[sdiy] as3340 PW/tuning issue
klangbau
sauterw at web.de
Mon Dec 30 22:12:44 CET 2019
I remember a Jürgen Haible hand drawing schematic of a TZ-VCO based on
two 3340 when I was researching about TZ-VCO's
It is JH3 Dual VCO with TZ option and a CD4077.
Good to have a hard copy to find it again:
http://jhaible.com/legacy/tonline_stuff/hj2vco.gif
willi
willi sauter
KlangbauKoeln
Am 30.12.19 um 20:55 schrieb ColinMuirDorward:
> Steve, you could ask Alfa Rpar if they would send you a 3345 sample.
>
> On Mon, Dec 30, 2019 at 10:17 AM S Ridley <spridley1 at gmail.com
> <mailto:spridley1 at gmail.com>> wrote:
>
>
> > I wonder if this is a good place to cast my vote (again!) for a
> through-zero 3340?
>
> The 3345 should be able to do linear FM through zero. There were
> some additional applications for the CEM3345 in the old CEM
> Synthsource newsletter, spring/summer 1981, including adjustable
> triangle symetry and linear through zero FM - needs a CD4077, an
> opamp and a comparator. I've never managed to get a 3345 to see
> if it works.
>
> The Synthesource newsletters are reproduced in Barry Klein's
> Electronic ICs databook but I haven't seem them anywhere else...
>
> Steve
>
>
>
> On Sun, 29 Dec 2019 at 01:19, ColinMuirDorward
> <colindorward at gmail.com <mailto:colindorward at gmail.com>> wrote:
>
> Thanks for chiming in, Alex. Interesting to hear of the
> possibility of a future revision.
>
> I wonder if this is a good place to cast my vote (again!) for
> a through-zero 3340?
>
> Jay, I think you're right, but on the other hand, using the
> chip means I don't need to source tempcos or matched transistors.
>
> Colin
>
> On Sat, Dec 28, 2019 at 3:13 PM Jay Schwichtenberg
> <jschwich53 at comcast.net <mailto:jschwich53 at comcast.net>> wrote:
>
> My personal thought is that for just a VCO I'd go with a
> classic design. To me these chips are more appropriate for
> something like a stand alone keyboard or poly synth. Using
> them as a regular VCO usually requires you to normalize
> the output waveforms bias and level, typically with
> additional op-amps. By the time you add that circuitry
> you're getting close to the number of chips you have in a
> classic VCO and a PCB of about the same size.
>
> I was wondering if you add the -5V regulator, set the PWM
> to some optimal value and then used an external PWM
> circuit off the saw wave whether or not that would either
> eliminate or considerably reduce the problem of
> PWM/frequency issues?
>
> Jay S.
>
> On 12/28/2019 2:47 AM, Aa Bb wrote:
>> (From ALFA RPAR AS)
>> Dear Sir's
>>
>> We've noticed discussion on DIY forum's about
>> AS3340 PWM issues.
>> It looks several opinions exist and some of them are
>> partly close to reality. We
>> wanted to provide some information about these question.
>>
>> 1.1 First important moment - all 3340
>> incarnations have influence PWM on
>> frequency (linear influence and spike at 50%). They
>> differ in character and level.
>> For better understanding curve - Freq.dev./ Pwm
>> level must be build an analyzed.
>> Example of such curve for AS3340-HYB is provided in
>> datasheet :
>> http://www.alfarzpp.lv/eng/sc/AS3340-HYB.php
>>
>> 1.2 Main source of such influence - very fast
>> switching of comparator output (pin 4). But also
>> some other minor effect exist. High slew rate makes
>> problems for internal circuitry (high current spikes
>> on different internal nets ) and also, if layout is
>> made not so good, on negative supply (pin 3).
>> Almost identical schematics of these comparator,
>> for better understanding, is provided
>> in AS3340-HYB datasheet:
>> http://www.alfarzpp.lv/eng/sc/AS3340-HYB.php
>>
>> 1.3 Different solutions may be used in different
>> situations and requirements.
>> 1.3.1 Old builds repair.
>> In old builds situation is "as is" and it is
>> almost impossible to change anything. For such case
>> we offer - AS3340-HYB - solution witch almost totaly
>> excludes PWM influence on frequency (in
>> comparison with all other 3340 variants !!!).
>> Main idea - DIP module is based on AS3345F (QFN)
>> and is pin-to-pin compatible with 3340.
>> Comparator, similar to the one inside of AS3340 is made
>> on separate transistors/resistors. Internal
>> comparator is turned OFF. So, high slew-rate current
>> spikes in these solution are flowing through
>> "external" comparator and it's influence on AS3340 is
>> minimized.
>> Certainly, for better immunity, output current
>> minimization, better to decrease output current
>> by increasing load resistor till 51k or more (depends
>> from application).
>> So, for such case, - our opinion - use AS3340-HYB.
>>
>> 1.3.2 For new designs.
