Is the AS3320 audibly noisy?

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AuFX
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Is the AS3320 audibly noisy?

Post by AuFX » Sun Sep 06, 2020 10:37 am

I finished up a AS3320 VCF and it sounds and works great.

Only bad thing is that it seems quite noisy, this noise is attenuated by closing the filter.
Is this typical or could there be some other issue at play in my circuit?
Last edited by AuFX on Sun Sep 20, 2020 10:09 am, edited 1 time in total.

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forestcaver
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Re: Is the cem3320 audibly noisy?

Post by forestcaver » Sun Sep 06, 2020 1:11 pm

It’s not noisy (as3320 anyway). I’ve designed a few modules with them and it’s not at all noisy!

AuFX
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Re: Is the cem3320 audibly noisy?

Post by AuFX » Sun Sep 06, 2020 1:37 pm

forestcaver wrote:
Sun Sep 06, 2020 1:11 pm
It’s not noisy (as3320 anyway). I’ve designed a few modules with them and it’s not at all noisy!
ok thanks for the info, the only thing it might be that I know of of is that it's using 220k resistors like the datasheet when apparently they should be 180k for a 12V supply.

im also using the as3320

Just to be clear, it's dead silent with no input signal for you?

KSS
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Re: Is the cem3320 audibly noisy?

Post by KSS » Mon Sep 07, 2020 12:08 am

Need to know thw circuit you're using to accurately answer your question. And your power supply, distribution and other gear.

Otherwise the answer is yes, the 3320 can be noisy. And no, it is not a noisy chip. Take your pick.
Treat utility modules as stars instead of backup singers.

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AuFX
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Re: Is the cem3320 audibly noisy?

Post by AuFX » Tue Sep 08, 2020 7:06 am

KSS wrote:
Mon Sep 07, 2020 12:08 am
Need to know thw circuit you're using to accurately answer your question. And your power supply, distribution and other gear.

Otherwise the answer is yes, the 3320 can be noisy. And no, it is not a noisy chip. Take your pick.
sorry, I thought I replied earlier but must've forgot to hit send.

It is the standard cem3320 datasheet lowpass circuit, except with 12V supply and 1.2k for Ree, the filter was tested on it's own.
Unless using 220k instead of 180k resistor is causing it I'm suspecting it could be the power supply, which is linear power supply board from ebay.

AuFX
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Re: Is the cem3320 audibly noisy?

Post by AuFX » Tue Sep 15, 2020 1:44 pm

I tried pretty much everything and the noise remains exactly the same:
Tested a different power supply entirely,
Changed 220k resistor to the correct value of 180k,
Added extra decoupling caps as close as possible directly on the chip's power pins (as it had much more severe noise when no decoupling at all were used),
Grounded res and cutoff cv inputs to see if they might be picking up noise,
Replaced AS3320 with a new one in case of a faulty chip.

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Re: Is the cem3320 audibly noisy?

Post by KSS » Tue Sep 15, 2020 2:13 pm

Where did you buy the resistors?
What kind of capacitors are you using?
Is this on a wite plastic breadboard or PCB?
If PCB, it is SMD or TH?
If PCB, where did the layout come from?

Can you define "noisy" better?
Treat utility modules as stars instead of backup singers.

Treat power supplies like Rockstars instead of roadies!

AuFX
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Re: Is the cem3320 audibly noisy?

Post by AuFX » Tue Sep 15, 2020 2:42 pm

Resistors are from mouser, 1% thin film.
Signal capacitors are PPS (SMD) + Polyester , electrolytic + ceramic for decoupling caps.
It's on a PCB from JLCPCB made be me , 90% SMD,
There are no faults in the PCB schematic, everything is connected where it should after thoroughly checking many times

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Re: Is the cem3320 audibly noisy?

Post by KSS » Tue Sep 15, 2020 5:19 pm

Thanks for the added detail.

Seems the only thing left -that would affect noise- is PCB layout.

That and the rare but not impossible PCB fault in mfg.

Am assuming you've cleaned the PCB of excess flux unless no-clean was used? That can be a factor if you've used TH filter caps.

Alfa's normally pretty responsive in threads where their chips are discussed. I wonder if they'd have any feedback for you?
Treat utility modules as stars instead of backup singers.

Treat power supplies like Rockstars instead of roadies!

AuFX
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Re: Is the cem3320 audibly noisy?

Post by AuFX » Sun Sep 20, 2020 8:06 am

I dont know much about PCB layout... everything was just laid out so that it had the shortest possible traces.
Pretty sure there is no mfg error.

Im still not sure how quiet the as3320 actually is, the datasheet does not give a figure, nor does Cem3320 datasheet.
Regardless, in normal use the VCA attenuates everything until an envelope is triggered and the VCO is loud enough that the noise is fairly well masked, so in the end it's not a huge deal

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Re: Is the cem3320 audibly noisy?

Post by KSS » Sun Sep 20, 2020 10:04 am

You might should change the thread title to reflect the actual discussion is about the AS3320, not the CEM3320. Again, that might also get Alfa to respond in-thread as they've done in several other threads where their products were brought up.

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