A-B comparison, stock 400s2 vs WOPL’d 400s2

NeverSatisfied

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#1
Soooo…some may know that Don (Wattsabundant) has been building a 400s2 for me. Well it arrived safe and sound a few days ago and I wanted to share my impressions with the group and publicly thank Don for his outstanding work and generosity. I would also like to thank Mark (mlucitt), he built the boards and of course Joe (Gepetto) for making all this possible with White Oak Audio.
To start with, this is not going to be a audiophile review with all the creative audio speak, just a real world opinion from someone who does not have golden ears or any formal musical training. I think I know what sounds good but I have learned that music reproduction and how good it sounds is a very personal and subjective subject.
This is also an initial test done in my shop with very modest gear just to get a baseline before it goes in the big system. Doing a real A/B test in my bigger systems is not easy and more work than I am willing to do right now.
I am using an old PL 3300 preamp being fed through the AUX from a BT dongle connected to my phone. The speakers are Acoustic Research Phantoms, they are actually amazing little speakers that use Illusion Audio drivers that were developed for high end car audio. Anyway, this is not exactly a high end setup but it is better than you might think and good enough for initial impressions.
The stock amp is in good shape and sounds great, it does produce the famous double pop from the caps discharging when you power it off.
So here is the setup. 18EFEA54-0B42-4CDF-BFCD-6B7DD5F98026.jpeg 319FC4F9-D504-4441-9A03-03C60BD945F0.jpeg D5B2268B-92FD-405D-B26D-7503370B8140.jpeg Not having ever heard a WOPL before, I honestly did not know what to expect and was worried that this was going to be a totally different animal.
I can happily report that this is not the case, in fact the tonal signature is very much the same. All amps have a sound that is unique to that design and I love the PL sound. So I was hoping that Joe had taken the physicians moto of “first do no harm” and to my ears that has been accomplished.
What is different is the noise floor, he WOLP is quieter at idle and stays that way as the gain goes up. Now the preamp does inject some hiss and both amps pass it through but with the music paused and the volume turned up all the way, it is easy to tell the WOPL is quieter.
Now for the more subjective part, I don’t hear any magical whispers of music that I never heard before, nor was I transported to some audio never-neverland. In fact the differences are very small in this setup but they are there, the WOPL is a tiny bit more crisp and punchy, still what I consider a warm sounding amp but with a cleaner leading edge. I obviously can’t really test the bottom end with these speakers and might just have to lug everything down to the house and give my B&W’s a chance to weigh in on all this but as far as first impressions go, I am very pleased.
 

laatsch55

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I had some light bulbs and flatscreen that would argue the point about tighter, faster, lower bass in a WOPL... I've run enough frequency sweeps on before and after conversions, on a WOPL it's flat to 10 hz, on a stocker they start rolling off around 25 hz...
It actually is a big difference with some speaks that go that low...
 

laatsch55

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One of Joe's objectives was to keep the Pl sound....I had some Spec 2's around the house since 1975 and theyu were the Alpha dogs until the first time I threw a WOA driver board in a 700, even with the factory backwall it was still enough for me to retire the Spec's...
 

NeverSatisfied

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I don’t believe in cable or interconnect burn in but absolutely believe in speaker, stylist and to a lesser degree component break in.
Today I let the WOPL run most of the day at medium volume and I swear it started sounding better. To the point that I had to swap back to the stock amp just to make sure I wasn’t getting high off the Koil fumes, sure enough, the differences I noticed yesterday seemed a little more evident.
I am sure Don test ran the amp but not sure how long. Can someone explain what is happening when am amp or other purely electrical component improves with use?
 

laatsch55

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That phenomenon was also witnessed by yours truly not long into the WOPL experience. After 2 solid days of being on it was like a veil had been lifted. No technical explaination has accounted for it. An audiophile bud in Phoenix was also a believer in it. When visiting our daughter in Phoenix every January Stephen would power up his tunebox when we got on the plane in Rapid City...
It is a TRUE thing that happens....why and how is still not understood.........totally......
 