>> Several variants , moments:
>> 1.3.2.1 If You use PWM - "protect" pin3 from pin
>> 4 - layout, bypass capacitor.
>> 1.3.2.2 Try to decrease slew rate of comparator
>> output:
>> - increase load resistor (it will decrease
>> comparator output current)
>> - connect pin 5 and pin pin 4 with MegaOhm
>> resistor and add to pin 4 capacitor.
>> But linear influence PWM on frequency still remains.
>>
>> 1.3.2.3 Use AS3340-HYB - witch it the best in
>> these moment.
>>
>> We just tried to explain "mechanism" of problem.
>> Other schematic tricks can be used.
>>
>> We hope, in some time, new revision of AS3340A will
>> be available.
>>
>> ALFA RPAR AS
>> Alex Zaslavsky
>> alfa at alfarzpp.lv <mailto:alfa at alfarzpp.lv>
>> http://www.alfarzpp.lv/eng/sc/application.php
>>
>> On Sun, 22 Dec 2019 at 01:17, Doug Terrebonne via
>> Synth-diy <synth-diy at synth-diy.org
>> <mailto:synth-diy at synth-diy.org>> wrote:
>>
>> Yes, the original rev F CEM3340s in the JP-6 don't
>> have this issue.
>>
>> Doug
>> synthparts.com <http://synthparts.com>
>>
>> On Saturday, December 21, 2019, 3:11:12 PM PST,
>> ColinMuirDorward <colindorward at gmail.com
>> <mailto:colindorward at gmail.com>> wrote:
>>
>>
>> Thanks, Doug.
>> Is it true that this problem didn't manifest with the
>> original CEM3340?
>> Colin
>>
>> On Sat, Dec 21, 2019, 3:08 PM Doug Terrebonne,
>> <dougt55 at yahoo.com <mailto:dougt55 at yahoo.com>> wrote:
>>
>> I just tried as AS3340 in my JP-6 and changing
>> the PW does affect the pitch (mostly noticeable
>> in the higher octaves). The autotune can
>> compensate for it though (adjust PW, hit Tune
>> button).
>>
>> Doug
>> synthparts.com <http://synthparts.com>
>>
>> On Thursday, December 19, 2019, 3:12:35 PM PST,
>> ColinMuirDorward <colindorward at gmail.com
>> <mailto:colindorward at gmail.com>> wrote:
>>
>>
>> Out of curiosity, does anyone have an mks80 rev4
>> and/or Jupiter 6 they could test for this problem?
>>
>> My brother sold his mks80 rev4 already, but
>> claims the pitch error was quite bad in his unit.
>>
>> In the next model, the rev5, Roland apparently
>> switched the 3340 for a proprietary VCO chip.
>>
>> Colin
>>
>>
>> On Thu, Dec 19, 2019 at 3:48 PM Tom Wiltshire
>> <tom at electricdruid.net
>> <mailto:tom at electricdruid.net>> wrote:
>>
>> My own view of it is that if you want cheap,
>> you buy the Alfa AS3340. If you want original
>> and can afford it, you buy the CEM3340 G. The
>> V3340 falls somewhere in the middle and
>> therefore doesn’t offer a unique selling
>> point for DIYers.
>>
>> Coolaudio don’t care, since Behringer needs
>> tons of ‘em! ;)
>>
>> Tom
>>
>>> On 19 Dec 2019, at 13:53, ColinMuirDorward
>>> <colindorward at gmail.com
>>> <mailto:colindorward at gmail.com>> wrote:
>>>
>>> I didn't see a lot of discussion on this
>>> topic include the v3340. Not sure if people
>>> had already collected the CEM and AS
>>> versions by the time the Vs came out, or
>>> what, but the coolaudios don't seem to be on
>>> as many work benches.
>>> I just checked a neutron and no surprise
>>> that I could not find any pitch error there.
>>> I have a lot of as3340s, so when my next
>>> prototype comes in, I could check for error
>>> variation between chips.
>>>
>>> Colin
>>>
>>> On Thu, Dec 19, 2019 at 10:01 AM Tom
>>> Wiltshire <tom at electricdruid.net
>>> <mailto:tom at electricdruid.net>> wrote:
>>>
>>> A quick test on my Pro-One doesn’t
>>> reveal any tuning problem. I routed the
>>> LFO to PW on oscillator A, then listened
>>> to Oscillator A’s ramp wave alone (so no
>>> beating to confuse things) and couldn’t
>>> hear any difference, even with maximum
>>> mod depth and maximum LFO rate. Checking
>>> the output on the oscilloscope showed no
>>> pitch variation either.
>>>
>>> That said, there’s some evidence
>>> Sequential *did* select 3340s. The ones
>>> regarded as “not good enough” were used
>>> for LFO duties, and if you check the
>>> PCBs you’ll see paint blobs on those
>>> ones. I’ve never seen anything
>>> documenting what the tests were though.
