Hi,
I'm putting together a pre-amp and would like to build the volume- and balance-control with a digital controlled potentiometer.
The plan is:
A digital optical encoder is used to provide an Atmel µ-controller with input. I found a nice one, named "Grayhill 62AD11-02-020C".
The Atmel in his place sends data to a PGA2311 (digital controlled analog pot).
datasheet Grayhill series62
Has anyone ever build something alike? Any tips, warnigs, alternatives?
Thanks for the input.
I'm putting together a pre-amp and would like to build the volume- and balance-control with a digital controlled potentiometer.
The plan is:
A digital optical encoder is used to provide an Atmel µ-controller with input. I found a nice one, named "Grayhill 62AD11-02-020C".
The Atmel in his place sends data to a PGA2311 (digital controlled analog pot).
datasheet Grayhill series62
Has anyone ever build something alike? Any tips, warnigs, alternatives?
Thanks for the input.
i built something like this, but because of costs with mechanical encoder and PIC instead of atmel. http://home.tu-clausthal.de/~tpa/PGA/index.html
And the Apox3 will be like this but in more complex http://www.apoxcontrols.com/apox3.htm
And the Apox3 will be like this but in more complex http://www.apoxcontrols.com/apox3.htm
I built one with 64 steps, -80dB attenuation, and an ATmega8 micro, with a Grayhill rotary encoder. Seems very similar to your idea.
http://www.diyaudio.com/forums/showthread.php?s=&threadid=17442
Search the forums for "relay attenuator" if you want the encyclopedia.
http://www.diyaudio.com/forums/showthread.php?s=&threadid=17442
Search the forums for "relay attenuator" if you want the encyclopedia.
? for me it works. Whats broken? http://home.tu-clausthal.de/~tpa/PGA/03.asm
maybe you need to dl with "safe target as" in case you browser doesn´t show the .asm file.
maybe you need to dl with "safe target as" in case you browser doesn´t show the .asm file.
1k is a typical number for flash, 1 mil. for EEPROM. At least with the pic its nonsense to write the balance information into flash - with most PICs not possible i think.
As you see in my code, i don´t use balance (but its not the big problem to make code for this funktion), but i write the volume setting to the EEPROM, so the chip remembers when powered up next time the old volume setting. This is writen every time the user changed the volume and then leave it unchanged a moment. I did not reach the million until now...
As you see in my code, i don´t use balance (but its not the big problem to make code for this funktion), but i write the volume setting to the EEPROM, so the chip remembers when powered up next time the old volume setting. This is writen every time the user changed the volume and then leave it unchanged a moment. I did not reach the million until now...
Control question. Just out of the blue, instead of using a rotary encoder which has somewhat a weird feel to it (I'm referencing to the non stop relative action, and also to the non linearity of the encoder after a year or two of abuse), why not use a log pot with one of the A/D Converter pin of the microcontroller. Something like the ATmega16. This would have the advantage of having a good tracking, very nice sound control through digital pots and better than average feel. The pot only needs to be fed 5V and the microcontroller will convert the value between 0 at 0V (pot full ccw) and 1024 at 5V (pot full cw). Since the PGA only requires 8 bits, you could always dump the two least significant bits and obtain a straight value from 0 to 256.
For an even better volume control, you could always unse a linear pot and calculate the log value with a true log function in the microcontroller...
As for balance and other controls, you could use that rotary encoder on a separate line. This would allow the volume to be adjusted anytime.
I'm not even close to starting on my preamp which will have this idea implemented (must finish the speakers, the gainclone and all those other projects first) but If someone has ideas in this general direction that would be interesting. (not trying to hijack your thread rho, just trying to pitch ideas in)
Hope this helps!
Sébastien
For an even better volume control, you could always unse a linear pot and calculate the log value with a true log function in the microcontroller...
As for balance and other controls, you could use that rotary encoder on a separate line. This would allow the volume to be adjusted anytime.
I'm not even close to starting on my preamp which will have this idea implemented (must finish the speakers, the gainclone and all those other projects first) but If someone has ideas in this general direction that would be interesting. (not trying to hijack your thread rho, just trying to pitch ideas in)
Hope this helps!
Sébastien
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do we talk about the same kind of device?
