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Per
Joined: Jun 09, 2004
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 Posted: Thu Dec 21, 2006 10:07 pm Post subject:
High Frequnecy Synthes, somebody? |
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Hi list,
I have done some experiment with the high frequency VCO output of the Doepfer BBD-modules. Using two of them with a frequency above hearing level in a ring modulator make some nice noise. It sounds a bit like an old AM radio in between the stations. And while one sideband get down in the audio area, the other reaches much higher, and get inaudible. As far as this, it is only sound experiment, not music that is coming out.
Is there anybody else out there who have experience of using HF oscillators for sound production?
Per |
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ian-s
Joined: Apr 01, 2004
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| Posted: Thu Dec 21, 2006 10:59 pm Post subject:
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Sounds like you patched a Theremin  cool. |
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Jari Jokinen
Joined: Sep 11, 2006
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| Posted: Tue Sep 25, 2007 3:05 am Post subject:
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| No experience yet, but I noticed, that Cwejman VCO-2RM goes over 170KHz with voltage control... |
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Beermaster
Joined: Oct 22, 2006
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Location: London
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| Posted: Tue Sep 25, 2007 10:36 am Post subject:
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I think the main use for HF vco would be as modulators and creating sideband effects
The Serge NTO is able to Mega Hz but I've not tried that yet - Hard to tell without a scope ! haha |
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mosc
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| Posted: Tue Sep 25, 2007 10:57 am Post subject:
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Oh, boy. I used to make a career out of this. 
My concern was allways that the speakers and amps tended to rool off highs. I wanted music that screamed with highs. Tape recorders also rolled off highs. Nowadays, digital recordings are by nature band limited.
So the challenge was, how to make a recording of sound that had frequencies higher than could be reproduced in the tape/amp/speaker technology.
The most success was this:
If you over drive the recording with a broad spectrum of highs and you drive the amp/speaker into non-linear operation, you'll get upper and lower sidebands. The upper sidebands can have frequencies above the normal reproduction range of the system.
I generated these high frequencies in the first place with a Moog using tons of FM.
Very few people like this. Some experience high frequencies as painful. But, I really dig it because it makes my ears wake up, so to speak.
Another problem, driving your speakers into regions of non-linear operation can ruin them. Who knows what this does to one's ears.
But back to your point, a primary difference between analog and digital is that in an analog circuit, there could be these ultra high frequencies mixing and beating down into the audio spectrum where as in digital these would most probably not be there, unless the sample rate is very high. (Mixing and beating are radio engineering terms for multiplying and such.)
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Last edited by mosc on Wed Sep 26, 2007 9:23 am; edited 1 time in total |
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Peake
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| Posted: Tue Sep 25, 2007 4:07 pm Post subject:
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The Serge oscillators are supposedly rated up to 100KHz. The Moog 921b, to 40KHz.
"Hysteresis", right? |
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mosc
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| Posted: Wed Sep 26, 2007 9:46 am Post subject:
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| Peake wrote: | The Serge oscillators are supposedly rated up to 100KHz. The Moog 921b, to 40KHz.
"Hysteresis", right? |
Hysteresis is a phenomena associated with switching or quantization. Most oscillators have some sort of switching or quantization circuit, but not necessarily. The operational range of a circuit is more probably the result of the design objectives of the designer.
One might ask, other than the fact that most people can't even hear above about 12 KHz, why not make all your circuits work as high as possible? There is no single answer, but noise is a big factor. Some people define radio as anything above about 30 KHz. (There are some rare uses of radio down to 3 Hz even). There are commercial AM radio stations at 54 KHz in some places. Generally, one doesn't want their audio gear to be radio receivers. Also, you don't want stray oscillations beating down into the audio range.
One way of limiting the response of circuits is to add a small capacitor across the feed back resistor of every op amp. These range in size from about 10 pf to 50 pf. Each designer has feelings about these because they have a cumulative effect on the sound. Buchla often said that the difference in the sound of a Moog and Buchla was the choice of these compensation capacitors. Moog used larger ones than Buchla, and Moogs sounded more mellow.
Rob Hordijk has speculated that the cumulative effect of these capacitors in an analog circuit is responsible for the preferred sound of analog synths compared to digital ones. To validate this theory, he he developed his famous tilt filter. When digital synths are passed though this filter they sound analog. Many people use Rob's tilt filter as the final touch on every Nord Modular patch. It has put to rest a lot of analog vs. digital debate.