>>> Maybe they just built the things and
>>> swapped out any that caused a problem,
>>> put a blob on them, and then used them
>>> later where it wouldn’t matter.
>>>
>>> A more interesting test which I might
>>> get to later would be an A/B/C
>>> comparison on my 3340 test board between
>>> CEM3340 G, AS3340, and V3340. Despite
>>> having all three chips on the shelf,
>>> I’ve never actually done this.
>>>
>>> Tom
>>>
>>> ==================
>>> Electric Druid
>>> Synth & Stompbox DIY
>>> ==================
>>>
>>>> On 19 Dec 2019, at 12:06, Mattias
>>>> Rickardsson <mr at analogue.org
>>>> <mailto:mr at analogue.org>> wrote:
>>>>
>>>> I remember talking to Dieter Doepfer
>>>> about this back in the day... Ah, here
>>>> it is:
>>>>
>>>> /mr
>>>>
>>>>
>>>>
>>>> At 17:52 2003-02-02, Dieter Doepfer wrote:
>>>> > > -----Ursprüngliche Nachricht-----
>>>> > > Von: Mattias Rickardsson
>>>> > > Gesendet am: Mittwoch, 29. Januar
>>>> 2003 11:10
>>>> > > An: hardware at doepfer.de
>>>> <mailto:hardware at doepfer.de>;
>>>> technik at doepfer.de
>>>> <mailto:technik at doepfer.de>
>>>> > > Betreff: A-111 problem? (PW affects
>>>> Frequency)
>>>> > >
>>>> > > Hi,
>>>> > > I have a problem with several of my
>>>> A-111 High-End VCOs:
>>>> > >
>>>> > > The pulsewidth (both PW knob and PWM
>>>> input+knob) affects the frequency
>>>> > > of the oscillator. I.e., when
>>>> turning the PW knob or PWM modulating with
>>>> > > a slow LFO, the frequency makes a
>>>> clearly audible change.
>>>> > >...
>>>> >
>>>> >Dear Mattias,
>>>> >I forward your inquiry to our A-111
>>>> specialist Matthias Marass
>>>> >(mailto:keyboards at doepfer.de
>>>> <mailto:keyboards at doepfer.de>). He is
>>>> responsible
>>>> >for the final tests and repairs
>>>> >of the A-111. He will answer you directly.
>>>>
>>>> At 15:36 2003-06-11, Döpfer
>>>> Musikelektronik - Keyboardservice wrote:
>>>> Dear Mr. Rickardsson,
>>>>
>>>> the influence of the external and
>>>> internal PW
>>>> control voltage to the oscillator
>>>> frequency is a
>>>> problem of nearly 80..90% of the
>>>> CEM3340 we ever
>>>> used. Unfortunately there is no chance
>>>> to repair
>>>> this problem. The only way would be a
>>>> strict
>>>> selection of the CEM3340 circuits.
>>>> ...
>>>> Best regards,
>>>> Matthias Marass
>>>> keyboards at doepfer.de
>>>> <mailto:keyboards at doepfer.de>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>> Den tors 19 dec. 2019 10:42Oakley Sound
>>>> via Synth-diy <synth-diy at synth-diy.org
>>>> <mailto:synth-diy at synth-diy.org>> skrev:
>>>>
>>>> > ... "So as a conclusion the goal
>>>> is to have on pin3 as close as
>>>> possible to -5V and the PWM to tune
>>>> error will not manifest itself."
>>>>
>>>> I did not find this to be the case
>>>> since I always run any 3340 circuit
>>>> from a precision 5V reference. The
>>>> solution for me was to get the
>>>> CEM3340 rev G. The CEM3340 has the
>>>> detune too, it's just that it is
>>>> quite small. I can't remember
>>>> exactly, but I think it's in the
>>>> region of
>>>> +/-1 cent. It would almost
>>>> certainly be there on the SH-101.
>>>>
>>>> Alfa's solution is to use the newer
>>>> AS3340-HYB. The other thing to do is
>>>> make your own triangle or saw to
>>>> pulse wave convertor from an op-amp or
>>>> comparator external to the chip.
>>>>
>>>> When repairing an OB-Sx I found
>>>> that the AS3340 did not work well as a
>>>> sub for the original CEM3340. Even
>>>> with the various resistor changes
>>>> required to get the AS3340 to work
>>>> properly, the VCOs in last three
>>>> voice card positions on the
>>>> motherboard displayed a very
>>>> audible pitch
>>>> instability at pulse widths at less
>>>> than 45%. Clearly, there was some
>>>> layout issue but although I tried
>>>> all sorts of things (including bus bar
>>>> 0V and liberal dousing of
>>>> capacitance) it wouldn't solve the
>>>> problem.
>>>> Again, the solution was to replace
>>>> all the VCOs with CEM3340 G.
>>>>
>>>> Tony
>>>>
>>>> www.oakleysound.com
>>>> <http://www.oakleysound.com/>
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>>
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