I started using a MC and no ADC anymore because of the disadvantages of pot+ADC. The first volume control i made with ADC0804 and relais like in alephp1.0
The disadvantage is the unstable ADC, what makes the volume change at the lower bits. Also a pot is sensitive to vibration - very important in case you play at real volume levels. Also its possible to tune volume with very high resolution, as you have you dB range one 2800° instead of 270° for a normal pot.
Also there is no need for motor pot in case you implement a remote control with a incremental encoder.
As I mentioned in my previous post, I've not actually done it, I'm merely suggesting it. I searched and did not find any similar solution on the web so I figured there might be something wrong with it or nobody ever considered it a good idea.
The non linearity I experience are from a Klipsh Pro Media 5.1 Control pod. If you turn the volume too fast or too slowly, it will behave very weirdly. Sometimes, I hover around 20 and want to get it to 25 and end up at 50+ in a fraction of second and back to 0 the next... anyway, I find it suboptimal.
For the vibrations, if we simply put a heavier button on the shaft, it should reduce the problem. Also you could lower the refresh rate of the A/D Converter. If it takes a read every 50ms or so, vibrations should not be recorded. By dumping the two lower bits, you could minimize the vibration effects also.
The remote control point is valid though... with the rotary encoder, it is easier to implement. As for precision, this is dependant on your needs, I don't need more than these 300d, but I reckon it could be useful. Although you're still limited with the 256 steps of the digital pot... this is less than 1 per degree of rotation...
Sébastien
The non linearity I experience are from a Klipsh Pro Media 5.1 Control pod. If you turn the volume too fast or too slowly, it will behave very weirdly. Sometimes, I hover around 20 and want to get it to 25 and end up at 50+ in a fraction of second and back to 0 the next... anyway, I find it suboptimal.
For the vibrations, if we simply put a heavier button on the shaft, it should reduce the problem. Also you could lower the refresh rate of the A/D Converter. If it takes a read every 50ms or so, vibrations should not be recorded. By dumping the two lower bits, you could minimize the vibration effects also.
The remote control point is valid though... with the rotary encoder, it is easier to implement. As for precision, this is dependant on your needs, I don't need more than these 300d, but I reckon it could be useful. Although you're still limited with the 256 steps of the digital pot... this is less than 1 per degree of rotation...
Sébastien
software problem. The software needs to sort out errors coming from the encoder. It all depends on how long you optimize your firmware to be stable in extrem situation like fast turns at encoder. I did not know Klipsch has worse firmware coders than me...
Take a look at the alephp 1.0 manual - 2 LSB are dumped. But 6 bit resolution is not really enough (for me) and the 3rd isn´stable everytime also... Ok you can live with this. I desiced to use the 8 Bit relays version as it tastes best for me - at the moment. http://home.tu-clausthal.de/~tpa/relais/index.html
This is also the version i recive much more emails and requests for preprogrammed MCs...
You could build my PGA VC for less than 20€ parts and the relays VC for less than 50€ and test it.
There are plenty - Apox, some people in this board build VCs - every modern car radio i know - www.schuro.de - http://www.mhennessy.f9.co.uk/preamp/ - older PGA threads like http://www.diyaudio.com/forums/showthread.php?threadid=10817
Well you know where to look for your next job
Actually the atmel offers 10 bit A/D so I was implying a loss of 2 bits so to get an 8 bit signal... clearly dropping to 6 bits might be a bit far fetched.
I meant a potentiometer control... all those use rotary encoders if I'm not mistaken.
I would order from you but then again, I'm a DIYer so, sorry about the lost business, I really hold to the point of doing it myself.
Thanks for the reply!
Sébastien
sorry, so i missunderstood you. I thought reverse way.
Its no business for me. I don´t earn money with this. The code is published and everyone is free to use it. For those DIYers who don´t have acess to a programmer, i offer to send them programmed chips - for what the chip costs me + all shipping costs and envelope, international letter 10€ für one PIC.
I don´t sell the other parts, they are cheap at you local dealer. Will be not more than additional a PGA free sample and < 10€ parts, or little more for the realys version as 8 or 16 relays do cost some money (about 2€ each at schuro)
In fact i only made this project because i try to diy as much as possible and the Apox was to expensive and complex to my taste.
Also everyone is welcome to help at the next code revision.
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