View Full Version : balanced phono to pre amp problem
hihave an astintrew phono stage and a musical fidelity a1fbp preamp,when in single ended mode all is well,but when i go to balanced mode it hums bad after a few notches,the balanced mode useing a cambridge audio dac magic is fine,could the pins in phonostage be wired different,tryed earths,moving it far etc,any thoughts would be most welcome,probley another bill,yours charlie
Think that may be the problem Charlie. there are differing configs to how these are wired, often by country I believe.
Think that may be the problem Charlie. there are differing configs to how these are wired, often by country I believe.
hi,there is no diagrams to show how there wired,need to get test meter out, thanks
What arm are you using Charlie? The 'earthing' arrangements used might be the cause of your hum problem.
What arm are you using Charlie? The 'earthing' arrangements used might be the cause of your hum problem. hi, its a origin live conqurer,
hi,there is no diagrams to show how there wired,need to get test meter out, thanks
Barry is your man for balanced stuff...and Neil...good luck
Charlie, can you check to see if the tonearm earth wire is not connected to the screen of either signal lead.
Audio Advent
04-08-2015, 17:01
If the hum is only apparent when using the XLR, balanced outputs of the phone stage (it's still a single-ended input, although I know some phono stages use pseudo-balanced/floating input) then wouldn't the wiring of the arm have been equally apparent with the single-ended outputs?
I'd perhaps be thinking about the earthing of the XLR cables and perhaps the shield needs lifting at one end of the cable?
In the pro world with balanced connections, you often get earth-lift switches on the back of equipment to do this very thing when earth loop hum occurs.
But then why is the DAC in balanced mode hum free?
How is the arm earth lead connected? Is it connected to the metalwork of the phonostage, or directly to the earth terminal of the preamp? If the latter how is the metalwork of the phonstage earthed?
Answer is possibly about halfway down the page-paragraph starting "Recall I had mentioned....."
http://www.originlive.com/tonearm-reviews-overview-origin-live/tonearm-review-illustrious/tonearm-reviews-positive-feedback.html
Answer is possibly about halfway down the page-paragraph starting "Recall I had mentioned....."
http://www.originlive.com/tonearm-reviews-overview-origin-live/tonearm-review-illustrious/tonearm-reviews-positive-feedback.html
The link doesn't work.
Think this is the appropriate paragraph
Recall I had mentioned that Origin Live utilized a unique lead-out cable. They allude to its superiority on their site, but give no details. It turns out that, while 99% of the phono cables out there use twisted pairs, spirals, or braids, OL uses co-ax—that is, the outer screen carries one leg of the circuit. Baker made that choice, like every other aspect of his design, for purely sonic reasons. With a single-ended (RCA) input phono stage, the screen helps lower the noise floor by taking RFI to ground. With the balanced input Aqvox, the screen became an antenna. Ooops. There was an easy fix—I wrapped the cables with foil, and connected that to the Aqvox ground post, and Rush retreated to his rat-hole. Ugly, but the sound was now excellent—the cable is indeed quite fine—but Baker asked that I return the tonearm so he could be sure nothing internal was amiss.
worked for me Barry
Nope, I've tried four times. Can you 'copy and paste' the relevant part for me please Grant?
Thanks
Barry
Nope, I've tried four times. Can you 'copy and paste' the relevant part for me please Grant?
Thanks
Barry
i did;)
i did;)
Thanks.
What I need to know now is the input connectors used on the phonostage. If RCA phono, used in a 'balanced' configuration, i.e. the outer is insulated from the metalwork of the case, then that might explain the problem.
next couple of paragraphs if of any help
What I heard was not just Rubinstein; Rush Limbaugh was carrying on about feminazis, li'bruls, and how well the war was going, despite what the drive-by media keeps putting on the 6 o'clock. Talk about RFI hell. It took a few emails back and forth across the Atlantic to figure out what was going on. It was mid-summer here in the desert, and to beat the heat I had replaced my Herron tube phono stage with the solid-state Aqvox II CI, largely on the recommendation of PFO colleague John Zurek (here is a link to his PFO review). While I can enthusiastically second everything he wrote about it, due to the unique circuit design and RCA to XLR adaptors, it is fussy about the phono cabling. On the Aqvox site there is a list of tonearms that have checked out fine with their system. Stock Regas are not suitable (no separate ground lead) but rewired ones are—my Incognito rewired RB250 had not had any problems at all. Just about every other tonearm imaginable makes the OK-list—except Origin Live.
Recall I had mentioned that Origin Live utilized a unique lead-out cable. They allude to its superiority on their site, but give no details. It turns out that, while 99% of the phono cables out there use twisted pairs, spirals, or braids, OL uses co-ax—that is, the outer screen carries one leg of the circuit. Baker made that choice, like every other aspect of his design, for purely sonic reasons. With a single-ended (RCA) input phono stage, the screen helps lower the noise floor by taking RFI to ground. With the balanced input Aqvox, the screen became an antenna. Ooops. There was an easy fix—I wrapped the cables with foil, and connected that to the Aqvox ground post, and Rush retreated to his rat-hole. Ugly, but the sound was now excellent—the cable is indeed quite fine—but Baker asked that I return the tonearm so he could be sure nothing internal was amiss.
