My 700w series 1 on the bench

[George S.]

George, when you were bench testing, what sort of resistive load were you using? Curious because I eventually want to progress to doing similar. Don "Watts Abundant" uses water heater elements in 5 gal buckets of water. Thanks.

 

[GeorgeP]

I made a box up with Four 2 Ohm 275 Watt Wire Wound Resistors, Now set up as Two Four Ohm Loads (Two in series each channel), with double Banana Jacks for each channel. You should be able to find resistors that work for you. I have had this for 40 Years!
Can Handle 550 Watts each side. I Tornado Blow air on them!

 

[George S.]

I made a box up with Four 2 Ohm 275 Watt Wire Wound Resistors, Now set up as Two Four Ohm Loads (Two in series each channel), with double Banana Jacks for each channel. You should be able to find resistors that work for you. I have had this for 40 Years!
Can Handle 550 Watts each side. I Tornado Blow air on them!

Thank you!!!

 

[GeorgeP]

Thank you!!!

I just ordered Four 8 Ohm 300 watt resistors to make a new box..A bit better. Resistors are $23 each. Then...I can set it up for any load and power configuration:
1. Single 8 Ohms at 1200 watts.
2. Two 4 ohms at 600 watts.
3. Single 2 Ohms at 1200 watts.
Build in fans with a switch.
Tap offs for scope connections.
Just havin fun!

 

[e30m3mon]

I assume these are wirewound?
Does inductance play a role (I assume it does) ... would you need to get the non-inductive types?
I had bought an 8ohm 250W resistor years - decades - ago when I was going to work on the PL400-II, but never used it. The PN would suggest it is the inductive type.

 

[GeorgeP]

The inductance is of no concern at 20 KHz. No worries, just heat sink those guys with 2" fins at 12 x12 or so, with a fan on it.

 

[GeorgeP]

Wow...the 700W series 1 doing way over 625 Watts each channel into 4 ohms 50V RMS.
Blows the 10 amp line fuse with both channels at IKW audio power...no problems, no failure. Replace fuse and all fine! Leaving the 10 amp line fuses, Rail fuses at 8 amps. Perfect. High volume high speed fans keep the heat sinks warm, but not boiling!
Looks very clean on scope at 625 Watts per channel @ 4 Ohms.
Ready for the AR9 listening test!
The modified UPC1237 400W Relay board and 700W relay boards working together, no false shutoff! +/- 1V Offset detection verified and working perfect. Covers on and retested. Done.
Next project...Hafler preamp. See Pics