Question for Joe or builders with appropriate test equipment.

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George S.

Veteran and General Yakker
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Feb 18, 2020
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What kind of numbers do you get out of full WOPL 400s and 700s using best building practices. I'm curious about usable output power and any differences in distortion between the two models.
 
The answer is 'it depends'. I test my completed WOPL into an eight ohm passive load, with a 1.4 VRMS 2KHz sine wave connected to the input jack, one channel at a time to determine the balance between each channel. If I connected both channels into dummy loads, that would be a worst case scenario for the power supply. I do that, too. If I hooked the outputs to the four ohm passive dummy load, the power output would go way up, but that doesn't tell me much diagnostically. I look at the output signals on the oscilloscope to check for clipping threshold, usually none. Then I test first one, then both channels musically. Each amp is different, mostly depending on the available voltage provided by the power supply. I have seen PL400's with anywhere between +/- 72VDC to +/- 85VDC. And the PL700 can range from +/- 98VDC to +/- 110VDC.
The last two PL700 amps I did measured well over 1000 Watts peak musical power, which is what you are listening to from your speakers. Depending on the efficiency of your personal eight ohm speakers, you may 'hear' between 500 Watts to 800 Watts. This is stadium level sound, you cannot be in a listening room at those levels, your hearing will be in peril at that sound pressure level.
 
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So, if you all are getting 1000 watts out of a 700, then how much out of a 400. Doing a little math, 700/1000:400/X, therefore 700X=400(1000), so X=571. Has anyone actually accurately measured a 400s output. Does the WOPLing increase output? I'm thinking it probably doesn't as output is limited by the original transformer? Just something I sometimes wonder about as I roll down the highway. Thanks.
 
242 to 258 per channel into 8 ohms, both driven, to1% distortion..
 
Grapplesaw had my 400 four-fin on his bench after installation of a REV-E board and output transistors. I was present when, using his anayizer, he obtained 265 WPC.
 
Hey thank you all, I'm a total noob when it comes to electronic theory. Am I correct in thinking that 1% distortion represents a bench mark indicating the beginning of clipping of the wave form?
 
1% THD is distortion not clipping. The clipping happen when a voltage source limit is reached and there is no more to provide. That is why a PL700 would have 110V power supply and low power amps a lesser amount.
If a amp gets to clipping the distortion will go up very fast as square waves have tons of THD in them and nowhere near 1%.
I usually get by with amps that can provide 30W/ch on the bench and so you guys are in a class much higher than what I typically deal with.
I have toyed with the idea of getting an Emotiva Integrated amp for the bench to replace an old Sansui I am using but it all cost money.
 
Going to spend some time reading about THD and see if I can gain some insight. Looking at the PL400 manual I see a spec of 210 watts RMS and .25% THD. Does the 1% distortion that laatsch55 quoted come from "overdriving" the amp? If not, then why this 1% distortion figure? Thanks.
 
The 3% THD is used by a lot of manufactures as that is where the human can hear it. 1% is better. Regardless of the amount for that power level other than in an auditorium these volume levels with efficient speakers are insane. Yes there are venues that must use many Crown DC300 to power all the speakers but that was the Royal auditorium where the Moody blues played as well as many others like McCartney. I forget the name exactly.
 
George S. said:
Going to spend some time reading about THD and see if I can gain some insight. Looking at the PL400 manual I see a spec of 210 watts RMS and .25% THD. Does the 1% distortion that laatsch55 quoted come from "overdriving" the amp? If not, then why this 1% distortion figure? Thanks.
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George I decided after getting my Audio Precision ATS-1DD that 1% distortion would be a repeatable spec that would represent the power level that you could stand. Distortion past that is really irritating, and it does represent the onset of clipping. Powering an amp after that would not be a continuous spec for long...
I feed the amp off the AP..till I reach 1% then see what power level its at... it's fairly consistent.
 
Thank you Gentlemen! I'm starting to get a grip on this subject. And, yes, the power levels from these amps are just overwhelming and insane. I never had anything over 60 WPC until I upgraded to two WOPLed 400s in a biamp configuration, mains and subs. My aged father always said Phase Linear was "esoteric" equipment, and he worked in the electronics fields all his life. Thank you, now I need to read more on the subject. Thanks.
 
