You can find some general information in my article on
phase coherent crossovers at www.passdiy.com
As I recall, the Symmetry is a 12 dB/oct adjustable frequency
low-pass and the high pass network subtracts that differentially
from the input to get a high pass function.
phase coherent crossovers at www.passdiy.com
As I recall, the Symmetry is a 12 dB/oct adjustable frequency
low-pass and the high pass network subtracts that differentially
from the input to get a high pass function.
Thank's M. Pass
I have already read your articles on your DIY site.
Very interesting !
But this crossover seems to be a little special: IC's numbers are erased but i can almost read one : The big M for Motorola and the number is like MPO6600 or MPO8800 with others (6) eight pins DIP IC's. Two of them are LF356. The others are erased and are working with the MPO's.
If someone know about...
I have already read your articles on your DIY site.
Very interesting !
But this crossover seems to be a little special: IC's numbers are erased but i can almost read one : The big M for Motorola and the number is like MPO6600 or MPO8800 with others (6) eight pins DIP IC's. Two of them are LF356. The others are erased and are working with the MPO's.
If someone know about...
HS, you are correct. The big chips are MPQ devices from Motorola that consist of 4 transistors. 2 npn and 2 pnp. These are the high beta types. I have some, somewhere, and can sell them to you, if you actually need them. The other device, an 8 pin DIP, is a special pin out dual fet, that is not made anymore. I might have these as well, but it would take some research. Unfortunately, I don't have a schematic for this crossover, at this time. Mine was lost in the firestorm in 1991. Perhaps someone has made a schematic and can put it up for view. I sure hope so. The actual circuits are simple transconductance amplifiers, much like a traditional first and second stage shown here, very often. There is no output buffer.
Thank you M. Curl
I have found the MPQ6600 IC on internet.
I take some measurements on these IC's and they seems fine.
I explain the problem if you can remember the schematic.
On low pass, i have a phase shift between the two channels on
X1 only: i have no longer the same crossover frequency.
On X10 it is OK.
On high pass, i have a hum on one channel only at X1 and X10.
I have a little phase shift on X1 at the extreme right of the
frequency pot. At X10 no phase shift but the hum.
If you have an idea.....
I have found the MPQ6600 IC on internet.
I take some measurements on these IC's and they seems fine.
I explain the problem if you can remember the schematic.
On low pass, i have a phase shift between the two channels on
X1 only: i have no longer the same crossover frequency.
On X10 it is OK.
On high pass, i have a hum on one channel only at X1 and X10.
I have a little phase shift on X1 at the extreme right of the
frequency pot. At X10 no phase shift but the hum.
If you have an idea.....
Thank's M.Curl but I have already checked
solder joints on pc board and the problem is not there.
I was thinking at the Fet IC's because fets give stranges problems sometime: maybe it is oscillating but my Hitachi 20MHZ
scope cannot see...
Or maybe the old style diode or current source next to each MPQ6600?
Again, thank's for your help.
solder joints on pc board and the problem is not there.
I was thinking at the Fet IC's because fets give stranges problems sometime: maybe it is oscillating but my Hitachi 20MHZ
scope cannot see...
Or maybe the old style diode or current source next to each MPQ6600?
Again, thank's for your help.
Symmetry Crossover
I own a Symmetry Electronic Crossover that I purchased in the mid 80's from Noel Lee of Monster Cable. This unit had been modified so that the low-pass was made to be active. Mr. Curl, you may have done the mod yourself, but I can't remember after so many years. It has run perfectly since I bought it, but only recently did a problem arise. One of the channels now has very low output with lots of distortion coming through it. At first I thought I had blown one of my Magneplanar ribbon tweeters, but it turned out to be the crossover. Since I am not a technician and since it is such an old unit, I was wondering if Mr. Curl could take a look at it or suggest someone who is qualified to repair it? I don't know what I'd replace it with... Thank you.
john curl said:
I own a Symmetry Electronic Crossover that I purchased in the mid 80's from Noel Lee of Monster Cable. This unit had been modified so that the low-pass was made to be active. Mr. Curl, you may have done the mod yourself, but I can't remember after so many years. It has run perfectly since I bought it, but only recently did a problem arise. One of the channels now has very low output with lots of distortion coming through it. At first I thought I had blown one of my Magneplanar ribbon tweeters, but it turned out to be the crossover. Since I am not a technician and since it is such an old unit, I was wondering if Mr. Curl could take a look at it or suggest someone who is qualified to repair it? I don't know what I'd replace it with... Thank you.
