Every time so far Jam tells me something that as an EE I find hard to believe, it always turns out to be right. Interesting, is all I can say.
I don't have the schematic handy to take another look, but, yes, those are close substitutes based on the specs of the diodes.
You're right, these are the diodes. But look at the mezzanine board. The D1..D4 diodes were supposed to be mounted on the edge of the board. Instead, they've mounted them where the C_X2, C_X3, C_X6, and C_X8 capacitors were supposed to go. This works because D1..D4 and C_X2, C_X3, C_X6, C_X8 are on the same traces... They might have planned to use C_X2, C_X3, C_X6, and C_X8 to get more capacitance, then realized that they did not need it, and they might have figured that mounting the diodes closer to the DAC chip would be better, or that mounting these SMD components so close to the mezzanine headers could create some problems during assembly... Not sure...
In any case, we now know what these diodes are...
And they have rainbow colors... Don't forget that... My kids love rainbows...
Rainbows have to make the resistors sound better. At least, that's what I'll tell my kids.
I just hope that they won't believe me...
Last edited:
You've been looking at the board far longer than I have... 😉
And so far, I was trusting the schematic. But no more...
I'll treat the board as the source of truth moving forward.
And I'll work as diligently as I can for us to get a trustworthy schematic.
If anything, this should be useful to anyone planning to use the AK4499EQ...
Last edited:
Diodes
Here is where the diode goes.
For reference purposes, I've picked the CRS09(TE85L,Q,M), because it was smaller than the other option recommended by Chris (thanks again Chris). The order of components on the PCB will match the one shown on the schematic (small capacitor closest to the DAC chip, diode furthest away, large capacitor in between).
Here is where the diode goes.
For reference purposes, I've picked the CRS09(TE85L,Q,M), because it was smaller than the other option recommended by Chris (thanks again Chris). The order of components on the PCB will match the one shown on the schematic (small capacitor closest to the DAC chip, diode furthest away, large capacitor in between).
Attachments
....listening longer, too 🙂
Hopefully, you're starting to collect some of the things you will need for that.
No Stereophile review yet, but ASR rates Benchmark HPA4 as slightly better measureing than the Neurochrome HP-1 here.
Massdrop THX 789 measures about the same as HP-1.
Well, I'm still on the fence regarding the headphones, trying to decide between the Audeze LCD-3 and the LCD-4. They have quite different requirements in terms of pre-amp, don't they?
Also, I am trying to figure out if the LCD-4z could be an option as well (no need for a pre-amp).
Fluke 116 is for HVAC use. They say it has low input impedance. Okay, found the manual where they say it also has a normal 10M input impedance mode.
Anyway, to measure caps usually requires disconnecting/unsoldering at least one lead from the circuit.
Last edited:
Jam says to use LCD-X. That's what he did most of the testing of the Pass Labs HPA-1 with, and also what I use.
Yeah... I'm not going to do that just quite yet. I think we'll have to trust the schematic on that one.
Well, that would save me quite a bit of money, which is always a good thing...
And in that case, the HPA-1 is pretty high on my list, if only for the homage to our friend.
I think I'll start with something "reasonable", like the LCD-X and a Massdrop THX 789. At $2,100, this combo is hard to beat. I'll train my ear on that, then upgrade to an HPA-1. Switching between the two pre-amps should help me appreciate the differences between switching power supplies and linear ones.
Before you do that, while it sounds very nice, I can hear more IMD in HPA-1 than I do in Neurochrome HP-1. (That seems to be part of the trademark sound of Pass Labs products, a little bit of low order HD for those who like it.) Anyway, Jam has an HPA-1 he might let you listen to, but you need to know what to listen for. For dac development, probably lower distortion is better since one might want to know how much distortion is coming out of the dac and not have it masked by another source.
Last edited:
Might make sense if you bring your Massdrop with you so you have something to compare with. Otherwise, how will you know where distortion is coming from, the CD recording, the dac, the headphones, etc.?