David's Phase Linear 700B Thread

[Phase Linear Phanatic]

Speaker Talk with Dave

Gentlemen; my speakers should have nothing to do with the hum issue? I know I am starting to sound like a broken record, but........as I have said; I can swap out the WOAPL and put in an old factory PL700B and NO HUM in my giant big speakers. No matter HOW they are built? Now.......could we have an issue? Is it because the superior REV D board and all the new componentry has made the speaker more sensitive to the "goings on" inside the amp? Heck. It's over MY head if it is? And ok, Jerr. Let me be more specific. It is not a 60Hz hum. It is "A" hum. I do not carry around an oscilloscope under my arm so I can't test this. But as I've said, the WOA amp is the only amp of the three that produces this hum. And it's audible.

Now Below I have scanned some old photo's from my speaker building day's. I dug in the archives to find these things. Let me tell you these speakers are five feet tall......three feet wide.....and two feet deep. They weigh 350lb's a piece because I used DOUBLE 1" thick MDF all around except for the back board. Each speaker houses four twelve inch woofers that weigh 50lbs a piece, two 6" midrange that weigh 25 lbs a piece, and eight three inch tweets in a center array that weigh a respectable 2lbs a piece. Now........I have FOUR of these speakers. In the photo's below, I show the old days and my speaker building process. When I ran these speakers in a bi-amp configuration, (A PL700B for low, and PL400 for high); I had each of these speakers wired internally in such a way that the four woofs combined in each speaker produced an 8 ohm load at output. Same for the high end. The back of the cabinet housed a 6 inch by 6 inch port of multiple binding posts. And the + and - of each post was soldered together for flexibility. So I could wire two sets of these huge speakers together and produce a 4 ohm load. So my PL 700B saw a 4 ohm load and was driving essentially 16 twelve inch woofers at a 4 ohm impedance. and similar was the PL400. You can imagine the raw power. In a basement that was padded with no windows. Keep in mind, this was ALL before my multiple PL700B's I have today.

But today, I only run one pair in a nice easy 8 ohm load per side. I don't talk much about my building of these things, as I do not want to be laughed off the map? You know the people? "oh what? You don't have KEF's? Or Klipshs? Or Altec's or whatever"? HOME-MADE?!! "Bwaahhhh haaa haaa!!!" But you see fellers...................I can blow away with both power and fidelity, anything ANY store ever sold in a speaker today. You run all four of my mammoth speakers like this............I show down ANY $100k speaker out there. But I have no need? I just play it for blips of a fraction of a second at those volumes THESE days? I just like CLEAN power, and clean sound, and that's what the WOA is all about.

My last picture is taken today. My PL700B's ready for testing tomorrow and Dougs VU meter there ready for install. We will take it from here, and see what we come up with then. Right now, the wifey is asking me if I am gonna spend ALL day on this computer typing a novel again; so I gotta go get something done. See you guys tomorrow.

 

[jbeckva]

Gentlemen; my speakers should have nothing to do with the hum issue? I know I am starting to sound like a broken record, but........as I have said; I can swap out the WOAPL and put in an old factory PL700B and NO HUM in my giant big speakers. No matter HOW they are built? Now.......could we have an issue? Is it because the superior REV D board and all the new componentry has made the speaker more sensitive to the "goings on" inside the amp? Heck. It's over MY head if it is? And ok, Jerr. Let me be more specific. It is not a 60Hz hum. It is "A" hum. I do not carry around an oscilloscope under my arm so I can't test this. But as I've said, the WOA amp is the only amp of the three that produces this hum. And it's audible.

(had to strip off the rest here, and address this specifically)

David you missed the point of my post. Your measurements actually vindicate both of us here. Yes it is your particular speakers, because of the calculations I made in my post earlier. You have FOUR of them per cabinet, and EIGHT in total. Furthermore you have stated they are wired in such a way as to maintain the 8 ohm impedance, so my assertion that they are two in series, the other two in series, and both of the "series pairs" in parallel is more than likely how it really is. Therefore, the maximum AC you have measured is presented across both pairs. And inside both pairs, all else being equal, they would be divided in half by the series orientation of each pair... .9 mVac... across each speaker...

Follow me so far, right??

So... and again I am only guessing at your actual SPL rating for EACH speaker... as previously stated... EACH speaker may be outputting 22db's of this hum.. noise.. whatever you might want to call it. Which at that level borders at the point of inaudibility...

BUT.. and here's the point I was making above.... that is EACH speaker... You have EIGHT total, so conceivably YES, I can see quite possibly that eight speakers each outputting a nominal 22db's of SPL can be audible. I can't say "for sure" since I don't really know what the actual "aural effect" of that situation is, but I'm leaning towards the fact that you CAN hear it...

