David's Phase Linear 700B Thread

[laatsch55]

Spaced that one Joe. I still tighten every set that goes through here..

 

[Phase Linear Phanatic]

Well I'm about a dumbf^%$. Try it in DC mode. Jwer was looking to see if the hum was measuable..

?? Son of a ^%$@! Those measurements I just gave you WERE in DC mode! Now I'M the dumbf&%#@! Ugh okay........ one more time. In AC mode:

-White Oak PL 700B
L channel~ 1.0mv R channel~ 0.7mv /without speakers
L channel~ 1.8mv R channel~ 0.7mv /with speakers

-International PL 700B
L channel~ 0.1mv R channel~ 0.1mv /without speakers
L channel~ 0.1mv R channel~ 0.0mv /with speakers

-PL 700B (700 watt R.M.S.) version
L channel~ 0.1mv R channel~ 0.3mv /without speakers
L channel~ 0.1mv R channel~ 0.3mv /with speakers

 

[laatsch55]

So, did you check the transformer bolts?

 

[Phase Linear Phanatic]

So, did you check the transformer bolts?

No. I don't think I ever noticed anything loose there while inserting into the wood case, then into my rack. Ask Jerry If he noticed? I have to take it all out soon anyway. I'll check for it when I get Dougs meter. At the moment, I just pushed it out of the box sideways to get measurements from the binding posts. And I'm crouching in a tight corner to do that. Just wanted to get you guys the quick readings.

 

[laatsch55]

It doesn't have to appear or look loose. A 7/16 combo wrench and take a turn or 2 on em..

 

[laatsch55]

After checking the bolts let's measure the output BEFORE Don's board by unhooking the outputs at the input to the board and hooking your meter directly to those. See what ya get.

 

[Phase Linear Phanatic]

After checking the bolts let's measure the output BEFORE Don's board by unhooking the outputs at the input to the board and hooking your meter directly to those. See what ya get.

Great. Internal tests huh? I better not get zapped. I left my alligator clips at my fathers. Just grabbed the multimeter. The more items I bring home from the ol' speaker building days, the more the lady scowls at me. She hates the mammoth speakers already. The amps didn't help the matter. And now parts and test equipment. Hmmmm me thinks flowers are next on the agenda.

We have to wait a week before I can get those measurements to ya Lee. Work calls now.

 

[laatsch55]

No problem, we'll be here...

 

[Phase Linear Phanatic]

Received the VU meter today. I must say Doug. That was fast! And that takes into account no delivery on Sunday? Thanks!!!! Now it sits here in a box till Saturday. (stupid work).

Say, what happened to that Nav guy? I haven't had my thread hijacked in a while? Is he feeling okay?

 

[laatsch55]

Work does suck when it bumps fun....

 

[fitz43]

Work does suck when it bumps fun....

I keep telling them at work, that I don't mind getting up and going to work each day. It's the waiting around for 8 hours before I can go home that is a drag.....

Maybe not for much longer.....

 

[laatsch55]

Retiring or getting the axe Doug??

 

[fitz43]

Retiring or getting the axe Doug??

possibly retiring. was offered a buy out package a couple of weeks ago. Got the money numbers being run to see if it's doable or whether I'd be eating Kraft Dinner broth for the rest of my life.

 

[fitz43]

Received the VU meter today. I must say Doug. That was fast! And that takes into account no delivery on Sunday? Thanks!!!! Now it sits here in a box till Saturday. (stupid work).

Say, what happened to that Nav guy? I haven't had my thread hijacked in a while? Is he feeling okay?

That WAS fast. Your postal system is much quicker than what we experience in Canada. Did my notes about the diffuser strips make sense?

 

[Phase Linear Phanatic]

That WAS fast. Your postal system is much quicker than what we experience in Canada. Did my notes about the diffuser strips make sense?

