[sdiy] as3340 PW/tuning issue
ColinMuirDorward
colindorward at gmail.com
Mon Dec 30 20:55:28 CET 2019
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> 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>
> 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> 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
>>> 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> wrote:
>>>
>>>> Yes, the original rev F CEM3340s in the JP-6 don't have this issue.
>>>>
>>>> Doug
>>>> synthparts.com
>>>>
>>>> On Saturday, December 21, 2019, 3:11:12 PM PST, ColinMuirDorward <
>>>> 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>
>>>> 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
>>>>
>>>> On Thursday, December 19, 2019, 3:12:35 PM PST, ColinMuirDorward <
>>>> 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>
>>>> 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>
>>>> 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>
>>>> 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> 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; 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). 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
>>>>
>>>>
>>>>
>>>>
>>>>
>>>> Den tors 19 dec. 2019 10:42Oakley Sound via Synth-diy <
>>>> 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
>>>> _______________________________________________
>>>> Synth-diy mailing list
>>>> Synth-diy at synth-diy.org
>>>> http://synth-diy.org/mailman/listinfo/synth-diy
>>>>
>>>> _______________________________________________
>>>> Synth-diy mailing list
>>>> Synth-diy at synth-diy.org
>>>> http://synth-diy.org/mailman/listinfo/synth-diy
>>>>
>>>>
>>>> _______________________________________________
>>>> Synth-diy mailing list
>>>> Synth-diy at synth-diy.org
>>>> http://synth-diy.org/mailman/listinfo/synth-diy
>>>>
>>>>
>>>>
>>>> --
>>>> https://www.instagram.com/colinmuirdorward/
>>>> -
>>>> <https://www.instagram.com/colinmuirdorward/>
>>>> https://www.instagram.com/ssdp_synthesis/
>>>>
>>>>
>>>>
>>>>
>>>> --
>>>> https://www.instagram.com/colinmuirdorward/
>>>> -
>>>> <https://www.instagram.com/colinmuirdorward/>
>>>> https://www.instagram.com/ssdp_synthesis/
>>>> _______________________________________________
>>>> Synth-diy mailing list
>>>> Synth-diy at synth-diy.org
>>>> http://synth-diy.org/mailman/listinfo/synth-diy
>>>>
>>>> _______________________________________________
>>>> Synth-diy mailing list
>>>> Synth-diy at synth-diy.org
>>>> http://synth-diy.org/mailman/listinfo/synth-diy
>>>>
>>>
>>> _______________________________________________
>>> Synth-diy mailing listSynth-diy at synth-diy.orghttp://synth-diy.org/mailman/listinfo/synth-diy
>>>
>>> _______________________________________________
>>> Synth-diy mailing list
>>> Synth-diy at synth-diy.org
>>> http://synth-diy.org/mailman/listinfo/synth-diy
>>>
>>
>>
>> --
>> https://www.instagram.com/colinmuirdorward/
>> -
>> <https://www.instagram.com/colinmuirdorward/>
>> https://www.instagram.com/ssdp_synthesis/
>> _______________________________________________
>> Synth-diy mailing list
>> Synth-diy at synth-diy.org
>> http://synth-diy.org/mailman/listinfo/synth-diy
>>
> _______________________________________________
> Synth-diy mailing list
> Synth-diy at synth-diy.org
> http://synth-diy.org/mailman/listinfo/synth-diy
>
--
https://www.instagram.com/colinmuirdorward/
-
<https://www.instagram.com/colinmuirdorward/>
https://www.instagram.com/ssdp_synthesis/
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://synth-diy.org/pipermail/synth-diy/attachments/20191230/cc8ab12d/attachment.htm>
More information about the Synth-diy
mailing list