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

 

[GeorgeP]

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!

I'm now 95 % completed the build. Ill attach pics I n a few days.
Added LCD metering for RMS voltage for each channel. Tested Perfect.
I attached the Schematic of the design. You cant buy this anywhere!
Ill add pictures of the box in a day or so.

 

[gene french]

I'm now 95 % completed the build. Ill attach pics I n a few days.
Added LCD metering for RMS voltage for each channel. Tested Perfect.
I attached the Schematic of the designView attachment 76153. You cant buy this anywhere!
Ill add pictures of the box in a day or so.

thanks for the edisin filament hack...worked perfectly...much brighter...

 

[GeorgeP]

thanks for the edisin filament hack...worked perfectly...much brighter...

You used the exact LED string I used (attached) ? If you think they are to bright, you can easily add an adjustable regulator. I didn't but its pretty easy.

 

[gene french]

You used the exact LED string I used (attached) ? If you think they are to bright, you can easily add an adjustable regulator. I didn't but its pretty easy.

no sir...that company would not ship to my freight forwarder....
i found another seller on ebay....
listed as 26mm @ 3v....
they look identical....
edisin=edison....
happy now sniff??
i used with the white oak led upgrade board...it has adjustment built in...
i will do the full hack on the spare set i have which is the original board...pl18 i think...
again...i enjoyed!!!
thanks

 

[GeorgeP]

no sir...that company would not ship to my freight forwarder....
i found another seller on ebay....
listed as 26mm @ 3v....
they look identical....
edisin=edison....
happy now sniff??
i used with the white oak led upgrade board...it has adjustment built in...
i will do the full hack on the spare set i have which is the original board...pl18 i think...
again...i enjoyed!!!
thanks

Great. Yes the 400s have that upgrade board... I did it to my 700 Series 1 just with the series resistors, No White oak board for it... I was thinking about designing one for that version 700W. I may do what you did to my one 400 Series 1 that I recently re-furbished also with that white oak board and their LEDs. Have fun!!! BYW... yours look great. I did add front panel Volume controls to mine, and the Speaker relay LED on the front panel to indicate No offset and functioning relay board indicator that I can see.
I did add a subsonic DC block also at the inputs Roll-off at 10 Hz, so DC from a Preamp wont get to the circuits in the first place. Just Belts and suspenders protection. No affect on sound.

 

[gene french]

i hate drilling the front...lol i can however see inside the amps from the top....through the slits...and can easily see the led...
when i added digital meters to both wopls...one of my units came in with bad meters....someone tried to fix/adjust them....
anyway....they messed up that little main spring on both....i found the digital meters...which i like...
and since the wopl is the new technology....i decided to do it at both....
order a ac voltmeter....gonna experiment with it on the speaker outs..
thanks!!!
good luck....please keep me posted....i love watching/doing this stuff...

 

[gene french]

Great. Yes the 400s have that upgrade board... I did it to my 700 Series 1 just with the series resistors, No White oak board for it... I was thinking about designing one for that version 700W. I may do what you did to my one 400 Series 1 that I recently re-furbished also with that white oak board and their LEDs. Have fun!!! BYW... yours look great. I did add front panel Volume controls to mine, and the Speaker relay LED on the front panel to indicate No offset and functioning relay board indicator that I can see.
I did add a subsonic DC block also at the inputs Roll-off at 10 Hz, so DC from a Preamp wont get to the circuits in the first place. Just Belts and suspenders protection. No affect on sound.

love your hacks...
thanks for sharing...