They also seem having convolved "balanced" to some degree as synonymous with "symmetric differential", making it difficult to differentiate dialog referring to signals or signal lines. This is in lieu of simply stating that their device is designed to maintain symmetric differential signals over balanced lines.
There also appears some further confusion In the review of the Project Phono Box rs2 by Stereophile
https://www.stereophile.com/content/pro-ject-phono-box-rs2-phono-preamplifier
"One of the most unusual features at the RS2's price is fully balanced operation. Coates described the advantages. "The Phono Box RS2 was designed to be a true differential balanced component," he said. "This exactly follows the balanced design of a moving coil phono cartridge, where the + and – audio signals are isolated from ground."
Notwithstanding what "true differential balanced" is intended to convey in the above, a moving coil cartridge cannot be described as generating a symmetric differential signal if in absence of a centre tap connection. Each coil generates a differential signal between its end points, hence can't even be incorrectly described as balanced. If the end points of a moving coil are connected to a twisted pair feeding the preamplifier this satisfies the condition of a balanced line.
Under circumstances that the coil and the twisted line is floating, as is the case prior to the connection to the preamplifier, their seems no clear advantage to referencing to ground or any other voltage as variant to the end points, being symmetric or otherwise. In many cases added noise is generated by incorrect reference grounding of variant networks inside of the preamplifier. This is considered proven in that the finest turntables in the world have used RCA connectors (unbalanced transmission lines) for decades.
Rythmik subwoofers, despite their relatively low cost, are one of the best performing commercially made subwoofers, impressing several members here
to buy or build and love them. https://www.diyaudio.com/community/threads/what-to-expect-from-4-subs-minidsp-mso.389941/#post-7364806
I have two on order in custom low diffraction sealed cabinets.
https://www.rythmikaudio.com/technology.html
https://www.rythmikaudio.com/servosurvey.html
But regarding their plate amps with XLR connectors, designer Brian Ding and his chief marketing rep Enrico Castagnetti are apparently reluctant
to provide schematics to confirm circuit design and parts. https://www.rythmikaudio.com/amplifiers.html
As my subs will be at least 20 feet from the balanced outputs of my DACs I am obviously concerned with the risk of induced noise, and whether
the A370XLR3 (and now discontinued A370XLR2) plate amp can reject it.
As per my understanding, the Rythmik A370XLR3 plate amp-even with its balanced line connection (XLR)-presumably cannot be a fully balanced amplifier from input to output, presumably due to how the woofer driver is servo controlled, as Brian Ding seems to likewise explain here on post # 54689
https://www.avsforum.com/threads/official-rythmik-audio-subwoofer-thread.1214550/page-2735
However, is the amp, in fact, still capable of rejecting common mode noise? For that to be true, when a noise voltage is induced in the twisted wire pair inside of the XLR cable-and which that voltage would therefore be of equal polarity-the amp would sense no difference between the voltages on its two inputs. Thus, the noise voltage can't get amplified and thereby rejected.
Is this exactly how the A370XL3 amp works?
If yes, then must it have a differential input stage, yes? In addition to that amp’s ability (or not?) to reduce common mode noise, that is my main question.
to buy or build and love them. https://www.diyaudio.com/community/threads/what-to-expect-from-4-subs-minidsp-mso.389941/#post-7364806
I have two on order in custom low diffraction sealed cabinets.
https://www.rythmikaudio.com/technology.html
https://www.rythmikaudio.com/servosurvey.html
But regarding their plate amps with XLR connectors, designer Brian Ding and his chief marketing rep Enrico Castagnetti are apparently reluctant
to provide schematics to confirm circuit design and parts. https://www.rythmikaudio.com/amplifiers.html
As my subs will be at least 20 feet from the balanced outputs of my DACs I am obviously concerned with the risk of induced noise, and whether
the A370XLR3 (and now discontinued A370XLR2) plate amp can reject it.
As per my understanding, the Rythmik A370XLR3 plate amp-even with its balanced line connection (XLR)-presumably cannot be a fully balanced amplifier from input to output, presumably due to how the woofer driver is servo controlled, as Brian Ding seems to likewise explain here on post # 54689
https://www.avsforum.com/threads/official-rythmik-audio-subwoofer-thread.1214550/page-2735
However, is the amp, in fact, still capable of rejecting common mode noise? For that to be true, when a noise voltage is induced in the twisted wire pair inside of the XLR cable-and which that voltage would therefore be of equal polarity-the amp would sense no difference between the voltages on its two inputs. Thus, the noise voltage can't get amplified and thereby rejected.
Is this exactly how the A370XL3 amp works?
If yes, then must it have a differential input stage, yes? In addition to that amp’s ability (or not?) to reduce common mode noise, that is my main question.
XLR connections addresses the problems associated with the secondary ground return paths through the power cords of a multiplicity of independently powered components. This is why XLR's are used in high noise environments like studios (as well as for their robustness). In such environments higher impedance signal cables can also exist next to power cables over long lengths back to mixing consoles, etc. Such an environment necessitates balanced XLR's, etc., to reduce noise (anything not signal).
