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Post by Morn Valley on Nov 29, 2020 23:44:59 GMT
Another build I wanted to add to my system was a classic passive ring modulator which takes 2 signals, a program/carrier and a modulator and puts out a sum of the two creating upper and lower sideband harmonics. It's a classic device which has been around since the 1930's for use in early communications systems. The schematic I used comes from a paper by composer Hugh Davies, there's an interesting analysis of Ring Modulators by Davies and a great read if you haven't come across them before. I added a DPDT switch to the circuit that allows me to flip the inputs between Program and Modulator signal although I found it useful to have some sort of attenuator between oscillators and the ring mod inputs so you can balance the two signals, I've been experimenting using the MM33 Mixer, signal amp and 2 x attenuator modules for this. Bill of materials includes; 2 x Xicon 42TL002-RC Transformers (LT44's will also work) 4 x OA85 Germanium Diodes (although you can use any other diode and this will work fine (1N34A's or even BAT48's) I did manage to find a seller on eBay who provides all the parts, I have no connection to the seller but thought it might be useful if you're wanting to buy everything you need in one go. I just followed the schematic and figured out how to pop it all in a single panel to mount for AE (this was probably the most time consuming part of this build). I also connected all the grounds to a single pin that I plugged into the AE's ground connection, it is completely passive so no power needed, just ground.    Next up I'll be reworking and posting a quick guide to a 4040 clock divider that, it'll be my second attempt as I didn't put protection resistors on the output and some errors with resistor values (I was rushing to build it and should have took a bit more time with it, but the panel work is done which takes the most time anyway). |
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Post by robertlanger on Nov 30, 2020 7:37:44 GMT
Wow, this must be some kind of telepathy 😱 Two or three days ago I was thinking and planning and parts researching for a - passive ring modulator! And here it is!
Please keep us updated about the results; might become an "official" AE module. Or maybe you want to make it as a product?
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Post by MikMo on Nov 30, 2020 9:54:05 GMT
Nice!
And as a little curiosity: a few hours before this was posted i ordered the components from the exact same ebay seller as linked in the post.
Mikael
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Post by Morn Valley on Nov 30, 2020 10:30:37 GMT
Wow, this must be some kind of telepathy 😱 Two or three days ago I was thinking and planning and parts researching for a - passive ring modulator! And here it is! Please keep us updated about the results; might become an "official" AE module. Or maybe you want to make it as a product? Thank you Robert! I’ve been speaking to Wonkystuff about sourcing a few bits for larger production and I’d definitely be up for producing this as kit or built module with your permission definitely. I’d probably add a couple of pots for input attentuators as well if I were to do this. I’ll start designing some PCB’s and get in touch when I’ve tested some prototypes and send them over. |
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Post by slowscape on Dec 2, 2020 17:32:05 GMT
Can't wait to hear it!
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Lugia
Wiki Editors
Ridiculously busy...ish.
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Post by Lugia on Dec 5, 2020 1:40:58 GMT
As long as it's a true BALANCED modulator (ie: input and output audio transformers), I say let's have 'em! Should be possible to cram two circuits into a typical AE space, if my Tenderfoot passive balanced mods (they're hiding in two of the racks) are any indication.
Of course, the REAL holy grail here is going to have to be a frequency shifter...but those are a tad more involved.
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Post by Morn Valley on Dec 6, 2020 14:01:15 GMT
As long as it's a true BALANCED modulator (ie: input and output audio transformers), I say let's have 'em! Should be possible to cram two circuits into a typical AE space, if my Tenderfoot passive balanced mods (they're hiding in two of the racks) are any indication.
Of course, the REAL holy grail here is going to have to be a frequency shifter...but those are a tad more involved.
I was looking for a frequency shift for a while as I think they produce either upper or lower sideband whereas a ring modulator produces both, please correct me if I'm off with this. I think Doepfer used to make one but it's no longer available and the only one I have currently is the Koma Field Kit FX one which I think may be realised in code as it's part of the looper section. I'm continuing to experiment with passive designs with active amp circuits for a ring mod, I'm just waiting on an order of parts at the moment. |
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Lugia
Wiki Editors
Ridiculously busy...ish.
