Good point.
I any case, with the Modi 3, I am now leaving the DACs category of tens of dollars, and entering the category of hundreds
I am not doing this happily, but simply due to necessity - the DACs in the tens category did not do a good enough job.
Evidence? How did you get to that conclusion? How sure are you that your 'hundreds' DAC will be good enough?
Don't get me wrong - I would've been really happy to find a tens DAC that is good.
Regarding how:
I bought and listened to several ones.
I must say that i did not cover all possible options, far from that.
There may be a very good one (or ones), that I just don't know of.
I wish I did, I tried asking here in the forums and getting the most info I could before I bought.
The nicest option in the tens category DAC that I found, is Behringer UCA202.
Amazon.com: BEHRINGER U-Control Uca202 Ultra Low-Latency 2 In/2 Out Usb/Audio Interface With Digital Output: Musical Instruments
It costs 30$, and would've been a wonderful DAC if it did not do that Bass Enhancement that it does.
Like I wrote in the beginning of this thread,
for people who have small speakers which lack on bass, this bass enhancement will be great.
But for people with bigger and more quality speakers, this bass enhancement is not needed, and actually disturbs.
If only they included a small switch, for selecting Bass Enhancement On/Off, that would've been a terrific DAC.
Actually this is the sad part.
I cannot be sure.
I read reviews, and compared several different options,
according to who designed and created the DAC, what the circuit contains, and more things like that,
and then took a gamble..
I hope that the Modi 3 will be as good as people reviewed it.
Do you have any DAC in the tens category that you can recommend?
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Sowter suggest their customers prefer the sound with the load resistor on the secondary.
So far I've used a 50R I/V resistor on the primary and the secondary direct to a 50k Alps pot.
Yes, I agree that this method, the transformer is not doing the I/V conversion on its own.
I've not yet experimented with adding a resistor in parallel with the pot.
(the above was with dual TDA1541s in balanced operation to cancel out the 2ma dac output offset.)
Thanks for pointing that out, I've so far been content that the experiment is producing sound. I've wound the trafo for the least possible leakage inductance, I'll see what kind of frequency response I'm getting sometime in the coming week. The load impedance seen by the DAC isn't a pure resistor in my case because I'm also using a passive LP filter for anti-imaging. LTspice modelling will doubtless tell me what's going on, once I've characterized the trafo.
That's an interesting data point. Perhaps its due to the LP filtering effect brought about by the transformer leakage inductance @MarcelvdG has just mentioned?
Do you have any DAC in the tens category that you can recommend?
If your figure means a DIY DAC with just the cost of parts included, then I'm working on a design in the low double digit $ that of course I'll happily recommend
Quite possibly and they promote the use with balanced dacs so any unwanted common mode noise will cancel out thanks to the bifilar windings.
Thank you.If your figure means a DIY DAC with just the cost of parts included, then I'm working on a design in the low double digit $ that of course I'll happily recommend
I can solder as long as it is thru-hole components.. Soldering SMD components seems to hard, in my opinion.
Do you plan your PCB design to be thru-hole or SMD?
Yes that's my plan also, to run the DAC bias current through two anti-phase windings so the DC flux cancels out.
@spaceman5 - its going to be all SMD. The DAC chips are key to getting the lowest price and they're only available in SMD (SO-8). Have you tried building SMD? If not you might be quite pleasantly surprised, I'm a devotee myself, no going back to thru-hole.
@spaceman5 - its going to be all SMD. The DAC chips are key to getting the lowest price and they're only available in SMD (SO-8). Have you tried building SMD? If not you might be quite pleasantly surprised, I'm a devotee myself, no going back to thru-hole.
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SOIC (1.27mm pitch) are easy but .65mm SSOP are tricky and when I've used them, have needed to clean up the solder bridges with solder wick.
I use a croc clip to hold the item in place until I've soldered a couple of pins.
The best compromise is to use SOIC chips and through-hole passives.
No, it seems like suicide..
abraxalito and batteryman:
There's an easier way to do SMD.
Seeed Studio Fusion PCB Assembly - Turnkey Prototype PCB Assembly Service
They do even small quantities - it's regarded as prototyping.
It's cheap, and the quality you will get from a machine doing the soldering, will surely be better than a human doing it..
I'd be more worried about the effect of leakage inductance on DAC settling and distortion than on frequency response. Anyway, you can always correct for it with an RC network on the primary side or split the resistor between primary and secondary sides, if it should cause any problems at all.
Small addition:
and the rest of the components can be thru-hole.
That way you can solder them yourself,
and also change them easily during the development and improvement stages.
This is similar to how many kits are sold:
You get the pritned PCB with the SMD chip already soldered on it,
and you're left with thru-hole soldering only.
Note that you can PCB Print the board, and have the PCB Assembly service solder the SMD DAC chip onto it,
and the rest of the components can be thru-hole.
That way you can solder them yourself,
and also change them easily during the development and improvement stages.
This is similar to how many kits are sold:
You get the pritned PCB with the SMD chip already soldered on it,
and you're left with thru-hole soldering only.
My DAC has two 48-pin TQFP ICs (a DIX4192 SPDIF interface and an SRC4392 asynchronous sample rate converter) and two 80-pin SMD connectors for the FPGA board, all with 0.5 mm pitch. I soldered them all with a normal soldering iron and thin tin-lead solder, I didn't dare to try it with lead-free solder.
For the TQFPs I first tried to get everything properly aligned and one pin soldered on each side, then soldered the other pins. It is easier to remove excess solder with solder wick than to see whether a pin has solder at all (on a board with HAL finish), so it is better to apply too much than too little solder (once the TQFPs are aligned properly, that is). The connectors are somewhat easier because they have two plastic pins that fit into holes in the board to align them properly.
Afterwards I inspected each and every pin visually (I'm near-sighted, so I have built-in magnifying lenses) and with an ohm-meter and sharp needles. There were a few connector pins that didn't make good contact and needed to be resoldered.
Soldering TQFP packages is much easier with solder paste and a hot air soldering station, although that would probably melt the connectors.
There is one connector pin that still doesn't make any contact, the one used for selecting the halfband filter option. I never bothered to correct that because I don't like halfband filters anyway.
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I don't for a moment doubt that a machine solders orders of magnitude more consistently than I do. However it seems to exchange all the fun stuff (finding components at the best prices, assembling and soldering) for boring stuff (paperwork). Perhaps that's just me though.
OK
I hope that at least I have introduced you guys to a nice and useful service, should you ever need it.
And again, the nice thing about it is that you don't need to have a minimum of 1000 units, in order to be able to enjoy it.
By definition it is for prototyping. So they will respect you with every quantity you have, you just pay an initial 25$ setup fee.
My eyesight even with magnifier and shaky hands make even .65 pitch tricky for me. I am always worried about overheating the chip when correcting mistakes.
I am going to be using a SRC4192 but have opted for the development board which is pricey but does have buffered ins and outs + PLL low jitter clock generators as well as SPDIF in and out, dip switches for all the functions and on board 3.3v regulator.
The buffered I2S out will be useful for driving a short Cat 6E cable to the dacs and I might connect the relevant jumpers to switches for quick change of output bit depth so I can easily compare 16bit TDA1541 with 18bit AD1865 and 20bit AD1862.
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