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Old 27th August 2011, 07:53 PM   #891
gychang is offline gychang  United States
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Quote:
Originally Posted by lossfound View Post
Cool, Nicholas, I will give that one a go. I wonder if the amp might also benefit from a voltage increase, although I also don't know if there's anything particular about the Lepai board that would make this a bad idea.
I noticed the ebay item may not come with the cable on the AC side... I have heard maximal is 13.5V but not sure how much Lepai can handle.
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Old 27th August 2011, 08:29 PM   #892
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OK, good to know, I was of the impression that the 2020 could take 15V or so.
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Old 27th August 2011, 09:10 PM   #893
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The TA2020 maximum supply is 16V, with 13.5V recommended. lossfound, have you tried just swapping the Lepai ps with one of those beefier supplies? As far as actual potential, have a look at the typical performance chart on the first page of the TA2020 datasheet.
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Old 27th August 2011, 10:09 PM   #894
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You can get some 15v, 4/5A laptop PSUs on Ebay, very cheap. The Toshiba-replacement ones seem to be the highest rated. 15v is pushing thngs a bit with a TA2020 and 4ohm speakers, although you can reduce it to more like 13.6 by putting two power diodes in series.

2A is adequate for 8ohm loads but definitely not enough for two channels loaded with 4ohms.

Also worth noting that with a beefy PSU or above-spec voltage the TA2020 will not tolerate output shorts, so make sure your speaker wiring is reliable.
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Old 29th August 2011, 10:31 AM   #895
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OK, I pulled the 12V / 5A supply that came with my Muses and did a little A/Bing yesterday with the Lepai, pulling a 4-ohm load. I have a demo track with a low, filtered "heartbeat" bass drum which, in initial testing, was particularly good at causing the Lepai to spit and sputter most audibly and violently. Using the stock 2A supply I brought the Lepai's volume knob *barely* up to the point where the bass drum caused clipping (right around 12.5 o'clock) and shut 'er down, switching to the 5A and turning things back on with all other variables held constant. The clipping was no better. I found the same to be true in more typical music... as soon as the 2A started clipping out, I'd shut the amp down and switch over to the 5A with no improvement.

Between this behavior and the incredibly loud hissing produced with a load (any load!) attached to the RCA jacks on all of these amps, I wonder if the problem is actually the EQ / gain circuit in the Lepai rather than the power amp section.
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Old 29th August 2011, 12:34 PM   #896
gychang is offline gychang  United States
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Quote:
Originally Posted by lossfound View Post
OK, I pulled the 12V / 5A supply that came with my Muses and did a little A/Bing yesterday with the Lepai, pulling a 4-ohm load. I have a demo track with a low, filtered "heartbeat" bass drum which, in initial testing, was particularly good at causing the Lepai to spit and sputter most audibly and violently. Using the stock 2A supply I brought the Lepai's volume knob *barely* up to the point where the bass drum caused clipping (right around 12.5 o'clock) and shut 'er down, switching to the 5A and turning things back on with all other variables held constant. The clipping was no better. I found the same to be true in more typical music... as soon as the 2A started clipping out, I'd shut the amp down and switch over to the 5A with no improvement.

Between this behavior and the incredibly loud hissing produced with a load (any load!) attached to the RCA jacks on all of these amps, I wonder if the problem is actually the EQ / gain circuit in the Lepai rather than the power amp section.
thanks for the test, at least high Amp rating does not seem to do much.
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Old 29th August 2011, 01:08 PM   #897
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Is this the LP-2020A+ being tested?
Several people have mentioned experiencing a noticeable lack of low frequency power out of these things. Everyone seems to want bigger coupling capacitors, but it might be that there are cases where a higher LF cutoff will give better overall results.
You'll have to explain attaching a load to the RCA jacks.
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Old 29th August 2011, 03:10 PM   #898
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When I say "load," I simply mean that there is an inordinate amount of hiss and noise when a device is connected to the RCAs. I've noticed this driving the Lepais with my phone, my laptop, and a turntable running through a very nice recent-era McIntosh preamp that was sitting around the shop. I have not tested the 1/8" in yet to see if the symptoms persist, but when the RCAs are disconnected, the white noise stops.

Also, I have no complaints about the lack of low end, at least through certain speakers I've tried (though they did sound unusually tin-canny through a set of Altec 604s). If anything the low kick drum test I used indicates that the amps are working far too hard to produce the lower end of the spectrum.
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Old 29th August 2011, 03:45 PM   #899
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Oh yeah, and it is the 2020A+. Sorry I forgot to mention that.
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Old 1st September 2011, 05:03 PM   #900
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Received my TA2020(A+) from Parts Express a few days ago.

Recapped using Panasonic FM/FR for the power supply electrolytics and Elna Silmic II for most signal path electrolytics. Also replacing the output film caps with polypropylene caps.

I am not comfortable with removing the SMDs but I was thinking about replacing the stock 10uH inductors.

Has anyone tried this on the new model yet? I think it sounds better in tone bypass mode than with tone controls in circuit - things sound a bit muddy and veiled - thinking this may be the stock 1.75uF electrolytics I left in circuit - I was going to try a pair of Nichicon Muse ES Bipolars here, 2.2uF - or 1uF depending on what sounds best.

Anyone try that either?

Thanks!
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