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Old 18th May 2007, 05:59 PM   #1
pjpoes is offline pjpoes  United States
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Default New HT amp, looking for feedback

I purchased three NX150 modules from Aussie amps back when he had those two on sale. Too good a deal to pass up. Anyway, I'm making a 3 channel amp to serve in my home theater for the front three channels and decided, as some might have noticed, to built a bit more extensive power supply than I have done in the past. The route I chose to take was a CLC filter using some surplus parts I ordered from ApexJR today. I bought 12 of the Hitachi 22,000uf 100v caps, 8 of the 8mh inductors, and 3 of the 90Vct transformers. I originally planned on doing an LC at some folks recomendation, but then realized I needed higher rales, and these transformers were too cheap to pass up. I will have to go with a CLC in order to get the needed voltage.

Now I could have one 22,000uf cap before the inductor, then the inductor in series, and the second cap after it. However, I have noticed a lot of these CLC designs prefer to have less capacitance before the inductor rather than after. In that case I thought about picking up some 4700uf 100V caps and using a pair of those before the inductor, and then 44mf after the inductor, possibly having it bypassed with a smaller 200-600uf cap of higher quality. I'm pretty sure that will lower the esr the most, having the two 22mf caps together, and having smaller ones before it as well. This setup with 45 volt rails gives me between .5uv at idle and 26uv at 10 amps draw, which is actually more than the transformer can produce. If those numbers don't seem right, let me know. PSUD2 seems to give me different results depending on when the last time I restarted my computer, last power supply I made, what phase of the moon, etc. Oh yes and the voltage at the load is from 61v at idle to 50 volts at peak. Seem's to be not too bad.

The amps will all be within one single chassis I think, which I had from a chipamp project, but was a bit excessive. I'm thinking of mounting the power supply in a seperate chassis in order to keep the inductors away from the amps and sensitive components. They look shielded, but I would rather not chance it. That and it will end up being huge if I don't split them up. As is 6 inductors and 3 transformers is going to make for one really really heavy amp. The last idea is to have 3 monoblocks, but again, we are talking sizable chassis here to support even 2 inductors and one transformer. The inductors are 8mh at 16amps and the transformer is 600va, so I'm expecting a very large project. I am thinking though that from a ease of moving standpoint, three monoblocks might not be so bad. Get two more of the same chassis I have possibly. Any thoughts on that?

After this is finished I plan to try tweaking the modules. As is I will be raising the bias some to raise idle current to around 400ma or so. From there I want to try different input caps, different localized power supply caps, and different resistors possibly. Hopefully I will have pictures of the parts soon, and a working amp soon after.
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