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05-28-2021, 06:26 PM | #15 | |
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05-28-2021, 08:01 PM | #16 | |
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C107,108,109,110 (blue cans) - I can see they are 4.7uf but is there a voltage rating on them? Probably the same value C111 C112 Probably the same value C207 C113 Probably the same value C117 C118 Probably the same value C201 C202 Probably the same value C203 C204 Probably the same value C302 C304 Probably the same value C307 C309 Thanks! |
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The Following User Says Thank You to LimitedSlip For This Useful Post: | soundman98 (05-28-2021) |
05-29-2021, 03:12 AM | #17 |
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I decided to set up my test station and go ahead with my plan to plot out the frequency vs. output voltage readings of the door speaker amplifier today.
I used an online tone generator from the Safari browser of my iPhone and through the headphone jack, I ran the left and right channels combined for a mono signal into both left and right signal inputs to the amp, with one volt meter reading the input voltage on both positive and both negative wires simultaneously. Then ran several individual test tones from 5Hz all the way up to 2200Hz while keeping the signal input voltage steady at .250 VAC and monitoring the output voltage at the left negative and right positive speaker output wires with my other volt meter, and without any speakers connected. Then proceeded to record each voltage output reading at each test tone frequency. Here is the graph I plotted out, It was just like I figured initially, a low pass crossover with a subsonic filter.
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05-29-2021, 03:21 AM | #18 |
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@LimitedSlip, I'll have to get back to you on those capacitor values.
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The Following User Says Thank You to FR-S2GT86 For This Useful Post: | LimitedSlip (05-29-2021) |
05-29-2021, 09:09 AM | #19 | |
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https://www.amazon.com/Capacitance-R.../dp/B08KGBMGVB
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05-29-2021, 12:34 PM | #20 |
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@FR-S2GT86 Just doing some quick calculations it looks like the amp has a usable bandwidth from about 8 to 350 Hz as it is currently being filtered. The op-amps and power output chip appear to be good for the entire audio spectrum.
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05-29-2021, 01:10 PM | #21 | |
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My multi-meter has capacitance measuring capability, but like you mentioned, when the capacitors are still in the circuit, the readings may be misleading. The only true and accurate way to measure them properly would be to remove at least one connection point from the circuit board. Due to how small these components are though, that's something that I don't have the ability to do. I'm going to get a good magnifying glass here in the next few days to try and make out the tiny writing on the smallest caps, like @LimitedSlip requested. My eyes just can't see as well as they did 20 years ago, and readers can only help so much. Trying to take extreme close-up shots that aren't blurry is almost impossible with a cell phone camera. If anyone would like the raw graphing data from my test results so they can read it and change the logarithmic scalings of the data point settings, I saved it all to a file that opens with Grapher Online. Just send me a PM and I'll e-mail the file to you, complete with a ReadMe text that shows you step-by-step how to load the file into the online tool. |
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05-29-2021, 02:38 PM | #22 |
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generally, SMD capacitors don't have markings unless they're polarized and then they only mark the one side of the component to indicate the polarity...
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06-11-2021, 03:40 PM | #23 | |
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Yeah, @soundman98 is correct. Unless they've been written in nanoscopic lettering, the capacitors don't have any values printed on them. The only really accurate way to measure them at this point would be to de-solder each one from the board and I'm not going to that extreme on this little side project. However, not particularly a big issue anymore since we have the frequency characteristics of the amp output now, which was what I was wanting to know all along. It would have been nice to simply use an oscilloscope or RTA and a pink-noise generator to test this amp's output characteristics, but I don't have one available, and Poppa needs to pay off his new head unit, so I won't be purchasing one any time soon. Priorities I suppose. It would also have been nice to have an amp dyno to measure the output with both channels loaded with 2 ohms each. Maybe that can be a project for someone else at some point. I've been feeling lately that this build is like a 90's Zelda game with all of it's side quests that I feel OCD enough to complete just so that I can get that one last heart container. |
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06-12-2021, 10:40 AM | #24 |
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o-scopes don't need to break the bank
i've got a much older version of this. don't use it very often at all, but it's a nice tool to have around for a cheap enough price that i don't feel bad not using it all the time. https://www.seeedstudio.com/DSO-Nano-v3.html then look up 'benf firmware upgrade'. makes it much easier to use.
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The Following User Says Thank You to soundman98 For This Useful Post: | FR-S2GT86 (06-12-2021) |
06-12-2021, 12:17 PM | #25 | |
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Thanks for the recommendation. I値l eventually get something at some time in the future that is built specifically for car audio testing, probably the DM-RTA by Audio Control. https://www.audiocontrol.com/pro-audio/dm-rta-pro-kit/ But for purposes of what I was after on this little side job, my two multimeters and the online signal generator worked okay. It just took a while longer than it needed to to get all the tests done and the information down in graphic format. Hey man......old school. |
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The Following User Says Thank You to FR-S2GT86 For This Useful Post: | soundman98 (06-12-2021) |
06-12-2021, 06:52 PM | #26 |
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Well, I certainly appreciate your effort. And you did confirm something useful about the frequency response of the amp for those who want to utilize it with an aftermarket head unit or speakers. Given the skill level required to work with surface mount devices, rather than trying to modify the amp to broaden it's usable frequency response it would probably be better to just plan on replacing it.
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The Following User Says Thank You to LimitedSlip For This Useful Post: | FR-S2GT86 (06-12-2021) |
06-12-2021, 09:56 PM | #27 |
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i was really hoping we could figure out a way to safely bypass some of the filtering in an easy 'solder wire here and here' method
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06-12-2021, 10:53 PM | #28 | |
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Agreed. There are many choices of inexpensive aftermarket class-D amps that can be chosen to replace this OEM amp that would give you gain control, adjustable filtering, etc. But at least I learned something on this project. It gives me more knowledge on why Mr. @Tcoat is unsatisfied with his factory system, and is giving me an opportunity to help him and others to increase the quality of sound coming from their "new and improved" factory systems by making a few tweaks of the wiring. |
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