Now going back to your non WO'd amps... you measured .1mV, and applying all of the logic above, that means with your other amps each of your eight drivers would have .05mV presented across them. And if you run the numbers based on that measurement, your effective SPL across all eight of your speakers is pretty much zero. What's zero multiplied by eight?.... So absolutely...

However, as I have measured, and as both Joe and Lee have measured on their own rebuilt PLWO's, between 1 and 2 mV of residual noise, hum, whatever, IS perfectly normal. Therefore, your amp as it is currently is operating well within normal expected parameters for a PL 700 that has been upgraded with the board. Dare I say... there is nothing really wrong with it?

But again, I'll offer to do those two additional steps and either they are going to get you to the point to where ... with your particular speakers and setup... you are satisfied, or we can sit here and bicker back and forth about it. But expect to pay the shipping to ship it back to me, because my conclusion at this point is your work that was done to your amp was done in perfectly good faith and of the same quality you would receive anywhere else, but it is due to your particular component and speaker arrangement that we have to take it to the next level. I will pay the shipping back to you when I am done with it so we are splitting the cost to address what I see as an "oversight".

I couldn't hear squat before it was sent to you, and I doubt I will be able to hear it when and if I get it back from you, but we will go with the actual before and after VAC measurements instead as the success/failure "test". And I'm not guaranteeing we will get it to the same level as before the board swap, but I'll give it my best try.

Your move...

 

[Phase Linear Phanatic]

(had to strip off the rest here, and address this specifically)

David you missed the point of my post. Your measurements actually vindicate both of us here. Yes it is your particular speakers, because of the calculations I made in my post earlier. You have FOUR of them per cabinet, and EIGHT in total. Furthermore you have stated they are wired in such a way as to maintain the 8 ohm impedance, so my assertion that they are two in series, the other two in series, and both of the "series pairs" in parallel is more than likely how it really is. Therefore, the maximum AC you have measured is presented across both pairs. And inside both pairs, all else being equal, they would be divided in half by the series orientation of each pair... .9 mVac... across each speaker...

Follow me so far, right??

So... and again I am only guessing at your actual SPL rating for EACH speaker... as previously stated... EACH speaker may be outputting 22db's of this hum.. noise.. whatever you might want to call it. Which at that level borders at the point of inaudibility...

BUT.. and here's the point I was making above.... that is EACH speaker... You have EIGHT total, so conceivably YES, I can see quite possibly that eight speakers each outputting a nominal 22db's of SPL can be audible. I can't say "for sure" since I don't really know what the actual "aural effect" of that situation is, but I'm leaning towards the fact that you CAN hear it...

Now going back to your non WO'd amps... you measured .1mV, and applying all of the logic above, that means with your other amps each of your eight drivers would have .05mV presented across them. And if you run the numbers based on that measurement, your effective SPL across all eight of your speakers is pretty much zero. What's zero multiplied by eight?.... So absolutely...

However, as I have measured, and as both Joe and Lee have measured on their own rebuilt PLWO's, between 1 and 2 mV of residual noise, hum, whatever, IS perfectly normal. Therefore, your amp as it is currently is operating well within normal expected parameters for a PL 700 that has been upgraded with the board. Dare I say... there is nothing really wrong with it?

But again, I'll offer to do those two additional steps and either they are going to get you to the point to where ... with your particular speakers and setup... you are satisfied, or we can sit here and bicker back and forth about it. But expect to pay the shipping to ship it back to me, because my conclusion at this point is your work that was done to your amp was done in perfectly good faith and of the same quality you would receive anywhere else, but it is due to your particular component and speaker arrangement that we have to take it to the next level. I will pay the shipping back to you when I am done with it so we are splitting the cost to address what I see as an "oversight".

I couldn't hear squat before it was sent to you, and I doubt I will be able to hear it when and if I get it back from you, but we will go with the actual before and after VAC measurements instead as the success/failure "test". And I'm not guaranteeing we will get it to the same level as before the board swap, but I'll give it my best try.

Your move...

Well then Jerr; it seems it IS true what i thought might have been possible in my earlier post. The amps upgrades has unveiled the weakness in my speakers that were once unheard. Since I cannot change my speakers, logic only dictates that further disection on the amp is required to minimize the effect? So yeah.....hmmmm i would agree with you that nothing is technically wrong? Now the question stands is how do I go about making the amp better to avoid this new affliction? I certaintly cannot change the eight $300 a piece woofers out? They were measured for the cabinet. (SPL, air movement, so on) and the cabinets were built around those mathematics. But i do not desire to change the original amps design? I.e. moving the AC cord.....

