Rushing to sleep (working tomorrow morning), so I'll be short.
Originally Posted by cobaltmute
Take a look on Pg 7 of the LT1033 datasheet. There is way to make your LM317/337 supply dual tracking there using one pot and two resistors instead of two pots.
Everywhere I've read lately comments on the fact that you shouldn't use the caps after the zener/follower supply. Obviously though this could be a choice to not install the part.
The jumpers are going right into the middle of the TPA? Hate to have to install them.
Wouldn't it be better to have the control pins for the DS1802 on a header block? I'd have them further away from the part to have the option at least.
- Interesting trick, I might use it... The main interest in my view would be to save a pot Dual tracking is nice for discrete designs with sensitive operation points, not really necessary for opamps imo.
- Any reason given for that ? Such stabilizers (one cannot really speak of regulators) are as old as npn transistors and zeners and I've always seen them with caps on the output.
- Ideally, they would be thick, twisted wires going flat under the board, soldered bottom side and carefully trimmed components side. I tend to design pcbs with "extra layers" in the air.
- Very good point and easy enough, I'll push them away. I'm a penny pincher, I solder everywhere I can rather than using connectors. It's not a good habit, I'm wasting time because of that.
Originally Posted by holland
curious if it would be advantageous to keep the signal differential and have the TPA6120 perform the conversion after the pot. I don't know if the DS1802 can be chained in that way, one for each channel.
one other curiosity, as I've been meaning to play with this myself, is similar to what audio-gd does. that is use the pot for I/V, following a current amplifier. DAC->current amplifier->I/V pot->buffer.
- This is the line of reasoning I've followed in my current DAC (well, the one that's broken until I get a new USB-I2S converter). However, there is one catch: you must usually drive the balanced receiver (the tpa6120 in this case) from a low impedance. Thus, the chain looks like this: DAC - I/V opamp - volume control - buffer - balanced receiver. An alternative is to use the pot in between the two phases (as a rheostat) but the ds1802 cannot be used that way. Another possibility is to use a balance receiver presenting a high input impedance, which is what I'm using based on a suggestion of PRR. See this thread (bottom of the page): http://gilmore2.chem.northwestern.edu/ubb/showpage.php?fnum=3&tid=7616&fpage=1 and http://www.head-fi.org/forum/thread/85561/post-pics-of-your-builds/7530 . The PCB in this thread are safer, more conventional options.
- The good old current conveyor... The practical problem with that approach is to present a signal without DC offset to the pot, or they get scratchy.
PS: I'm currently listening to the small dac I designed with Guzzler and my cheapie amp ( http://gilmore2.chem.northwestern.edu/ubb/showpage.php?fnum=3&tid=7773 )... Honnestly, considering how good this combo is, everything discussed here is well into the diminishing returns' realm. But it's fun to skin the cat in a dozen ways