[sdiy] as3340 PW/tuning issue
ColinMuirDorward
colindorward at gmail.com
Fri Jan 3 02:47:47 CET 2020
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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>>>>>>
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