Well, if THIS aint a bummer to me? I am not sure where I want to go from here. Jerr, I can give you the SPL rating of the woofers when i get to it Sunday. They are not manufactured anymore, but i bought two spares and keep them under the stairwell. Inside the box is the original spec sheet. I have to dig it out. My plan now is to take the amp open still and replace that VU meter. I mean, a dead meter is useless for anyone. So if we go on the conclusion that the amp is fine, and the flaw is the speakers, and the fine tuned amp has revealed a once inaudible speaker flaw; then i am pretty much saying that this is the way it is. Hum and all. Unless i want to take more measures. I may just decide to throw in the ol spare 700B and get a blue light board for it to match my other lab standard 700b. Yeah, its not white oaked, but theres no hum. Had i known my speakers weakness, i wouldn't have W.O.'d? But I bet this amp would be killer to someone on Phoenix? I hear El Magnifico is in the market? Just a thouht? Not sure what I should do...........

 

[jbeckva]

Well then Jerr; it seems it IS true what i thought might have been possible in my earlier post. The amps upgrades has unveiled the weakness in my speakers that were once unheard. Since I cannot change my speakers, logic only dictates that further disection on the amp is required to minimize the effect? So yeah.....hmmmm i would agree with you that nothing is technically wrong? Now the question stands is how do I go about making the amp better to avoid this new affliction? I certaintly cannot change the eight $300 a piece woofers out? They were measured for the cabinet. (SPL, air movement, so on) and the cabinets were built around those mathematics. But i do not desire to change the original amps design? I.e. moving the AC cord.....

Well, if THIS aint a bummer to me? I am not sure where I want to go from here. Jerr, I can give you the SPL rating of the woofers when i get to it Sunday. They are not manufactured anymore, but i bought two spares and keep them under the stairwell. Inside the box is the original spec sheet. I have to dig it out. My plan now is to take the amp open still and replace that VU meter. I mean, a dead meter is useless for anyone. So if we go on the conclusion that the amp is fine, and the flaw is the speakers, and the fine tuned amp has revealed a once inaudible speaker flaw; then i am pretty much saying that this is the way it is. Hum and all. Unless i want to take more measures. I may just decide to throw in the ol spare 700B and get a blue light board for it to match my other lab standard 700b. Yeah, its not white oaked, but theres no hum. Had i known my speakers weakness, i wouldn't have W.O.'d? But I bet this amp would be killer to someone on Phoenix? I hear El Magnifico is in the market? Just a thouht? Not sure what I should do...........

Well, like I said there are still two things short of rerouting the main AC cord that can be done. Basically what we have to do here is reduce that residual AC measurement, the goal being .1mV AC as you have measured with your other amps. I'm willing to give both a try, and from there if I can get that measurement down just enough, that may be all you need. And with Lee and Joe giving a few pointers along the way, we have a good chance to succeed.

First is the AC line that runs right down the middle of the back wall, between the two thermal cutouts. Right now that's the main AC line, running smack dab down the middle... crossing both channel's +/- 100 volt rails. What we will do there is reroute it, up the top side, then down and right back up again where the thermals are located.

The second is to use a twisted pair type arrangement for the AC that runs from the BR to the DC protect. That I hope will help cancel any spurious AC that might be lurking around.

Some other idears come to mind too... but in any case I do guarantee I will make all effort to get that measurement down to where it needs to be for your speakers not to pick it up as well as they are doing now..

Or.. hmmm.. egads... make ME an offer in PM, LOL... because I still drool over how well the "B" looks...

In any case, the situation's not as bleak as you think....

 

[laatsch55]

Dave, it may seem like we are ganging up on ya, but we're really not. As far as laughing at your speakers--HELL NO!!! I dig em. We'll have to have a "Speaker off" when I get my other bass bin to put on top of my K's. Floor to ceiling K-Horns, gives me shivers just thinking about. I'm impressed with your speaker building and that's what this forum is all about.