However there is no necessary advantage to internal balanced amplification, rather perhaps that the input contains a balanced to single ended converter. Once converted the difference between the signal and the ground requires that the ground and signal lines be maintained as pristinely clean as possible, using such techniques as single point grounding or other means to prevent noise currents being imposed on those lines. Internal single ended operation to balanced outputs (as a normal practice in studio gear) is used to address the unknown pickup sources outside the box to another box. Design engineers have control over what is inside an amplifier box. A single ended amplifier design can far exceed the quality of a questionably designed balanced amplifier. There are many intangibles that can at minimum require graphs and numbers to sort.
It should be noted that the current leaving the output of the +ve terminal of an amplifier to a speaker load returns on the -ve terminal an amplifier, regardless of the amplifier being single ended or balanced. The conclusion is that there is no "unbalancing" path for current to flow other than between the two terminals. Speakers are not normally connected to a power source, whereupon a "third" path (through a power cord) can unbalance the current leaving and returning to the amplifier. Hence there is no necessary significance of an amplifier being balanced or otherwise to deal with unbalanced currents, though balanced can imply other things.
However there is no necessary advantage to internal balanced amplification, rather perhaps that the input contains a balanced to single ended converter. Once converted the difference between the signal and the ground requires that the ground and signal lines be maintained as pristinely clean as possible, using such techniques as single point grounding or other means to prevent noise currents being imposed on those lines. Internal single ended operation to balanced outputs (as a normal practice in studio gear) is used to address the unknown pickup sources outside the box to another box. Design engineers have control over what is inside an amplifier box. A single ended amplifier design can far exceed the quality of a questionably designed balanced amplifier. There are many intangibles that can at minimum require graphs and numbers to sort.
It should be noted that the current leaving the output of the +ve terminal of an amplifier to a speaker load returns on the -ve terminal an amplifier, regardless of the amplifier being single ended or balanced. The conclusion is that there is no "unbalancing" path for current to flow other than between the two terminals. Speakers are not normally connected to a power source, whereupon a "third" path (through a power cord) can unbalance the current leaving and returning to the amplifier. Hence there is no necessary significance of an amplifier being balanced or otherwise to deal with unbalanced currents, though balanced can imply other things.
You'd call that 2VRMS.
However, in your second scenario there isn't a defined reference to measure the 1VRMS relative to. 🙂
Dave.
To be careful you'd say the differential voltage is 2Vrms in the second scenario, that removes any ambiguity. With 15V opamp circuits the usually maximum single-ended signal is about 9Vrms, max balanced differential signal is double that at 18Vrms. You get greater headroom, but oddly enough usually the Johnson noise is often worse as handling differential signals is awkward and converting differential to single-ended is hard to do in a low-noise manner (3 opamps or more), and usually you may drop 6dB to avoid loss of headroom (which compounds the noise issue).
But noise pickup is definitely reduced (no ground loops!) and that is usually the big win.
But noise pickup is definitely reduced (no ground loops!) and that is usually the big win.
Also, don't forget that balanced lines in themselves don't cancel noise, it is the common mode rejection at the receiving side that does that.
Balanced lines only help to keep the noise equal in both wires. The receiving stage has the task to subtract and thereby cancel the noise on the two wires.
Jan
why are balanced connection conversations so riddled with conflicting/confusing information?
well for one as someone who has for years in my PA career been dealing with balanced lines can attest to is that there not so simple to understand and can easily be misapplied and produce strange effects.
even years later i won't say i'm an expert and still come across all manner of problem with balanced connections.
we tend to think in absolutes and as a result when we talk "grounds" we are conditioned to "they need to be connected", and when it comes to balanced lines that's where the problems start...and add the Pin 1 problems created by poorly designed gear or misapplication of a standard because of disinformation....that's almost a separate discussion,no?
and this may me being a tad ocd but a "balanced in" or "receiving stage" is neither subtractive nor is it additive...unless you include "phase" with respect to the signal return(yes i have a reason to not call it ground!)
if you've ever had an instance of a miswired XLR where pin 2 and 3 are reversed across the cable so that you are driving the plus input with a negative going signal and vice versa...funny thing is it will work, but just not the best!(that would be based on the design of the input stage)
i did come across and instance involving a Klark EQ and a BSS x-over where pin reversal produced cleaner signal.
to me a mic line which is a low level, low impedance and easy to degrade signal benefits from a balanced connection (anybody but me remember high impedance Shure mics and VocalMaster mixers?) but at line level and potentially at less then ten feet in length is there really an advantage to going balanced as far as signal quality, i'd venture that source impedance and the increased gain makes most feel it's "more"...being able to isolate electrical grounds and eliminate hum is one of it's biggest features but simple "repeat coils" can do that...
another OCD rant... i dislike the term "ground loop" is it not a "link"? (and whether it becomes inductive or capacitive and at what frequency is a function of the link impedance?)
well for one as someone who has for years in my PA career been dealing with balanced lines can attest to is that there not so simple to understand and can easily be misapplied and produce strange effects.
even years later i won't say i'm an expert and still come across all manner of problem with balanced connections.
