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In Reply to: RE: for those who built Signal DU/SU-based conditioners posted by jad on July 06, 2012 at 07:07:35
I built mine with a DU-5 to Batman's schematic and use a 15amp thermal breaker (instead of fuse) which is fed from a dedicated 20amp line.
Used as balanced power system.
5000Va derated by 1/2.
2500Va divided by 120V = 20.8 amps.
20.8 X 125% = 26 amps. Minimum wire size #10 awg. (Minimum if full power potential of xfmr is desired.)
Breaker size 30 amp.
Depending on the total length of the #12 branch circuit wire, times 2, the transformer could be starved for dynamic head room power and thus not be able to supply the full power needed by a power amplifier connected to the balanced power xfmr.
(Also keep in mind the power efficiency of the xfmr is some what reduced because you are feeding the the primary winding with half the voltage the xfmr was designed to be fed by.)
I believe your math and wire size are correct if I had a 26amp load on it, however, my equipment is less than 10amp load.
The Signal DU-5 transformer is capable of delivering about 23 amps @ 120V continuous connected load when used in a balanced power mode per the data sheet in the link provided. (Secondary windings are in series.)
Note I said continuous connected load.
In the case of a power amp the mains current draw will fluctuate depending on the dynamics and gain of the source material that is fed to the inputs of the amp. (Dependant on how good the power supply of the power amp.)
The better the supply mains power to the Signal xfmr the better the chance the xfmr will have in handling the dynamic current draw pulses placed upon it by the connected power amp.. Also the better output voltage regulation of the xfmr.
I should note the Signal DU-5 would probably sound better in your system if you fed the primary balanced power 240V (nominal) and paralleled the secondary windings for single ended 120V (nominal) out.
OK, from what you say the DU-5 is mismatched for my system which is triamped-290 watts each, total 870 watts, active crossover-10 watts, preamp-25 watts, CDP-25 watts, plus tuner,reel to reel, cassette etc that might bring the total around 1100 watts if I'm lucky. P=IV the total current draw with everything running is 1100/120 = 9.2 amps. The amps are Yamaha B2's - each have dual power supplies each with their own transformer and each with 36,000 mfd power supply capacitance. Components are powered up and down in sequence with a 15 sec interval (to allow settling) between components. From what you said in this thread and others is that I'm starving the amps of head room with the DU-5 and the 12awg mains wire coming from a 15amp panel breaker. I have a surplus DU-2 that I didn't use as I thought it might be too small. Is is a better match for may system? Thanks.
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