Symmetry ACS-1 active crossover
hello, I need to know what the voltages are at the power supply for the symmetry acs-1 crossover, by John Curl, I need to make up one of equivelent voltage rating, or find a good new or good used power supply ACS-1 It's about 2" X 3" X 1" thick., has 5 pins. The two at one end are obviously 120 volt, what are the 3 output terminals ? anyone know?
thanks for any help, I want to revive this crossover, have for years, and i'm finally getting around to doing it.
Jeff Engle
jeffreyengle@juno.com
hello, I need to know what the voltages are at the power supply for the symmetry acs-1 crossover, by John Curl, I need to make up one of equivelent voltage rating, or find a good new or good used power supply ACS-1 It's about 2" X 3" X 1" thick., has 5 pins. The two at one end are obviously 120 volt, what are the 3 output terminals ? anyone know?
thanks for any help, I want to revive this crossover, have for years, and i'm finally getting around to doing it.
Jeff Engle
jeffreyengle@juno.com
ACS-1 Power supply
Jeffrey,
The power supply your inquiring about was manufactured by Semiconductor Circuits of Haverhill, MA. The outputs consist of plus and minus 15 volts at 100 milliamps. Two other companies with similiar specifications that also come to mind are Analog Devices and Calex.
Hope this helps.
Jeffrey,
The power supply your inquiring about was manufactured by Semiconductor Circuits of Haverhill, MA. The outputs consist of plus and minus 15 volts at 100 milliamps. Two other companies with similiar specifications that also come to mind are Analog Devices and Calex.
Hope this helps.
Symmetry crossover schematic needed
Hi everybody
Just acquired a Symmetry ACS-1 & ACS-2 crossovers and need schematics for both They are missing a lot of parts such as , powersupplies, fets, caps
Would love to get these back to original
Joe at jjjmsjz@aol.com
Hi everybody
Just acquired a Symmetry ACS-1 & ACS-2 crossovers and need schematics for both They are missing a lot of parts such as , powersupplies, fets, caps
Would love to get these back to original
Joe at jjjmsjz@aol.com
Symmetry ACS-1 crossover
Is there a part number for that power supply? Also, Mine trips the circuit protector on my Carver amp for the low pass. I substituted my Snell crossover and it worked fine. It trips and stays that way even without a signal so could it be that DC is leaking from the Symmetry? Also does anyone know where I could find information on the Symmetry amplifiers?
Is there a part number for that power supply? Also, Mine trips the circuit protector on my Carver amp for the low pass. I substituted my Snell crossover and it worked fine. It trips and stays that way even without a signal so could it be that DC is leaking from the Symmetry? Also does anyone know where I could find information on the Symmetry amplifiers?
Hello, If anyone is listening might they answer a question? I'm a real amateur at this so pardon if my descriptions are a bit unprofessional. I'm an expert with racing engines in sports cars. Electronics, not so much. I have one of these crossovers with a problem. I measured the voltages out of the power supply and they seem fine. Problem is on the channel 2 + input I read @ 6 VDC. On the low pass output for channel 2 I read @ 12vdc.
This is with the crossover powered up but not connected to anything in the way of an input or output. So the voltage must be leaking through from the power supply. I have supply voltages to three components for each channel. Four, I think, are resistors. On the good channel I read .85 VDC and .67 VDC. On the bad channel they both read about .67 VDC. The third component on each channel may be a cap? Two leads, cylindrical with a dome shaped top? Across these 'caps' I read 16.04 on the good channel and 9.75 VDC on the bad channel. These power sources then feed into some IC's, on which I'm truly lost. There are two "orange drop" 'caps' on each channel across which I read near identical voltages.