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Nosferatu
Joined: Jul 27, 2007
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Location: Planet Rock.
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| Posted: Wed Sep 26, 2007 6:58 pm Post subject:
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Hmm, so what your saying is that by adding a digital filter to an
numbercrounching routine in a digital sound box makes it sounding
analog? 
Im elaborating in my mind about doing the reverse! |
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mosc
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| Posted: Thu Sep 27, 2007 11:38 am Post subject:
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Ha ha, that thought occurred to me when I was writing that too..
Rob's filter doesn't really sound like a filter because it tilts the total spectrum. That's why it's nice. A regular filter, like a high cut (low pass) colors the sound because there is not only a high frequency roll off, but a filter cut off point. Somehow, the ear/brain picks this out as a color or effect and, to my ears at least, it is noticeable and becomes tedious. The tilt filter has no filter cut of point, or more precisely, it has several, so it has a more gentle and pleasing effect.
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Peake
Joined: Jun 29, 2007
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| Posted: Thu Sep 27, 2007 12:05 pm Post subject:
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| mosc wrote: | | Rob Hordijk has speculated that the cumulative effect of these capacitors in an analog circuit is responsible for the preferred sound of analog synths compared to digital ones. To validate this theory, he he developed his famous tilt filter. When digital synths are passed though this filter they sound analog. Many people use Rob's tilt filter as the final touch on every Nord Modular patch. It has put to rest a lot of analog vs. digital debate. |
Sorry to pick nits, but what about the combination of nickel-wound transformers, oil-filled paper capacitors, passive EQ, inductors, and tube make-up gain? Transformer non-linearities are very important, and no solid-state EQ is as sweet and clear as what I've just described, especially at high frequencies (which is the acid test of EQ, IMO).
I say this because it would be nice to have that actual sound in digital someday. As well as selective grounding, PS dirt, etc.
And by "hysteresis" I meant the Theremin effect of extremly (at least in terms of "analog synthesis") HF signal blending/modulation causing signal in the audible range... |
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mosc
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| Posted: Thu Sep 27, 2007 12:23 pm Post subject:
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Well, most analog stuff in the synthesis area doesn't have too many inductors, but your point is well made. There are many other effects. But Rob's work does produce satisfying results; that's the most important thing, IMHO.
Tubes are another topic, I think. To get the tube sound, Rob has developed a 2nd order harmonic distortion patch for the Nord Modular. This works good, but really excellent tube amps don't have too much 2nd order harmonic distortion anyway. These days, there aren't that many people around that can even recognize that mysterious tube sound.
Hysteresis? I think you might possibly be thinking of heterodyne.
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elektro80
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| Posted: Thu Sep 27, 2007 12:42 pm Post subject:
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| Peake wrote: | | Sorry to pick nits, but what about the combination of nickel-wound transformers, oil-filled paper capacitors, passive EQ, inductors, and tube make-up gain? |
Yup.
It is easy to forget that there are far more high end analogue outboard devices in studios these days than say 40 years ago. What is way down is the number of big analogue mixers. It seems these are coming back as well, but the significant thing here is that high quality analogue preamps, compressors, EQs and more are back in numbers. We also have more channels these days and generally the quality is much higher now.
Analogue audio is better than ever.
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Nosferatu
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| Posted: Thu Sep 27, 2007 4:07 pm Post subject:
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del
Last edited by Nosferatu on Mon Nov 26, 2007 3:39 pm; edited 1 time in total |
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blue hell
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| Posted: Thu Sep 27, 2007 4:49 pm Post subject:
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| Nosferatu wrote: | | And the question are, can we actually hear that? |
Yes we can, in the high ends some nasty things can happen related to discrete time steps in syncing, fm, pm. Robs filter will not take that away, if you don't like it you should not generate it, this is limiting in a way, no matter how much fun the Nords are. |
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Peake
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| Posted: Thu Sep 27, 2007 11:10 pm Post subject:
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| mosc wrote: | | Well, most analog stuff in the synthesis area doesn't have too many inductors, but your point is well made. There are many other effects. But Rob's work does produce satisfying results; that's the most important thing, IMHO. |
This is a shame. I've only learned (here) recently that it's because they're expensive. But so is the entirely metal pitch bender in the SH5, and it feels damn good. These are the things we've lost, and we can tell.
| Quote: | | These days, there aren't that many people around that can even recognize that mysterious tube sound. |
There is nice puff and blur in the CGS tube VCA. This is one type of tube sound, not the clean one you'd mentioned, which is certainly possible. Add the transformers, etc., and you're in heaven. Once you get used to hearing it, you'll know when it's not there. Perhaps these things are not as massive as turning up the resonance on a filter, but they are euphoria when they're right. Look to the gear lists at mastering houses and high-end studios.
