Flex 6500 creating 30db pad on line going in rear

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  • Problem
  • Updated 3 years ago
Got my 6500 today.....W2IHY cable from iPlus to 1/4 jack balanced in rear. Using it that way creates a 30db pad compared to going in the front. I have to take the line gain pretty much to 100. My friend thinks (and he has a 6500) that a resistor or something is bad in the rear. I don't know, not even sure I explained this right....lol. I traded my 6300 in for this, and my 6300 had no issue when running it. True, it was fed unbalanced in the front, but it ran smooth, and is why I decided to go ahead and jump to the 6500. Thanks in advance for any help / replies.  73
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Steve Parker

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Posted 3 years ago

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George Molnar, KF2T, Elmer

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Does the mic work okay on the front panel? Check the 20 db gain button in your Settings (Radio Setup, Phone). Does your microphone require a bias voltage?
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Steve Parker

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Checked that, it's a dynamic mic.
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Doug K0DV

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Check to see that you do not have the -20 dB pad checked on the Flex turn on screen in SmartSDR.
(Edited)
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John n0snx

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First I would bypass all the outboard pieces including the Iplus and run from the mic directly to the rear input of the radio...Turn on the 20db under phone tab in the startup and go from there.... Take everything out of the equation that you can...
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James Watts

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I'll add a couple things here. During our initial troubleshooting of Steve's issue, when he first put the 6500 in line, it worked normally, normal levels for about 5 minutes. Then, all of a sudden it was like someone engaged a 20 to 30db pad in his audio chain. Again, nothing changed, it just abruptly dropped. We then tried a hard reset of the 6500 and that did not help. We then used a different cable from the front mic input, without touching anything else and still running through the rack and into the same iPlus port and levels are all normal and stable. This eliminates anything in the rack and iPlus as he used the same port there. In my opinion, that leaves two things, the cable or the 1/4" bal input in the back of the flex. I lean more to something going on with the input of the 6500 because I've never seen a bad cable have these symptoms, it's normally you have audio or don't with a bad cable.

I think it's important to realize this worked fine for about 5 minutes and then the audio level dropped 20 to 30db without any change what so ever. We, for testing, did engage the the 20db setting under phone and that brought the audio up, but he had to run the mic level and rack level at abnormally high settings.

Steve, one thing we didn't do in our troubleshooting is unplug the cable at the 1/4" input and then firmly reinsert.

James, W8GN
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Jay / NO5J

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This has probably already been checked, but it has happened to me several times with very similar behavior. Be certain that the correct input type stays selected, ie. Balanced, or Line. Switching profiles and mic profiles sometimes changes the input type, The rear jack can do both, and will have mic audio in either case. But the levels are very different. The +20dB preamp will be available with both and helps to confuse things too. It's not totally obvious when it switches. The input types are stored in the profiles, if you created profiles and didn't resave them with the correct input selected then they will switch without warning sometimes even when just changing from one band to another, or changing modes. It all depends on whatever you last saved it as and then, persistence that gets saved when you restart SmartSDR also complicates things too.

Jay - NO5J    
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Steve Parker

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Yeah,  we checked and double checked line, mic, everything. I just don't know. My 6300 played fine without a hitch. 
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Larry - W8LLL

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I have had my 1/4 inch balanced jack in the back act like it was dirty and needed to be unplugged and plugged back in a couple times, I switched to an XLR type plug/cable. I will say that my mic gain on my 6500/PR-781  going in the rear balanced jack is set at over 90% with the 20 db turned on in setup.
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Jay / NO5J

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Larry

I'm also using the 6500/PR781 combination, with the +20dB preamp on, and mic level set so that the mic never peaks into the red, above 90% but never full scale. I think that's just what's required, but I'm curious if anyone else that also using the 6500/PR781 combination is getting good audio reports without the preamp and a +90% mic level. My other balanced dynamic mics need similar settings. Maybe, it's just that +90%, is the +90% right setting.

Jay - NO5J
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Jim K4JAF

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I use the balanced input on the 6500, mic gain at 55 with +20 db preamp,processor on the DX level,  mic never peaks above the yellow level.  Good audio reports.  I do find the mic level has to be a bit higher with the balanced input vs the front 8 pin mic jack.

Jim K4JAF

(Edited)