[mojo]

I feel compelled to post an old project of mine:

http://www.head-fi.org/forums/f6/usb...5/#post4034939

It all works perfectly now, including the Winamp plugin. I am looking at doing a new version using an LCD though. Might look at adding source selection too, or possibly a motorised pot but I think the IC is probably more accurate and of course it can change volume instantly.

I was looking at doing kits but the problem is that one of the ICs is not available in a DIP package so I have been looking at other options.

 

[Fuzzy OneThree]

Just finished my Millet Hybrid Starving Student

 

[linuxworks]

Quote:

Originally Posted by mojo /img/forum/go_quote.gif It all works perfectly now, including the Winamp plugin. I am looking at doing a new version using an LCD though. Might look at adding source selection too, or possibly a motorised pot but I think the IC is probably more accurate and of course it can change volume instantly.

want to share code?

I have the lcd stuff working just fine on the arduino. the IR reading works well (sony only, so far) and local buttons are also easy. all the basics are there. I just need to interface to the PGA (or relays) for the real-world connection.

Quote:

I was looking at doing kits but the problem is that one of the ICs is not available in a DIP package so I have been looking at other options.

which?

 

[mojo]

Quote:

Originally Posted by linuxworks /img/forum/go_quote.gif want to share code?

Sure, it will all be GPL when I am finished anyway. I'm away from home at the moment though so it will have to wait until I get back.

Quote:

I have the lcd stuff working just fine on the arduino. the IR reading works well (sony only, so far) and local buttons are also easy. all the basics are there. I just need to interface to the PGA (or relays) for the real-world connection.

The PGA is really easy to use. As for IR stuff, I was planning on having it learn codes by itself for universal compatibility. A rotary encoder will provide manual control.

Quote:

which?

The TPS60403. I'm not sure what I will replace it with. Power is very important for audio quality... Probably the best thing would be to use a dual +/-5V supply, but it would be nice to allow it to be USB and single +5V powered as well. I think what I might do is make the PSU a separate board, and then offer a reference design. That way anyone can use their own PSU and tweak to their heart's desire.

 

[linuxworks]

from what I can tell, the 5v version of the chip might be easier to integrate than the 12v version. if you have a 12v source, you can always derive dual-5 from that and still not resort to 'switching'

 

[mojo]

Quote:

Originally Posted by linuxworks /img/forum/go_quote.gif from what I can tell, the 5v version of the chip might be easier to integrate than the 12v version. if you have a 12v source, you can always derive dual-5 from that and still not resort to 'switching'

I am using the 5V version. Line levels are only +-2V anyway. That is a very good idea though... 10V might be better though, and if you wanted USB power as well then it would mean having to build in power switching.

Other options include using the pin compatible CS3310, which is supposed to be even better than the already pretty good PGA chip, or using an entirely passive attenuation method. I already mentioned a motorised pot, but a set of switched (e.g. relays) and resistors could be used, especially if you are only going to need a relatively small range of attenuation values for ReplayGain. You could be clever and use a ladder to get any value but more resistors means more noise. The nice thing about these methods is that the audio side can be completely isolated from the digital stuff and noise becomes almost a non-issue.

Another interesting option would be to use an op-amp with a digital pot to set the gain. That's basically what the PGA/CS chips are, but you could use a separate op-amp to give people the choice of which one they prefer to use.

 

[adamus]

Remote controlled, unity gain buffered preamp. Uses an R2R network for the the volume control, vishays in the signal, 64 steps.

for the buffers the pedja rogic buffer cicuirt, but may try the pass labs buffer b1 in there. There is a good quality discrete regulator in there for the +/- 15v for the buffers.

Shaeffer (euro FPE) used for the faceplate. the two knobs on the right will have the same surround as the power knob, but i need to figure out how to extend the shafts, or reduce the depth of the knobs... ideas welcome.

 

[rhys h]

Nice pre Adam.

To reduce the depth of the knobs, you could allways get them on a metal lathe.

 

[adamus]

cheers rhys, looking forward to trying the b1 in it too.

 

[rhys h]

You know what, ive organised the bloody group buy for the B1 now im switching my system over to balanced.

Time to think of a new volume control...

 

[adamus]

try BBP on diyaudio forums, i got the R2r from him, and its cheap to make it balanced (just another relay board, adds another $20 or so. that and 2 B1's wouldnt be that expensive.
The only issue with the r2r is the current draw, it needs @5v it wants 0.5amps for the relays.

 

[rhys h]

Thanks, i will take a look. The current draw isnt really a problem. The problem is i dont really want to start paying for panels etc. I may stick with the digital volume control on the squeezebox for now...

I am selling the gamma so i can get hold of a dacmagic, too lazy to build an opus (i need the balanced outs).

 

[rhys h]

Adam, problem solved with the volume control.

 

[mojo]

The only other issue with R2R is that it has to be switched some way. If you have a manual volume control that is usually fine, but it can be more of an issue if you want to do it digitally and instantly (so it can be done between changing tracks on the PC for ReplayGain). It's something I'll look into though.

 

[linuxworks]

more talk of volume controls

I changed my lcd for one with a backlight. it was surplus from my local junk store.

there is now a new UI that I'm trying out; input selector name on top left, attenuation in DB on top right and volume 'graph' on bottom line.

as you change inputs, the 'memorizes' the last value you used for that input and restores it.

at power up, it restores the last input and last volume for that input (as you'd expect).

still no active volume element - just playing around with pure code right now and tinkering with different user interface styles.