Working on some of the amps that I have recently built and working on the next version of one that is higher power I figured I better start beefing up my dummy load for the amps. My 4 soldered together 20w 2ohm resistors would not be adequate for the next amp so figured time to take a break and work on test equipment.
I picked up 5 200w 4ohm resistors from EPay and fabricated a simple way to have a flexible very high powered load for testing. Bringing out each 4ohm resistor to binding posts I could have a bunch of combinations to test with, i.e., stereo 8ohms at 400w per channel, etc. I do guess the ratings for these large resistors are when dipped in liquid nitrogen, but even derating 50% plenty of head room for any amp I'm going to build and will not have to worry about things getting too hot or the messy tangle of soldered up resistors.
I also found a small fan in the junk pile and figured I would add that too just for fun.
Cabinet was an aluminum hammond 6"x10"x2" primed and painted. Other aluminum was scrap in the garage.
I picked up 5 200w 4ohm resistors from EPay and fabricated a simple way to have a flexible very high powered load for testing. Bringing out each 4ohm resistor to binding posts I could have a bunch of combinations to test with, i.e., stereo 8ohms at 400w per channel, etc. I do guess the ratings for these large resistors are when dipped in liquid nitrogen, but even derating 50% plenty of head room for any amp I'm going to build and will not have to worry about things getting too hot or the messy tangle of soldered up resistors.
I also found a small fan in the junk pile and figured I would add that too just for fun.
Cabinet was an aluminum hammond 6"x10"x2" primed and painted. Other aluminum was scrap in the garage.
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Hey Sandy, nice job. I use six 12R 100W wirewounds on a heatsink. Don't worry too much about de-rating unless you plan to run them at full power for long. These type of resistors don't mind being overloaded for a short time. I have tested an 800W RMS per channel amp flat out into mine, they got toastie but no problems. Could you give a link to those resistors? I have not seen any so long. The 200W types I have seen are short and fat.
Cheers Matt.
Cheers Matt.
Thanks Matt -
I would expect they should be ok for the 100-150w amp that is coming up. Figured do it over the top and not have to do it again
Here is the link the the EBay seller. I had him do 4 4ohm and 1 8ohm at the same price. So I have one more 8ohm 200watt, might make a smaller one shot for that.
5pcs 4 Ohm 4R 200W Watt Power Metal Shell Case Wirewound Resistor | eBay
He has them in 2 ohm, 8 ohm as well and same in the 100watt size which are a bit more economical. He shipped them very quick as well.
Sandy
I would expect they should be ok for the 100-150w amp that is coming up. Figured do it over the top and not have to do it again
Here is the link the the EBay seller. I had him do 4 4ohm and 1 8ohm at the same price. So I have one more 8ohm 200watt, might make a smaller one shot for that.
5pcs 4 Ohm 4R 200W Watt Power Metal Shell Case Wirewound Resistor | eBay
He has them in 2 ohm, 8 ohm as well and same in the 100watt size which are a bit more economical. He shipped them very quick as well.
Sandy
Since you showed yours I will show mine. Made from all scrap parts with the exception of some high power resistors purchased at scrap prices.
http://www.ebgusa.com/NEWPDF/EBGCAT33.pdf
Mine uses 600 watt 4 ohm resistors in a series parallel config and gives me 2) large 4 ohm loads for testing or I can jump the binding post for one large 8 ohm load.
I used a JBL heat sink to mount the resistors to and a fan assembly from a commercial rack that uses 3) 55cfm fans to cool the heat sink.
http://www.ebgusa.com/NEWPDF/EBGCAT33.pdf
Mine uses 600 watt 4 ohm resistors in a series parallel config and gives me 2) large 4 ohm loads for testing or I can jump the binding post for one large 8 ohm load.
I used a JBL heat sink to mount the resistors to and a fan assembly from a commercial rack that uses 3) 55cfm fans to cool the heat sink.
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Burnedfingers - I like your way of thinking!
Loren42 - I thought about doing something similar like the old dummy load from some of my old ham gear the 'Cantenna' which was something like that, then I though of the mess of the oil when I drop the can on the floor or something to that effect
Might come in handy as a room heater at some point, this winter was cold!
Sandy
Loren42 - I thought about doing something similar like the old dummy load from some of my old ham gear the 'Cantenna' which was something like that, then I though of the mess of the oil when I drop the can on the floor or something to that effect
Might come in handy as a room heater at some point, this winter was cold!
Sandy
A lot of money being spent on simple resistor. Most dummy loads are temporary... why not use an old heater modified for the desired load. Old heating element from central a/c unit will sink thousands of watts. (5 KW element on old heater frame will sink 1000 watts with out fan. It will get HOT but wont melt.
Burnedfingers - I like your way of thinking!
Loren42 - I thought about doing something similar like the old dummy load from some of my old ham gear the 'Cantenna' which was something like that, then I though of the mess of the oil when I drop the can on the floor or something to that effect
Might come in handy as a room heater at some point, this winter was cold!
Sandy
Thanks, I bought the resistors for $4 ea. Since I use it all the time I needed something that was large enough to load a very high output amplifier on.
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