|
|
Post by Jim on Nov 23, 2012 22:05:09 GMT -5
I just found that same post and was about to post it.  |
|
|
|
Post by Jim on Nov 26, 2012 16:05:56 GMT -5
does anyone know if the XPR amps are fully balanced like the XPA-1 ? I confirmed with Emotiva that at least the XPR-5 is NOT fully balanced (which makes sense). |
|
KeithL
Administrator 
Posts: 10,274
|
Post by KeithL on Dec 17, 2012 1:22:38 GMT -5
OK, you're mixing apples and oranges. Strictly speaking, "Idle" is when the amp is on but nothing is playing (lights are blue). In that situation, the main power supply and the amp modules are still running, but the output power is zero - and everything remains "warmed up". When the trigger drops, the amp goes into standby. In standby the main power supply is Off, and all that remains on are the parts that listen for a signal to turn back on. In standby, all our amps draw in the vicinity of just under 1 watt. How much current does this amp draw when in idle (preamp 12V signal off)? |
|
KeithL
Administrator
Posts: 10,274
|
Post by KeithL on Dec 17, 2012 1:39:21 GMT -5
There is a lot of confusion about what "differential" and "balanced" mean. The term balanced is generally used to refer to connections. With a balanced connection, there are two "hot" leads, one of which carries "signal +" and the other "signal -", and the input is the DIFFERENCE between them. The great benefit is that and noise (like hum) that is picked up equally by both input signal leads cancels out. (Since you are subtracting the two inputs, and it is common to both of them, it subtracts to near zero.) This is called "common mode rejection". You can take this balanced signal and feed it to an amplifier that is "balanced", or not, and still get this benefit. In order for an amplifier to be "differential", you need two entirely separate amplifier circuits, each driven out of phase from the other. When you do this, most of the distortion and some of the noise that is present equally in both amplifiers will cancel out. You usually end up with slightly lower distortion this way (how much you benefit depends on other design considerations). In a fully differential amplifier, NEITHER speaker binding post is grounded (they are "out +" and "out -"). In order for an entire system to be "fully balanced" AND "fully differential", all of the individual components would have to be differential and all of the connections balanced. So, for example, if you connect an XDA-2 to an XSP-1, and the XSP-1 to a pair of XPR-1's, using all balanced connections, and run the XSP-1 in Differential Reference mode (Tone trims off, etc), then the entire system would be balanced and differential. The XPA-1, and the XPR-1 are fully differential amplifiers, and they have balanced inputs. The XPA-2, XPA-3, XPA-5, XPR-2, and XPR-5 are NOT differential amplifiers (the black speaker binding post IS grounded), but they do have balanced inputs. |
|
|
|
Post by repeetavx on Dec 17, 2012 13:28:26 GMT -5
Thanks Keith,
Your explanation is clear and makes perfect sense to me.
|
|
|
|
Post by garbulky on Dec 17, 2012 14:06:22 GMT -5
The XPA-1, and the XPR-1 are fully differential amplifiers, and they have balanced inputs. The XPA-2, XPA-3, XPA-5, XPR-2, and XPR-5 are NOT differential amplifiers (the black speaker binding post IS grounded), but they do have balanced inputs. Then why does it say dual differential for instance under the xpa-2 if it is not differential? I guess I'm wondering the difference between quad and dual differential. |
|
|
|
Post by Jim on Dec 17, 2012 14:11:54 GMT -5
To quote KeithL "In order for an amplifier to be "differential", you need two entirely separate amplifier circuits, each driven out of phase from the other. "
But the XPA-1 says quad, so maybe each "circuit" is really 2 (dual)?
I'm just guessing. I seriously need to find a good book on amplifier design.
|
|
KeithL
Administrator
Posts: 10,274
|
Post by KeithL on Dec 18, 2012 14:25:19 GMT -5
Engineering speak can be a bit confusing....  (which is why it's sometimes best left to engineers) A differential input stage is NOT the same thing as a differential amplifier. A differential input stage is a specific configuration of input devices, which has lots of benefits and no serious drawbacks. A differential input stage can be used with ANY sort of amplifier, including those that don't even have balanced inputs. (Most modern amplifier designs use differential inputs, as do almost all op-amps.) Each amplifier module (channel) in the XPA and XPR series amps uses a dual-differential input, which means that EACH HALF (plus and minus) of the input has its own differential input pair. Our implementation is slightly more sophisticated than the basic one, but not at all hard to recognize. You can Google "differential input" if you want lots of details. In the audio industry, a differential amplifier is an amplifier that amplifies the plus and minus halves of a balanced signal separately, using two separate amplifiers (or circuits; or channels). The benefit is that most of the distortion generated by each of the amplifier halves will be equal but opposite to that generated by the other, so they will cancel out, giving you lower overall distortion and possibly lower noise. (There is another, slightly more general, usage of the term "differential amplifier" to mean: "an amplifier that amplifies the difference between two inputs". We're using the definition more narrowly - as it is used in the audio industry.) All of our XPA and XPR amplifiers have dual-differential inputs. Our XPA-1 and XPR-1 are DIFFERENTIAL AMPLIFIERS because they each use two separate amplifier modules for the plus and minus halves of the signal, AND each of those amplifier modules has a dual-differential input topology. Occasionally, we shorthand "dual differential amplifier, each half with dual differential inputs" to "quad differential"...... (but sometimes not). Maybe it's time to forget about the schematic and get back to how it SOUNDS...Hmmmmmm....  The XPA-1, and the XPR-1 are fully differential amplifiers, and they have balanced inputs. The XPA-2, XPA-3, XPA-5, XPR-2, and XPR-5 are NOT differential amplifiers (the black speaker binding post IS grounded), but they do have balanced inputs. Then why does it say dual differential for instance under the xpa-2 if it is not differential? I guess I'm wondering the difference between quad and dual differential. |