mlucitt said:
The answer is 'it depends'. I test my completed WOPL into an eight ohm passive load, with a 1.4 VRMS 2KHz sine wave connected to the input jack, one channel at a time to determine the balance between each channel. If I connected both channels into dummy loads, that would be a worst case scenario for the power supply. I do that, too. If I hooked the outputs to the four ohm passive dummy load, the power output would go way up, but that doesn't tell me much diagnostically. I look at the output signals on the oscilloscope to check for clipping threshold, usually none. Then I test first one, then both channels musically. Each amp is different, mostly depending on the available voltage provided by the power supply. I have seen PL400's with anywhere between +/- 72VDC to +/- 85VDC. And the PL700 can range from +/- 98VDC to +/- 110VDC.
The last two PL700 amps I did measured well over 1000 Watts peak musical power, which is what you are listening to from your speakers. Depending on the efficiency of your personal eight ohm speakers, you may 'hear' between 500 Watts to 800 Watts. This is stadium level sound, you cannot be in a listening room at those levels, your hearing will be in peril at that sound pressure level.
Click to expand...

Peak music power????? Pshaw!!!!
 
When running the numbers, does anybody pay attention to the line voltage at the AC receptacle? Looking at the manuals, 400/700B has no spec, Series II's are 120 volts.
 
Line voltage is not all that critical until you get into sags that are pretty serious. The amp all convert the AC to DC and then depending on secondaries make what split supplies that are needed. You can have plus and minus 100Vdc supplies in amps and the higher voltage is required due to ohms law.
I once said how do these Auto amps get such high power from out of 12Vdc? Well what they do is trade current for voltage and some elaborate heat sinked supplies get some higher voltage even in car amps that are even before and Audio transistors see the heat sink. They are like switching power supplies but up the voltage in trade for higher currents then with the higher voltage and 4 ohm speakers the power rating can be more than 20 watts per channel. There are voltage stabilizing transformers that you can buy if the voltage bothers you but this is all being a bit too picky.

It kind of reminds me of the Church installed back auditorium amp system that was a 5000 watt rating when it was supplied from one 20 Amp wall circuit and it was not 220Vac. Does anyone see the problem with that for the full power? This is what happens when you hire idiots when there are Radio Engineers around that could have done the job correctly.
 
wattsabundant said:
When running the numbers, does anybody pay attention to the line voltage at the AC receptacle? Looking at the manuals, 400/700B has no spec, Series II's are 120 volts.
Click to expand...

400 700, 700B were rated at 117 vac...
 
Skywavebe said:
Line voltage is not all that critical until you get into sags that are pretty serious. The amp all convert the AC to DC and then depending on secondaries make what split supplies that are needed. You can have plus and minus 100Vdc supplies in amps and the higher voltage is required due to ohms law.
I once said how do these Auto amps get such high power from out of 12Vdc? Well what they do is trade current for voltage and some elaborate heat sinked supplies get some higher voltage even in car amps that are even before and Audio transistors see the heat sink. They are like switching power supplies but up the voltage in trade for higher currents then with the higher voltage and 4 ohm speakers the power rating can be more than 20 watts per channel. There are voltage stabilizing transformers that you can buy if the voltage bothers you but this is all being a bit too picky.

It kind of reminds me of the Church installed back auditorium amp system that was a 5000 watt rating when it was supplied from one 20 Amp wall circuit and it was not 220Vac. Does anyone see the problem with that for the full power? This is what happens when you hire idiots when there are Radio Engineers around that could have done the job correctly.
Click to expand...


If need be, I'll agree to disagree.

I think we all agree the P/L power supply is a conventional unregulated power supply. If line voltage drops, the +/- DC drops and so does maximum output power. Therefore, I contend that if output power is being stated, line voltage is relevant.

Ed B. is noted for being a stickler for specs, sometimes to the dismay of others. I applaud him for acquiring and paying attention to standards. If line voltage is 117 VAC for 400/700B etc (which I do not dispute, I just couldn't find it stated in the manual) and 120 VAC for series II amps so be it.

Legit car stereos do have switching power supplies that step up the +/- DC voltage. Yes they have large heatsinks. A kilowatt of audio power at 12 volts DC requires something like 100 amps from the alternator/battery. There is this thing called efficiency. That's why headlights flash on bass transients when the amplifiers demand more than the alternator can supply. Some people go to the extreme of adding farads of stiffening capacitors or a trunk full of batteries to stabilize the DC voltage. The typical car stereo enthusiast seems more concerned about sound pressure level than fidelity. Otherwise the car wouldn't sound like a bad case of intestinal gas as it passes by.

In 1978 I got my first real job at a transformer shop. I hated it. BORING! 40 years later I still find my self educating people on line stabilizing transformers such as tap changers, mag amps (not the Carver audio amps) and ferroresonant transformers. If there is an interest in these I can supply supporting documents. Be careful for what you ask.
 
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