John M

I can see the advantage of laptop or tablet based systems but they still need a decent audio interface, can be subject to software glitches and I just don't trust myself with a mouse or finger tap for selecting and playing tracks- although the space bar is a good option . My son is a DJ and he uses a very nice Dennon prime go player that is stand alone, can run off batteries or mains, nice large screen, plays FLAC as well as MP3 etc and can also control a laptop but I just don't want or need the level of complexity of that model and Dennon do not seem to have a stripped down version that I can find. Hi Robin. I now have the pro version but I cant see anywhere that lists the cue operations eg how would I do the following - play track 1 using the space bar then auto stop at the end, Play track 2 play and continue to track 3 without a break, Auto stop at the end of track 3. I cant see a drop down list of functions/cues so I assume they have to be typed in. If thats the case what order are the commands and what format are they. I have looked at the help menu but I am obviously missing something.

Thanks for the tip. I have downloaded the demo. My first thought is that it looks ideal but the setting up for playlists looks a bit complex... But I have only spent about 5 minutes with it so far.

I have been using a laptop running Mixmeister with USB DI box for playback of backing tracks. I have had some bad experiences where tracks don't play or the wrong track is selected. So I am looking for a standalone device that faces upwards with nice clear indication of the song to be played and large start, stop, next buttons. The DJ controllers that I have seen are overly complex and rack mounts generally have small screens and are not ideal for working in the dark. Any suggestions? Ideally less than £400. Or is there better software than Mixmeister that is worth a try

OK - here is a final closure for this saga The original power supply - I decided to completely remove this and replace with a switched mode power supply. The switched mode power supply was very noisy so I put a 680µF capacitor across the output and a 4.7µH coil in series with the +48v rail. Still noisy. Spoke to the manufacturer and was advised that its OK to connect the mains earth to the 0v rail. This has cured the problem but not 100% perfect as there is still a slight background noise if I turn the gain up to a very high level. As the original power supply was now out of the case and much easier to follow the (simple) diagram it was immediately apparent that I had identified the wrong diode as being the Zener! Fortunately I found someone on ebay selling the exact required diode (about £5 with postage), changed that and now its running very nicely. Took the new module out of the power supply box and reinstalled the old one - all working fine - at last. Phew! That was the longest 5 minute job ever.

Just how fantastic is this forum! Many thanks to all of you for such good thought out answers as well as your patience with my persistent questions! Special thanks to journey man for taking the time to measure the voltage.It seemed unlikely that a faulty transformer could generate excess voltage but I couldnt imagine going to the trouble of putting in a transformer and then giving out almost the same volltage as was being put in. Isolation springs to mind but why not lower the voltage to a safer level at the same time? Well I am off to maplin now for some resistors - thankfully just a 10 minute drive.

Richard! You are spot on thats exactly what happened - a whinny tone and odd ticking in the background. I touched the mains earth onto the -ve rail and that did stop most of the noise - but I guess its not a great idea to leave it this way with the possibility of earth loops and maybe safety implications? I have connected a 100µF/100v capacitor across the output and in a hopeful effort put some silver foil over the module and connected that to the mains earth - but its still noisy. The pcb originally had an LED with a resistor across the output and the resistor started smoking- A call to Vigortronix confirmed that when using a 48v model a higher resistance needs to be installed. I disconnected the resistor and havent got around to putting a new one in (it cant be seen when inside the box) I will give the 1k resistor a go. The -ve from the microphone comes via the output jack socket to the circuit board DC output (I used the vigortronix pcb board) and then the circuit hits the -ve of the 100µF capacitor and then onto pin 4 of the module. The mic/DC power lead routes into the box next to the mains input but doesnt touch it I contacted Vigortronix and they also suggested using the capacitor and a 5µH choke - I managed to get a 4.7 but not sure if it goes in parallel or series with the supply. In your experience does the physical proximity of a switch mode module to the signal wire have any effect or is it all electrical interference? And...yet another pain. The screws for mounting the new circuit board block the lid from sliding into place - hopefully I can countersink the screw holes and then use coutersunk screws as opposed to the existing round heads. I did toy with going back to the original circuit and building one from scratch - maybe even splash out on a full wave rectifier! Problem is I suspect the old transformer is faulty as the secondary is giving out about 225 volts. There does not seem to be much available for off the shelf transformers - most are 12v, 5v etc.What would be the ideal quoted output voltage to allow for 48v (or 51v) DC output? Would it be practical to use a lower voltage transformer and then use what I guess is a voltage multiplier to raise the DC voltage? This seems to be how most mixers provide 48 volts from 18v transformers. By the way - Not sure if its general knowledge but in order to get µ just hold down the Alt key to the left of the spacebar and type 230 on the numeric key pad - it doesnt work with the numbers across the top of the keyboard though and you need numlock on. .

I connected up 5 x 9v batteries all new. Voltage was 49v. I tried 6 batteries but showing about 58v which seemed a bit excessive. Mic works fine with no interference. Current to the microphone was 2.5mA so my new power supply should be well within spec at 100mA. Getting a bit fed up with the old supply now as it seems to be never ending problems. Going to contact the new power supply manufacturer (vigortronix.com) and see if they recommend anything so subdue the noise. This is the module I used (48v one) http://www.vigortronix.com/5WattACDCPCBPowerModule.aspx

I had a delivery from CPC today including some 51v zeners, another capacitor and other odds and ends. The output from the transformer seems very high at about 200volts - is that usual - and if so does that mean the zener needs to be higher rated than normal. I measured across the existing zener and reading 200v so that seems to be blown as I understand it should show 51v. Please correct me if I am wrong! I tried the new 48 vigortronix power supply again and still quite noisy. I think perhaps its underpowered at 100mw. I will measure the current and see. Guess what - I found another "project" in my loft. The great british spring reverb unit. Its built into a drainpipe and apparently quite sought after. It also needs a power supply. This time 20v at about 200ma. There are quite a few laptop power supplies that are rated at anything from 2 to 6 amps which seems a bit excessive so I have ordered a smaller (and more expensive) one from Amazon. This time I tried first with batteries and it works fine!

