boatman

See this post for version 1.2b of the parts list.

Parts list version 1.2b.BluecomBeltpackPartsList_V1_2b.pdf

The BlueCom system might receive a low level from the ClearCom box and the ClearCom box might receive a high level from the BlueCom system. The only way to find out is to plug them together and see what happens. BlueCom has the advantage that it's possible to quickly adjust the mic amplifier gain on all the beltpacks to compensate for different line levels.

The 3-pin XLR is pin compatible but that ClearCom data sheet specifies -20dB for the audio line signal which might be a bit quiet for BlueCom. No harm will come to either system by plugging them together to experiment. One caveat is that the ClearCom PTT may not work with Granite Audio (Stonewood) systems as they pulse the signalling voltage rather than having a constant level.

Correct. Be careful with the connections to the transformer on the Bluecom side as they will have to be modified from the original box you linked to.

No, the schematic shows that it doesn't have a centre tapped transformer nor an isolating capacitor. However, if you don't need to supply power to the Telex system from the Bluecom system it would be easy enough to just add the capacitor yourself.

The quick start guide for the Clearcom analogue single-channel beltpack (RS-701) is here: http://www.clearcom.com/userfiles/file/User%20Manuals/Partyline/RS-701_QuickStartGuide-399G034.pdf The XLR pinout is compatible and the beltpack will accept 24VDC on the power line but I don't know about the signal levels. Also, as the user guide says that the range of voltages for the power supply is 15VDC-30VDC, it's possible that the master station only supplies 15VDC and things may not work as expected. Bluecom was designed to be compatible with (and was fully tested with) both Tecpro and Granite Audio systems. It hasn't been tested with any other systems so you are exploring unknown territory.

I suspect that the Telex box has pin 1 of the 3-pin XLRs connected to the chassis. None of Bluecom, Tecpro or Granite Audio systems have this so they are all interchangeable. The Telex box must have a DC level on the bus which activates the call light in Bluecom. Again, neither Tecpro or Granite Audio systems have this. It looks as though Telex is the odd one out.

Sorry I have no beltpack boards, but do have a two version 1.1 (prototype) PSU boards with minor surgery. I have just received an order for another project from Elecrow. I ordered 10 boards for $9.50 (approx £7.50). They arrived within two weeks, are of superb quality and there were 14 in the package! That comes in at approximately 50P per board. At that price I have a mind to order a few batches of BlueCom beltpack boards and make a fortune reselling them! Part of the original inspiration for the BlueCom project was that the Blue-Room would be able to market the boards under their merchandising scheme and use the profits to fund the server costs, but it might as well go into my pocket instead and offset some of the development costs.

PM sent.

Yes, adjusting the DIP switches changes the mic gain. Your Clearcom headsets should work OK with the Telex boxes as well as with Bluecom. Just remember that Bluecom is the only system I know of which uses a bridge configuration for the headphone amp so is potentially much louder than the rest! It also has the capability of altering the minimum headphone level (change the value of R27, currently 10R) which no other system has.

There are a couple of differences between the Bluecom and Telex systems. Bluecom uses -10dBm as the signal level on the comms line. This is directly compatible with Tecpro & Stonewood/Granite Audio systems, but (taken from the spec. for the BP319) Telex appears to use 0dBm. It will work but you may have to increase the mic gain on Bluecom, adjust the sidetone setting and reduce the headphone gain. More significant is that the Telex system (again from the spec.) appears to use 20kHz signalling rather than DC so it won't be possible to use the all buttons between different types of beltpacks. Bluecom beltpacks should still be able to call other Bluecom compatible beltpacks and Telex beltpacks should be able to call other Telex beltpacks on a mixed system. The main thing is that nothing should be damaged by connecting the two types of beltpacks together but there will probably be a significant difference in the audio levels.

The fact that two power supplies can be attached to the same circuits means that they must be isolated with a diode. The two power circuits within the Bluecom PSU are also isolated with diodes so there shouldn't be a problem. Whichever power supply has the highest output voltage will take over.

Does a Clearcom master station contain a power supply?

P.M. sent. The signal level on the bus is about -10dB. I haven't experimented with a line-level input, but you could try changing R5 to 4k7 and use a 2:1 transformer to reduce the line level before it hits the mic-amp.

I would be totally against adding programme sound into the comms system but, if you really want to do it, you will need a beltpack PCB for each point. The Bluecom beltpack has a pin strip connector so that various signals can be injected or extracted and the headphone amp is easily capable of driving a transformer to create a balanced feed for an external monitor. The PCBs won't need to be fully populated, only the sections of the circuit needed for the particular purpose you have in mind. Also note that there are mounting holes on the PCB so that it can be built into any suitable housing and doesn't have to be in the extruded aluminium case.

Errm, not at 48V you won't. The forward voltage of an LED is about 2V and the forward current is between 5mA and 10mA, so the resistor has roughly 46V across it and let's say 7.5mA running through it. Ohm's Law tells you that you need a 6.133k resistor (6.2k is close enough) and it needs to be rated at 345mW so needs to be a minimum of a half-watt (a quarter-watt resistor will burn out).

According to the CPC web site, the 51V zener I mentioned in my previous post has a stock level of 21.

51V zener is 18 pence + VAT from CPC! By the time you've added your other bits and pieces you should be over the £5 minimum charge for free delivery of online orders.

Or the 51V zener has been replaced with a 5.1V zener by mistake!

We used to use the Calrec 600 series at Wood Norton 40+ years ago! Mike Talbot-Smith was a great fan. You might find this link useful.

Good work. Are the 3D-printed buttons OK? One caveat with the XLR Y-splitters: You will probably find the Y-ends are the same sex which isn't ideal. What you really need is 1xM and 1xF on the dangling ends.

Another Blue-Room member has just completed a system with four beltpacks. There are now Bluecom systems in Chile and Holland as well as several in the UK with at least one other under construction. I appears that some builders are being charged import duty and VAT on the PCBs which I didn't have to pay, so it might be worth considering European PCB suppliers instead of the cheap Chinese suppliers which I have always used.

The audio line level on Clearcom systems is -14dB whereas Bluecom is designed to work with Tecpro & Granite Audio systems using a line level of -10dB. However there is more than enough headphone and mic gain in Bluecom to adapt to the Clearcom line levels. The only issue I can see is being able to get it small enough to fit in a reasonably sized enclosure. The PCB is double-sided and very tightly packed. I have been building circuits on stripboard for more than 45 years and I certainly wouldn't want to try building a Bluecom beltpack that way.

Yes. The only change on the beltpack schematic to 1.3 was to add a four-pin header to the four-pole jack so that it can be wired to the user's requirements. If you are needing a power unit PCB see this post and send me a PM.