|
|
Post by Gary Cook on Dec 4, 2014 18:45:06 GMT -5
Ground loop hum is one where XLR's usually make no difference. On the contrary, this is were they shine. You must lift the ground to break the ground loop path. I have run 100m+ lengths of balanced leads as well as instrumentation cable with no ground noise. Regard I'm confused, whether old America or European/Current standard, in an XLR connection Pin 3 is the earth/ground. So help me out here, how is the ground "lifted"? Cheers Gary |
|
|
|
Post by audiosyndrome on Dec 4, 2014 20:22:02 GMT -5
 ?? I agree, whether it's dual differential or quad differential, it's still balanced.  Cheers Gary Gary- Dual differential, quad differential, etc. does not mean the amplifier is fully balanced. It is, in Emotiva's case, only referring to the input stage of the amplifier. The only Emotiva amps that are fully balanced are the XPR-1, XPA-1 and the XPA-1L. A fully balanced amplifier requires two complete amplifiers for each channel. Look at the cutaway pictures for the three amps I mentioned. You'll see two amplifiers for each channel. One for the positive signal, and one for the inverted signal. The two signals are subtracted from each other at the output of the amp yielding twice the original signal and zero noise (as the noise is the same for the positive and inverted signals). Russ |
|
|
|
Post by Gary Cook on Dec 4, 2014 21:25:39 GMT -5
Because he explains it far better than I could; A differential INPUT is NOT the same thing as a "fully differential amplifier". These are both well-defined engineering terms (try Google). A fully differential amplifier MUST have a balanced input (to maintain a fully differential signal path). A fully differential amplifier has two separate amplifiers, one amplifying an in-phase signal; the other an out-of-phase signal; with the two added together to make the output. This results in lower overall distortion because most distortion generated by the amplifiers is equal and opposite, and so cancels out. (You can have an otherwise differential amplifier with a non-differential input; the input is changed to differential at the earliest possible moment; and everything after that is fully differential... like if you use the unbalanced input on an XPA-1.) However, differential INPUTS are popular with all sorts of amplifiers - differential or not - because they have all sorts of engineering benefits. A differential input does not mean that the rest of the amp is differential. In fact, virtually all modern solid state amplifiers, "fully differential" or not, have differential inputs (and even some tube ones do). I believe that includes out VTAC tube amps. "Quad differential" is a little less specific term - and can mean either simply dual dual-differential inputs or dual dual-differential inputs where the inputs are also cross linked. In our case (with the XPA-1) it means a differential amplifier, with each of the two amplifier modules having a dual-differential INPUT... but other folks may use the term differently. If that already sounds confusing, then don't worry about it. In simple terms, 'cause I'm a simple guy, within the XPA range the XPA-2/3/5/7 all are fully balanced as they have dual differential inputs for their balanced connections. The XPA-1/1L are similarly fully balanced as they also have dual differential inputs, and they have the added advantage of having dual differential amplifiers. Which is where the quad differential comes in (ie; dual + dual = quad). Cheers Gary |
|
|
|
Post by audiosyndrome on Dec 4, 2014 22:45:44 GMT -5
Because he explains it far better than I could; A differential INPUT is NOT the same thing as a "fully differential amplifier". These are both well-defined engineering terms (try Google). A fully differential amplifier MUST have a balanced input (to maintain a fully differential signal path). A fully differential amplifier has two separate amplifiers, one amplifying an in-phase signal; the other an out-of-phase signal; with the two added together to make the output. This results in lower overall distortion because most distortion generated by the amplifiers is equal and opposite, and so cancels out. (You can have an otherwise differential amplifier with a non-differential input; the input is changed to differential at the earliest possible moment; and everything after that is fully differential... like if you use the unbalanced input on an XPA-1.) However, differential INPUTS are popular with all sorts of amplifiers - differential or not - because they have all sorts of engineering benefits. A differential input does not mean that the rest of the amp is differential. In fact, virtually all modern solid state amplifiers, "fully differential" or not, have differential inputs (and even some tube ones do). I believe that includes out VTAC tube amps. "Quad differential" is a little less specific term - and can mean either simply dual dual-differential inputs or dual dual-differential inputs where the inputs are also cross linked. In our case (with the XPA-1) it means a differential amplifier, with each of the two amplifier modules having a dual-differential INPUT... but other folks may use the term differently. If that already sounds confusing, then don't worry about it. In simple terms, 'cause I'm a simple guy, within the XPA range the XPA-2/3/5/7 all are fully balanced as they have dual differential inputs for their balanced connections. The XPA-1/1L are similarly fully balanced as they also have dual differential inputs, and they have the added advantage of having dual differential amplifiers. Which is where the quad differential comes in (ie; dual + dual = quad). Cheers Gary Read Keith's last paragraph where he states ......."with each of the TWO amplifier modules".....the only Emotiva amps with TWO amplifier modules per channel are the XPR-1, XPA-1 and XPA-1L as I stated earlier. These are the only BALANCED amps manufactured by Emotiva. You're confusing the inputs to the amps with the overall topology BALANCED of the amps. Russ |
