[sdiy] as3340 PW/tuning issue
Pete Hartman
pete.hartman at gmail.com
Fri Jan 3 03:12:38 CET 2020
If I had a dollar for every time I did that or something similar, I'd be
able to do this stuff for a living :-D
Pete
On Thu, Jan 2, 2020 at 7:49 PM ColinMuirDorward <colindorward at gmail.com>
wrote:
> Ooops, it's just an artifact of setting my scope to ac coupled input.
> Sorry folks.
> Colin
>
> On Thu, Jan 2, 2020 at 4:48 PM ColinMuirDorward <colindorward at gmail.com>
> wrote:
>
>> Is it a shortcoming of all my 3340 designs, or is PWM supposed to do a DC
>> offset, as well?
>> So at the smallest duty cycle, I get 0 to +10v, and at the other end, I
>> get 0 to -10v.
>> At 50% duty is -5v to +5v.
>>
>> Sorry to drag this thread out...
>>
>> Colin
>>
>> On Mon, Dec 30, 2019 at 1:15 PM klangbau <sauterw at web.de> wrote:
>>
>>> 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> 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
>>>>>>> _______________________________________________
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