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Old 25th August 2019, 01:55 AM   #791
Markw4 is offline Markw4  United States
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Quote:
Originally Posted by chris719 View Post
I really don't think just because you alone think you hear something that this design should have to rule out DC-DC converters. This design is already not likely to satisfy your idea of audio perfection given the design goals and constraints already mentioned.
Sure, you're right. However, presumably the project is intended to produce better sound than could be obtained by simpler means using AK4497. I only strongly encourage the project manager here to setup the evaluation board with linear supplies, at least to begin with. He needs to have his own point of reference in order to decide for himself what performance above or below that he is willing to deem as acceptable. He wants to the final project to run from 5v. That should be doable (I think), but maybe some problems will have to be solved along the way to get it working satisfactorily. I know other people who have tried, and to my ears, failed at that with dac designs. But, I don't give up easily if I do decide to undertake to resolve a problem.

Last edited by Markw4; 25th August 2019 at 02:13 AM.
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Old 25th August 2019, 03:59 AM   #792
ishizeno is offline ishizeno
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Default Kit #6

Kit #6 is heading to Connecticut.
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Old 25th August 2019, 02:40 PM   #793
ishizeno is offline ishizeno
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Quote:
Originally Posted by Markw4 View Post
You can if you want. Two 1,200uf Oscons might be enough space allowance for whatever you eventually decide.
Mark, for the first schematic and PCB layout, I will do exactly what you recommended. Thanks!
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Old 25th August 2019, 02:41 PM   #794
ishizeno is offline ishizeno
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Default MELF Resistors

Following Jam's advice, I will look into using Vishay MELF resistors for some parts of the design.
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Old 25th August 2019, 03:19 PM   #795
ishizeno is offline ishizeno
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Originally Posted by ishizeno View Post
Following Jam's advice, I will look into using Vishay MELF resistors for some parts of the design.
I managed to find MMA 0204 and SMM 0204 MELF resistors for all the resistor values that we need for the DAC board and PSU board (all from Vishay). They're bigger than the 0603 thin film resistors that we had selected earlier, but comments from Jan Didden on the SilentSwitcher thread suggested that 1206 is as small as we should go, and 0204 and 1206 are roughly the same size. I am not sure that they will all fit on the board, but we'll give it a shot, unless someone has valid objections against it.

It should also be noted that tolerances for these resistors are not as low as what we can find with 0603 or 1206 alternatives (some do not go lower than 1%, yet this relatively-high tolerance complies to the AKM datasheet's recommendations), but the reduction of thermal noise seems to be an important factor to consider when using MELF resistors. That being said, I will let the experts voice their opinions, for I am totally ignorant on the subject.

Last edited by ishizeno; 25th August 2019 at 03:24 PM.
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Old 25th August 2019, 03:56 PM   #796
Markw4 is offline Markw4  United States
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How about: http://www.vishay.com/docs/28715/umx020x.pdf
and or: http://www.vishay.com/docs/28714/melfpre.pdf
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Old 25th August 2019, 04:29 PM   #797
ishizeno is offline ishizeno
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These would be even better indeed, but I can't find them on Mouser. Let me look some more... Might be a case of Sunday morning fog on my part...

Thanks!
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Old 25th August 2019, 05:15 PM   #798
ishizeno is offline ishizeno
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Quote:
Originally Posted by ishizeno View Post
These would be even better indeed, but I can't find them on Mouser. Let me look some more... Might be a case of Sunday morning fog on my part...

Thanks!
For the UMA 0204 series, Mouser only offers these: 33Ω, 42Ω, 100Ω, 1kΩ, 10kΩ, 100kΩ.

For our application, we need the following:

5.1Ω, 10Ω, 200Ω, 270Ω, 360Ω, 510Ω, 2kΩ, 3.6kΩ, 3.83kΩ, 33kΩ.

We've managed to find the following in MMA 0204 (Precision MELF):

270Ω, 360Ω, 510Ω, 2kΩ, 3.6kΩ.

This leaves the following:

5.1Ω, 10Ω, 200Ω, 3.83kΩ, 33kΩ.

We could do 200Ω with two 100Ω Ultra Precision MELF resistors.

Newark offers these in Ultra Precision:

270Ω, 511Ω, 2kΩ.

The 511Ω model has a tolerance of 0.25%, which is great than 1Ω. Therefore this could be an acceptable part for the 510Ω (R302, R307, R322, R327).

The other resistance values are not produced by Vishay in Ultra Precision.

Bottomline: we'll go with MELF for all resistor values and use the best precision we can find for each.

Last edited by ishizeno; 25th August 2019 at 05:34 PM.
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Old 25th August 2019, 05:57 PM   #799
ishizeno is offline ishizeno
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Quote:
Originally Posted by ishizeno View Post
For the UMA 0204 series, Mouser only offers these: 33Ω, 42Ω, 100Ω, 1kΩ, 10kΩ, 100kΩ.

For our application, we need the following:

5.1Ω, 10Ω, 200Ω, 270Ω, 360Ω, 510Ω, 2kΩ, 3.6kΩ, 3.83kΩ, 33kΩ.

We've managed to find the following in MMA 0204 (Precision MELF):

270Ω, 360Ω, 510Ω, 2kΩ, 3.6kΩ.

This leaves the following:

5.1Ω, 10Ω, 200Ω, 3.83kΩ, 33kΩ.

We could do 200Ω with two 100Ω Ultra Precision MELF resistors.

Newark offers these in Ultra Precision:

270Ω, 511Ω, 2kΩ.

The 511Ω model has a tolerance of 0.25%, which is great than 1Ω. Therefore this could be an acceptable part for the 510Ω (R302, R307, R322, R327).

The other resistance values are not produced by Vishay in Ultra Precision.

Bottomline: we'll go with MELF for all resistor values and use the best precision we can find for each.
With a bit more research, I could find Precision or Ultra Precision parts for all values but 5.1Ω, 10Ω, and 3.83kΩ.

For 3.83kΩ, there is the SMM02040E3831BB300, which is a Thin Film Mini-MELF Resistor with a 0.1% tolerance. Not sure why it's not called Precision or Ultra Precision, but it definitely fits the bill...

And for 10Ω, we have the WRM0207HPC-10RBT2 at 0.1% as well.

The only one left is 5.1Ω, for which we cannot find anything better than 1%.

Now, we should keep in mind that some of these resistor values are not stocked by a lot of distributors...

Last edited by ishizeno; 25th August 2019 at 06:27 PM.
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Old 25th August 2019, 06:00 PM   #800
ishizeno is offline ishizeno
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Default TT Electronics MELF Resistors

Does anyone have any experience with the TT Electronics MELF Resistors? At $0.28 for 0.1% tolerance, they seem surprisingly cheap...
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