|
|
|
Post by cwt on Dec 4, 2014 23:35:35 GMT -5
This has happened before in other threads with some referencing completely balanced input to output and others referring to balanced outs [after conversion from unbalanced circuitry] . Will happen again no doubt at a guess  Its true enough that some implementations of balanced out avoid the shielding in the unbalanced cable and its consequent shunting to ground . The xmc1 has better unbalanced conversion than some older model Marantz' as an example www.presonus.com/news/articles/balanced-unbalancedTheres a school of thought that if the full chain of components isnt truly balanced input to output unbalanced is fine . If anyone has a erc3 [true balanced] and a couple of xpa1l's with their xmc1 that would be a true comparison to unbalanced instead  Otherwise its the lowest common denominator methinks.. |
|
|
|
Post by Gary Cook on Dec 5, 2014 0:16:59 GMT -5
Read Keith's last paragraph where he states ......."with each of the TWO amplifier modules".....the only Emotiva amps with TWO amplifier modules per channel are the XPR-1, XPA-1 and XPA-1L as I stated earlier. These are the only BALANCED amps manufactured by Emotiva. You're confusing the inputs to the amps with the overall topology BALANCED of the amps. Russ I read that differently, my view (using your terminology) is that that the only Emotiva amps with TWO amplifier modules per channel are the XPR-1, XPA-1 and XPA-1L and hence these are the only quad differential amps manufactured by Emotiva. Quite deliberately I used the first of Keith's quotes to set the scene. In which he stated "the setup would be fully BALANCED, but not fully differential". By "the setup" he is referring to the Stealth amplifiers, of which there are 2 but that's one for each driver. My view would be that if a Stealth amplifier is "fully balanced" then I'm not sure why an XPA-2/3/5/7 wouldn't be? I can distinguish the difference between fully balanced and fully differential, and it reads like Keith does as well. Using your view it would be impossible for Stealth set up to be fully balanced because it isn't fully differential. What am I missing? Cheers Gary |
|
|
|
Post by Gary Cook on Dec 5, 2014 0:31:32 GMT -5
Theres a school of thought that if the full chain of components isnt truly balanced input to output unbalanced is fine . If anyone has a erc3 [true balanced] and a couple of xpa1l's with their xmc1 that would be a true comparison to unbalanced instead Otherwise its the lowest common denominator methinks.. This I can understand, a balance/differential source (ERC-3) using balanced connections (XLR) to a balanced/differential pre/pro (XSP-1 or XMC-1) using balanced connections to a balanced/differential power amp (XPA-1,1L etc) would be a "fully balanced/fully differential system", all the way from start to finish. Cheers Gary |
|
|
|
Post by moko on Dec 5, 2014 0:34:32 GMT -5
According to the Emotiva Products Page the XMC-1 using Balanced input to Balanced output has a SNR od 123db. In Unbalanced output to Unbalanced input it has a measured SNR of 114db. Can any of you speak to the differences, if any, that you hear when switching from Unbalanced connection to Balanced connections with the XMC-1. For instance, are you using the XPA-1 or XPA-1L with the XMC-1 now vs any other Emotiva amp or an unbalance amp from another manufacturer? i HIGHLY doubt that human ears can tell the difference of SNR 123 vs 114. inaudible is inaudible. i could totally tell the difference when i switched to XLR from RCA connections. i was using the XSP-1 G2 with my UPA-1's and using RCA connections. the highs on my speakers weren't there enough to my liking. they didn't exactly cut through the air like they should. i then switched to monoprice XLR cables and the highs were better all of a sudden. problem solved with my speakers! i was so pleased and had no i idea the solution to my tweeter problem could be the type of connections the cables used were. then again, these RAAL tweeters are extremely acurate and therefore very revealing and aware of ANYTHING you put in front of them. and it never hurts to be lucky this is a proof that upa-1 is actually balanced amp like other push-pull design amp. the rca (unbalanced input) goes to an op-amp as a phase splitter which may reduce transparency in higher frequency. Because he explains it far better than I could; In simple terms, 'cause I'm a simple guy, within the XPA range the XPA-2/3/5/7 all are fully balanced as they have dual differential inputs for their balanced connections. The XPA-1/1L are similarly fully balanced as they also have dual differential inputs, and they have the added advantage of having dual differential amplifiers. Which is where the quad differential comes in (ie; dual + dual = quad). Cheers Gary Read Keith's last paragraph where he states ......."with each of the TWO amplifier modules".....the only Emotiva amps with TWO amplifier modules per channel are the XPR-1, XPA-1 and XPA-1L as I stated earlier. These are the only BALANCED amps manufactured by Emotiva. You're confusing