David's Phase Linear 700B Thread

[Phase Linear Phanatic]

The top white and grey are left channel +/- in that order. The red and grey are right channel+/- respectively.

Ohhhh. I see. So I will just unhook say the two wires on the right channel and hook to the woof and see what plays eh?

 

[laatsch55]

Ya need to do this in both channels, due to crosstalk and common ground if you don't isolate both channels you may get to the problem and never notice it.

 

[Phase Linear Phanatic]

Ya need to do this in both channels, due to crosstalk and common ground if you don't isolate both channels you may get to the problem and never notice it.

Okay. I'll have to dig out the other spare woof. Give me a moment.............

 

[laatsch55]

10-4

 

[Phase Linear Phanatic]

No change. Alligator clips to both speakers. Both meters moving. (by the way, the right meter moves but is more sensitive than the left. And thats even when swapping channels. So it's not the meter.) Anyway, Buzz is still there bypassing Don's Board. Is it premature to think the LED's are causing it?? The buzz? (hum).

 

[Phase Linear Phanatic]

I see you have the AC feeds for Don's board wire tied to the output wires, separate those. And the white wire between those AC sources, where does that go??

I believe Jerr has it going to the left Channel chassis ground on Joe's driver board. I did not unhook the two AC wire or that white ground wire when I tested the outputs. Should I unhook the WHOLE thing? Is that what you were saying about no influence?

 

[laatsch55]

Yes, that's what I'm saying. The white wire between the 2 ac wires needs to go to the star ground. The only ground to the board should be the one from the input RCA's and then from the board to the star ground. Having those 2 AC wires bundled to the output wires is not a good idea. We try to keep them separate.

 

[laatsch55]

I've never experienced a hum from Joe's light board.

 

[laatsch55]

Need pics of the pot wiring next. Where it is soldered at the inputs, on the pots themselves and at the board termination.

 

[Phase Linear Phanatic]

Need pics of the pot wiring next. Where it is soldered at the inputs, on the pots themselves and at the board termination.

The whole DCP is disconnected. Nothing else is connected to the amp either. Hum still. If the white wire that is connected to the right channel on Joe's board; is just hanging in space, and no longer connected to Don's Board, would that not eliminate the ground loop? I still get the hum, so for education purpose; how does running the wire from the DCP to star ground, alleviate my hum? (since its disconnected and I still have hum)? I have to pull Joes board off to give you a pic. Jerry has the DCP wire zip tied there, so I have to snap those off too. Here's the pots.

 

[laatsch55]

The AC ground from the DCP goes to star ground. NOT to the board. Because that would be the same as taking it off the negative speaker binding post. Also, don't assume that taking something loose and stuill having hum isn't partr of the problem. We are going about this in a systematic way to eliminate possible causes. When the amp is on do you still have the pre amp on and hooked to that amp.??

 

[laatsch55]

Before going any further take that white ground wire to star ground. The thing about hum is, there can be multiple sources.

 

[laatsch55]

I will stress again, any test is invalid without the pre-amp hooked up and on, or shorting plugs inserted into the RCA's.

 

[laatsch55]

Gotta trouble call. One of my water plants are down. See ya in a couple hours.

 

[Phase Linear Phanatic]

The AC ground from the DCP goes to star ground. NOT to the board. Because that would be the same as taking it off the negative speaker binding post. Also, don't assume that taking something loose and stuill having hum isn't partr of the problem. We are going about this in a systematic way to eliminate possible causes. When the amp is on do you still have the pre amp on and hooked to that amp.??

No. Nothing connected. I don't think that white wire from the 5R solder input to Don's board is long enough to make it if I go from dons board over to star ground. I have to dig up something................

The board unbolted sir.......................

 

[jbeckva]

No. Nothing connected. I don't think that white wire from the 5R solder input to Don's board is long enough to make it if I go from dons board over to star ground. I have to dig up something................

The board unbolted sir.......................

View attachment 9873 View attachment 9874 View attachment 9875

For all retests, have the preamp connected, on, selecting aux (anything but phono), and the volume turned all the way down. Is that how you have it now?

 

[Phase Linear Phanatic]

For all retests, have the preamp connected, on, selecting aux (anything but phono), and the volume turned all the way down. Is that how you have it now?

No. And yes. I have had it with nothing connected as Lee is asking, and with it connected as you are suggesting. Before I run ANY tests, all day I have tried each test with and without the preamp connected and pots down. Hum is the same no matter which method I choose. And its the same for each test so far.

 

[Phase Linear Phanatic]

Gotta trouble call. One of my water plants are down. See ya in a couple hours.

Good luck Lee. If I can't get this thing solved today, we will have to wait till next weekend. I only get one day a week, and during that one day, my woman bitches that I don't do anything HERE. I'm damned no matter what it seems. (sigh)...........

 

[Phase Linear Phanatic]

Okay, HERE is a real interesting one? I only took off Joe's board for those pictures right? Well.......I put the board back on. I unplugged the amp while off and turned the prongs around. I also unplugged all the fuses on the amp. And put them back in because I was hearing slight distortion from the speakers. I turned the Main AC fuse around and put it back in. Now.........with the preamp ON and music playing, but with the pots all the way down........I have NO HUM. H-O-W-E-V-E-R....with the preamp ON, the CD NOT playing, I can turn those pots UP and I get HUM. The hum increases with the pot increase. So.............here is what I did. I hit "play" on the CD player, and started to turn the pot UP on the left channel. All good. I turned it down and then went to the right woofers pot and turned IT up. All good. I then phased BOTH of the pots up together to the same midpoint on the amp and the speakers play music with some distortion. Fade a pot down, one woofer sounds good again. Fade them both together, and both sound shitty. Crosstalk of some kind? How do I go from total HUM regardless of input signal and volume, to hum only when volume in increased at the pots and with the added bonus of distortion? Lee.......I AM going to be bald by the end of this "unique" exercise..................

The main AC fuse good sirs, just in case you think the crackled yellow glass on one end may have something to do with it. (was like that prior to Jerry) I don't have spares.

 

[Phase Linear Phanatic]

I ran one last and final test for today. I decided to switch out input sources. I dropped my stereo racks preamp in favor of a cell phone with a 1/8" mini cord to L/R RCA's. Well......the result is the hum is now less audible. You have to turn the pots up pretty good with the phone on pause to hear it. The speakers still distort. It's almost as if they are playing out of phase? But they can't be since I wired + and - correctly. I triple checked this. I mean....It "looks" as if when a base note hits, the woofer caves IN instead of pumps out? But its too fast for me to see. And when one pot is all the way down, and the other up, you can hear like a farting noise with every base note in the woofer that has its pot all the way down. Its sorta like the left channel is leaking into the right and vise versa. And when both play, that's just amplified and they stab each other? Do I sound like an ass clown here? I change sources with the same results sooooooo are all of these shenanigans tied somehow to the same thing? It's the goofiest thing I have ever seen.............