we tend to think in absolutes and as a result when we talk "grounds" we are conditioned to "they need to be connected", and when it comes to balanced lines that's where the problems start...and add the Pin 1 problems created by poorly designed gear or misapplication of a standard because of disinformation....that's almost a separate discussion,no?
and this may me being a tad ocd but a "balanced in" or "receiving stage" is neither subtractive nor is it additive...unless you include "phase" with respect to the signal return(yes i have a reason to not call it ground!)
if you've ever had an instance of a miswired XLR where pin 2 and 3 are reversed across the cable so that you are driving the plus input with a negative going signal and vice versa...funny thing is it will work, but just not the best!(that would be based on the design of the input stage)
i did come across and instance involving a Klark EQ and a BSS x-over where pin reversal produced cleaner signal.
to me a mic line which is a low level, low impedance and easy to degrade signal benefits from a balanced connection (anybody but me remember high impedance Shure mics and VocalMaster mixers?) but at line level and potentially at less then ten feet in length is there really an advantage to going balanced as far as signal quality, i'd venture that source impedance and the increased gain makes most feel it's "more"...being able to isolate electrical grounds and eliminate hum is one of it's biggest features but simple "repeat coils" can do that...
another OCD rant... i dislike the term "ground loop" is it not a "link"? (and whether it becomes inductive or capacitive and at what frequency is a function of the link impedance?)
"...prevent ground loops". No. You still have ground loops. They don't matter because the signal is no longer ground-related.
@turk 182: your anecdote that 'it still works' when you swap the XLR connections to pin 2 & 3 should not come as a surprise for anyone grokking balanced connections. You see, it's the difference between the two pins that constitute the signal.
That difference does not change in magnitude when swapping the pins, it only flips the phase by 180 degrees.
Which, as we know, will be very hard if not impossible for anyone to tell from just listening.
Jan
That difference does not change in magnitude when swapping the pins, it only flips the phase by 180 degrees.
Which, as we know, will be very hard if not impossible for anyone to tell from just listening.
Jan
Absolute polarity is a rabbit hole.
Even assuming it were audible, you have no way to know which way is correct without auditioning every piece of program material you have and noting/recording the result. If you tabulated it all you'd probably find it was 50/50. 🙂
A much more likely accidental Pin 2/3 swap issue might occur if a particular source has no active signal on Pin 3. If maybe you were doing some adapting into an unbalanced destination, you'd have no sound. 🙂
There are some other instances that might cause issues as well. But pretty unlikely though.
Dave.
Even assuming it were audible, you have no way to know which way is correct without auditioning every piece of program material you have and noting/recording the result. If you tabulated it all you'd probably find it was 50/50. 🙂
A much more likely accidental Pin 2/3 swap issue might occur if a particular source has no active signal on Pin 3. If maybe you were doing some adapting into an unbalanced destination, you'd have no sound. 🙂
There are some other instances that might cause issues as well. But pretty unlikely though.
Dave.
No. It doesn't matter whether pin 3 has a signal or not.
If there is any signal between pin 2 and pin 3, swapping them doesn't change the signal level.
That's basic.
Jan
If there is any signal between pin 2 and pin 3, swapping them doesn't change the signal level.
That's basic.
Jan
yet another anecdote about balanced interconnects...when old or even cruddy contacts make a pin behave like a capacitor you can get some interesting filter affects.
@jan.didden Yeah, but that's not what I said. 🙂 I was highlighting a specific adapting configuration that would cause an issue if Pin 3(2) had no signal, and you had mis-wired cable.
Please read closely before responding.
Dave.
Please read closely before responding.
Dave.
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Is that at least one reason why some preamps and DACs have a phase inversion switch?
Because polarity inversion ( there is no phase inversion, but you are switching polarity) can happen in a signal path because of miswiring or any other 'fault' within the chain and for some people it does mater to solve the issue without using a soldering iron.
I agree with Davey, absolute polarity is most often all over the place on a record collection.
But as pointed by Turk182 some people can be sensible to it.
It can make a difference on some kind of records ( minimalist recording technique using a single pair of microphone, so most likely classical or acoustic) not at all on others ( multi mic close proximity, 'pop' records).
I agree with Davey, absolute polarity is most often all over the place on a record collection.
But as pointed by Turk182 some people can be sensible to it.
It can make a difference on some kind of records ( minimalist recording technique using a single pair of microphone, so most likely classical or acoustic) not at all on others ( multi mic close proximity, 'pop' records).
XLRs alone do not make a balanced circuit. They are just a connector, true they have three pins which allows for the +- signals plus a separate screen but in consumer devices it is not unusual to find one of the signal pins wired to earth along with the screen. As has been said a true balance circuit provides an equal and opposite signal across across two conductors. No reference to earth is required. In the transformer days it would have been frowned upon to have a centre tap to earth, this only came about with 'electronic' balanced inputs which require an earth reference.
There is no reason why a MC cartridge cannot be wired as balanced especially if you are feeding step up transformers. The problem comes with getting a screen to the cartridge with only four wires running through the tone arm.
The simplest option would be to mount step up transformers in the turntable as close the the arm as possible then feed from the secondaries as balanced. However hum pickup from motor may be an issue.