By integrating a complete analog VCO on a chip, it made more compact and cost-effective synth designs possible. Together with the classic analog polysynths themselves, the Curtis chips have long been out of production.

In however, thanks to the new boom in analog synthesis, the VCO chip is once again available, from no less than three sources. This module is designed to be a basic but complete application of the VCO for Eurorack modular synthesizers. It further exposes the FM and Sync features of the chip to the user. The chip is known for good tracking and temperature stability, making the build of a robust VCO uncomplicated and affordable.

Further, this module uses onboard voltage regulators to reduce sensitivity to power supply fluctuations and limit self-heating of the VCO chip. ModularGrid uses so-called cookies to ensure it's so-called functionality.

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Right Now on eBay. ModularGrid Marketplace sell and buy used modules Visit our Marketplace. Buy on Reverb. YouTube unfiltered search results for VCO Search for VCO in Forum.Curtis chips integrated circuits made by Curtis Electromusic Specialties are a common component in vintage synths.

A comparison is achieved using the Oberheim OB-8 with half of its s replaced and setting the keyboard in dual mode. By assigning the same sound to both splits in dual mode, a comparison can be made by fading between both sounds using the program balance knob.

We are evaluating demand and are very interested in new designs that our chips might foster. The newer filters are slightly cleaner than the old ones, with the older one showing more harmonics on the first notes of the triangle wave than the second ones.

But only in the lower frequencies oddly. And this observation gets thrown out the window when he plays notes slightly higher, as the newer filter adds more harmonics than the old one. The jury is pretty much out for the Saw wave. I can hear the difference but the new chips are of more than acceptable quality. I will certainly be purchasing a set of these.

The pursuit of synthesis should be based on sound quality and innovation not cheaper price points and lackluster uniformity. SSM and Curtis chips made it possible for companies to produce affordable polyphonic analog synths. There was nothing bland about those instruments, but they were priced out of reach of most musicians. Polyphonic digital voice and filter chips from companies like E-mu and Ensoniq brought the price of samplers, romplers and digital synths down to the point that anyone could own them.

As a result, we were inundated with unimaginative regurgitation of fairlight voice samples, orchestral hits and all manner of cliche string sounds. None of this had anything to do with Curtis chips.

The fact that people love the sound of Curtis-based instruments three decades later speaks to their quality. It the CEM is a building block. A stable and reliable one at that. Arguably the filters set a good bit more in the way of character - I preferred the CEM to the … but that is well understood by all.

It is the VCO chips that tend to go out the most on these synths, which is why they are so sought after. The best part is that many older synths will not be cannibalized for spare parts now, they may get repaired and played again. Skip to content. Great job calibrating the voices perfectly for an excellent comparison. Great news!I had the same erroneous tuning issue on a couple voices with an otherwise perfectly working P when autotuning with the GliGli mod --would doing this resistor swap resolve this?

I'm not clear how changing the resistors for the old CEM s Rev? Thanks for the rundown! Supposedly the GliGli autotune routine is more accurate than the stock P, so that may be a source of the variation though how it could be more accurate, I'm not clear--current autotuning on mine is pretty darn tight.

But the resistor test at least sounds pretty non-invasive. Analogue Heaven. Search everywhere only in this topic. Advanced Search. Classic List Threaded.

cem3340 rev g

CEM revG reissue In case anybody was wondering about these Received my order of new CEMs from Onchip. Installed them in my P running firmware v6. Replaced the I realize that one point on a graph doesn't give the most accurate information; if anybody else is using these as replacements in vintage synths Roland, SCI, etc it would be helpful if you report your experience to the list.

Eric Frampton. Re: CEM revG reissue In reply to this post by gm. You could test by clipping a K resistor across the In reply to this post by M V. As to "why" this is necessary, I don't know -- but I suspect that the gligli tuning routine is different enough from the stock P routine that small variances may make a big difference. Before changing the resistors, try tweaking back the VCO trim pots on the voices that are having the issue and run the tune routine again -- this helped on one of the gligli Ps I worked on.

And, as always, be cognizant of the many possible causes of tune problems on the P -- bad 1uf caps feeding the VCO signal into thefaultyfaulty sockets on the I've solved a number of VCOs not tuning on a P by simply swapping two s -- apparently the slightest bit of faulty contact on the socket pins can cause tuning failure.

Also, keep in mind that the outputs of all six s are tied together leading to the tune buffer, so a fault in one can cause problems in all of them. Free forum by Nabble. Edit this page.First, the datasheet design. The datasheet design uses pretty much all the features of the chip, and shows one or two of its quirks too.

The CEM is extremely unusual in that it offers both Hard and Soft Sync inputs pin 6 and pin 9and neither of them work the way you might expect.

However, the datasheet does offer alternative circuits for synchronization which can give you the classic sync effect, and manufacturers seem mostly to have gone with variations on this instead.