Tube compression, like tape compression, are worthy avenues of research for people who are seriously into solving the mysteries. That and leading-edge ringing. Also, the "head bump" in a reel-to-reel (15IPS vs 30IPS). And RIAA artifacts (beefier mid and upper bass than CD!!!)
I have a feeling that the process of 60KHz tape biasing has some sort of effect on sound, something.
| Quote: | | Hysteresis? I think you might possibly be thinking of heterodyne. |
Yes! Thank you! The A6 self-oscillating Filter 2 goes up to about 40K for this reason. |
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Peake
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| Posted: Thu Sep 27, 2007 11:28 pm Post subject:
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| Quote: | | Electro 80: Analogue audio is better than ever. |
In some ways I agree. In some ways, at the very high end, I disagree. We’re starting to recognize what is missing, -because- it’s been missing, and people have been quantifying it (thankfully).
In terms of synthesis, we’ve lost the beauty of using 5-20% tolerance parts from people who were cramming what they could into a particular price point, such as the Putney. Nothing will ever sound like that again, especially modern gear. The totality of the thing, nearly shaking apart into some total self-oscillation, makes it something that those after engineering-related concerns fail to either take note of, or to respect and repeat. I don’t think that some engineers –can- “lower” themselves to the level of what was good about the older gear. Pushing the edge with very limited parts!
The art of oil-filled paper caps is gone. Tubes are surviving, barely, and transformers haven’t died due to their usefulness. But the days of the Fairchild limiter, the LA2A, and other amazing innovations are gone. Despite cloning. It’s posited that the very dirt in the old tube-making processes were partly responsible for the resulting color. New designs may be, physically, too clean. I’m just trying to figure out why; I’ll leave it to the experts to answer the question.
| Quote: | Nosferatu: Coloring are more an effect of phase, group delay of the filter,
you can test this for your self easily, build a 4 stage OTA filter without
fet buffers, it will be so dry it sounds like you had cotton in your mouth. Very Happy
(i.e not dull, just very dry). |
Do inductors have greater phase displacement than gyrators/solid-state replacements? None of the active FFBs sound like the Moogs. |
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mosc
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| Posted: Fri Sep 28, 2007 7:54 am Post subject:
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I lived through the vintage era and unfortunately don't share many of the younger folks lust for the old days. We used to dream of digital equipment. I'm quite satisfied with the new technology, personally.
I've argued many times that the digital vs. analog debate is not fruitful. Both are just different sides of the same coin. I formally designed DRAM chips. These are the most challenging analog designs there are.
The best designers are motivated to do new things with new technology. The Buchla e series is an analog synth that uses lots of digital technology internally.
It is very true that analog equipment is much better these days, but so is digital equipment.
Using parts with loose tolerances won't make a circuit sound good or bad, but it may make each instance sound different. Every Moog Modular and Steinway piano I've played sound different. In the days of tape, every pro recorded sounded different too, because the techs that tuned them had personal tricks and techniques.
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Peake
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| Posted: Fri Sep 28, 2007 11:44 am Post subject:
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| mosc wrote: | | I lived through the vintage era and unfortunately don't share many of the younger folks lust for the old days. We used to dream of digital equipment. I'm quite satisfied with the new technology, personally. |
Personal satisfaction is what it's all about. I don't get that from digital equipment (recording, processing, etc.) Generative digital is a different story (Absynth, FM, etc.)
I've had the pleasure of owning some high-end gear, and you can't go back once you've heard it. Mind you, this is modern tube gear, from Manley and Groove Tubes. Excellent stuff. Who can afford the Fairchild? Not I.
| Quote: | | Using parts with loose tolerances won't make a circuit sound good or bad, but it may make each instance sound different. Every Moog Modular and Steinway piano I've played sound different. In the days of tape, every pro recorded sounded different too, because the techs that tuned them had personal tricks and techniques. |
Conny Plank is said to have biased each tape track differently, to accomodate each instrument's character. That is mastery. It is lost, and it is not missed by the Pro Tools crowd. It -can't- be missed by them, or they'd be doing something about it instead of using digital.
