[jtavrisov]

So I'm building a project with an integrated Cmoy amp inside. Only difference is that I don't want the potentiometer there for volume control. Instead I need a digital one that I can control via microcontroller.
 
Any opinions on the matter, this isnt a super hi-fi project so I don't need top of the line sound characteristics. Would a digital pot just be a drop in for the physical one?

 

[deltaydeltax]

Analog Devices makes some nice digital pots. I worked on a project many years ago where a digital pot was an option for replaced resistive pots. It was a short lived idea. The digital pots all had problems with "zipper noise" Each time a signal was sent to attenuate, or boost a signal, the pot made a "clicking" sound. If someone held down the up or down button for volume, these clicks were all strung together, and sounded almost like a zipper.
 
An option might be to use a digital pot, and a voltage controlled amplifier. You won't get zipper noise this way, but will get a noticeable attenuation or boost step. Unless you pick a digital pot with a high number of steps. The this step end up being very small, and not as noticeable.
 
Another problem, memory. The digital pot has to start somewhere. You'll need to find a way to set it up so the volume is blaringly loud. You may also not want your device to always start with no signal. Or, you may want it to always remember where you last left the volume set.
 
In any case, it's a fun project.

 

[jtavrisov]

Im a bit confused. First you said you used a digi pot but they all had zipper noise, but you solution was to use a digi pot. Forgive me if I'm simply misunderstanding.
 
As for memory, I don't really think its a super necessity but if its just a matter of code I think I can figure it out. I dont know exactly how these things work, been reading datasheets and such trying to find out something.

 

[Avro_Arrow]

The DS1802 has a zero crossing detector to prevent "zipper" noise.

 

[deltaydeltax]

My project ended up not using a digital pot at all. The cost of adding a VCA into the design was too great. For my own circuit, I'd go with a VCA.
 
I can't ever use a Maxim or Dallas Semiconductor part ever again. They bit me hard while working in the audio industry, and failed to deliver a million piece order. For a onesy twosy hobby project, they may be fine.

 

[jtavrisov]

DS 1802 is quite expensive but seems to be what I'm looking for. I don't quite understand what a VCA is and doesnt seem like a simple drop in circuit.
 
Any other (cheaper) alternatives. That digi pot is more than half of the cost of the entire amp section of my project.

 

[Avro_Arrow]

If you ask nicely, Maxim might send you a Sample.
 
Quote:

DS 1802 is quite expensive but seems to be what I'm looking for. I don't quite understand what a VCA is and doesnt seem like a simple drop in circuit.
 
Any other (cheaper) alternatives. That digi pot is more than half of the cost of the entire amp section of my project.

 

 

[jtavrisov]

dunno why I didnt think of that. I got the opamp as a sample (didnt plan on it but I needed a msp430 sample for school and figured hey might as well)

 

[Avro_Arrow]

You can use a level shifter like in the data sheet or you
can try a dual rail power supply like this:
 

 

[Avro_Arrow]

You could add a tacky "70's VU meter while your at it if you like...
 

 

[Reticuli2]

So the noises people complain about with the worst digital volume controls are only from when you adjust the volume, right?  This is not a present problem when the volume is left alone?

 

[Avro_Arrow]

I can't speak for all digital volume controls, but for DS1802, there should be no noise
even when changing the volume.

 

[jtavrisov]

Yea I had no noise when using the DS1802.
 
Which as an update to this semi-old topic, my project is more less complete but still stuck on a breadboard. I was unable to finish before classes started and now I have little time. I wasn't very happy with the end result, I'm thinking of redesigning and maybe making a dual version (two seperate headphone outputs). I would like to draw up a PCB as well but lol time and lol money.