Dave, your WO'd 700B is no longer like your other stock PLs. They are wired differently enough they probably won't respond the same way to the same set of conditions (thank God).
I warned ya this stuff could make ya want to pull your hair out, I would If I had any left. We seem to be going about this willy-nilly. When you get the meter in let's start at the beginning. Let's retrace the grounding scheme and go from there. Notify us OF ANY CHANGES you make no matter how small. If we don't know what you've done since the last set of suggestions we are simply missing it.. I've done that to Joe a couple times and it drove us both bonkers. I think (and that's all ot is, I THINK) it's something simple we are missing because we've used different terms for the same thing or the same term for different things. You would think that electronics would be predictable and the results repeatable, perhaps in all but audio that might be true. In Joe's latest project he asked me how it sounded, because all his modeling programs and expected results based on previous modeling could determine every electrical parameter youy could think of ---EXCEPT how it sounds. When what a resistor's composition can determine sonic signatures Joe has certainly got his work cut out for him, but he's one of the few that can do it at his competency level. That's one of he reasons I listen to an amp or other components I've worked on for a week, to stress test it and really LISTEN to it's differences(if any). we are dealing with sooooooooooo manmy variables(different dates of manufacture, batch compositions, quality control, varience in compounds, etc) that differences in sound are a real possibility and are more probable than not.
I do not doubt you are hearing hum. I have hesitated to ship a couple amps because HERE they hummed, at the customers home, ABSOLUTELY NONE. I can't quite wrap my head around it either.
When you say you don't want to change the original amps design.......a little late for that isn't it? If Joe had that attitude his improvements could only go so far...and when Joe says we are at the state of the art for residual noise floor, that's not bragging, just absolute fact.
In Joe's day job he has a small army of engineer's he's responsible for, this shit he does for fun!! Something that makes most of us want to tear our hair out at times he does for fun. he knows this subject WELL and I'm glad he's here and feel lucky to be able to draw on what I see as a most valuable resource in him, besides he's a funny sumbitch too. With all that said Joe has hum problems sometimes too, so does Ed, so does Jer, so do I......welcome to a very exclusive club....

 

[laatsch55]

I don't think there's a weakness in your speakers, I think there's a weakness in our communication of the problem.

 

[Phase Linear Phanatic]

I just returned from the folks. Grabbed the alligator clips and a voltmeter I had sitting around for ages. My father gave me a PL 2000 original manual too?! I said "How did you get this"? He said he has had it as long as I've been alive? Guess he had one for a while and then sold it sometime in the 80's. So that's great for me. I have this pre-amp in the garage.

I told my father about my situation and he looked at me like I had three arms. He said; "A speaker only puts out what you feed into it"? "That makes no sense. It's not the speakers." Well......... he was there when I was building them. His help in the design was based off of the Bozak Concert Grands. A hi-Fi speaker in the 60's and 70's. The wiring elements are identical to them. He re-affirmed Jerry's thought on how I wired the woofers. It was so long ago, I just don't remember. But he said it WAS a series/parallel configuration I used to maintain the overall 8 ohm load impedance. So I do remember now as he explained how I wired them in the build. He also said he has heard the K-horns Lee. If only briefly. A sound-off eh? That would be doable, if I had the other set of speakers like my previous photo's show? I'd rock your horns off their clamps my man! LOL! Quad-amp 700B's! Two pairs of my speakers bi-amped each. Mmmmmm I will need new drywall!


As far as the mis-communication here.....Noooooooooo?? That's possible over the internet? With people you have never physically met nor heard speak? LOL! Lee, the only real inconsistency I see here is the font you use when typing. The way it changes so much I guess you figured out hot keys for that? LOL! (rib, rib) But hey folks, I'm here all night........ I also did not realize you were follically challenged? If these things make you want to tear your hair out; then I can see why Carver ended up the way he did! OHHHH....Bazinga! Again, the clubs open all night folks..........

Lee.....I can understand where an amp would produce different results in different set-ups. As far as my comment on not wanting to alter the amp; you say I have already done that. What I mean to make clear is cosmetic alteration. No missing switches, no holes for trim pots where there used to be knobs, no new holes drilled in the amp for re-routing power cords.......you understand? Its like the classic car that looks original on the outside; but under the hood.....whoa baby! Better look out! Cause someone sent this thing to the hot rod garage! LOL! I know there are ways to better the thing. But when it hinders the cosmetics, I usually stop. Sorry, I'm just that kind of customer. You know..high maintenance and all?

Anyway, below..............the items I picked up today. The second pic from a cell phone. (bad quality). My dad still rocks the reel-to-reel. A Teac. Above it the Audio Research SP3-A. Then a Rotel Tuner. A Polk XM radio Tuner, a pioneer six disc magazine changer and at top the bi-amp Phase Linear 400's. To the far left you can see ONE of the big Bozak concert grand speakers. (pictures on it). He's got a tape deck there somewhere. His LP's on the next shelf. But lately he has been all into the new Rotel gear. He has the tuner, but now wants the pre-amp and the big 500w per channel monster they have out. He seems to have gained an ear for it lately. He's become iffy on the vintage stuff because of age.