|
|
|
Post by monkumonku on Dec 18, 2012 14:31:01 GMT -5
Engineering speak can be a bit confusing.... (which is why it's sometimes best left to engineers) A differential input stage is NOT the same thing as a differential amplifier. A differential input stage is a specific configuration of input devices, which has lots of benefits and no serious drawbacks. A differential input stage can be used with ANY sort of amplifier, including those that don't even have balanced inputs. (Most modern amplifier designs use differential inputs, as do almost all op-amps.) Each amplifier module (channel) in the XPA and XPR series amps uses a dual-differential input, which means that EACH HALF (plus and minus) of the input has its own differential input pair. Our implementation is slightly more sophisticated than the basic one, but not at all hard to recognize. You can Google "differential input" if you want lots of details. In the audio industry, a differential amplifier is an amplifier that amplifies the plus and minus halves of a balanced signal separately, using two separate amplifiers (or circuits; or channels). The benefit is that most of the distortion generated by each of the amplifier halves will be equal but opposite to that generated by the other, so they will cancel out, giving you lower overall distortion and possibly lower noise. (There is another, slightly more general, usage of the term "differential amplifier" to mean: "an amplifier that amplifies the difference between two inputs". We're using the definition more narrowly - as it is used in the audio industry.) All of our XPA and XPR amplifiers have dual-differential inputs. Our XPA-1 and XPR-1 are DIFFERENTIAL AMPLIFIERS because they each use two separate amplifier modules for the plus and minus halves of the signal, AND each of those amplifier modules has a dual-differential input topology. Occasionally, we shorthand "dual differential amplifier, each half with dual differential inputs" to "quad differential"...... (but sometimes not). Maybe it's time to forget about the schematic and get back to how it SOUNDS...Hmmmmmm.... Then why does it say dual differential for instance under the xpa-2 if it is not differential? I guess I'm wondering the difference between quad and dual differential. Thank you Keith for another enlightening and intelligent post! I really do appreciate the time you've taken to give us this information. Also, as an owner of a pair of XPA-1's, I just want to say to owners of other Emo amps (except the XPR-1), SO NYAH!!! ;D |
|
|
|
Post by Jim on Dec 18, 2012 14:44:25 GMT -5
Thank you Keith for another enlightening and intelligent post! I really do appreciate the time you've taken to give us this information. Also, as an owner of a pair of XPA-1's, I just want to say to owners of other Emo amps (except the XPR-1), SO NYAH!!! ;D My thanks to Keith as well! I think that's as clearly explained as it can be made... without drawing it out! Thanks for all the time invested in explaining that! NYAH!! ... Now that's funny. |
|
|
|
Post by garbulky on Dec 18, 2012 17:53:17 GMT -5
Engineering speak can be a bit confusing.... (which is why it's sometimes best left to engineers) A differential input stage is NOT the same thing as a differential amplifier. A differential input stage is a specific configuration of input devices, which has lots of benefits and no serious drawbacks. A differential input stage can be used with ANY sort of amplifier, including those that don't even have balanced inputs. (Most modern amplifier designs use differential inputs, as do almost all op-amps.) Each amplifier module (channel) in the XPA and XPR series amps uses a dual-differential input, which means that EACH HALF (plus and minus) of the input has its own differential input pair. Our implementation is slightly more sophisticated than the basic one, but not at all hard to recognize. You can Google "differential input" if you want lots of details. In the audio industry, a differential amplifier is an amplifier that amplifies the plus and minus halves of a balanced signal separately, using two separate amplifiers (or circuits; or channels). The benefit is that most of the distortion generated by each of the amplifier halves will be equal but opposite to that generated by the other, so they will cancel out, giving you lower overall distortion and possibly lower noise. (There is another, slightly more general, usage of the term "differential amplifier" to mean: "an amplifier that amplifies the difference between two inputs". We're using the definition more narrowly - as it is used in the audio industry.) All of our XPA and XPR amplifiers have dual-differential inputs. Our XPA-1 and XPR-1 are DIFFERENTIAL AMPLIFIERS because they each use two separate amplifier modules for the plus and minus halves of the signal, AND each of those amplifier modules has a dual-differential input topology. Occasionally, we shorthand "dual differential amplifier, each half with dual differential inputs" to "quad differential"...... (but sometimes not). Maybe it's time to forget about the schematic and get back to how it SOUNDS...Hmmmmmm.... Then why does it say dual differential for instance under the xpa-2 if it is not differential? I guess I'm wondering the difference between quad and dual differential. Well I think understanding what is actually balanced is actually important because balanced products costs $$$. The unbalanced and balanced are in two different price ranges. Also, I haven't heard them because emotiva is internet direct. Same goes for any other technical specs. So if I'm considering spending my money, I would want to know why. Thanks for the explanation Keith. That was very clear. So what I'm getting is that quad-differential is emotiva's code word for differential and balanced. |
|
(which is why it's sometimes best left to engineers) 
