I have 2 sets of BEL Signal trans of the same type . They Produce mechanical buzz, low level but irritatingly audible.
From my experience playing with different DAC IC's (mainly TDA1504, and PCM1704, which were worth of any serious mention...):
I will elaborate just a bit on the low input impedance I/V stage.... it was only when I used AD811, as explained in the attached pdf, that I heard the real potential of those DAC ICs. So... have a read.... AD811 max Vcc/Vee is + and - 10V DC; also, they are current feedback ICs and as such, require a good PCB layout. But, all the trouble will be worth 100%. AD811 was able to provide the necessary gain, as well as the dynamic input impedance of close to 0, to make those DACs shine.
- do your best to provide as low as possible I/V stage input impedance.
- power supply regulation has to be of very low noise - today's day& age we have outstanding low noise LDO's; you must use the LT3045 & LT3094 if you are (once you become) serious about the result.
I will elaborate just a bit on the low input impedance I/V stage.... it was only when I used AD811, as explained in the attached pdf, that I heard the real potential of those DAC ICs. So... have a read.... AD811 max Vcc/Vee is + and - 10V DC; also, they are current feedback ICs and as such, require a good PCB layout. But, all the trouble will be worth 100%. AD811 was able to provide the necessary gain, as well as the dynamic input impedance of close to 0, to make those DACs shine.
Its important to note that Walt Jung's Rs (stabilization resistor) has a noise penalty. There might be lower noise ways of stabilizing CFB amps, for a suggestion see this paper : https://www.ti.com/lit/an/slyt081/slyt081.pdf
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The paper you attached uses Cf in its application... I did not use Cf; the important factor in obtaining stability was the very low impedance resistors I used as Rf. The measured performance was excellent; the subjective result was the best I heard (with 1704). This implementation provided the best-looking, true staircase output, after the I/V. This was my goal.
Also, the paper refers to IT ICs which I did not use/I do not have experience with. After a very quick glance, it seems that AD811 has lover noise / is much faster, compared to ICs the paper you attached discusses.
I know your I/V stages use inductors... same as the suggested paper you attached. I think this might be where you are coming from... not sure. I do not have any experience with your DAC. It seems it performs well and keeps many people quite happy.
The inductors I used when I was experimenting with I/V stages always provided inferior listening results, so much so that I discarded them altogether, compared to AD811 and low inductance resistors I used to obtain stability.
I moved to DDDAC after my experiments with 1704 and AD811 as I/V, only to realise that (after I spent a lot of money & time), when it comes to DIY and DAC design.... I had to go to the finished product to obtain what I was looking for. DDDAC was very good, though. Due to its very high current output, It allowed me to try just a single 33 ohm TX2575 naked Z foil resistor as an I/V, which sounded the best of all I/V solutions I tried.
Also, the paper refers to IT ICs which I did not use/I do not have experience with. After a very quick glance, it seems that AD811 has lover noise / is much faster, compared to ICs the paper you attached discusses.
I know your I/V stages use inductors... same as the suggested paper you attached. I think this might be where you are coming from... not sure. I do not have any experience with your DAC. It seems it performs well and keeps many people quite happy.
The inductors I used when I was experimenting with I/V stages always provided inferior listening results, so much so that I discarded them altogether, compared to AD811 and low inductance resistors I used to obtain stability.
I moved to DDDAC after my experiments with 1704 and AD811 as I/V, only to realise that (after I spent a lot of money & time), when it comes to DIY and DAC design.... I had to go to the finished product to obtain what I was looking for. DDDAC was very good, though. Due to its very high current output, It allowed me to try just a single 33 ohm TX2575 naked Z foil resistor as an I/V, which sounded the best of all I/V solutions I tried.
That's pretty much coincidental. The inductors being used in that paper are ferrite beads, hence lowish Q. In the filters I use, such low Q is a significant disadvantage. Where I'm coming from is - there may be ways to reduce the noise in Jung's circuit as described in your attached paper.
Incidentally AD811 is typical amongst other CFBs in the current noise department, which is the most relevant. As the paper says, CFBs generally have in the region of 15-20pA/rtHz and AD811 is no different.
Miro is currently working on one..Other 1541 dac board suggestions? (need USB and COAX spdif)
https://www.diyaudio.com/community/...st-tht-i2s-input-nos-r-2r.354078/post-7128519
I2S input only though I think
Russell, I would strongly consider Miro’s AD1862 DAC as one to consider. Sounds phenomenal and is super easy to build/implement. Also variations for PCM63, and others (soon tda1541, as Jimk mentioned). After implementing Zen IV, I happily sold off my previous ‘over the counter’ dac.
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Unfortunately he is now sold out and won't be ordering more. However, I just ordered 11 from Rochester Electronics (same distributor that Paddy used). I paid about $25 each and will sell them for the same $25 plus actual shipping. Also I have ordered Miro's PCB using his gerbers. I will have a couple extra if anyone wants a set. Drop me a PM if interested.
Cheers.
