Hiiiiiii!
I'm tying to get the maximum level from a Source player that has both options of RCA's and XLR's outputs. The Balanced out is a higher line level that suits my equipment, the unbal line output is to low an output.
I would like to unbalance the balanced source, does that mean a straight short between pin 1 and 3 or ...
Decoupling capacitor between pin 1; Negative and pin 3; Gnd ? If so what type, material, size?
I'm used to studio gear and this Source player is a quasi balanced CD player, too sensitive for my likings.
O/C between 1 an 3 results in buzzzzzz
I'm tying to get the maximum level from a Source player that has both options of RCA's and XLR's outputs. The Balanced out is a higher line level that suits my equipment, the unbal line output is to low an output.
I would like to unbalance the balanced source, does that mean a straight short between pin 1 and 3 or ...
Decoupling capacitor between pin 1; Negative and pin 3; Gnd ? If so what type, material, size?
I'm used to studio gear and this Source player is a quasi balanced CD player, too sensitive for my likings.
O/C between 1 an 3 results in buzzzzzz
Yeah I know it sounds stupid, but there is more output from the XLR's and it sounds better.
Would really appreciate suggestions.
I don't want to blow up my gear!
Would really appreciate suggestions.
I don't want to blow up my gear!
So you want to connect a balanced source to an unbalanced input? That it?
If so, connect pin 2 to the unbalanced hot and pin 3 to the unbalanced ground.
If the source output is really balanced, it will work like a charm.
Jan
If so, connect pin 2 to the unbalanced hot and pin 3 to the unbalanced ground.
If the source output is really balanced, it will work like a charm.
Jan
Thanks for replying.
Yes.
Tried that. Which is exactly why I thought it ain't a true balanced connection.
When the connection is wired as you suggest, open connection between 1 an 3 results in buzzzzzz.
A straight short between pin 1 and 3 fried a small earth resistor elsewhere in the circuit. Not doing that again. I was lucky thats all that it was.
It's not as was assumed, not a professional Balanced output.
Hence thinking something like a low voltage 10uf non-polar Nichicon Muse type cap between 1 and 3 ?
Decoulpling is as close to a solution as i got, maybe someone here has had more experience?
The RCA input to the pre amp is Directly coupled.
Yes.
Tried that. Which is exactly why I thought it ain't a true balanced connection.
When the connection is wired as you suggest, open connection between 1 an 3 results in buzzzzzz.
A straight short between pin 1 and 3 fried a small earth resistor elsewhere in the circuit. Not doing that again. I was lucky thats all that it was.
It's not as was assumed, not a professional Balanced output.
Hence thinking something like a low voltage 10uf non-polar Nichicon Muse type cap between 1 and 3 ?
Decoulpling is as close to a solution as i got, maybe someone here has had more experience?
The RCA input to the pre amp is Directly coupled.
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Pin 1 is normally a chassis ground connection, not involved in the signal.
In a pseudo-balanced connection, the 'signal' on pin 3 is coming from signal ground through an impedance equal to the output impedance that feeds pin 2, to maintain the balanced condition.
A cap between 1 and 3 is an interesting idea. Did you try just leaving pin 3 open, use pin 2 as signal and pin 1 as gnd?
Manufacturers often have their own idea of how a balanced connection should look and don't follow the AES recommendation. So it's a jungle.
Jan
In a pseudo-balanced connection, the 'signal' on pin 3 is coming from signal ground through an impedance equal to the output impedance that feeds pin 2, to maintain the balanced condition.
A cap between 1 and 3 is an interesting idea. Did you try just leaving pin 3 open, use pin 2 as signal and pin 1 as gnd?
Manufacturers often have their own idea of how a balanced connection should look and don't follow the AES recommendation. So it's a jungle.
Jan
The "interesting idea" is based on the fact many separately interconnecting amplifiers and preamplifiers (assuming transistor based) will have a decoupling capacitor either in the power amp or the preamp dependant on the manufacturers design. Often a film cap between 10μF and 100μF, that is when they are not a directly coupled design, and they are attempting to facilitate the inter operability of different equipment by way of the line level.
The events that put the machine out of use were many years ago. I successfully repaired the machine recently. The main fault was a design flaw of which there were two, both improved upon in that session along with the unconfirmed fault assuming the moded bal to unbal cable in causing a small earth resistor to fry Open Circuit.
What a relief the design corrections worked, awed that it sounds better than it did new.
My test equipment is lacking, Scopes long gone and a pile of other support equipment gone.