Yes. I just must not have clearly remembered seeing them taped to the bottom of the meter like that? (Like the honeywell has on it that you sent me) and I got the extra diffuser strips in the envelope. I had this wild idea that on the Jewels they were buildt into the plastic housing that encased the meter? I must be on crack if thats wrong? And i just may be on crack? I won't get a good looksee until the day i do the meter swap. (Surgery). I think that and the tests will be Sunday. I will be visiting my folks Saturday instead. That will give me a chance to grab my alligator clips while over there. So i hope Lee n Joe n Jerry and you are all around on that day. Its all I have till its back to work again. (I so need a vacation) :-/

 

[laatsch55]

I should be..

 

[jbeckva]

?? Son of a ^%$@! Those measurements I just gave you WERE in DC mode! Now I'M the dumbf&%#@! Ugh okay........ one more time. In AC mode:

-White Oak PL 700B
L channel~ 1.0mv R channel~ 0.7mv /without speakers
L channel~ 1.8mv R channel~ 0.7mv /with speakers

-International PL 700B
L channel~ 0.1mv R channel~ 0.1mv /without speakers
L channel~ 0.1mv R channel~ 0.0mv /with speakers

-PL 700B (700 watt R.M.S.) version
L channel~ 0.1mv R channel~ 0.3mv /without speakers
L channel~ 0.1mv R channel~ 0.3mv /with speakers

David,

Here's where I am a bit confused and have a concern (but hey... I'm thinking more as I type this sooo... bear with me). I had you measure AC direct from the speaker outputs to compare the "hum" signal. Since you stated the hum is 60hz, it should be measurable as most AC meters are going to measure that frequency quite accurately (think about it... they would definitely need to measure accurately standard AC "wall voltage", correct?).

This stated, the measurements above (1.8mV maximum) don't quite indicate an issue. I measured my own WO 700, and I have around 1mVAC on both channels.

Going further... with 1.8mVAC and even with an 8ohm woofer rated at 100db SPL 1W/1M, the actual db level would be 64 decibels down from the SPL rating. 36 db, barely above a whisper. 39 db is typically the threshold of hearing at 60hz.

Now hmmm (pardon the pun.. lol)... You stated that in your enclosures you have FOUR woofers, eh? (yowza bet you get punched in the solar plexus pretty good at "mach 8" eh??)... So... I'm thinking that in order to maintain the nominal 8 ohm impedance, you'd have to have them wired with 2 pairs in series with each other, and then in parallel with the other pair.

So given that scenario, we'd be seeing about .9VAC across each... and still with an 8 ohm impedance. What model woofs ya got? Let's say we be more realistic and rate 'em at 92db SPL... with .9 mVAC applied, the power factor is now -70db, which equals 22db of output. Now mind you.. hmm.. that's 22db "per speaker", and you have four of them (8 ... stereo!)... so now I have to wonder if it's "additive" and due to 4 woofs the total SPL is audible (how many decibels "total" do four... no.. EIGHT.. woofers, each outputting 22db's, make??). Yeah.. hmmmm indeed, because with your non WO measurements, the power factor would be -95db... almost "zero" for output. So I can sort of "see" how your peculiar situation is calling for a much MUCH quieter amp!

Just a few points of observation and some questions. Basically I don't know if *I* am going to hear the hum with what I have here, which is a single 15 woofer (correction.. TWO for stereo). Seems that I'll have to rely on my AC meter to determine if whatever further work I perform makes a difference or not. Which.. yep... there are two things we can do if you send it back my way - I will reroute the internal AC lines and see about how to minimize the interference that running the AC for the DCP might be introducing... Probably take the ground that the DCP needs, and twist all three in "twisted pair" fashion.

BUT... if those two corrections don't throw it over the threshold... then we need to talk about actually doing a "mod", which would be relocating the power cord and fuse from the right to left side of the amp. In that arrangement, with the exception of the AC for the DCP to function there would be ZERO AC lines crossing the back wall.. We can try the first two steps above first, obviously.. but bear in mind if they don't produce the desired results, this more drastic step may be what is called for.

