WOPL Rev E PC Board (w/ or w/o Backplane Boards) Performance Specifications Wanted

Northwinds

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#21
A carefully assembled conversion will do better in some or all areas of those original specs. One that is not so carefully assembled may do worse. Since each conversion is a creation of the owner and the care invested in that conversion, it will vary as much as kit built Dynakits did in their heyday
This is EXACTLY what Perry and I were discussing on the phone today. My concern is the people that build these and just try to rip through the build and do a shit job... then sell the amp to someone else and bad shit happens that gets spread word of mouth. The brand then suffers, not the person who did the shit job building it
 

laatsch55

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#22
And that Ron is one of the downsides of kitbuilding, and a good reason to test and document. If it's quiet, SNR is good, frequency response is what it should be and crosstalk is good, it's a safe bet the amp is built well. Having a minimum of test results is a good place to stand your ground.
 

Northwinds

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#23
And that Ron is one of the downsides of kitbuilding, and a good reason to test and document. If it's quiet, SNR is good, frequency response is what it should be and crosstalk is good, it's a safe bet the amp is built well. Having a minimum of test results is a good place to stand your ground.
LIKE :headbang:
 

oldphaser

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#24
To all the folks here on the forum who have built, rebuilt or modified any Phase Linear amps, I would like to know which of the parameters noted below you are currently testing.
All I need are the corresponding numbers (i.e. 1a, 1b, 2a, 2b and so on).

Let me be the first to say, I am not currently testing all the parameters noted below.

As with the case with measuring damping factor, I know of at least (4) or (5) methods to do so. I have only tried one of the methods so far and am not convinced it works well with amplifiers with a high damping factor.
NOTE: Even Bob Carver had his own way of measuring damping factor which appears to be different than the methods I am currently aware of.


1.) Power Output RMS
a.) Watts per channel, both channels driven into 8 Ω 20Hz – 20kHz:
b.) Watts per channel, both channels driven into 4 Ω 20Hz – 20kHz:

2.) Power At Clipping Point
a.) Watts per channel, both channels driven into 8 Ω 20Hz- 20kHz
b.) Watts per channel, both channels driven into 4 Ω 20Hz – 20kHz:

3.) Total Harmonic Distortion (THD+N) (20Hz to 20 kHz) (4Ω and 8Ω)
a.) Maximum levels at rated output
b.) Maximum level at 1W
c.) Maximum level at 250mW

4. ) I.M. Distortion (SMPTE) (60 Hz: 7kHz=4:1)
a.) at Rated power into 8 ohms:
b.) at Rated power into 4 ohms

5.) Frequency Response
a.) at 1W +0 dB / -1 dB
or
b.) at 1V +0 dB / -1 dB

6.) Power Bandwidth
a.) Frequency Response +0 dB/ -3 dB

7.) Signal To Noise Ratio
(inputs shorted) (Ref. Rated output)
a.) Unweighted
b.) A weighted

8.) Damping Factor (at 8 ohms)
a.) at 20 Hz
b.) at 1kHz

9.) Input Sensitivity (at 1 kHz)
a.) Volts RMS for rated output

10.) Slew Rate
a.) Volts per microsecond

11.) Rise Time
a.) Microseconds

12.) Phase Shift
Leading At 20 Hz
Lagging At 20 kHz

13.) Square Wave Response
a.) Tilt(%)
b.) Undershoot (%):
c.) Overshoot(%):

14.) Input Impedance
a.) Controls fully CCW
b.) Controls fully CW

15.) Channel Separation (Crosstalk) vs Frequency
(output level set at -3dB down from rated output)
a.) at 100 Hz
b.) at 1 kHz
c.) at 10 kHz

16.) Dynamic Headroom
(IHF-A-202 3.2 or CEA-490-A 5.2)


Thanks!
Ed
 
Last edited:

marcok

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#25
Hi all ,
are you sure that good measurements mean good sound ?
For me it' s impossible to answer .
In my opinion there two critic points in hifi systems :
1) the matching between power amp and speakers
2) the matching between speakers and the listening room
There are no reference models due to too many variables .
It' s correct to modify circuits to improve reliability and
performance , but it's not enough .
If I don't know the model , I don't know what I have to test .
For example it's very easy to test a power amp on 8 Ohm ,
but the impedance diagram is a complex function .
At this point you must test with your ears .
Two examples : the matching of PL 400 ( stock ) is ugly with B&W DM 6.
but very good with Allison , AR , Klpisch
Yamaha 2010 measurents are fantastic , but this is amp
is not able to drive many speakers . This is my experience .
My suggestion is not to exxagerate with tests .
If I have understood well a normal final factory test is good
to certificate a WOPL amp . IMD and square wave test are expansisive and complicated ;
In other words they are lab tests . IMHO !
Anyway I appreciate very much these activities.
Comments ?
Ciao
Marco
 

oldphaser

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#26
Lies, Damn Lies and Audio Gear Specs “How Audio Gear is Spec’d And Measured†VIDEO

Lies, Damn Lies and Audio Gear Specs “How Audio Gear is Spec’d And Measured” AES 2013 Workshop Panel; Ethan Winer, David Moran, Mike Rivers, Scott Dorsey

https://www.youtube.com/watch?v=Zvireu2SGZM

NOTE: I don't agree with a few of the comments made here. But overall it is an interesting video.


By the way, Ethan Winer also wrote a book: "The Audio Expert: Everything You Need To Know About Audio".

He lives nearby. Maybe I will get a chance to talk to him soon.

Ed
 

laatsch55

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#28
Buried in the various build threads...yep....I had all of that stuff archived but lost it when my old computer took a shit.
 

laatsch55

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#29
Nick, I don't think you'll see a quasi "E" board mated up with a set of WO backplanes. OR, a Quasi "E" board mated up with the original backwall.

All the "E" boards seem to be going full comp with WO backplanes....
 

laatsch55

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#30
Any WO control boards that were paired with the old backwalls will be the "A", "C" and maybe a "D" board or two...
 
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