the inputs to the amps with the overall topology BALANCED of the amps. Russ is correct. dual differentials contains 2 differentials : 1. in-phase and ground 2. inverted-phase and ground all push-pull amps (which are more than about 90 % modern amps) need dual differential : in-phase and inverted phase. you can read it here. so each amp module has 2 differentials. the quad differentials is actually a paralled 2 push-pull amp modules. the audiophile term for this is "fully balanced". but to fully exploit the advantage you need to cross-connect them between the left module and right module. that means you need 4 matching transistors : 2 npn and 2 pnp transistors. the only emotiva amp that i'm sure has this cross-connection is xpa-1 gen 1. this amp has high SNR of 100 db and they said it has " cross coupled active current sources". |
|
|
|
Post by richardrc on Dec 5, 2014 4:43:52 GMT -5
This causes so much confusion. Modern Class A/B amps are push pull and SiNGLE ENDED not differential. The UPA-1 is single ended not differential and is effectively a blade from an XPA-5 put in a chassis. To achieve a differential amplifier (or as called quad differential or fully balanced) you get two single ended amplifiers and feed one of them "signal A" and the other one the inverse of "signal A". You then take the output across the positive terminals of the amplifiers and the speaker becomes the summing junction or the point where the common noise will be cancelled out. You may recognise this topology as a bridge mode amplifier. Hopefully if you fed a bridge mode amplifier a balanced signal then you should bypass the inversion circuitry (fingers crossed) and achieve a differential amplifier.
Regards
|
|
|
|
Post by moko on Dec 5, 2014 5:47:22 GMT -5
This causes so much confusion. Modern Class A/B amps are push pull and SiNGLE ENDED not differential. The UPA-1 is single ended not differential and is effectively a blade from an XPA-5 put in a chassis. To achieve a differential amplifier (or as called quad differential or fully balanced) you get two single ended amplifiers and feed one of them "signal A" and the other one the inverse of "signal A". You then take the output across the positive terminals of the amplifiers and the speaker becomes the summing junction or the point where the common noise will be cancelled out. You may recognise this topology as a bridge mode amplifier. Hopefully if you fed a bridge mode amplifier a balanced signal then you should bypass the inversion circuitry (fingers crossed) and achieve a differential amplifier. Regards single ended amp is not the same as single ended connection (rca). just because an amp only has single ended connection doesn't mean it's a single ended amp. it could be push pull amp. single ended amps has low efficiency so i highly doubt that upa-1 which has 300 va transformer and can produce 200 wpc @ 8 ohms is a single ended amp. i believe it's push pull amp. all emo amp are push pull class AB but some amps like xpa-1l and xpa-1 gen 2 has bias switch that increase class A operation. i think this following video can give better explanation : btw there's no such thing called single ended class AB. |
|
|
|
Post by wizardofoz on Dec 5, 2014 6:14:29 GMT -5
The upa-1 like all the xpa-2/3/5's are no fully balanced...only the input has an option to allow a balanced input that converterted to the same input as the rca on the input boards using a differential op amp There is a very good series of posts on Paul's PS Audio's posts...here www.psaudio.com/pauls-posts/true-balanced/ and others adjacent in the series on balanced. |
|
|
|
Post by moko on Dec 5, 2014 6:38:39 GMT -5
The upa-1 like all the xpa-2/3/5's are no fully balanced...only the input has an option to allow a balanced input that converterted to the same input as the rca on the input boards using a differential op amp There is a very good series of posts on Paul's PS Audio's posts...here www.psaudio.com/pauls-posts/true-balanced/ and others adjacent in the series on balanced. nobody said upa-1 is fully ballanced. i only said it's a push pull amp which need in-phase and inverted phase like the one explained in this article : www.circuitstoday.com/push-pull-amplifierand how do you know it's differential op-amp not a phase splitter ? |
|
|
|
Post by wizardofoz on Dec 5, 2014 8:29:27 GMT -5
If I recall correctly ( been a while since I looked) that's what the chip was
My bad I admit it...you didn't say it was balanced in but that it was push pull..I've seen too many people imply that just as these amps have balanced inputs they are running fully balanced. Having had 5 xpa-1's and 5 upa-1's in my emotiva stable and still have some of each...I do know the differences.
|
|
|
|
Post by hcsunshine90 on Dec 5, 2014 12:13:51 GMT -5
earlier in this thread, "moko" states that to fully exploit the advantage (of quad differential) you need to cross-connect the left and right modules. he then goes on to say that the only emo amp to ever have "cross coupled active current sources" was the XPA-1 gen 1. i'm just wondering why emo doesn't have this feature on the new XPA-1 G2 and all their quad differential amps.
|
|
|
|
Post by audiosyndrome on Dec 5, 2014 13:53:10 GMT -5
Last time. Emotiva makes THREE FULLY BALANCED AMPLIFIERS. The XPR-1, the XPA-1 and the XPA-1L. None of the other amplifiers made by Emotiva and especially not the amps in the Stealths are fully balanced input to output. Forget about dual differential, quad differential, etc. Just marketing terms for the INPUT stage(s) of the amps.
