FLEX 6500 with Class D Speaker Amps

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  • Updated 11 months ago
For several months I successfully used a Lepy LP-2020A amp with two bookshelf speakers to provide very nice audio from my FLEX-6500. Then one day, the left channel failed. I replaced the Lepy unit with an SML SA-50 amp, and it too worked for a few months before the left channel failed. Checking internet posts, I found several others who reported left channel issues with these low cost Class D amps, but it still appeared to be the exception rather than the rule. However, after trying and returning 2 additional SML SA-50 amps and a Fossi Class D amp, all having immediate dead left channels, I began to suspect a potential incompatibility with the FLEX-6500.

I purchased a Dayton Audio DTA-2.1BT Class D amp, and tried it with another source before hooking it up to the FLEX, and the left channel worked fine. I then tried it with the FLEX, and sure enough, no left channel. However, I then connected the FLEX to a second Lepy LP-2020A amp that I was using with my PC speakers, and the left channel worked correctly with the FLEX. I then checked the Dayton Audio amp with the other source, and the left channel worked correctly as before.

So, what to make of this? Has anyone else tried using Class D amps with the FLEX-6500 and if so has anyone had a similar left channel issue? I do not know if all the amps I tried use the same Class D chip or not, that might be a key to why some work (at least for awhile), and others don't. Does anyone have any idea why the FLEX might be stressing the left channel of these amps? Any thoughts or suggestions greatly appreciated.

Randy, K0FA
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Randy Hollingsworth

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Posted 11 months ago

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WA2SQQ

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Using a Lepy for almost one year. Absolutely no problem. So I live abt 2 miles from WABC (770 kHz 50 kw). They get into many devices. My input cable goes through about 6 turns on a ferrite choke. No more WABC. Maybe you have RF getting in and killing it?
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Randy Hollingsworth

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Possible - I do have an AM radio station about two miles away, but only 5KW. What type of ferite choke did you use?
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WA2SQQ

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Honestly, have no idea. I just wound as many turns through it as I could. Think you may have misunderstood me. Maybe you have RF from the flex getting into it. My choke to kill WABC might be s@ving my amp!
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Martin Ewing AA6E

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I tried an LP-2020A also. It worked fine for audio, but I found that it had tremendous spurious outputs that wiped out 2 meters for me. Tried the usual ferrite tricks, but without luck. A cheap amp, but too cheap.

Now I'm using a "real" amp, an AudioSource AMP100VS. This has a dual input that lets me run both the direct Flex audio and the PC audio with automatic switching.

73 Martin AA6E
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Ed - NZ1Q

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Randy, I noticed an issue with my 6500 and audio output from the rear jack dropping the left channel occasionally. Found that the rear mini stereo connector on the back of the Flex is a bit flaky. Just moving the wire/plug made connection - though still occasionally a big problem when the cat walks behind the rig!

Opened the flex and could not get to the socket - Grrr
(Edited)
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WA2SQQ

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I've seen many comments about this jack. Next time I open my 6500, I'm going to get a pix and see if I can find a better quality replacement. Since getting to the back of my radio is not easy, I created a remote panel (rack panel) that sits beneath my 6500. It has all the connections the rear panel has, now easily accessible. The less I play with that audio connector, the longer it should last!