need sound recorder for long durations - Page 1
Forum section: electronics / general

author: Simon
author_rank: Unknown
timestamp: June 03, 2012, 01:17:52 pm
content: My sister is having problems with neighbours so the police have decided to give her a CCTV camera. I doubt this will help much but I think if we get sound too it may aid matters. So I need something I can plug an external mic into and record sound in MP3 at good quality, any ideas ?I was thinking a pc can do this but that means leaving a whole PC running 24/7

author: SeanB
author_rank: Super Contributor
timestamp: June 03, 2012, 01:27:43 pm
content: It does not have to be a high end computer, any cheapie or recycled unit will do. It just needs a sound card that works, and a hard drive of 2G or more. Slap on a Linux disro and use the audio recorder to do the recording. Turn off the monitor and there you go. If you want it to be totally headless use any remote Xterm you want, and just let it run.You do want a recorder that records to the hard drive, not memory, in case the power goes out. If you get a slightly more powerful unit and a cheap analogue TV card ( might be free as no more analogue TV in Blighty any more soon) then use a MythTV install to make a DVR.

author: Simon
author_rank: Unknown
timestamp: June 03, 2012, 01:31:44 pm
content: yea I do have a little pc I could use. any suggestions on the program ? I suppose now I need to look at a microphone and or preamp, I expect a decent one that plugs into the line in socket might be better quality than a crappy mic in the mic socket ?

author: PeterG
author_rank: Frequent Contributor
timestamp: June 03, 2012, 01:34:33 pm
content: Simon, you could try something like this i found on ebay.http://www.ebay.com.au/itm/8GB-Digital-Voice-Audio-Telephone-Recorder-MP3-Player-/390417948124?pt=AU_Gadgets&hash=item5ae6b91ddc#ht_3685wt_1139Most of these things will take an external microphone and are cheap. Also you could run this off external power will little effort.Regards

author: Psi
author_rank: Super Contributor
timestamp: June 03, 2012, 01:36:12 pm
content: That says 650hour!!Sounds perfect for what he wants.Although, it's hard to know if it can do one single 650hour record.Some of them fall over when they hit the 4GB fat32 limit. Others just start a new file.

author: PeterG
author_rank: Frequent Contributor
timestamp: June 03, 2012, 01:42:05 pm
content: I am thinking the 650hr refers to the 8GB storage. I think it should do the required 24hrs easily tho.This type of system also provides mobility.Regards

author: Simon
author_rank: Unknown
timestamp: June 03, 2012, 02:18:55 pm
content: looks good, I just need to find one in the UK now

author: mariush
author_rank: Super Contributor
timestamp: June 03, 2012, 02:35:42 pm
content: If you're in UK, I suppose there's no legislation saying you're not allowed to record audio of other people without their consent - I know in US some states have that two party consent rules where you can get arrested for recording so I guess that's why surveillance cameras don't have sound by default.As for recording, you might want to check to be sure the recorder won't crap out when you go over 2 GB of audio file size.. even when saving in mp3, some recorders store in a WAV container and with some recorders, they use the old style WAV files which are limited to 2-4 GB.When I was a lot younger, a lot of years ago, maybe 6-8 years ago, I remember I was using MusicMatch Jukebox to record from Line in or Mic and it encoded straight to mp3. They removed the feature or made it harder to use it in later versions but you can get older versions here:http://www.oldversion.com/MusicMatch-Jukebox.html(page says version 4 introduced these line in recording feature)Now I suppose you can do that now with plenty of freeware applications or Linux tools but then I didn't know better and that worked well enough, especially when I had 3 GB hard drive.You may also be able to just get a Leadtek winfast 2000 xp card from eBay and connect a camera on composite/s-video in and the audio at audio-in and use its software to record for days. I have such card and the software is solid and it can encode to mpeg2, so it won't use a lot of cpu to do it.

author: Simon
author_rank: Unknown
timestamp: June 03, 2012, 03:52:09 pm
content: To be honest given the gravity of what is going on I don't give two tits about what the law says about me recording, I need to get proof of who these people are. If they call each other by name I may have them if it is corroborated by the video. The camera is provided by the police so the two will be separate and I have no control over the camera not that I want any as I don't have the hardware to deal with video.The recording can be stopped every 24 hours and a new file started, this mainly needs to run over night.

author: MikeK
author_rank: Super Contributor
timestamp: June 03, 2012, 04:29:26 pm
content: Simon, if you get one of those recorders let us know about the quality. It looks like a useful thing to have.

author: Simon
author_rank: Unknown
timestamp: June 03, 2012, 04:32:18 pm
content: I'm actually thinking of using a mic on a preamp, I have a little stereo preamp from Craplins I want to use but I'm not sure about the input impedence as it is 1K, I was thinking of cascading to two channels to get more gain. What mic can I use on a 1K input impedence ? Actually I think none, unless I go for something like a speaker

author: T4P
author_rank: Super Contributor
timestamp: June 03, 2012, 06:21:20 pm
content: Every single normal dynamic mic can run on 1KJust a slight impedance mismatch.As for condenser mics you can perfectly run them on 1K with their given circuitry if you provide a bias voltage ( a simple CC circuit with 3V will do )

author: siliconmix
author_rank: Frequent Contributor
timestamp: June 03, 2012, 07:32:49 pm
content: sony diskman is a cheap option.