Not long after that, another wooden box arrived from OL, another Illustrious with of all things, a standard 5 pin "DIN" socket in the arm pillar, and a DIN to XLR cable. These options were not on the OL web-site before I managed to get Mark at OL and Norman at Aqvox equally exasperated, but they are available now. So, if you want to put a Kimber or Hovland (I am blessed with both) or whatever cable on an Origin Live arm, you can do so. Conversely, if you have known or possible RFI problems and/or a single ended (RCA plugs) system, the stock OL co-ax will be just the ticket. One of the advantages of small-firm sourced products is flexibility in meeting customer needs. Assuming the substitute OL cable was a one-off accommodation and not a standard item, most of my listening with the Illustrious and Aqvox was done with the very fine Xaus Phono from Zu Cables, terminated by those kind folks exactly as recommended by Aqvox. Come the cooler months, I switched back to the single-ended, tube-based Herron Audio gear with the Kimber and Hovland cables. Brilliant!
next couple of paragraphs if of any help
What I heard was not just Rubinstein; Rush Limbaugh was carrying on about feminazis, li'bruls, and how well the war was going, despite what the drive-by media keeps putting on the 6 o'clock. Talk about RFI hell. It took a few emails back and forth across the Atlantic to figure out what was going on. It was mid-summer here in the desert, and to beat the heat I had replaced my Herron tube phono stage with the solid-state Aqvox II CI, largely on the recommendation of PFO colleague John Zurek (here is a link to his PFO review). While I can enthusiastically second everything he wrote about it, due to the unique circuit design and RCA to XLR adaptors, it is fussy about the phono cabling. On the Aqvox site there is a list of tonearms that have checked out fine with their system. Stock Regas are not suitable (no separate ground lead) but rewired ones are—my Incognito rewired RB250 had not had any problems at all. Just about every other tonearm imaginable makes the OK-list—except Origin Live.
Recall I had mentioned that Origin Live utilized a unique lead-out cable. They allude to its superiority on their site, but give no details. It turns out that, while 99% of the phono cables out there use twisted pairs, spirals, or braids, OL uses co-ax—that is, the outer screen carries one leg of the circuit. Baker made that choice, like every other aspect of his design, for purely sonic reasons. With a single-ended (RCA) input phono stage, the screen helps lower the noise floor by taking RFI to ground. With the balanced input Aqvox, the screen became an antenna. Ooops. There was an easy fix—I wrapped the cables with foil, and connected that to the Aqvox ground post, and Rush retreated to his rat-hole. Ugly, but the sound was now excellent—the cable is indeed quite fine—but Baker asked that I return the tonearm so he could be sure nothing internal was amiss.
Not long after that, another wooden box arrived from OL, another Illustrious with of all things, a standard 5 pin "DIN" socket in the arm pillar, and a DIN to XLR cable. These options were not on the OL web-site before I managed to get Mark at OL and Norman at Aqvox equally exasperated, but they are available now. So, if you want to put a Kimber or Hovland (I am blessed with both) or whatever cable on an Origin Live arm, you can do so. Conversely, if you have known or possible RFI problems and/or a single ended (RCA plugs) system, the stock OL co-ax will be just the ticket. One of the advantages of small-firm sourced products is flexibility in meeting customer needs. Assuming the substitute OL cable was a one-off accommodation and not a standard item, most of my listening with the Illustrious and Aqvox was done with the very fine Xaus Phono from Zu Cables, terminated by those kind folks exactly as recommended by Aqvox. Come the cooler months, I switched back to the single-ended, tube-based Herron Audio gear with the Kimber and Hovland cables. Brilliant!
Well that explains matters. :)
Dunno I only look at the pictures[emoji3]
Charlie, can you check to see if the tonearm earth wire is not connected to the screen of either signal lead.
hi tester not working,will do that tomorow,thanks
Thanks.
What I need to know now is the input connectors used on the phonostage. If RCA phono, used in a 'balanced' configuration, i.e. the outer is insulated from the metalwork of the case, then that might explain the problem.
hi its xlr inputs,and single ended inputs,what i have noticed is if i leave phono,s in place,it cuts the humming when useing balanced xlr
Looking at the photo showing the connectors:
http://www.astintrew.co.uk/images/at8000c.jpg,
it’s not immediately obvious whether the input is balanced or unbalanced. I suspect the input is unbalanced. So we are back to the original problem of why hum occurs when the balanced outputs are used with the preamp (using XLR terminated leads), whereas no hum is encountered when a balanced output DAC is used.
The next question to ask is how the metalwork of the phonostage case is earthed? If using the unbalanced RCAs, the case is earthed via one of the conductors of the interconnect that connects to the outer of the phono socket.
