Jerry's " ONLY ONE IN THE COUNTRY" Phase Linear 700 Thread
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Re: Jerry's " ONLY ONE IN THE COUNTRY" Phase Linear 700 Thre
You will note on the White Oak board that the signal ground (pin 2) is paired with the signal input from the RCA jack (pin 1) and physically away from the other signals and connections. This separation is on purpose to keep the lowest signal levels on the board isolated from the larger signal areas. You will also notice that the input signal from pin 1 is a clean, straight run up to the top of the board with an adjacent signal ground run. All to keep the signal to noise ratio as good as possible.
You will note on the White Oak board that the signal ground (pin 2) is paired with the signal input from the RCA jack (pin 1) and physically away from the other signals and connections. This separation is on purpose to keep the lowest signal levels on the board isolated from the larger signal areas. You will also notice that the input signal from pin 1 is a clean, straight run up to the top of the board with an adjacent signal ground run. All to keep the signal to noise ratio as good as possible.
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Re: Jerry's " ONLY ONE IN THE COUNTRY" Phase Linear 700 Thre
Hmmm.. after all that about different grounds I have a beeeg beeg (big) question. Is the 700B a common-ground amp, in respect the L and R outputs? In other words, if I hook up my Polks with SDA cable in place, will really bad things happen? If that's the case.. no biggie... I can "somewhat" live without the SDA effect, but I'll probably see about building an adapter that uses an isolation transformer.
Hmmm.. after all that about different grounds I have a beeeg beeg (big) question. Is the 700B a common-ground amp, in respect the L and R outputs? In other words, if I hook up my Polks with SDA cable in place, will really bad things happen? If that's the case.. no biggie... I can "somewhat" live without the SDA effect, but I'll probably see about building an adapter that uses an isolation transformer.
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Re: Jerry's " ONLY ONE IN THE COUNTRY" Phase Linear 700 Thre
In addition to the main L and R speaker cables from amp to each speaker, I actually have a 3rd cable going *between* L and R speakers. This provides the feedback between L and R speakers that via the magic of the SDA crossover, drives a dedicated driver in each speaker. That driver emits an out of phase cancellation signal that cancels out the crosstalk between the two speakers. Net effect - when a sound is output and meant to be heard only in one speaker or the other, you really do only hear it from that speaker. That's the "SDA Effect".. peeps either love it or hate it. I'm of the "love it" section. heheh
(that's sort of it in a nutshell)... But... for amps that are not common grounded between L and R, that 3rd cable poses a major problem... I'd have to trace around the skeezers, but basically it forces a dead short between the two (-) amp outputs. Never use Polk SDA's with the cable in place if the amp is not common ground... etc.
In addition to the main L and R speaker cables from amp to each speaker, I actually have a 3rd cable going *between* L and R speakers. This provides the feedback between L and R speakers that via the magic of the SDA crossover, drives a dedicated driver in each speaker. That driver emits an out of phase cancellation signal that cancels out the crosstalk between the two speakers. Net effect - when a sound is output and meant to be heard only in one speaker or the other, you really do only hear it from that speaker. That's the "SDA Effect".. peeps either love it or hate it. I'm of the "love it" section. heheh
(that's sort of it in a nutshell)... But... for amps that are not common grounded between L and R, that 3rd cable poses a major problem... I'd have to trace around the skeezers, but basically it forces a dead short between the two (-) amp outputs. Never use Polk SDA's with the cable in place if the amp is not common ground... etc.
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Re: Jerry's " ONLY ONE IN THE COUNTRY" Phase Linear 700 Thre
Without confusing this any further Lee, I'll mention that the White Oak board has the option to totally separate both Chassis (CH_GND) and Signal (GND) grounds on the PCB. The signal grounds coming in on pin 2L and pin 2R are ALWAYS totally separate. The Chassis grounds are joined by the 24AWB bus wire jumper that you installed on the back of the board between pad 5L1 and 5R1.
