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Max Watts of Soundcraft 400b psu Utility Plugins
Old 15th August 2007
  #1
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Brian M. Boykin's Avatar
Max Watts of Soundcraft 400b psu

Anyone know the watts rating of 400b psu. It's not written on the psu, nor can I find it in the manual. The mains fuse is rated at 15a if that helps.

Thanks,

Brian

I also bought the schems the other day and it's not listed on them either.
Old 18th August 2007
  #2
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Hi
Rummage on the Soundcraft site and you may get full info there.
Matt S
Old 18th August 2007
  #3
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Brian M. Boykin's Avatar
I have and found nothing definitive. It does'nt matter so much, I know it is going to have to be replaced for me to do what I want to do. I just was wondering how far I could get with it before I smoked it.

Thanks,

Brian
Old 18th August 2007
  #4
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Hi
Power supply ratings are more often about how hot they get rather than specific ratings at which point they would 'burn'.
If you know you are tinkering with your desk and keep an eye on how warm the various parts of the supply get, transformer, rectifier and regulator transistors primarily, then there is not much danger. Allowing extra airflow is always a good idea. Electronic components are usually happiest at up to say 25 Centigrade but it may be that the design temp for a given supply unit may allow the transistors to run at 50 or 60 Centigrade, possibly more. To design a supply which runs at say 35 Centigrade without forced cooling would be VERY expensive with massive heatsinks. It is all a matter of compromises. It is those who stick a small supply in a non ventilated cupboard with other hot gear around who have the most problems. Depending on what you are doing to your desk the consumption may actually go down if you are using newer, low power chips in the majority of places.
Matt S
Old 19th August 2007
  #5
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Brian M. Boykin's Avatar
Hey Matt,

Good to hear from ya. I figure the original power supply is over 20 years old and rather than recap it I thought I would just build a new one using power one modules. I just bought the book "Optimizing Opamp Performance" so I would imagine the math is in it to figure out total amps for my console. I'm going to send the master module to Jim and let him do his thing to it and then I'm going to do the input modules myself. I've read more than a few times to first do the master and monitor section so you can hear changes elswhere. I'd like to balance the direct outs, mains and add balanced monitor outputs. That's at least 28 extra opamps. I'm thinking of using the Burr Brown dvr134 which can draw up to 5 milliamps. Also, I'm going to experiment with different opamps in the input modules to find out what I like sonically. Of course I'm going to do all this after its recapped and fitted with metal film resistors. A lot of work ahead of me, but I'm just the recluse to do it.

Thanks,

Brian
Old 20th August 2007
  #6
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Hi
If the desk is currently working you could simply measure the DC current draw on each rail when idle (no audio). Add 20 percent for increased current taken while delivering audio then add say 2 Amps (for your proposed mods) to give you a ballpark current consumption.
You would then probably settle for the 15 Amp 15 Volt Power one modules, and mod them to give 17 - 18 volts as used on some of the AMEK desks. Strictly the 15 amps should be 'derated' as they are 250 watt modules but I expect they would be fine.
Matt S
Old 22nd August 2007
  #7
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Brian M. Boykin's Avatar
Here's another thought,

I am thinking of adding 16 channels in a split console design. I would track from the 16 channels and return to the 24 to the left of the console. This leaves room for a friend of mine, who wants to produce, to play screw around with the mix while tracking. I am currently adding ground compensated direct outs to the 24 current channels. If I went with this design, I would leave them unbalanced and only balance the 16 I would be tracking from. Jim said because of the loop gain circuit of the summing amps this would be a bad idea; you chimed in on that thread and mentioned distributed mixing. Please explain that if you can. I am assuming that if I limit the mix to 24 channels distortion will not be much of a problem, only if I dig into the additional 16. And last, is it possible to split the power scheme and power the 16 off of one psu and the original 24, groups, and mix buss of another. It seems that if I picked up another console I could power it with its psu and only bring the signal over to the master module, terminating the rails at the last channel. I think I'm going to do the Tangible Technology ground scheme for all the modules, don't know if your familar with that or not.

Thanks,

Brian
Old 22nd August 2007
  #8
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Hi
Distributed mixing is where you have summing on each bay of (say) 16 - 24 modules. Then when it is at line level you mix the 'bays' together.
If the modules you have available have mix amps available in them then this could work. Rather than using another 'summing' amp to join the two together you could simply use a resistor of the same value as the existing mix resistors to add it the the (24) main mix. Make sure that the new summing presents the signal IN phase. A simple VE mixer stage inverts normally so would need reinversion.
Don't know about the earthing mods but I presume it is some fancy name for an established principle.
Matt S
Old 22nd August 2007
  #9
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Brian M. Boykin's Avatar
Hey Matt,

I was wondering about what it seems that you are explaining. I have an empty slot where the aux retuns module is suppose to be. I'm going to use the tape returns as aux returns, there are 8 so I'll have 4 stereo returns. I presume I could build a summing stage for the extra 16, attach it to the blank and send it on to the master module at the appropiate level to join the 24. If I wanted to get fancy, I could do the same for the 24 and further reduce the strain on the master summing amps. This would alos invert both bays and bring them in in phase. Correct???

As for the ground mod, each module has 4 ground wires in the wire loom. They are daisy chained from one end of the board to the other. All you do is add a buss bar to the frame and run a seperate ground to each module, similar to a star ground scheme. It is suppose to lower the noise floor and internal hum. Little time consuming, but cheap and easy.

Thanks Again,

Brian
Old 27th April 2008
  #10
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800B project

Hello, I am trying to rack up 4 modified 800B modules for random use. I want to put in a XLR direct output on them and then use a S400B PSU to power them. Does anyone have advice? I know that each 800B module need +17 and -17volts VDC and this is what the S400B PSU distributes. Thanks
Old 2nd May 2008
  #11
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Hi
Basically just wire it up and you are very likely to have no problems at all.
If the supply is being 'shared' with other kit then there may possibly be a 'ground loop' issue if you are very unlucky.
Matt S
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