The result is wishing to be oh so careful in any interconnect mod's, to use the nomenclature of the day 'reach out', find out more...
It's my best player.
"Did you try just leaving pin 3 open, use pin 2 as signal and pin 1 as gnd?"
That cable was 'live wire' tested to find the combo on a test rig system (long gone), the best result was wired 1 and 3 bridged,
what the reason was then, is lost to the mists of time, but yes It would have been tried, and decided against by ear.
Not recommended unless you've built a few studios and encountered all the earthing problems under the sun and the moon!
The only other solution in mind is the back to back zener diode (from pin1 to pin3?). inductive dissipation?
Common in PSU's as one of the earth lift solutions, with for e.g. two 470nF caps from both rails to earth.
Dont know if this senario would connect to both lines, probably only the zeners to earth from the cold line?
The events that put the machine out of use were many years ago. I successfully repaired the machine recently. The main fault was a design flaw of which there were two, both improved upon in that session along with the unconfirmed fault assuming the moded bal to unbal cable in causing a small earth resistor to fry Open Circuit.
What a relief the design corrections worked, awed that it sounds better than it did new.
My test equipment is lacking, Scopes long gone and a pile of other support equipment gone.
The result is wishing to be oh so careful in any interconnect mod's, to use the nomenclature of the day 'reach out', find out more...
It's my best player.
"Did you try just leaving pin 3 open, use pin 2 as signal and pin 1 as gnd?"
That cable was 'live wire' tested to find the combo on a test rig system (long gone), the best result was wired 1 and 3 bridged,
what the reason was then, is lost to the mists of time, but yes It would have been tried, and decided against by ear.
Not recommended unless you've built a few studios and encountered all the earthing problems under the sun and the moon!
The only other solution in mind is the back to back zener diode (from pin1 to pin3?). inductive dissipation?
Common in PSU's as one of the earth lift solutions, with for e.g. two 470nF caps from both rails to earth.
Dont know if this senario would connect to both lines, probably only the zeners to earth from the cold line?
Shorting pins works alone for rca to xlr input. If xlr pin 2 to rca middle and pin 1 to rca massa not works for you, you need to use transformer or standard balanced to unbalanced opamp circuit. Or modify rca output to higher output of your source player.
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A problem with connecting balanced outputs to unbalanced inputs is that you generally don't know whether the balanced output essentially works as:
A. a floating signal voltage source between pins 2 and 3,
or
B. as a sort of floating signal voltage source between pins 2 and 3 that misbehaves when there is too much common-mode voltage between pins 2 & 3 and pin 1,
or
C. as two signal voltage sources with opposite polarity between pins 2 and 1 and between pins 3 and 1
or
D. something in between,
and on top of that, it could also be only impedance balanced rather than really differential.
A signal transformer should always work, but is expensive when you want a good one. Connecting only pins 2 and 3 may work for case A, but will probably not work properly in the other cases. Connecting pin 2 to the centre pin of a cinch plug and pins 1 and 3 to each other and to the cinch plug ground should work for cases A and B, but may burn out a resistor in case C.
Connecting pin 1 to the cinch ground, pin 2 to its centre pin and pin 3 via 220 ohm to the cinch ground usually sort of works in all cases.
A. a floating signal voltage source between pins 2 and 3,
or
B. as a sort of floating signal voltage source between pins 2 and 3 that misbehaves when there is too much common-mode voltage between pins 2 & 3 and pin 1,
or
C. as two signal voltage sources with opposite polarity between pins 2 and 1 and between pins 3 and 1
or
D. something in between,
and on top of that, it could also be only impedance balanced rather than really differential.
A signal transformer should always work, but is expensive when you want a good one. Connecting only pins 2 and 3 may work for case A, but will probably not work properly in the other cases. Connecting pin 2 to the centre pin of a cinch plug and pins 1 and 3 to each other and to the cinch plug ground should work for cases A and B, but may burn out a resistor in case C.
Connecting pin 1 to the cinch ground, pin 2 to its centre pin and pin 3 via 220 ohm to the cinch ground usually sort of works in all cases.
I use transformers every day for pro audio. Cost 30 euro for stereo.
Works two way.
Or schematic below.
Works two way.
Or schematic below.
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I use a pair of very good signal transformers in my valve DAC, they cost well over 100 euro each.
Food for thought MarcelvdG, thankyou.
As is often the way, there is much more to this than my knowledge encompasses. Time for me to look again.