I changed both capacitors and put them the wrong way round... high voltage reversed with low voltage. Smell of burning, turned off and realised the problem. Took them both out and they seem to measure OK, put them back in the right position but still low voltage output - it could only now be the diodes as the resistors are ok. Seems like high voltage coming out of the transformer at about 200volts. Another problem - the physical size of the 450v capacitor now blocks the Jack socket and now that I have cut the legs there is no movement - probably take the capacitor out and solder an extension on! I have done quite a lot of searching on the web for the zener BZX61C51v which is a 51v 1.3w (dissipation) but not really very sure about what other parameters are applicable. Does anyone know if there is a straight equivalent. I thought I found some on the Farnell web site but they come from USA and charge about £15 for delivery. I hooked up a new Vigortronix 48 v power supply to the mic. Smoke came out of the new power supply LED resistor - disconnected the LED and measured voltage @ 48v good! Called Vigortronics and they advised that for 48volts I need to change the LED resistor to a higher value as its only suitable for lower voltage units. Not too sure about how best to connect earth to the microphone. On one hand I feel like perhaps the safest option is to connect the mains earth to the cable screen but this is not done with the original power supply. So - I cut the mic cable, connected the +ve (red) to the new power supply (PS) and disconnected it from old PS connected the screen to the -ve (new) PS, to the mic and to the old PS box (to give connection to the jack socket output) and left the signal lead connected to the mic and the old PS box so that the jack socket could be used to plug into my (bass guitar) amplifier. Turned the amp and the PS on - loads of clicks and hum. Maybe the mic? So the saga continues. Any help with the zener and earthing arrangements will be appreciated. Maybe that suggestion of using multiple 9v batteries would be a great way of discovering whether the mic is faulty or not.

Hi - No its not two capacitors in parallel, there is a resistor between the two top tags with the bottom tag going to earth. the circuit is something like this - dont know how to do attachments !! The diodes seem ok from transformer +ve......>|.................47ohm.........|.39k.|.........................................48v but measure 5v Chunky diode | | | 300v 32uF === === 300v 32uF ^ cylindrical diode | | | From transformer -ve..............................................|........|...........................|.............-ve That didnt work very well!. How on earth are pictures etc uploaded? Anyway the diagram is xfmr.....diode..>|...47R ......32uF 300v to -ve rail.....39k R.....32uF 300v to -ve rail....|< diode to -ve...48v Hope that makes sense! But anyway - I will change the single capacitor for 2 x 32uF

Many thanks for that. I am quite rusty with electronics and my power supply seems to be different to the diagram. I could be wrong but I have what seems to be an electrolytic capacitor (its old enough to be still labelled a condenser) which seems to have two 32 microfarad capacitors in a single cylindrical unit. There is a red blob on one of the two tags on the "top" and the tag/terminal on the bottom goes to the -ve. I can measure capacitance between the two top terminals (about 0.1 ufarad) but higher capacitance (about 2.0 ufarads) between each tag and the bottom. So unless my meter is faulty it looks like the capacitor is faulty. Can anyone confirm if its likely to be 2 capacitors in one container? The label does state 32 + 32ufarads so that does seem to answer my question. Its coloured green, manufactured by TCC, Type CE509KC, states that can is neg, TCB/YA 0852. Couldnt find the info on google. But ultimately I could just build the circuit as per your drawing. Just worth mentioning that the mic is actually marketed by Orange with a model number of CM660.

Thanks for all the very helpful comments. I will look up the maplin wall warts - that could be a nice simple resolution although I am tempted by the phantom power option. Yorkie - how much for one or your wall warts - I hope your house isnt like mine - I usually end up buying duplicates because my wife clears up and eventually eveything ends up in no mans land (my loft) under a pile of other bits and pieces!

Yes - very useful. I did do a search previously but only found a post from 2008 without much info

I have an old Calrec condenser mic that connects to a box that provides 48volts to power the mic and also has an attenuator (just a simple pot). Its NOT phantom powered - the 48volts use two wires and then the signal goes on the 3rd wire providing an unbalanced connection. The 48v supply is testing just 5 or 6 volts so appears to be faulty Its possible to buy a cable from Saturn electronics (I think that's their name) for £50 that allows the mic to work off of a standard phantom supply, bypassing the need for the separate power supply - so thats got me thinking there must be a pretty simple way of doing the same. I am thinking perhaps a capacitor (0.05micro farad?) to the unbalanced mic input to stop the 48v hitting the mic cartridge. The wire before the capacitor would go to the +ve voltage input, the earth and -ve voltage would be connected together and go to the remaining terminal. I wouldnt bother recreating the attenuator as its just another fault liability. Problem might be in connecting an unbalanced mic to a balanced XLR input and of course I dont want to damage the 48v supply on my mixer. Anyone with a better grasp than me with any suggestions. If all else fails I will just buy one of those Vigortronix power supply units and replace the existing one but it would be nice to do away with the power supply box if possible.