If you can read the mult-tone chart above correctly then you will know what I was talking about. If not, sorry, you are still not there yet.
Again, it is not about slow or fast feedback, it is the phase shift on different frequencies.
I always find this amusing... people all talk about showing me the measurement numbers to prove the machine is good yet most of them can not read the measurement results correctly.
That's present in every single multitone I see produced by an AP. It depends on how many FFT bins the tone lands in. It could be the generator for all I know. Seems more likely to me to be the signal source, FFT window, or any other number of factors depending on how AP actually does this test. If you could be more clear about what you are actually proposing it would help.
Well, it seems they are doing windowless FFTs with AD/DA clock sync.
Are you proposing there are non-harmonic components if you take an FFT at 100 Hz?
Are you saying the first pole placement is causing "phase noise" here?
Well, it seems they are doing windowless FFTs with AD/DA clock sync.
Are you proposing there are non-harmonic components if you take an FFT at 100 Hz?
Are you saying the first pole placement is causing "phase noise" here?
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What are you reading into the lack of sharp lines? There's a simple reason they're wider at LF, the FFT bins are a fixed number of Hz wide and the plot (actually a histogram for FFT) is logarithmic. Hence the number of bins per cm along the X axis decreases as the frequency decreases.
Here is the shared shopping cart at mouser.com
Mouser Electronics
Attached is the BOM in Excel/ZIP format. Part locations are shown in the comment column.
Standard disclaimer - I am not responsible for any damage done to the machine as well as any hazard brought up by the mod. There is no guarantee the change on sound quality will meet your expectation either. In other words, you are doing the mod at your own risk!
Thank you finneybear, I really appreciate it. I expect I'll just go ahead and order everything from Mouser and then figure out where everything goes.
No problem on the disclaimer. I know that I'm taking a chance whenever I work with SMDs.
As long as you have adequate magnification you'll be fine. That is the number one aid to SMT soldering.
Yes, scaling in the chart is one factor. What you have to look at is the bottom opening is wider than the scale. Also look for extra spikes around base frequencies. After you compare many multitone charts then you will find the patterns.
The OP is optional. If you want bright sound with sharp image, you can keep the original OPA1612. If you like full smooth sound, wide stage by sacrificing the details a bit, the Muses will be a good choice. There are many other good options. Just remember dont swap the OPs too many times as the solder pads can get damaged.
Just stopped by the ASR forum earlier tonight in a long while. They talked about bad soldering around OPA2140. Mmmm... cant see how this would lead to the auto stand-by problem but it will be a good idea to reheat the OP's legs anyway, just to be safe.
If you run into any problems just post them here. Usually I would come here once a week. Dont rush the work.
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Thanks finneybear! I'll check out all of the above. I'll get a muses because I may like it but I'll check out the 1612 very well first. I definitely don't want to mess up the traces and I've read that many boards can't take much rework.
After I get the parts I check them against my notes/pictures to identify where they go. I'll be back if/when I have questions.
Thanks again.
I don't understand what you are trying to say. A log plot is hard to interpret for things like distortion. The multitone plot can be useful except many of the HD and IM products fall on other source tones making it all harder to interpret.
I would only get meaning if it starts with a reference plot showing what you would see without the DUT. Digital in and analog out make that more difficult. You also need to know what the noise floor looks like to be sure you aren't attributing artifacts to the DUT that are in the noise floor of the analyzer.
Also without knowledge of the sample rate, FFT resolution, the windowing etc. its really hard to make comparisons. The FFT of a 1 KHz tone on a modern opamp will usually be limited by even the best analyzer. All the chip vendors use a technique increasing the noise gain to get meaningful distortion plots. The plots you showed were definitely not opamp limitations. Virtually all analyzers have their best performance at 1 KHz and 3V in. Compromises in the design of analyzers will degrade above and below that frequency. Its not necessarily a reflection on the opamp if you get different results at other frequencies. I would expect harmonics of -130 dB or less for a closed loop gain of 10 for any premium opamp designed for this application. The high harmonics in the FFT are from some other source (the DAC?).
I agree with you on the AKM sound signature. To me it's simply smooth and silky. My primary listening is done using a RaspPi HAT DAC based on an older AKM4490EQ chip. I love the sound of it - at least in my system. My only 'upgrade' is I'm using an external linear PSU.
I also bought the Topping DX3 Pro for the latest dual-mono chip design, so I'm watching/following this thread with interest. While I like the ESS chips, I keep coming back around to the AKM44xx series DACs.
The Khadas Tone Board has some promise as well, and I'm waiting for their host SBC board for testing and possibly building an all-in-one, network based streamer using roon.
I try to consolidate your mod within this spreadsheet, it seems the lpf part is not consistent between two of your post, also I cannot find some parts to change in bom, could you please help us to correct it? Thanks.
Attachments
Nevermind! I found it. Ingenious design!
For those who care: two screws are removed from the back with a 2mm hex wrench. Then a long 2mm hex wrench is fed through these holes, where the screw was removed, and pushed all the way to the front of the unit. There is a 2mm hex nut on each side that is then removed.
The front can be slide partially out at this point, however, removing the nut that holds on the bluetooth antenna will allow the whole unit to be removed.
Putting it back together is a bit more fun.
In the US, a long hex wrench can special ordered from Home Depot for less than $4.00.
from Finneybear's Mouser BOM:
Mouser Electronics
Isn't this the cap?
HZA107M025X16T-F Cornell Dubilier - CDE | Mouser
Is it possible to remove all those 8 caps completely? If use the original OPA1612..
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