As for input transformers, an ace tool in the live arena and studio were so often chaos reigns,
but IMO something is lost in the isolation transformers when the role of reproducing a recording in high fidelity is concerned.
As is often the way, there is much more to this than my knowledge encompasses. Time for me to look again.
As for input transformers, an ace tool in the live arena and studio were so often chaos reigns,
but IMO something is lost in the isolation transformers when the role of reproducing a recording in high fidelity is concerned.
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droppin this here for now...
OPA1632 High-Performance, Fully Differential Audio Operational Amplifier
Is the last stage of the balanced output (XLR)
OPAx134 High-Performance, SoundPlusTM Audio Operational Amplifiers
is the last stage of the unbalanced line out (RCA)
Looks like the balanced differential output of the OPA1632 is going straight to the OPA2134 then to the unbalanced output.
OPA1632 High-Performance, Fully Differential Audio Operational Amplifier
Is the last stage of the balanced output (XLR)
OPAx134 High-Performance, SoundPlusTM Audio Operational Amplifiers
is the last stage of the unbalanced line out (RCA)
Looks like the balanced differential output of the OPA1632 is going straight to the OPA2134 then to the unbalanced output.
It's essentially case C from post #8 then; the common-mode loop of the OPA1632 makes the output behave as two voltage sources in antiphase with an average equal to the voltage at pin 2 of the OPA1632. For some reason pin 2 of the OPA1632 is driven from a DC servo loop that tries to regulate the DC voltage at XLR pin 2 to zero.
You can connect XLR pin 2 to the centre pin of the RCA connector, XLR pin 1 to the shield of the RCA connector and leave XLR pin 3 open. You then get only half the output voltage. I don't know what the effect on noise and distortion will be, that depends on how good or bad the common-mode loop of the OPA1632 is.
You can connect XLR pin 2 to the centre pin of the RCA connector, XLR pin 1 to the shield of the RCA connector and leave XLR pin 3 open. You then get only half the output voltage. I don't know what the effect on noise and distortion will be, that depends on how good or bad the common-mode loop of the OPA1632 is.
C, yes. Thanks for the detail.
The XLR pin 2 and pin 1 connection; The output is half the 'full swing' of the differential output.
A pair of Sowters are more than the secondhand value of the player !
Balancing the unbalanced inputs on the Pre amp inputs sounds like too much of a project for my lack of experience of a Dan D’Agostino design.
The XLR pin 2 and pin 1 connection; The output is half the 'full swing' of the differential output.
A pair of Sowters are more than the secondhand value of the player !
Balancing the unbalanced inputs on the Pre amp inputs sounds like too much of a project for my lack of experience of a Dan D’Agostino design.
This was further into in the data sheet.
That this opamp has 'immunity' to common mode noise, Affirms Post #8 that it's not possibility B
The output from the AD1955 DAC is balanced to OPA1632. That's good.
Some of the predecessor players to this one have a virtual earth circuit/ mute/ output relays, which I couldn't get the 'why' of.
A previous owner removed the relay, shorting it. This would cause random tray eject errors and random drive motor free spin on start up.
Yeah this post is repetition of a sort, but it's the most complex CD player yet worked on, coming to the conclusion that there are too many sensitive devices involved in the "Balanced" Opamp topology and the unbalancing of that to a line output.
At least now I know some of the reasons why the Balanced output sounded better with the 'Studio modded' cable to unbalanced.
I'm an analog man in a digital world.
That this opamp has 'immunity' to common mode noise, Affirms Post #8 that it's not possibility B
The output from the AD1955 DAC is balanced to OPA1632. That's good.
Some of the predecessor players to this one have a virtual earth circuit/ mute/ output relays, which I couldn't get the 'why' of.
A previous owner removed the relay, shorting it. This would cause random tray eject errors and random drive motor free spin on start up.
Yeah this post is repetition of a sort, but it's the most complex CD player yet worked on, coming to the conclusion that there are too many sensitive devices involved in the "Balanced" Opamp topology and the unbalancing of that to a line output.
At least now I know some of the reasons why the Balanced output sounded better with the 'Studio modded' cable to unbalanced.
I'm an analog man in a digital world.
I think that's a general remark about differential circuits. The sentence starts with: "Differential signal processing offers a number of performance advantages". It's true, of course, hence the use of differential (balanced) connections in professional audio.
It doesn't tell you which of the cases of post #8 applies, because when connected to a differential input, common-mode interference is suppressed to a large extent with all of them. The description of the functionality of the common-mode loop in the datasheet does tell you which case applies, it's case C.