Any chance you can post the file here rather than drop box then I may be able to help with identifying the noise problem which I suspect is originating from your source device as this particular pre-amp is one I have used for a long time in studio and live stage situations and can attest to it it being quite noiseless for audio work.
If your files have an element of noise in them to start with then the pre-amp will magnify that noise accordingly, try using a wav created from a P file using a program like wintzx which creates wavs with signal and little if no noise, as opposed to one saved by a zeddy to establish if the noise is created by the 81 or your recording device.
Also your charger is regulated and the output should be centre positive if the polarity is wrong a loud deep buzz will emanate from the pre-amp and the chip will get hot and burn out.
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Step up to red alert. Sir, are you absolutely sure? It does mean changing the bulb
Looking forward to summer later in the year.
As you know Mark I'm not the most tech savvy so if you could post the audio part I would be grateful.
As for the leads the input for this pre amp should indeed be screened and short as possible otherwise it will be noisy though oddly enough a twisted pair will usually suffice for the output but screened is better.
mrtinb wrote:I zipped the file, because this forum wouldn't upload it if it was MP4.
Unfortunately I can't play Mp4 on my ancient system tried installing codec but seems something is missing to play the audio I'm not tech savvy enough with modern computing so in the absence of a simple audio file being posted I'll have to bow out at this point and leave it to Mark.
Standby alert
There are four lights!
Step up to red alert. Sir, are you absolutely sure? It does mean changing the bulb
Looking forward to summer later in the year.
Standby alert
There are four lights!
Step up to red alert. Sir, are you absolutely sure? It does mean changing the bulb
Looking forward to summer later in the year.
I would say in all certainty that that is not mains hum as such, at least not the kind I have experienced with this pre-amp. I honestly think this is caused by his prime mover IE the phone, tablet or whatever is generating the audio to begin with. I have known cheap guitar effects pedals exhibit the same noise, either that or the stereo to mono "Y" adapter being used is badly wired.
Another thought occurs, if indeed a phone of some description is providing the audio then if the pre-amp is not inside a shielded metal case then the chip/leads may be picking up radio emissions which although outside the audio spectrum can effect unshielded audio devices, like the "Nokia-next-to-crap PC speaker effect"
Standby alert 