The question is this, The power supply is the same. and the voltage 'across' that first cap is different, and different by about the voltage I'm seeing at the RCA jacks. Could that 'cap' be the problem? or somewhere else in the circuit? Also the numbers are gone so how can I identify this part?
This is with the crossover powered up but not connected to anything in the way of an input or output. So the voltage must be leaking through from the power supply. I have supply voltages to three components for each channel. Four, I think, are resistors. On the good channel I read .85 VDC and .67 VDC. On the bad channel they both read about .67 VDC. The third component on each channel may be a cap? Two leads, cylindrical with a dome shaped top? Across these 'caps' I read 16.04 on the good channel and 9.75 VDC on the bad channel. These power sources then feed into some IC's, on which I'm truly lost. There are two "orange drop" 'caps' on each channel across which I read near identical voltages.
The question is this, The power supply is the same. and the voltage 'across' that first cap is different, and different by about the voltage I'm seeing at the RCA jacks. Could that 'cap' be the problem? or somewhere else in the circuit? Also the numbers are gone so how can I identify this part?
If the power supply is giving +/- 15V, then the power supply is working. You have something broken somewhere in the main unit, AND these parts are hard to find. I can help you, but I have to hire a technician to do the work. My eyes just won't do it anymore. Is it worth paying for a technician's time?
Thank you for responding!
Dear Mr. Curl,
I took the crossover to a tech here in Toledo. But he was averse to committing to repair it without a schematic or part numbers to work with.
If you have a technician in mind out there in Berkley that might be best. Someone with whom you have a relationship.
Meanwhile could I ask a couple easy questions? If I'm seeing DC in the audio input on channel 2 and the low pass output on channel 2. Is it logical that the problem is in the channel 2 low pass section? If that is so, might I simply acquire the parts for that section, if possible, and replace them all? And do you still have any of them you could sell me? I suspect the small black part between the power supply trace and the large IC. The voltage across this part is different for channel 2 low pass than the others. It's round, black and domed, about the size of a pencil eraser. Is that a capacitor?
I'm just a car mechanic. In a world where the choice is to have throwaway electronic trash or extremely expensive new equipment. I choose to preserve the works of electronic art made in the USA in the 70's and eighties.
Thanks for any help you could provide, Kevin.
P.S. Joachim Gerhard said he would fix it. But to ship it to Brilon and back would cost over three hundred dollars.
Dear Mr. Curl,
I took the crossover to a tech here in Toledo. But he was averse to committing to repair it without a schematic or part numbers to work with.
If you have a technician in mind out there in Berkley that might be best. Someone with whom you have a relationship.
Meanwhile could I ask a couple easy questions? If I'm seeing DC in the audio input on channel 2 and the low pass output on channel 2. Is it logical that the problem is in the channel 2 low pass section? If that is so, might I simply acquire the parts for that section, if possible, and replace them all? And do you still have any of them you could sell me? I suspect the small black part between the power supply trace and the large IC. The voltage across this part is different for channel 2 low pass than the others. It's round, black and domed, about the size of a pencil eraser. Is that a capacitor?
I'm just a car mechanic. In a world where the choice is to have throwaway electronic trash or extremely expensive new equipment. I choose to preserve the works of electronic art made in the USA in the 70's and eighties.
Thanks for any help you could provide, Kevin.
P.S. Joachim Gerhard said he would fix it. But to ship it to Brilon and back would cost over three hundred dollars.
Mr, I will help if I can. IF it is the 8 pin round IC (I think that it is metal round can, is it?) that is the problem, then it can be replaced with any fet input single IC. I do have the parts, and just today I found the general schematic for the discrete op amps, but I don't have the overall schematic available to me at this time. IF it is the discrete op amps that look like two IC near each other and some added resistors, the problem is more difficult, but I do have the parts, somewhere. They are more difficult to replace with just anything.
It does appear to be channel 2 that is the problem.
It does appear to be channel 2 that is the problem.
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