Read Emotiva's description for each of their amps. Fully balanced only shows up .... three times....
Russ
|
|
|
|
Post by moko on Dec 6, 2014 2:01:24 GMT -5
i think it's simple. single ended amp = single differential = unbalanced push pull amp = dual differential = balanced (IF using xlr connectors) 2 push pull amps = quad differential = fully balanced (emotiva)/pure balanced (ati)/true balanced (ps audio) but if you think to maintain balanced connection you need quad (4) differential per channel, think again. that means using emotiva gear to maintain balanced, you would need 8 (!) differential (4 for each channel) erc-3, 8 differential xsp-1 and 2 xpa-1 amps. or for less budget 8-gang audio-taper potentiometer control freak. that is not correct. now, if you ask KeithL or Lonnie this question : "do erc-3 and xsp-1 have 8 differential ?", then my humble guess the answer will be : "no, it has 4 differential. 2 for EACH channel." |
|
|
|
Post by richardrc on Dec 6, 2014 4:12:08 GMT -5
Moko, please do not claim that single ended and class AB are mutually exclusive. You are probably confusing facts about single and dual voltage rails, both of which can be designed for class AB. Furthermore many class of amplifiers have a diff amp at the input but it is not configured in the way you might think as the inverting input is used for negative feedback. The output of the front end of the diff amp is in class A to maintain linearity. This signal can be fed to an intermediate amplifier stage or directly to the output stage of the amplifier. Now this is where the push pull comes in as the positive half of the signal will cause the output devices connected to the +ve rail to conduct and vice versa. After a bit of a search I managed to find some text that explains the operation of a class B amp, so it is missing the biasing circuit of class AB but this is just an extension on the theory. You will notice that it operates in fully single ended mode with a dual rail power supply. www.uotechnology.edu.iq/dep-eee/lectures/3rd/Electronic/Analog%20electronic/5.pdfAs for cross connection of current mirrors in the input of a balanced amplifier, this is not the only way a balanced amplifier can be designed. As I stated above. |
|
|
|
Post by Audiozealot on Dec 6, 2014 10:44:19 GMT -5
Hi fbczar - I can't answer your question regarding the XMC-1, since I don't own one, but I can speak to the balanced / unbalanced differences on the XSP-1 (generation 2) stereo preamplifier by Emotiva. To my ears, and with my equipment, the differences can be summed to a single word: none! Perhaps some listeners can tell the difference between the XLR and RCA circuitry, but to my ears, both are quiet, dynamic, and grain-free. I currently run fully balanced from my source (Oppo BDP-105) to my amps (Emotiva XPA-1Ls). Prior to this, though, I ran RCA all the way. Both were perfect, so far as I could tell. HOWEVER - All my interconnect runs are short (1 meter from Oppo to preamp, 2.5 meters from preamp to power amps). With longer runs, perhaps the theoretical advantages of the balanced circuitry would prevail? Not sure. Boom I believe the circuit difference is an op-amp and the only only difference I've heard is that it's slightly louder using XLR interconnects and if I put my ear to the speaker when silent the XLR's are quieter. |
|
|
|
Post by Audiozealot on Dec 6, 2014 10:47:32 GMT -5
I could hear no difference switching from RCA to XLR connectors; both were dead quiet. I changed because I thought the XLR connectors were more secure (and sexy). My XLR's were from Emotiva, and I'm pleased with them. Sincerely /b Did you check the wiring on the Monoprice cables? They are not built correctly, they connect the shell to the ground pin which they even said is not proper. I just cut that connection on mine instead of try to return them. |
|
|
|
Post by solarrdadd on Dec 6, 2014 11:11:37 GMT -5
I could hear no difference switching from RCA to XLR connectors; both were dead quiet. I changed because I thought the XLR connectors were more secure (and sexy). My XLR's were from Emotiva, and I'm pleased with them. Sincerely /b Did you check the wiring on the Monoprice cables? They are not built correctly, they connect the shell to the ground pin which they even said is not proper. I just cut that connection on mine instead of try to return them. can you provide a link to where this is actually stated by monoprice? |
|
??
Otherwise its the lowest common denominator methinks..