This was to allow flexibility to change the ground scheme used in the Phase Linear if desired. This option does not exist on the Phase Linear boards. I suspect that there is a better ground and power distribution scheme that can be configured within the Phase chassis and one day when I have some spare time, I intend to prove that
The +75/100V rails and -75/100V rails are also totally independent on the White Oak board for this same reason. These are also conjoined by the other 2 bus wire jumpers (11L1 and 11R1 and 12L1 and 12L2)
Without confusing this any further Lee, I'll mention that the White Oak board has the option to totally separate both Chassis (CH_GND) and Signal (GND) grounds on the PCB. The signal grounds coming in on pin 2L and pin 2R are ALWAYS totally separate. The Chassis grounds are joined by the 24AWB bus wire jumper that you installed on the back of the board between pad 5L1 and 5R1.
This was to allow flexibility to change the ground scheme used in the Phase Linear if desired. This option does not exist on the Phase Linear boards. I suspect that there is a better ground and power distribution scheme that can be configured within the Phase chassis and one day when I have some spare time, I intend to prove that
The +75/100V rails and -75/100V rails are also totally independent on the White Oak board for this same reason. These are also conjoined by the other 2 bus wire jumpers (11L1 and 11R1 and 12L1 and 12L2)
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Re: Jerry's " ONLY ONE IN THE COUNTRY" Phase Linear 700 Thre
Eh? Same thing here.. work is a bitch. I am getting the urge to really answer the phone next time with "Would you like a Slurpee with your new computer program? I am very willing to help you, as long as I can spell your name in 15 minutes or less." Crazy crap man... I'm trying hard to head off a disaster, but I swear it's going to take just one time for a support thing to "come up", and nobody bothers to call me in 15 minutes.. and next thing you know I have the Trans VP calling me directly saying "hey.. my damn trucks are going to be 4 hours late and counting!" (and then.. THEN.. the shit really starts rolling)
Yep, had to mention "work" to me eh??
Aint nothin... but I can rant on with the best of 'em in my current situation LOL.
Anywhoo... aint no rush man! Ya gotta "provide" and so do I, so do that first of course...
Eh? Same thing here.. work is a bitch. I am getting the urge to really answer the phone next time with "Would you like a Slurpee with your new computer program? I am very willing to help you, as long as I can spell your name in 15 minutes or less." Crazy crap man... I'm trying hard to head off a disaster, but I swear it's going to take just one time for a support thing to "come up", and nobody bothers to call me in 15 minutes.. and next thing you know I have the Trans VP calling me directly saying "hey.. my damn trucks are going to be 4 hours late and counting!" (and then.. THEN.. the shit really starts rolling)
Yep, had to mention "work" to me eh??
Aint nothin... but I can rant on with the best of 'em in my current situation LOL. Anywhoo... aint no rush man! Ya gotta "provide" and so do I, so do that first of course...
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Re: Jerry's " ONLY ONE IN THE COUNTRY" Phase Linear 700 Thre
Gepetto, your description is very clear. My PL 700B schematic is for the PL20 board and dated 9/9/74. It covers serial numbers after 574-000 and after 1000. This schematic does show the difference between signal ground and chassis ground. The signal ground comes into the PL20 board at R3, C6, and Q3-C as you mentioned. I agree that these should tie back from each channel's 2R to a common point, possibly at the RCA input jacks using the existing shielded coax cable. At the RCA jacks the input commons are grounded, the speaker outputs are grounded, the main caps are grounded, the transformer is grounded, and the chassis is grounded all in one general area with 2-3 buss bars. I was taught that the inputs should not be directly grounded to the outputs... Never mind that the chassis does not use an IEC three prong cord, that is another discussion.
What is the point of lifting the signal ground on the board by 2.7 or 56 Ohms then just tying it to chassis ground on the other end?