author: Simon
author_rank: Unknown
timestamp: June 03, 2012, 08:23:04 pm
content: isn't he diskman a cd player ?

author: siliconmix
author_rank: Frequent Contributor
timestamp: June 03, 2012, 08:39:29 pm
content: record as well depends on what model .i have one.it'll do 72 hours

author: G7PSK
author_rank: Super Contributor
timestamp: June 03, 2012, 09:30:41 pm
content: I have an mp3 type recorder similar to the one posted earlier, the problem I found with it is it turns itself off after a while when it does not detect any sound, so you would need to check on this, or try to disable that feature.

author: Satchmoeddie
author_rank: Contributor
timestamp: June 03, 2012, 10:18:56 pm
content: It might need some form of synchronization, but I think I would use one of those hand held audio recorders, or a device like I used to put my old fashioned cassette recorded phone calls onto CDROM. I was having problems with the construction contractor from hell. She was a total b***h and refused to warranty anything. She was claiming anything that was broken they did for free. (yeah, WTF?) Recording a conversation is legal in my state "IF" one person knows it is being recorded "AND" they participate in the conversation.The program and the adapter that goes from an RCA jack or 3mm jack to USB should load in hours of audio. The other option is a hand held digital audio recorder. I was stunned to see they make one with 72 hours recording time for under $100 USD now. I used the old Dictaphone cassettes when I worked to keep track of the myriad complaints, problems, and promises made at work. Now I can go for 72 hours of this straight. (no vomiting yellow or green emodicon availible) A cheapo microphone, big ear kit, or other mic should run into the adapter I got for running phonograph into USB. Those need a preamp. You are not after hi fi but intelligible dialog. Also, regarding the CCTV camera. I got one of those cheesy ones for $400 that came with 4 cameras. The resolution was so poor that even if you could say that you were 100% sure the guy in the video was "John Doe Jr" a jury would have trouble with the terrible resolution. So a $1200 video card, and good surplus cameras were used after my first debacle with the apathy of our police department. (you really did need to be within 2 or 3 meters of the camera to be seen clearly) An old cassette tape recorder was used by me with the tape on record and pause with headphone out monitoring my audio and with that signal I could run directly into the USB audio adapter. If you just have the one with no preamp this trick works. Old Panasonic hand held cassette players can be found for around $20. Usually if there is a headphone out it will work as a monitor (through a pre-amp) while the tape is paused and thus not moving with record and pause engaged. I went to that arrangement so I would not have to change tapes during legal issues with our contractor and her ever changing stories. She may got to jail for fraud and forgery now. Recording outdoors you will have loads of background noise, so a good audio program where you can clear things up would help. Good luck! I can sympathize with her. Having neighbors that were shooting an AK47 at their house warming party then the blatantly sold drugs until the economy crashed, I know how she feels. >:(The USB to RCA jack or 3mm Stereo device was maybe $40. The phonograph one with a preamp was around $200. I think the hand held one was on sale, and normally $179. Some have that VOX or whatever the voice operated controller, and it was usually switchable from off to on in better products. I am hoping for the best with the situation, but I have seen these things go on for years. Good luck, Cheers.

author: DrGeoff
author_rank: Frequent Contributor
timestamp: June 03, 2012, 11:43:52 pm
content: You could use something like audacity on an old PC, run the sampling rate at 11kHz or 22kHz mono for long time voice recording.As for mic and preamp, how sensitive does it have to be? Is it directional? Contact mic? A condenser will be more sensitive than a dynamic mic, but will need phantom power to operate. If the signals are very low (ie much gain being required) then you will need a very low noise high gain preamp in order to get anything intelligible.

author: DrGeoff
author_rank: Frequent Contributor
timestamp: June 03, 2012, 11:48:36 pm
content: For field recordings I've used the R09HR (Roland/Edirol) recorder and can recommend it. Just looked at the manual and with an 8GB SDHC card it will do 7980 minutes at mp3 128kbps. This is about 5.5 days, not sure if this is enough? It has a pair of sensitive omni mics and a reasonably good preamp on board.

author: jh15
author_rank: Frequent Contributor
timestamp: June 04, 2012, 04:01:28 am
content: FYI the latest Audacity has timer record if that helps, just have it on at night. It also has VOX to record only when sound gets to certain level.

author: Simon
author_rank: Unknown
timestamp: June 04, 2012, 07:53:42 am
content: The thing with audacity is that it does not directly encode to mp3 so need quite a hard drive for 24 hours and then it can take 2 hours to encode it to MP3 on an older pc

author: DrGeoff
author_rank: Frequent Contributor
timestamp: June 04, 2012, 08:13:20 am
content: Any reason for it to have to be encoded as mp3?