But back to my affliction................ plan is we will proceed tomorrow.

 

[laatsch55]

I understand completely the aversion to not alter the cosmetics, not a problem.Make sure the camera is charged...

 

[Gibsonian]

Coming in late to the party here. Probably in the thread somewhere already, but does the amp alone (nothing connected to inputs) produce the hum in the speakers?

 

[Phase Linear Phanatic]

Coming in late to the party here. Probably in the thread somewhere already, but does the amp alone (nothing connected to inputs) produce the hum in the speakers?

Yes. You have to click back a page or two, but that's how this started. Lee, I forgot about that. The camera battery is charging as we speak. Prepping the table now for the meter swap. Be back in a bit...............

 

[Phase Linear Phanatic]

Testing In Progress......

Okay fellers. I have opened it up. First pic is I touched NOTHING! LOL! Can't screw up yet eh? Next, I went to work on the meter. Doug; you sent me the whole housing, and the meter inside the housing. Thank you. The housings are the same, so I just popped out the meter and put in in my existing housing, then screwed Joe's Light board back down to it. No power up yet. I took a pic of a diode on the board though that looks like it may singed the board a little. Jerry; was this one of the things you replaced while trying to figure out the meter thing? It looks to be the only solder joint not in sync with the rest of the board. You think that may have anything to do with a dead meter? Not accusing? Just asking? I also have a pic of Don's DCP board untouched by me. So we have it. Next the Jewel and honeywell meters side by side. Doug, the diffuser strips ARE taped to the bottom of the housing in BOTH meters. So that clears that up. Since I was able to just swap the meters and no need for the housing, I didn't use the diffuser strips you sent. But thanks all the same! Last is a pic of the transformer area. Okay Lee...........you were right. The bolts WERE loose. I mean; not "loose loose", but you know, loose enough to where I could turn three times with the socket wrench before they were tight enough they wouldn't GO anymore? But if tightening them down can cause the hum or ground loop; then doesn't that serve to reason that the bolts need to be touching the chassis on the inside? Here in my pic there are washers in between the nut with the star ring underneath that usually grabs into the paint and to the metal chassis. If the washers are there in the way of that , then are we making contact with the chassis? Or should we NOT be? If you don't mind explaining the bolt thing to me please.

Okay. Nothing powered up yet or touched beyond what you see here. I await further instructions from the PL gods....................

 

[laatsch55]

Joie is more qualified to explain the bolt thing. If you could make 3 turns , it needed tightening. Did you replace the RCA jacks?

 

[Phase Linear Phanatic]

Joie is more qualified to explain the bolt thing. If you could make 3 turns , it needed tightening. Did you replace the RCA jacks?

No. Well I mean not today. I DID at the beginning of this whole project? (see first page of the thread). But we get hum with no RCA inputs. And if we are thinking that the RCA's could be the culprit (touching chassis), I have to consider that Jerry had the amp with my gold RCA's and didn't hear a thing? So that confusing?

 

[laatsch55]

What value caps are on the BR. They should be .01uf polypros, like the pic...Mouser part #DME4S1K-F

 

[laatsch55]

No. Well I mean not today. I DID at the beginning of this whole project? (see first page of the thread). But we get hum with no RCA inputs. And if we are thinking that the RCA's could be the culprit (touching chassis), I have to consider that Jerry had the amp with my gold RCA's and didn't hear a thing? So that confusing?

From here on out we assume nothing. A quick way to eliminate that possibility, one lead of your meter on the copper ground plate of the rca's the other to the chassis, scale 10 ohms, or lowest setting.

 

[laatsch55]

If in doubt about the 1N4148 diode----check it----

 

[Phase Linear Phanatic]

What value caps are on the BR. They should be .01uf polypros, like the pic...Mouser part #DME4S1K-F

I have those exact caps. I have those exact mouser parts. When I made my bridge rectifier I used those. But I think Jerry replaced the whole rectifier to be on the safe side. He used something a little different. .01 or .1? I think I see .1uf here..............

 

[laatsch55]

Factory was .022. Doubt it makes a difference.

 

[Phase Linear Phanatic]

From here on out we assume nothing. A quick way to eliminate that possibility, one lead of your meter on the copper ground plate of the rca's the other to the chassis, scale 10 ohms, or lowest setting.

Eliminated. Nothing on the meter. That's a good sign.

 

[Phase Linear Phanatic]

If in doubt about the 1N4148 diode----check it----

Good point. Diode checks out. So where do we go from here? Put the face plate back on and hook it up? See if the meter works and we get hum after tightening? Or wait before I put the caps back in to be clear on the bolts thing?