Michael F

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I think your findings will be, pardon the pun, amplified proportionally once you get the PL into your main system which is much more revealing than what you are currently testing with.
Component break-in is a real phenomenon. It is more apparent and quantifiable in loudspeakers when changes in mechanical properties occur altering TS parameters.
I attribute tonal changes in electronic components to capacitors forming. But..., it can also be argued that no physical or electronic changes are occurring at all and that the listener is simply getting used to the sound or even a case of expectational bias.
Have fun with your new acquisition and report your findings once the amp is installed in the main system. That would be a great place to do a more objective A-B comparison.
 

NeverSatisfied

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I think your findings will be, pardon the pun, amplified proportionally once you get the PL into your main system which is much more revealing than what you are currently testing with.
Component break-in is a real phenomenon. It is more apparent and quantifiable in loudspeakers when changes in mechanical properties occur altering TS parameters.
I attribute tonal changes in electronic components to capacitors forming. But..., it can also be argued that no physical or electronic changes are occurring at all and that the listener is simply getting used to the sound or even a case of expectational bias.
Have fun with your new acquisition and report your findings once the amp is installed in the main system. That would be a great place to do a more objective A-B comparison.
I agree and will be stuffing it in one of the main systems tomorrow. It won't be a true A/B though because it's going to replace my D500 and that's a though act to follow. I plan to listen to the 500 before swapping in the 400 and then compare using the same source material but it's too much work to swap amps back and forth.
 

George S.

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Yes, both had G boards...
My 700 has 50k attenuators, the 400s have 100k. From the little I understand, this directly affects gain at the amps due to a difference in input impedance. From observing the 700 drive the subs, and a 400 drive the JBLs, there is a marked difference readily seen in the Cylon meters between the two. It appears to me the 700 with the lower input impedance is "seeing" a higher signal level than the 400 with the higher input impedance.
My grasp of input impedance and it's effects is sorely lacking, even after studying it for several weeks. So much of this I just fail to understand. Joe did state in a post that the gain structure of a 400 and 700 is exactly the same, limited only by the number of outputs and available voltage.
So does a lower input impedance make a difference in a amps output? I think so.
Next step on my system is to replace the 100k attenuators in the 400s to 50k as to match the 700. Hopefully this will match the gain structure between the two amps as used in the bi-amped system.
There is a lot of this I don't understand and hopefully Joe will comment.
 

George S.

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#19
The pots are attenuators, at full rotation there should be no resistance. The Pig is a 400 Sre I... the 700 was a B...
Yes, no resistance to speak of from the RCA center conductor to the control board. But the input impedance would be different. Does it matter? I don't know, but think it affects gain structure. Going to find out.
I do know the 700 with 50k attenuators seems to have higher "sensitivity" to signals than the 400s with 100k attenuators. At normal listening volumes that difference in attenuators should be the only factor that makes a difference between the two, given what Joe said about gain and the control boards all being "G".
I need to get the "input sensitivity" balanced between the amps, at the amps if possible. I'm thinking 50k attenuators in the 400s will do it.
 

NeverSatisfied

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#20
Well, I am doing better than Lee but I think I tweaked my back pulling the D500. Man that is one heavy mofo. The upside is after the swap, I had a good excuse to just sit around and listen to music instead of the twenty other projects I need to do.
After getting everything back together I started with some vinyl but my back wasn’t having it, so I switched to streaming.
First, this is definitely “the little 400 that could”, no she ain’t the beast that the 500 is but damn she ain’t no porch puppy either, she can definitely run with the big dogs.
As suspected, once she could grab some real woofers then the real fun started. Excellent bottom end, still sweet in the mid’s and clean on the highs. I don’t push for ear splitting SPL’s but after an hour of jamming I did push it up to a level that was pretty damn ridiculous, she never sounded strained or out of gas. The bass is tight and controlled with the B&W’s which have always produced better bass than a speaker that size has any right to. I am very impressed and when you add in the fact that she should be solid for another 40 years, I am sold on the WOPL process.
Damn Joe, your the man !!!
(Don is coming down this week and I am hoping he has time to come by the house this weekend, he doesn’t know it yet but his return luggage is going to be a tad heavier, doubt he’ll notice if hide a 700 in there, shh). 583184E5-2721-4D19-968B-A0DA7B0BF71B.jpeg
 
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