author: westfw
author_rank: Super Contributor
timestamp: June 04, 2012, 08:14:48 am
content: The "Zoom H1" microphone that Dave recently did a teardown of will record to microSD card in MP3 format, giving you something like 17 hours on a 2G card with "medium" quality. Put a 16G card in there and lower the quality a bit, and it could go for a week (though the single AA batter probably won't last that long.)About $100; a really sweet device.(also works as a stereo mic with line out, or as a USB microphone.)

author: EEVblog
author_rank: Unknown
timestamp: June 04, 2012, 08:30:24 am
content: Quote from: westfw on June 04, 2012, 08:14:48 amI also have a Tascam now. Either will record direct to MP3 on micro SD card.They also both support external DC input, so trivial to add either a plugpack or bigger battery.These would certainly be the choice here, cheap and easy, and big dynamic range.Dave.

author: Simon
author_rank: Unknown
timestamp: June 04, 2012, 08:32:07 am
content: the mic needs to be outside, the recording device inside or we are in the same boat as we will be with the pathetic camera the police are giving her where if it is damaged we loose the proof

author: EEVblog
author_rank: Unknown
timestamp: June 04, 2012, 08:35:52 am
content: Quote from: Simon on June 04, 2012, 08:32:07 amIt would be trivial to hide one of these recorders outside.Dave.

author: G7PSK
author_rank: Super Contributor
timestamp: June 04, 2012, 08:59:06 am
content: Those Police cameras are next to useless so you should get your own, A freind of mine had trouble with repeated break in's at his works so a police camera was installed, it was so low definition that despite the security lamps when the thieves next visited and they spent two hours loading up a lorry which they stole from the yard next door the owner of the truck could not read his own number plate and you certainly could not recognize a face from the video. In the end the only solution for my freind was to up sticks and move his works further away, the problem is that where he was there is a diddycoy camp 12 miles away so if it is not bolted down or is left alone for more than 30 seconds it's half inched.

author: DrGeoff
author_rank: Frequent Contributor
timestamp: June 04, 2012, 09:16:17 am
content: Quote from: Simon on June 04, 2012, 08:32:07 amHow about a wireless mic or even a baby monitor and wire the receiver to the recorder.

author: siliconmix
author_rank: Frequent Contributor
timestamp: June 04, 2012, 10:37:32 am
content: i think the police have palmed your sister off with an old crappie set up.they do have hd quality kits as it's needed for evidence in cases.keep on at them .if you do catch anything it'll need a time and date stamp to be admissable .does the area have neighbourhood watch ?

author: Simon
author_rank: Unknown
timestamp: June 04, 2012, 12:33:43 pm
content: the area is a shit hole and the police don't want to admit it and tell her not to move........Yes I made my views on the usefulness of the camera. All the guy could answer with was "who is this person".Getting back on topic I have set up my little craplins preamp with each channel cascaded and using a 8ohm speaker as a mic. Result ok for a PA system but certainly not enough gain/signal for covert listening. How do I bias a capacitor mic ? is it just a resistor in series ?

author: siliconmix
author_rank: Frequent Contributor
timestamp: June 04, 2012, 12:45:36 pm
content: yes resistor in series .they all vary .stick a pot on there adjust until you get best results.

author: Simon
author_rank: Unknown
timestamp: June 04, 2012, 12:51:07 pm
content: Quote from: siliconmix on June 04, 2012, 12:45:36 pmhm I only have 1K Potts is one cave like he should be the top value I should want, or shall I put something minimum in serious.

author: siliconmix
author_rank: Frequent Contributor
timestamp: June 04, 2012, 12:59:31 pm
content: try other resistors in series until you get the right value.when i've used them at 9v they seem to work between 10k and 15k

author: Simon
author_rank: Unknown
timestamp: June 04, 2012, 01:05:37 pm
content: well one K gave me reasonable results, at first I had both channels going to turn up to the maximum, is overloaded the PC card as it thought something had been plugged into the other socket as well because it was coming in so strong. I'll try 10 K as well.

author: T4P
author_rank: Super Contributor
timestamp: June 04, 2012, 01:09:19 pm
content: Audacity does encode to mp3 ... old version or what? My newer one already comes with LAME i think

author: Simon
author_rank: Unknown
timestamp: June 04, 2012, 01:13:53 pm
content: Quote from: DaveXRQ on June 04, 2012, 01:09:19 pmyes but it does the recording in wave, so while the recording is taking place aged use temporary file is being created in what is essentially wave. I then have to save it encoding it as MP3, this can take some considerable time. I have already tried this when we tried to record through the wall after they pushed the front wall down. I need something that will create an MP3 file as it records because of the space required and in time to process it if I do the encoding afterwards.The capacitive microphone works well with 10 K I think maybe better than with 1K. I guess I can give her the good news now.

author: siliconmix
author_rank: Frequent Contributor
timestamp: June 04, 2012, 01:18:48 pm
content: good luck.hope your sis gets some peace.

author: Simon
author_rank: Unknown
timestamp: June 04, 2012, 01:27:55 pm
content: Quote from: siliconmix on June 04, 2012, 01:18:48 pmnot very likely, she wants to move ASAP