For the chassis grounds, my schematic shows a connection to R2, C10, the junction of D11 and D12, (and also to R58 on the VU meter range switch) and to C22 and C23 (equivalent to the C3 you mentioned which my schematic does not list). This was the genesis of my question, should we run one wire (because they are tied together on the board) from 5R to the enclosure ground and leave 5L with no connection?
BTW, I ran a new ground for your light board to the main capacitor common. That should be the star point for chassis ground but not signal ground which by design floats above chassis ground with some resistance.
Gepetto, your description is very clear. My PL 700B schematic is for the PL20 board and dated 9/9/74. It covers serial numbers after 574-000 and after 1000. This schematic does show the difference between signal ground and chassis ground. The signal ground comes into the PL20 board at R3, C6, and Q3-C as you mentioned. I agree that these should tie back from each channel's 2R to a common point, possibly at the RCA input jacks using the existing shielded coax cable. At the RCA jacks the input commons are grounded, the speaker outputs are grounded, the main caps are grounded, the transformer is grounded, and the chassis is grounded all in one general area with 2-3 buss bars. I was taught that the inputs should not be directly grounded to the outputs... Never mind that the chassis does not use an IEC three prong cord, that is another discussion.
What is the point of lifting the signal ground on the board by 2.7 or 56 Ohms then just tying it to chassis ground on the other end?
For the chassis grounds, my schematic shows a connection to R2, C10, the junction of D11 and D12, (and also to R58 on the VU meter range switch) and to C22 and C23 (equivalent to the C3 you mentioned which my schematic does not list). This was the genesis of my question, should we run one wire (because they are tied together on the board) from 5R to the enclosure ground and leave 5L with no connection?
BTW, I ran a new ground for your light board to the main capacitor common. That should be the star point for chassis ground but not signal ground which by design floats above chassis ground with some resistance.
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Re: Jerry's " ONLY ONE IN THE COUNTRY" Phase Linear 700 Thre
I understand we want to shield the input (inner conductor) from stray signals and voltages. We also have to bring in a difference of potential for the input to reference. Are you saying we can leave the input shield disconnected from 2R and 2L and let the input draw its difference of potential on the board from 5R and 5L through R2R and R2L? This is an interesting option. It would bring all the grounds on the board to the same potential, which is the same as the enclosure, if the RCAs are grounded to the enclosure.
If the RCAs are not grounded to the enclosure (I don't think they should be because PL designed them to float) then the enclosure ground has to go to 5R ( and through the jumper to 5L).
It seems like the board engineer and the chassis engineer at PL each had ideas of how the system should be grounded...
I understand we want to shield the input (inner conductor) from stray signals and voltages. We also have to bring in a difference of potential for the input to reference. Are you saying we can leave the input shield disconnected from 2R and 2L and let the input draw its difference of potential on the board from 5R and 5L through R2R and R2L? This is an interesting option. It would bring all the grounds on the board to the same potential, which is the same as the enclosure, if the RCAs are grounded to the enclosure.
If the RCAs are not grounded to the enclosure (I don't think they should be because PL designed them to float) then the enclosure ground has to go to 5R ( and through the jumper to 5L).
It seems like the board engineer and the chassis engineer at PL each had ideas of how the system should be grounded...
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Re: Jerry's " ONLY ONE IN THE COUNTRY" Phase Linear 700 Thre
Like Joe said though, at the end of the day all grounds wind up on the Chassis. The shield and input grounds I'll ground with the outputs and flyback diodes ands we'll see how it works.
the chassis ground is put in at #6, the small white wire that comes from the solder tabs.
Like Joe said though, at the end of the day all grounds wind up on the Chassis. The shield and input grounds I'll ground with the outputs and flyback diodes ands we'll see how it works.
the chassis ground is put in at #6, the small white wire that comes from the solder tabs.
Re: Jerry's " ONLY ONE IN THE COUNTRY" Phase Linear 700 Thre
When I get around to rewiring one of my lab mules for a better grounding scheme, this is what I plan to do (using the White Oak Audio PL14_20 universal board).