Posts: 556
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Post by Lugia on Dec 7, 2020 5:34:35 GMT
There actually is a way to do frequency shifting with NO frequency shifter (as such), but it involves some technical poking around with an RF signal generator that has _suppressable carrier_ in AM mode and a communications receiver with single sideband (SSB) modes. The basic upshot is that once your audio is converted to a radio signal, you use the receiver to DEmodulate one or the other sidebands once you've slightly detuned either the RF gen or the receiver by whatever frequency offset you want. LSB is "subtract" and USB is "add", if I recall.
You can also use this to frequency-invert a signal. Just set the receiver for one sideband, but then tune to the _other_ one. This will sound like total electronic gibberish with some signals (like voice, where you see frequency inversion used sometimes for voice scrambling that doesn't require a digital "key") but with simpler ones, the results can be stunning!
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Post by Morn Valley on Dec 8, 2020 16:03:15 GMT
Never really looked into radio technology much only that I have an awareness of many of the tools we use in electronic music started off within the field of radio, even dynamics compression was initially created for radio broadcasting.
I'd love to look into it more and will be focussing on ring modulation before looking into frequency shifters, thank you for the useful info.
On a side note I have some AM radio receiver chips in a TO92 package that I'm hoping to shove into a panel, with the ferrite rod and variable capacitor on the the front. They run off 1.5-5.5v so should be easy to incorporate them for an additional noise source. I previously built one over the summer for my solar powered lunetta running off a 3v panel...
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Post by robertlanger on Dec 9, 2020 7:45:16 GMT
There actually is a way to do frequency shifting with NO frequency shifter (as such), but it involves some technical poking around with an RF signal generator that has _suppressable carrier_ in AM mode and a communications receiver with single sideband (SSB) modes. The basic upshot is that once your audio is converted to a radio signal, you use the receiver to DEmodulate one or the other sidebands once you've slightly detuned either the RF gen or the receiver by whatever frequency offset you want. LSB is "subtract" and USB is "add", if I recall.
You can also use this to frequency-invert a signal. Just set the receiver for one sideband, but then tune to the _other_ one. This will sound like total electronic gibberish with some signals (like voice, where you see frequency inversion used sometimes for voice scrambling that doesn't require a digital "key") but with simpler ones, the results can be stunning!
Now that's what I call really freaky stuff...! |
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Post by rodney on Dec 10, 2020 10:06:00 GMT
It's a grand tradition.
The Theremin is kind of a malfunctioning radio where you (and the planet) are the tuning capacitor.
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ean
New Member
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Post by ean on Jan 28, 2021 18:30:56 GMT
I have the same kit from the same ebay seller. I think I've had it about six months. I decided to wait for the BrAEdboard in my delivery to try it out.
Let us know how it sounds and if it works OK. I guess we're always on the look out for simple circuits we can incorpoarte. Originally I was looking at the synthrotek passive ring mod, but I looked around on ebay and found a cheaper option.
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Post by MikMo on Jan 28, 2021 19:43:57 GMT
I finished mine a few days ago, and at first i was a little disappointed, then i discovered a tiny solder error that allowed one strand of a hookup wire to touch an adjacent stripboard strip fixed it, and that changed the sound. As with all other modules you have to learn how to use it, and now i am more than pleased with the sound.
You get classic ring mod sounds. I own two of the first gen. VCO's that does not track so well and are a bit temperature unstable, but they have fine tune, and i actually really like the sound.
They work really well with the ring mod because you can dial in the coarse tuning, and then make very small changes with the fine tune to get both classic ring mod sounds, but also really good "non ring mod sounds" like new timbres that can be played with the sequencer.
I have not yet had much time to play with percussive sounds through the ring mod, but i hope to cover that over the coming weekend.
All in all it is a really nice supplement to the great AE modules.
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