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Sometimes people just want what they know and love. One of the quirks of the CEM is the waveform outputs. For a start, these are all different levels. Usually this would just be grounded, but it could be taken to the negative supply.

Most synths compensate for the differing levels in the following waveform mixer stage. This is easily done by changing the input resistors in an inverting op-amp mixer. Another quirk is the supply voltage. Curtis dealt with this by adding a zener diode to limit the negative supply connected to pin 3 to The zener diode needs to be protected from over-current, so you typically see a current limiting resistor hanging off pin 3 R with V in the datasheet circuit.

The circuit breaks up into various functional units quite neatly. Starting numerically at Pins 1 and 2, this is the temperature compensation circuit.

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This works by generating a temperature-dependent voltage which is then multiplied on-chip by the incoming CV. There are still some minor errors from the multiplication process hey, this is analog, after all but the datasheet gives details of how to trim those out too if you can be bothered. Pins 4, 5, and 6 are inputs and outputs all labelled above, so no need to discuss those.

Pin 7 is more interesting. The lower half of the preset resistor serves as a resistor to ground which converts this current to a voltage, and the upper half and the series resistor 1M feed a small portion back into the Frequency CV input at Pin Pin 11 is the next important one. Use a good quality capacitor here, with low leakage and low tempco.

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Pin 13 is the Linear FM input, with an associated bias network. Pin 15 is the Frequency CV input. This is a virtual ground summing node, and you usually see a bias network as shown K, R, 10nalthough often with the values tweaked, followed by the summing resistors coming from the various CV sources.

In addition there are Ground and -5V power connections. The recommended value is 1. You can argue about the relative merits of one versus the other, but the fact is that they were having tuning problems, and using the CEM helped them solve them.

Notice the sync circuit.

Doug Curtis

Also note that this is Oscillator A, the Sync Slave. There are several differences to note from the Prophet 5 design.Moderators: lisaluketeafordKentJoe. Privacy Terms.

cem3340 rev g

Quick links. Curtis Has been remanufactured Any music gear discussions that don't fit into one of the other forums. We have tested them and they are revision G and pass our tests on the original Curtis test boards and also various synths we tried them in. The person to contact is susanonchip covad.

onchip cem3340 vco ic

Please be aware that revision G has meant the following: "After reviewing the prior specifications I did decide to change the minimum VCC spec. The old VCC min.

CEM3340 Oscillators, first time with CV input

This is based on my own bench experience with several versions of the device. I am in communication with them and will continue to push for the other chips to be brought back but to be honest the release of the is great news as that was the most common curtis chip used.

I hope you enjoy and spread the word!! I've previously had to pay handsome sums for these when repairing synths. I'll keep digging and see what's happening but this could change the world of modern synths and modular synths with new found availability of the CEM chips!

I ordered 6 a month or two back when I first heard about this and onchip was happy to sell them in those quantities. New deals here friends.One of the most important and least known synthesizer pioneers of the 20th century, [1] Curtis was the designer of many original analogue ICswhich have been used in a number electronic music instruments. In high school with an interest in sound and music electronicshe designed and built a synthesizer.

He majored from Northwestern Universitywith radio-TV-film. While here he perfected several more synthesizers. Upon graduation, he qualified for a post as junior engineer by showing circuit boards of his designs. He entered a competition to design a semi-custom chip and as a result was offered a job atwhere he worked for four years.

He founded Curtis Electromusic Specialties, which produced the integrated circuits that were used in a variety of analog synthesizers for decades. There are several patents in his name. In [3] with the advent of digital technology, Doug formed the company OnChip Systems.

Instruments with CEM ICs are said to have that Curtis sounddescribed as "fantastically saturated, brash and powerful". The CEM IC is seeing somewhat of a renaissance due to its reissue by a few semiconductor companies ref to go here. Notably, one such company appears to have garnered the blessing of Mary Curtis Doug's widow herself, touted in these words appearing on a graphic on their sourcing page: [5]. Many of you who are active on synth forums have recently contacted us regarding another company's claim of producing VCO chips that are the equivalent to the CEM that was used in many legendary synthesizers.

To avoid any confusion, please know that there is only one manufacturer of the authentic CEM designed by my late husband, Doug Curtis.

MUFF WIGGLER

Any claims, use of this product designation, and use of the name Curtis Electromusic by other companies are made without permission from OnChip Systems our current company name or the Curtis Family. As much as Doug would be humbled and so very happy about the legacy his products enjoy, we can assure you that as a person of the highest integrity he would be deeply saddened by the attempt of others to trade on his name and to make unsubstantiated claims of equivalency to his original inventions.

In his loving memory and gratitude for the community of musicians and synthesizer enthusiasts, Doug's family is committed to making his authentic designs available as demand presents itself.

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Thank you for your continued support of Doug's analog synthesizer legacy. From Wikipedia, the free encyclopedia. This article has multiple issues.

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