay chip is noisy by design but not this noisy...

The build document did say to keep the wires on the switches as short as possible (the switches can be implemented in different ways, that's why they're not board mounted, I think) but I can't really go much shorter than this. Maybe I should try using shielded wire. Although shielding the whole thing didn't make any difference and other builds I've seen all seemed to be using unshielded wire. 

To me the noise sounds like clock whine from the delay chip but I triple checked the resistor that's supposed to dampen it and it's the right value.    

 

 

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1 hour ago, user said:

Thanks for the response.

The noise might disappear but that wouldn't necessarily mean that that ic is the direct cause of the noise. The delay chip is noisy by design but not this noisy...

The build document did say to keep the wires on the switches as short as possible (the switches can be implemented in different ways, that's why they're not board mounted, I think) but I can't really go much shorter than this. Maybe I should try using shielded wire. Although shielding the whole thing didn't make any difference and other builds I've seen all seemed to be using unshielded wire. 

To me the noise sounds like clock whine from the delay chip but I triple checked the resistor that's supposed to dampen it and it's the right value.   

Yeah, I agree with your impression on the noise, it definitely gives me those vibes. I wonder if you got a dud chip, or somehow fried it? Ugh. Debugging electronics can be so damn frustrating. I don't think the switches are a problem, honestly, but if it was me I would start removing any variables I could, i.e. isolate things as much as possible.

Are there static voltages you can check at any particular spots? That's given me some clues a few times too.

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On 10/16/2020 at 7:56 AM, sweepstakes said:

Yeah, I agree with your impression on the noise, it definitely gives me those vibes. I wonder if you got a dud chip, or somehow fried it? Ugh. Debugging electronics can be so damn frustrating. I don't think the switches are a problem, honestly, but if it was me I would start removing any variables I could, i.e. isolate things as much as possible.

Are there static voltages you can check at any particular spots? That's given me some clues a few times too.

It’s possible. I got new chips from circuitbenders, they say they test the ic’s before sending them out but maybe one slipped through. Or I fried one somehow. 
I should definitely check the voltages on the ic’s, just been putting it off because I don’t have that much experience making measurements on live circuits and my probes tend to slip a lot still. 
 

Can be very frustrating indeed, for me the combination of being mostly clueless combined with the fear of fucking up can be nerve wrecking. 
Otoh the reward from finally figuring something out is great. 

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  • 2 weeks later...

Considered posting this in the fm synthesis thread but was afraid not everyone would be able to appreciate the joke.

Someone gave me a Model TE-20 RF test signal generator. It appears to be in good working condition and according to my super cheap diy kit oscilloscope it goes down well into the audible frequency range (as per the te-20's specifications) plus it has an input to modulate the frequency. So I was hoping to use it as a sound source for my eurorack stuff but was wondering if there is any risk of damaging modules should I accidentally feed  frequencies in the mhz range into my modules... Did a couple of google searches but gave up after 20 min of just radio related info but nothing on using this type of signal generator in tandem with a synthesizer.

 

Can't really think of a scenario where this would be an issue but then again I'm pretty ignorant. The voltages never seem to read anywhere above 5v or so but I'd rather be safe than sorry...

Tried to add a short clip of the scope showing various waves but icloud's being weird and now I can't delete the player from my post. Hnnggg.

 

E20. Edited by user
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As long as the voltage is in a safe range you should be OK, but depending on your meter you might be missing the actual peak voltages coming out of it, so you might want to see if you can find a manual for it online and check the specs to be sure.

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I’ve added a pwm cv input to my ms20 mini. Super simple mod and highly recommended, the most grating part for me was drilling the hole for the input socket. 
I’d also like to add individual waveform outs but one of the criticisms on the mod seems to be that there is no buffer on the output mentioned on any of the sites describing which points to tap.  Would it be sufficient to just add a 100k resistor on the + of the output jack? 
 

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  • 3 weeks later...

Another question from my ignorant ass...

I’ve an erica synths dual psu that crapped out on me a year ago. After at least gaining enough knowledge to open it up and do some basic troubleshooting I found that one of the 2 din connectors that are attached to it had cut into the cable and was causing a short. 
One other thing I noticed, was that even though the psu uses a 3 prong mains plug and the din connector has a GND pin (I know gnd and earth aren’t the same thing but the gnd is not connected to anything either) the psu is not wired to mains earth. The psu comes in a metal chassis and the erica case that goes with it is also made out of metal. Should I wire up the incoming mains earth and connect this to the psu and the chassis or would this be an incredibly stupid thing to do? 
I recall a thread on mw where Girts from erica was catching some flack for having designed the psu in this way but it’s a while ago and can’t remember if there was a conclusion and can’t find the thread right now. 
 