 

[Gepetto]

David,

Here's where I am a bit confused and have a concern (but hey... I'm thinking more as I type this sooo... bear with me). I had you measure AC direct from the speaker outputs to compare the "hum" signal. Since you stated the hum is 60hz, it should be measurable as most AC meters are going to measure that frequency quite accurately (think about it... they would definitely need to measure accurately standard AC "wall voltage", correct?).

This stated, the measurements above (1.8mV maximum) don't quite indicate an issue. I measured my own WO 700, and I have around 1mVAC on both channels.

Going further... with 1.8mVAC and even with an 8ohm woofer rated at 100db SPL 1W/1M, the actual db level would be 64 decibels down from the SPL rating. 36 db, barely above a whisper. 39 db is typically the threshold of hearing at 60hz.

Now hmmm (pardon the pun.. lol)... You stated that in your enclosures you have FOUR woofers, eh? (yowza bet you get punched in the solar plexus pretty good at "mach 8" eh??)... So... I'm thinking that in order to maintain the nominal 8 ohm impedance, you'd have to have them wired with 2 pairs in series with each other, and then in parallel with the other pair.

So given that scenario, we'd be seeing about .9VAC across each... and still with an 8 ohm impedance. What model woofs ya got? Let's say we be more realistic and rate 'em at 92db SPL... with .9 mVAC applied, the power factor is now -70db, which equals 22db of output. Now mind you.. hmm.. that's 22db "per speaker", and you have four of them (8 ... stereo!)... so now I have to wonder if it's "additive" and due to 4 woofs the total SPL is audible (how many decibels "total" do four... no.. EIGHT.. woofers, each outputting 22db's, make??). Yeah.. hmmmm indeed, because with your non WO measurements, the power factor would be -95db... almost "zero" for output. So I can sort of "see" how your peculiar situation is calling for a much MUCH quieter amp!

Just a few points of observation and some questions. Basically I don't know if *I* am going to hear the hum with what I have here, which is a single 15 woofer (correction.. TWO for stereo). Seems that I'll have to rely on my AC meter to determine if whatever further work I perform makes a difference or not. Which.. yep... there are two things we can do if you send it back my way - I will reroute the internal AC lines and see about how to minimize the interference that running the AC for the DCP might be introducing... Probably take the ground that the DCP needs, and twist all three in "twisted pair" fashion.

BUT... if those two corrections don't throw it over the threshold... then we need to talk about actually doing a "mod", which would be relocating the power cord and fuse from the right to left side of the amp. In that arrangement, with the exception of the AC for the DCP to function there would be ZERO AC lines crossing the back wall.. We can try the first two steps above first, obviously.. but bear in mind if they don't produce the desired results, this more drastic step may be what is called for.

To reinforce what Jer stated above, recent PL400 overhaul stats (WO RevD control board, WO 16.8KuF 100V cap kit, WO PL400 Light Board with White LEDs, Backwall refurbishment, WO single point grounding scheme, RCA410 pre-drivers, MJ15024 drivers, quasi-comp configuration), equipment DC operated DMM Fluke 179:

DC Offset (DC scale):
L Channel = -15mV
R Channel = -12mV
These are very typical readings that you should expect.

AC measurement (AC scale, inputs with no connection to RCA jacks and floating):
L Channel = 1.5mV
R Channel = 0.4mV
Meter leads shorted = 0.4mV
Frequency reading = unable to acquire, below meter threshold of resolution
Audible results = no perceptible output with ear placed 3" from woofer or tweeter (black hole)

AC measurement (AC scale, inputs with 10K shorting plug into RCA jacks):
L Channel = 0.4mV
R Channel = 0.4mV
Meter leads shorted = 0.4mV
Frequency reading = unable to acquire, below meter threshold of resolution
Audible results = no perceptible output with ear placed 3" from woofer or tweeter (black hole)

Basic executive summary, AC noise measurements below threshold of equipment to measure. Audible results confirm the same.

A PL700B conversion done recently produced extremely similar results.

 

[Gepetto]

Also these measurements confirm Lee's recent AP measurements that we have cracked below the 200uV noise floor level which is state of the art.

 

[Gepetto]

OK now back to listening to some fine music through this...