Charlie, can you check to see if pin 1 of the two XLRs connects to the case metalwork and also to the outer conductor of the RCA phono sockets?
Looking at the photo showing the connectors:
http://www.astintrew.co.uk/images/at8000c.jpg,
it’s not immediately obvious whether the input is balanced or unbalanced. I suspect the input is unbalanced. So we are back to the original problem of why hum occurs when the balanced outputs are used with the preamp (using XLR terminated leads), whereas no hum is encountered when a balanced output DAC is used.
The next question to ask is how the metalwork of the phonostage case is earthed? If using the unbalanced RCAs, the case is earthed via one of the conductors of the interconnect that connects to the outer of the phono socket.
Charlie, can you check to see if pin 1 of the two XLRs connects to the case metalwork and also to the outer conductor of the RCA phono sockets?
hi,there is reading between pin 1 and the negative phono,but nothing between pin1 and outer case,yours charlie
Audio Advent
05-08-2015, 22:12
If the hum is only apparent when using the XLR, balanced outputs of the phone stage (it's still a single-ended input, although I know some phono stages use pseudo-balanced/floating input) then wouldn't the wiring of the arm have been equally apparent with the single-ended outputs?
I'd perhaps be thinking about the earthing of the XLR cables and perhaps the shield needs lifting at one end of the cable?
In the pro world with balanced connections, you often get earth-lift switches on the back of equipment to do this very thing when earth loop hum occurs.
Hate to say it but I addressed whether we were talking about balanced phono stage INPUTs or not yesterday which is why I dismissed the idea of it being about the earthing of the tonearm - in both cases (of the outputs used on the phono stage) the arm wire earthing and connections stay the same. The Aqvox mentioned in those forum posts has the uncommon feature of balanced (or pseudo-balanced as there is no ground reference... think that makes it "pseudo balanced") input from the cartridge which is a different situation altogether.
Reading my post back I didn't do it very clearly, but it was this point/clarification I was trying to make (because I'd already looked up the phono stage and seen the connections, just didn't post up the photo).
Audio Advent
05-08-2015, 22:18
But then why is the DAC in balanced mode hum free?
Because not all equipment has its balanced outputs connected in the same way. Some connect the case ground to the XLR shield, some leave the shield floating. Then each piece of gear has different possibilities of ground loops. Then, can it also depend on how the balanced signal is attained? Not sure about that last point..
If the phono stage connects the tonearm earth to the case ground and then this ground to the XLR shield and then the pre-amp ALSO connects the shield to ITS case earth, it can cause a ground loop. This won't necessarily be the situation when the RCAs are used and actually unlikely because the phono stage won't re-connect the arm earth to the signal earth otherwise they'd be daft and ruin people's careful arm wiring considerations.
Audio Advent
05-08-2015, 22:29
I'd test the connection between the housing of the XLR plug at one end and the other at the other and see if they are connected. That will tell you if the shield is lifted at one end of the cable or not. Perhaps even test the connection between the earth connection on the phono stage and a screw or some other earth on the MF pre, when all is connected by XLRs. If the grounds/earths are connected it should be apparent too when all is switched off.
If there is no connection, then it's not an earth loop and I'll have to drop the idea! :lol:
I'd test the connection between the housing of the XLR plug at one end and the other at the other and see if they are connected. That will tell you if the shield is lifted at one end of the cable or not. Perhaps even test the connection between the earth connection on the phono stage and a screw or some other earth on the MF pre, when all is connected by XLRs. If the grounds/earths are connected it should be apparent too when all is switched off.
If there is no connection, then it's not an earth loop and I'll have to drop the idea! :lol:hi,do you mean the xlr should be conected to pre and phono amp when i do this
Audio Advent
05-08-2015, 23:00
You can see if the cable seperately has the shield connected at both ends or not testing the connection between the housings of both xlrs with the cable not connected at all. That might hint at the possibility of a ground loop.
Then connect it all with the balanced set-up. Test the connection between the case earth of the phono stage (the specific earth screw connection) and the pre-amp's earth, this could be the casing itself or a screw, but something unpainted, exposed metal if you can find some.
To complicate matters, it could be the pre-amp is what's called class 2 equipment where none of the case is earthed anyway.. So then instead of the pre-amp case earth just test to the xlr housing at the pre-amp end.
If you get a connection between the two then it's likely you're getting an earth loop. To solve this, you break the connection between the two earths by disconnecting the balanced cable's shield from one of the XLR connectors' housings.
I hope that makes sense? Pictures or a personal demo speaks thousands of words.
hi,tried the phono stage in balanced mode and the humming has gone,the only thing iv,e changed is the power amp,i had tried it 4or5 times over last 3 months and it always hummed,thanks to all who replied,your input was much apprieciated.
Audio Advent
06-08-2015, 00:41
Haha! Excellent! Always good to end up with a surprise solution.
Earth loops can cause hum in equipment seemingly unconnected to the point at which the loop is created. All about how the currents/voltages find their way around the expanded circiut/loops.
Can even be about which power sockets you plug into and how they are related to each other..
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