1. Declare that the Single Point Ground is the copper bus bar that runs between the 2 main filter capacitors.
2 Run each speaker ground from each negative binding post back to that Single Point Ground (already done, this is what Phase Linear traditionally has done)
3. Run a separate ground wire from each channel on the PCB pin 5L and 5R back to this Single Point Ground point using 20AWG white wire.
4. Run a 20AWG white wire from the Single Point Ground to one chassis tie point (already done, this is the wire that Phase Linear runs from the copper bus bar to the middle leg of one of the 3 pin terminal blocks that ties to the chassis)
5. Do not install the 5L1 to 5L2 jumper on the White Oak PL14_20 board (that is, to let each channel operate separately)
6. Install a zero ohm resistor in location R2L and R2R on the White Oak PL14_20 board, tying Signal Ground to Chassis Ground on the board.
7. Float each RCA jack input from the chassis ground and use either twisted pair or better yet, shielded coax wire to attach RCA jack grounds (shell) to pin 2L and 2R respectively. Each signal wire would go to pin 1L and 1R respectively.
8. Run a separate 20AWG white wire from the Single Point Ground to the ground connection on the White Oak PL18A (PL400) or PL17(PL700B)) Light board depending on which amp you are modifying (already done in most cases as this is standard Phase Linear practice)
9. Run a separate 20AWG red wire from the positive bulk cap +75/100V capacitor terminal to pin 11L and 11R of the White Oak PL14_20 board. Uninstall the jumper between 11L1 and 11R1 making each channel powered as 2 independent channels.
10. Run a separate 20AWG black wire from the negative bulk cap -75/100V capacitor terminal to pin 12L and 12R of the White Oak PL14_20 board. Uninstall the jumper between 12L1 and 12L2 making each channel powered as 2 independent channels.
This is my view of what effective single point grounding looks like (and is a starting point, then reality often clicks in .
When I get around to rewiring one of my lab mules for a better grounding scheme, this is what I plan to do (using the White Oak Audio PL14_20 universal board).
1. Declare that the Single Point Ground is the copper bus bar that runs between the 2 main filter capacitors.
2 Run each speaker ground from each negative binding post back to that Single Point Ground (already done, this is what Phase Linear traditionally has done)
3. Run a separate ground wire from each channel on the PCB pin 5L and 5R back to this Single Point Ground point using 20AWG white wire.
4. Run a 20AWG white wire from the Single Point Ground to one chassis tie point (already done, this is the wire that Phase Linear runs from the copper bus bar to the middle leg of one of the 3 pin terminal blocks that ties to the chassis)
5. Do not install the 5L1 to 5L2 jumper on the White Oak PL14_20 board (that is, to let each channel operate separately)
6. Install a zero ohm resistor in location R2L and R2R on the White Oak PL14_20 board, tying Signal Ground to Chassis Ground on the board.
7. Float each RCA jack input from the chassis ground and use either twisted pair or better yet, shielded coax wire to attach RCA jack grounds (shell) to pin 2L and 2R respectively. Each signal wire would go to pin 1L and 1R respectively.
8. Run a separate 20AWG white wire from the Single Point Ground to the ground connection on the White Oak PL18A (PL400) or PL17(PL700B)) Light board depending on which amp you are modifying (already done in most cases as this is standard Phase Linear practice)
9. Run a separate 20AWG red wire from the positive bulk cap +75/100V capacitor terminal to pin 11L and 11R of the White Oak PL14_20 board. Uninstall the jumper between 11L1 and 11R1 making each channel powered as 2 independent channels.
10. Run a separate 20AWG black wire from the negative bulk cap -75/100V capacitor terminal to pin 12L and 12R of the White Oak PL14_20 board. Uninstall the jumper between 12L1 and 12L2 making each channel powered as 2 independent channels.
This is my view of what effective single point grounding looks like (and is a starting point, then reality often clicks in
.