Jivemaster Posted July 14, 2015 Share Posted July 14, 2015 I need to assemble a project that doesn't come near anything that I have found available. I'm looking for some project boards ready made -Mic preamps etc. There used to be a stand at Plasashow but I can't remember the name. Does anyone have a contact to share, who can supply mic preamps and some line preamps, ready made on PCBs please? Link to comment Share on other sites More sharing options...
sandall Posted July 14, 2015 Share Posted July 14, 2015 Canford used to do a range of ready-made pre-amps, etc ("rack-it-up", or something vaguely similar) Link to comment Share on other sites More sharing options...
Jivemaster Posted July 14, 2015 Author Share Posted July 14, 2015 OOH! Thanks the RDL-EZ units look just what I'm looking for. What's with 24v phantom? Link to comment Share on other sites More sharing options...
sandall Posted July 15, 2015 Share Posted July 15, 2015 Cost-saving - they run off a 24v power supply, so why go to the expense of anything higher? Except at the high-end, providing 48v phantom is mostly a fashion statement - most capacitor mics are happy with anything above 9v. My CPC Chinese gun mics claim to need 48v, but (having been prompted to check by your post) I find they are quite happy with 12v. Public-address mixer-amps often come with 12v or 15v phantom. Link to comment Share on other sites More sharing options...
Mixermend Posted July 16, 2015 Share Posted July 16, 2015 Phantom power is tightly specified in International standards - and deviations from this due to cost saving are not to be encouraged. Some items do need the full Phantom supply - and users are often perplexed when something doesn't work properly, due to a lower voltage being available - which isn't always clear. Link to comment Share on other sites More sharing options...
sandall Posted July 16, 2015 Share Posted July 16, 2015 Phantom power is tightly specified in International standards - True; 24v is one of the specified voltages. Top-end brands like DPA do need 48v, but the majority of capacitor mics are specified as 9 - 48 (or 52)v. Link to comment Share on other sites More sharing options...
J Pearce Posted July 16, 2015 Share Posted July 16, 2015 To what extent is 48V specified to ensure a usable voltage at the end of a long cable run? I've never bothered to measure the volt drop. Link to comment Share on other sites More sharing options...
alistermorton Posted July 17, 2015 Share Posted July 17, 2015 The specification of 48V is largely historical. Link to comment Share on other sites More sharing options...
Brian Posted July 17, 2015 Share Posted July 17, 2015 To what extent is 48V specified to ensure a usable voltage at the end of a long cable run? It's not. The value was chosen, back in the day, when it was the lowest voltage that would run a valve. The actual phantom voltage is fed to the line via a 6k8 resistor which imposes a maximum current, per leg, of around 7mA. The presence of the 6k8 totally swamps any cable run resistance meaning voltage drop is not a problem. However, cheap kit which only gives out 12v often uses (wrongly) the same 6k8 meaning you can only get 1.7mA per leg. With modern condenser mics with FET preamps this isn't usually a problem although some phantom-powered DI boxes will struggle. Link to comment Share on other sites More sharing options...
GR1 Posted July 17, 2015 Share Posted July 17, 2015 The User Manual for my DPA4080 microphones states their required power supply voltage as 5-50 volts. Link to comment Share on other sites More sharing options...
sandall Posted July 17, 2015 Share Posted July 17, 2015 The value was chosen, back in the day, when it was the lowest voltage that would run a valve. Not strictly true. Back in my Merchant Navy days my (all-valve) emergency transmitters were powered directly off 24v batteries. Lower voltages were used before 48v; chosen by Neumann because NRK already used 48v in their studios (if the BBC had spec'd first we would probably have 50v instead, as it was used universally for comms & switching). Re GR1's post: Curious - I looked up a couple DPA spec sheets & thought they said 48V (obviously time for an eye-test :() Link to comment Share on other sites More sharing options...
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