Regading the differences in the same pieces of gear due to large-tolerance components: That's my point. Some sounded great, some sounded dead. Find the great ones, measure them, and let the world know -why- they're great. Are the transistors in the ladder filter off by a little? How much? And where? Let us know how to repeat what's good.
The Audities Collection has a Minimoog prototype. It sounds like it's about to blow up. It's amazing. I wish to know why, and recreate it.
Sometimes there is beauty that can only be found by mistake, or through moving outside of the goal of so-called perfection. Perfectly matched laser-trimmed components aren't the solution, they're the problem.
If you don't click to what I'm saying, I hope that you do someday. I don't mean that to be patronizing or insulting; I just want more people who are interested in playing with this set of sonic boundaries, learning them, and employing them. I'm heartened by your talk of the G2 tilt filter, and folks who are looking around for the causes of quality. This is not mystic stuff; it can be qualified and then applied. Look into the bad grounding of the SEM, and the effect it has on ratting up the pitch, differently on every note, just like the old combo organs. Loop those to single-cycle and they sound lie crap. Loop them with respect to the mains interference, and they're all right.
Accuracy is idiocy, if I may be absolutist. Engineering over music is an insult to music. Engineering is a means to an end, not an end in itself. |
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mosc
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| Posted: Fri Sep 28, 2007 12:11 pm Post subject:
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So, on what do you record; tape, direct to vinyl, magnetic wire, wax cylinders?
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elektro80
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| Posted: Fri Sep 28, 2007 12:29 pm Post subject:
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I don´t see much of a problem with digital recording these days.
I also don´t see much of a problem with processing audio in the analogue domain.
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Peake
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| Posted: Fri Sep 28, 2007 1:10 pm Post subject:
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| mosc wrote: | | So, on what do you record; tape, direct to vinyl, magnetic wire, wax cylinders? |
Currently, nothing. Although I intend to get another Manley Variable-mu, EQP1a stereo copy, and find some tape format that's workable considering the lack of new tape manufacture.
I could spend millions. Please give me millions.
And regarding Per's original question, sorry, yes, I intend to try out HF experimentation. Thanks for posting on it. |
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Nosferatu
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| Posted: Fri Sep 28, 2007 6:37 pm Post subject:
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del
Last edited by Nosferatu on Mon Nov 26, 2007 3:41 pm; edited 4 times in total |
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Beermaster
Joined: Oct 22, 2006
Posts: 42
Location: London
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| Posted: Sat Sep 29, 2007 2:17 am Post subject:
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This is a great debate ! - So much knowledge here thats way over my head ( an honour to be in such company ! )
At the end of the day if it it sounds good then I'm happy. I don't have any experience in electronics as such but music and composing are my life. I guess its a very subjective thing whether one person finds the sound of one synth more pleasing than another - I've never really been passionate about the minimoog sound but I love the SEM sound. Its so destinctive and to me .. Again its hard to put into words .. its like trying to describe how Selmer Mk6 saxaphones sound better than Yamaha YS64s - describing a sound is a pointless exercise.
Now back to my Harvetman Malgorithms... come here you little digital hell raisers ! |
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blue hell
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| Posted: Sat Sep 29, 2007 4:46 am Post subject:
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| Beermaster wrote: | | describing a sound is a pointless exercise. |
Yet the ones building the instruments making the sounds should have a few words of description for at least some parts of the sounds those instruments make. So maybe not pointless but difficult rather? |
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mosc
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| Posted: Sat Sep 29, 2007 9:56 am Post subject:
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When I was working for Buchla many many years ago, I quickly learned not to describe sounds, especially when talking about his circuits. He wasn't into that. I mean, most descriptions are at best ambiguous. After I got to know him, he would show me something, usually with absolutely no explanation of what it was, and say, "What do you think". He responded most to a facial expression. Often, he'd just want to see a musician play the device (turn the knobs). He got feedback by seeing what people would do with it.
I don't think Buchla designs for sound, he designs for possibilities. Maybe that is a gross oversimplification, but when people started using terms like warmth, depth and balls, he'd often take that as an opportunity to go to the men's room.
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