Protect BOM
I'm putting together a Mouser BOM for the protect, and am stalled at D5. The TVS Schottky diodes that I've looked at so far are all surface mount. The eagle file has P2-15 as the package designation, I can find little or no information as to what a P2-15 package is. Do you have a part number from any supplier that I can compare?
Thanks,
Adam
When (if?) I get a BOM together for this, I'll post it. Thanks to NealJ (and 00940, obviously) for their published BOMs for the other boards.
I'm putting together a Mouser BOM for the protect, and am stalled at D5. The TVS Schottky diodes that I've looked at so far are all surface mount. The eagle file has P2-15 as the package designation, I can find little or no information as to what a P2-15 package is. Do you have a part number from any supplier that I can compare?
Thanks,
Adam
When (if?) I get a BOM together for this, I'll post it. Thanks to NealJ (and 00940, obviously) for their published BOMs for the other boards.
D5
Thanks!
I'm going to use P6KE100A-T for the D5 (unless I've misunderstood you).
I think 227 is where I got the PSU BOM, but I"ll double check. Both NealJ's amplifier BOM and the PSU BOM uploaded and processed no problem with Mouser Canada.
Once again, I really appreciate the effort that has gone into this project to date!
Thanks!
I'm going to use P6KE100A-T for the D5 (unless I've misunderstood you).
I think 227 is where I got the PSU BOM, but I"ll double check. Both NealJ's amplifier BOM and the PSU BOM uploaded and processed no problem with Mouser Canada.
Once again, I really appreciate the effort that has gone into this project to date!
Yes. But...
My rule of thumb to keep lm3886 happy is : about +/-28Vdc rails into a 4R load, +/-35Vdc rails into a 8R load. Bridging "halves" the load, paralleling "doubles" it. Combine at will.
It's easier to bridge (you only need an inverter stage in front of one amp) than to parallel (you need to match accurately the gain setting resistors and add a low value load sharing resistor).
My rule of thumb to keep lm3886 happy is : about +/-28Vdc rails into a 4R load, +/-35Vdc rails into a 8R load. Bridging "halves" the load, paralleling "doubles" it. Combine at will.
It's easier to bridge (you only need an inverter stage in front of one amp) than to parallel (you need to match accurately the gain setting resistors and add a low value load sharing resistor).
So if I did something quick and dirty like this:
Can I expect it to just work? The speakers I'm planning to with use with this are all 8 ohms.
I'm worried about the dynamic performance degradation in this configuration, ignoring the contribution of the buffering opamp. It would be greatly appreciated if you can share some measurements of this amp in bridge mode if you ever get a chance.
Can I expect it to just work? The speakers I'm planning to with use with this are all 8 ohms.
I'm worried about the dynamic performance degradation in this configuration, ignoring the contribution of the buffering opamp. It would be greatly appreciated if you can share some measurements of this amp in bridge mode if you ever get a chance.
I've built multiple modules (#58 post files) and all of them (some with other components and filtering caps) show some degree of hiss. I powered them from 2 mean well LRS-24 smps in series. I also tried some other smps (same, in series) with extra filtering with multiple ferites and feed through capacitors - and the hiss is still there.
Could it be to smps (those extra filters though...)? Would it be worthy to try a classic liniar PSU?
Could it be to smps (those extra filters though...)? Would it be worthy to try a classic liniar PSU?
The speakers sensitivity is 91dB, but the hiss is audible also on lower sensitivity sepakers
The source is a smartphone, it causes no hiss on other amps. The thing is the hiss level is quite high and it's present on all 6 modules I built. I guess a linear PSU test should be next. I'll report back when done.
The source is a smartphone, it causes no hiss on other amps. The thing is the hiss level is quite high and it's present on all 6 modules I built. I guess a linear PSU test should be next. I'll report back when done.
Well, there is no shielding for audio input cables, just a regular jack cable from phone to LM module.
The same input cable was succesfully used in other class D amps with the same smps. The hiss is present even without input cable present, so I think the input cable is not the problem. Truth is, with input cable connected (but not also into the phone's jack) there are other noises present, beyond the hiss.
The smps switching freq. is 65Khz, so I think it shouldn't be audible, at least if it doesn't cause some other higher oscilations which further, somehow, impacts the stability of ic and so, the audible band.
I don't have a picture taken (also all is back in the closet for now), all the cables used were tiwsted, with generous awg, and quite far from the smpss.
The same input cable was succesfully used in other class D amps with the same smps. The hiss is present even without input cable present, so I think the input cable is not the problem. Truth is, with input cable connected (but not also into the phone's jack) there are other noises present, beyond the hiss.
The smps switching freq. is 65Khz, so I think it shouldn't be audible, at least if it doesn't cause some other higher oscilations which further, somehow, impacts the stability of ic and so, the audible band.
I don't have a picture taken (also all is back in the closet for now), all the cables used were tiwsted, with generous awg, and quite far from the smpss.
I have designed a soundcard based on the TI PCM2900/2902 that can sample at least up to 20 kHz:
GitHub - profdc9/AudioMapperUSB
I am having five of them made and populated for about $70 USD by JLCPCB. It is for my room audio characterization project. It can be jumpered for gain to use microphones or unity gain for line input.
Also, for my amplifier, I designed a power conditioning board to remove the RF on the input and rectification which I placed between the transformer and amplifier PCB:
GitHub - profdc9/PowerAmpAudio: Power Amplifier based on Michael Chua's C300 amplifier
PowerAmpAudio/PowerCond at master * profdc9/PowerAmpAudio * GitHub
It contains two stages of filtering including common-mode chokes on both positive and negative rails. It is a bit overkill but the output is quiet.
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All components are high quality sourced from mouser... Vishay/Dale metal film, Wima, Panasonic/Nichicon/TDK caps and so on.. As I said, I've build 6 modules of wich 2 uses different components (same quality from mouser but different PN). All of them worked from first power on, with no mistake, all behave the same - audible hiss - not extremly loud, but considerable - with the volume turned a bit higher can't hear it anymore. Anyway, I didn't expect that... To me, the smps seems to be the common source of flaw since the design was previously checked and built by others. Or a mistake I made on al 6 modules? I gues I should have built 1-2 first. 
Thanks all for input!
Thanks all for input!
@profdc9: I've got soundcards working at up to 192khz sample rates. The problem is that, as explained in the posts mentioned above, their thd and noise performances aren't really up to the task at that point.
@selwe: I'm really sorry to hear that, especially with 6 modules. Do you use a high value pot in front of the amps ? There are some more general advice here
@selwe: I'm really sorry to hear that, especially with 6 modules. Do you use a high value pot in front of the amps ? There are some more general advice here