Any advice is highly appreciated. 

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  • 2 weeks later...

Finally got over my instinct to stay away from high voltage capacitors and got the old Ampeg back in business.  Sounds better than ever, the old caps were really starting to make it sound off. The modern caps sure don't have the style of the huge yellow Sprague.  I'm kind of considering drilling out the ends, cleaning it out, mounting another 30uf/600v inside it and swapping it back in but that's kind of ridiculous.

 

The black paper covered multi-cap always looked bad to me and I'm glad to have a big aluminum can on there now.

20201202_153650.thumb.jpg.2bac17abdf5c1ec905b186871f41ad94.jpg

 

 

Did the two bias caps after this, too, even though they probably had some life left in them.

Edited by TubularCorporation
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I built this rack stand over the past couple days to hold my new mixer and audio interface combo. Cost about $35 in materials.  I couldn't find anything similar to this that was a small/desktop design.

spacer.png

 

Edited by Hautlle
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  • 2 weeks later...

I spent literally a month looking for the right tool to mount these stupid 2mm banana jacks, finally found one made for one specific brand of micro-BNC connectors but it's not actually available through any of the company's distributors or direct, so I finally just got some 6mm inner diameter stainless steel tube, drilled it out to 6.5mm and made my own.  Took about 15 minutes.

 

image001-480p.thumb.jpg.7e2f552ab1d75d9b61466b27ba3923aa.jpgimage002-480p.thumb.jpg.a05d344f9079f07f7fc2a78a76dbaa3e.jpgimage003-480p.thumb.jpg.8c0fb03aa23924bc788799fe613b535d.jpgimage004-480p.thumb.jpg.f429f6c8f9f84c48350222afd70ca766.jpg

 

Works great, and his style of banana jack is WAY cheaper than any comparable quality type I've used that has a standard nut but these cost me about $10 for 50 and the 4mm variety is proportionally as cheap, so it was definitely worth the trouble. In a pinch it should work on those off-brand 1/8" jacks with the round knurled-and-slotted nuts that you can get cheap on Tayada and eBay, too. 

 

I've got plenty of tube left so eventually I'll make one that's open on one side for working with jacks that already have a wire soldered on.

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  • 1 month later...

Finally got around to more or less finish modding the DD-11 I posted about earlier in this thread. Added the variable clock, broke out the voice ic connections for shorting, added trigger inputs and put it in a different case. Will also post some pictures when the case is in a slightly less embarrassing state. Anyway, here is a sound example, first part is drummy, then some more drummy but with more glitches and then it's just drones. Just DD-11 with some effects. 

 

Resampling 2 [2021-02-01 042131].mp3

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3 hours ago, TubularCorporation said:

 

 

 

Sounds great!

Thanks! And thanks again for the circuitbenders ltc tip, this is what started it. Installed one in a behringer fx unit as well and have one more ltc left for future use. Builds a whole different relationship with equipment when you've modified it.

Those are some lovely crunchy rolls from that 2600...  

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21 minutes ago, user said:

Thanks! And thanks again for the circuitbenders ltc tip, this is what started it. Installed one in a behringer fx unit as well and have one more ltc left for future use. Builds a whole different relationship with equipment when you've modified it.

Those are some lovely crunchy rolls from that 2600...  

The Virtualizer? I did one of those too, sounds great even though it's hard to use because all the controls go wrong when you slow the clock down far enough to get the best sounds.

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16 hours ago, TubularCorporation said:

The Virtualizer? I did one of those too, sounds great even though it's hard to use because all the controls go wrong when you slow the clock down far enough to get the best sounds.

Yeah, had one for ages but wasn't using it so much until I realized it would probably happily accommodate an ltc. Took a couple of tries to find the right value pot for it to get a usable range, initially it was mostly crashing and producing very loud noises while doing so, still a bit iffy if the clock is too fast but at least I can hear it coming now. I'm too impatient for the parameters to update when the clock is slow so I more or less leave the settings as they are after slowing things down. Would be nice to replace the pot with a cv controllable one some day.             

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Mine works great at high clock speeds but when the pot's below 11:00 or so the LEDs all start strobing and none of the buttons actually respond, so you have to turn the clock up, choose a patch, adjust it, turn the clock down, see how it sounds, turn it back up, adjust, repeat.

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Mine does the same thing where the display and the leds start freaking out, it does register knobs turns/button presses but it can take up to 10 seconds or something like that. 

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