Troubleshooting Zoom H4

[FireAlarmPoet]

Did another teardown with no luck; found a dead earwig underneath a piece of tape, that was lovely.
I'm not positive, but maybe the power supply killed it? I read an AC voltage of 20v coming out of it (9v is what the Zoom takes) but of course it worked fine for years so maybe it shit itself? But then why didn't it just fry the boards... I don't know, it's time to start saving my pennies again.

[xdugef]

Did another teardown with no luck; found a dead earwig underneath a piece of tape, that was lovely.
I'm not positive, but maybe the power supply killed it? I read an AC voltage of 20v coming out of it (9v is what the Zoom takes) but of course it worked fine for years so maybe it shit itself? But then why didn't it just fry the boards... I don't know, it's time to start saving my pennies again.

Have you tried running it off batteries?

[FireAlarmPoet]

Yes.

[Misomusist]

Is it an AC supply or a DC supply?

AC supplies are generally unregulated, most DC ones too. This means if it says it puts out 9V 1A AC is you're not actually pulling 1A out of it, the voltage will be considerably higher.

It seemed like Croch was getting close, as he obviously read all your symptoms, it only happens on one input? Only when you use one particular device?

[FireAlarmPoet]

No, both outputs. Happens regardless of the source.

[crochambeau]

Yeah, I think I jumped ship as soon as I read of 20 volts AC being fed into the power jack.

This thing wants 9 volts negative center. If it survived 20 vac it clearly has some polarity protection in place. If you were on a desert island and absolutely had to repair this, I'd start by looking at the power rails. If there's a charge pump feeding one rail of the opamps its failure might be observed by measuring at the power legs of the ICs...

Which will be determined by jotting down the part numbers and looking them up.

Your logic rail is fine, since the thing works and will record okay from the on board electrets. I would avoid, incidentally, cobbling an input on those lines. My memory is foggy so I don't recall if this was a voiced option or not..

[FireAlarmPoet]

So, a bit of an update here, if for nothing else than to indulge myself:
I ultimately didn't put any more effort into fixing the H4 and decided to just keep it for the built in mic function e.g. for field recordings, for reasons which will become apparent below.

I eventually did invest in the H4N Pro, and one of the things that really struck me after a few test runs-aside from the abundance of modes and features I haven't even begun to read into yet-was how low I had to set the input levels. There's no lo/mid/hi preamp switch like with the H4, none that I've found at any rate; instead it's this abstract scale that goes from 0.1-0.9, then from 1-100.

To put this into perspective, I often used the H4 to record tapes from my tape deck, so for the H4N I made a test tape of 440hz square waves recorded at different volume levels, Dolby noise reduction settings, etc. with the goal to find the point where the tape was at its loudest, then based on this point I'd calibrate the H4N's input levels to where the maximum possible volume from this tape would be displayed as -6db on the H4N.

Completing this initial test, I found the ideal input levels to be at 0.5. That either means theres 100+ input level settings that are completely useless, either because they're too quiet or they'll clip the audio unless a mixer is introduced as a middleman, or I'm doing something wrong.

This occurs on both line-in and mic settings, which worries me for future field recording applications because even low input levels could potentially clip the waveform of an (un/)expectedly loud sound and the sensitivity of the mics for picking up breaths and exhales from common speaking virtually guarantees the necessity for a wind shield to be used at all times.

[crochambeau]

If the input scale runs from 0.1 to 100, and you have settled on 0.5 as nominal input setting it stands to reason that you are already expecting loud sounds. Think of those numbers as amplification factors:

Anything in the 0.1 to 0.9 range is turning the outside signal DOWN prior to record, and anything above 1 (unity) will turn the levels UP.

You should probably invest in a windscreen if you do recording outdoors anyway, regardless of input level.

[FireAlarmPoet]

Hmmm, interesting. I heard about unity gain before but never paid it any mind. I did some more research after reading your reply and found this:

http://www.dvxuser.com/V6/archive/index ... 49646.html

Meter readings going over 0dB make no sense on a digital peak reading meter. At 0dBFS, all the bits in the signal are ones and the signal can go no higher. That is the absolute point at which it clips... The normal recording level for voice should be about -12dBFS while the alignment level should be -20dBFS when sending the recorder a 0VU sine wave tone. -3dBFS should be considered the 'never exceed under any circumstances' mark in order to give you a proper safety margin.

I've always tried to aim for -6dB when recording myself, but damn, -20? For real? I mean sure we're talking niche non-music and not pro audio, but with that much disparity between safety and practicality, I'd think the recording would have to be amplified so much in postproduction the resultant noise floor would just consume the entire recording.

Similarly, I experienced a strange problem with the old H4, where if I took an onboard mic recording and amplified it enough (not out of boredom but to actually hear the quieter sounds) there would be this tone popping up in a consistent pattern that was also visible in the waveform. It was sort of like when you play a blank tape, how there's this sort of in-and-out warbling of white noise until it eventually peters-out (due to the displacement of the weight of the tape changing as it's being played e.g. the less work the pinch roller has to do over the course of playback, I figure) except this didn't peter-out.

Thanks for all your help so far, by the way.

[Bipolar Fucking Joe]

I honestly wouldn't worry about most of what "Audiophiles" say or tell you. It's the golden-ears fallacy. There's some truth to what they say, but it gets garbled up due to misunderstandings of technology, physics, etc., so the end result is largely nonsense.

[crochambeau]

^

What he said. I'll try and adjust my levels so the loudest part is under or just hits the ceiling. This generally falls at -6 or -12 depending on what I'm recording.

What I record is generally pretty steady state material, and not like an actual orchestra which can have impressive dynamics.

[xdugef]

I had to trouble shoot my Zoom H6 awhile back... the tip of a goddamn 1/4 cable came off inside the jack.. It took me awhile to figure out the best way to remove it which turned out to be to remove the metal tod that the tip connects to from the cable and then jam it back into the tip and simply pull it out. The end of the rod is knurled and is normally press fit into the tip rather than soldered.. fucking hosa