The AM Forum

Hello looking for some assistance with my Heathkit DX100.  Lately I have been getting reports that my audio is so bassy that it is unintelligible.  I am only learning about these older tube radios so any help would be appreciated.   

A DX-100 with too many lows is a new one. Some more info would be helpful such as if the mic or transmitter has been modified. Is it an amplified or unamplified D-104? How close are you speaking to the mic?  A 6” distance will yield much less bass than close talking in many cases.

The only modification in the DX100 that I know of sure is that the rectifiers are solid state and the D104 is amplified.  I have used the radio for a few years now and never had any major trouble with it.  I did change out the battery in the mic but that didn't make a difference.

Even so, could there be a mismatch with the mike due to an out of spec component? Or maybe a bad part in the speech amp?

Do you have another microphone you could try? That would isolate the problem to either the D-104 or DX-100.

Power supply caps going bad can cause this by imposing 60Hz hum in the audio, giving the impression of bassiness and unintelligible audio. I haven't studied the audio circuit of that transmitter but it's also possible that a component has drifted out of tolerance.

Have you heard your audio either with a nearby receiver and the transmitter in a dummy load or by using an SDR where your signal is strong?

You may have lost all the highs leaving only the bottom end.

Fred

It's an amplified d104.  If they are bassy, it's typically a bad element, or a high quality operator stuffed a hand mic element into it.

My two pence worth.

--Shane
KD6VXI

Thanks to everyone that replied! My audio trouble ended up being isolated to my HO-10 scope I had recently put back in line.  I didn't think it would cause audio trouble but once I removed it I stated receiving good audio reports again.