| CARTRulz |
Hi guys,
I've got another silly question. As I was about to order the EP2500 I saw this:
http://www.partsexpress.com/pe/show...tnumber=248-722
So, do you guys have any opinions on using pro audio amps and equalizers in the home? All of these things use XLR inputs, so I'm assuming I have to buy XLR to RCA adapters, correct? Are there any problems with this setup?
Thanks. |
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| jleaman |
| quote: | Originally posted by CARTRulz
Hi guys,
I've got another silly question. As I was about to order the EP2500 I saw this:
http://www.partsexpress.com/pe/show...tnumber=248-722
So, do you guys have any opinions on using pro audio amps and equalizers in the home? All of these things use XLR inputs, so I'm assuming I have to buy XLR to RCA adapters, correct? Are there any problems with this setup?
Thanks. |
I run all balanced stuff at home. If you look at lots of the amps that are currently being built on this forum, some have balanced inputs and some are singled ended. ( ie Rca ) You don't have to buy any thing special you can build your own adapters if some of your existing audio gear is RCA. My aleph amps ( pass labs designs ) are all balanced.. |
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| jleaman |
No, you can build this your self with a few wires a few rca connectors and some xlr connectors. If you need help / schematic i can draw one up for you. |
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| CARTRulz |
| Yeah some help on building them would be great. Currently, all my stuff is RCA as its all home audio. Im adding the EP2500 to power 2 Snell SUB1800's that I just built, and I'm looking at something like that Behringer EQ as my old 6 band equalizer just crapped out. |
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| jleaman |
| quote: | Originally posted by CARTRulz
Yeah some help on building them would be great. Currently, all my stuff is RCA as its all home audio. Im adding the EP2500 to power 2 Snell SUB1800's that I just built, and I'm looking at something like that Behringer EQ as my old 6 band equalizer just crapped out. |
Yup i can help no problem there. All you ned is the opposite xlr connector that is on the back of the eq that you buy. |
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| CARTRulz |
Very cool, now Ive got one last question. Im looking at these EQ's, and theres a version of that behringer that has "limiters" which is $180 and then theres one without "limitors" for $130. What the hell are limitors? Is it worth the extra 50 bucks? Also, is there any audio quality loss when converting from XLR to RCA? Does it make more sense to just buy a 6 band graphic equalizer for home audio for about the same price?
Thanks again. |
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| jleaman |
Exactly.. But it's cheaper to buy them from partsexpress and make them your self :) |
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| CARTRulz |
What about the 1/4 inch inputs? Ive seen balanced 6 foot RCA to 1/4" adapters liike these:
http://www.amazon.com/gp/product/B0...5Fencoding=UTF8
Is there any difference in audio quality between XLR and 1/4 inch? I just don't want to lose any signal in these adapters. |
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| BlackCatSound |
The XLR and the jack are wired in parallel, there is no difference between them.
You will loose signal level going from unballanced to ballanced like that but you won't loose quality. |
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| Nigel Goodwin |
| quote: | Originally posted by CARTRulz
Very cool, now Ive got one last question. Im looking at these EQ's, and theres a version of that behringer that has "limiters" which is $180 and then theres one without "limitors" for $130. What the hell are limitors? Is it worth the extra 50 bucks? Also, is there any audio quality loss when converting from XLR to RCA? Does it make more sense to just buy a 6 band graphic equalizer for home audio for about the same price?
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The reason for the limiter is so as not to overload the power amplifiers - it's not a concern for domestic use, but for PA use it's very much a concern - as you have a much wider dynamic range.
A six band graphic is pretty poor?, presumably the Behringer one is much larger?.
No problems XLR to RCA, it's all just audio anyway!. |
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| CARTRulz |
| Yeah the Behringer is a 31 band. |
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| Nigel Goodwin |
| quote: | Originally posted by CARTRulz
Yeah the Behringer is a 31 band. |
Doesn't look much of a decision then?. |
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| JohnL |
If you are getting humming, first make sure you don't have a ground loop problem. Run down to a local hardware store and pick up one of these.
Ground Isolator
There may be balanced/unbalanced problems, but when you get a hum, this is the easiest place to start. |
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| CARTRulz |
Well Ive never had any problems with humming before, and when I play with the xlr to rca adapters the noise changes, so I'm pretty sure its that. Plus every single component in my system is 3 pronged and plugged into a surge supressor.
I hate these little problems. |
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| Nigel Goodwin |
| quote: | Originally posted by CARTRulz
Plus every single component in my system is 3 pronged and plugged into a surge supressor.
I hate these little problems. |
That probably why, you may have an earth loop - you should only have a single earth on all the connected equipment. Obviously it's NOT recommended to disconnect the power earths, so you can interconnect with a screened lead with the screen only connected at ONE end. |
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| paulspencer |
I have Behringer EP2500 and Ultracurve DEQ2496 for home use. I recommend both.
I would not run balanced unless you need to since there is a circuit involved and more components added in the signal path.
If you have worked out where all your audio components will go, then I would make DIY cables and make them to the correct length with an XLR on one end, RCA on the other, or as required. It's simple, cost effective and neat.
6 band graphic eq is pretty useless.
Ultracurve is very powerful. Put a mic in the listening position and it will auto EQ the whole thing flat! It will remove peaks from room modes, fix up anything that the crossovers didn't quite get right and balance room effects so the tonal balance is much more neutral and natural.
It has dynamic eq which can tailor the response at different SPL levels to match the changing sensitivity of the ear. It can boost bass at low levels then remove the boost as you turn it up. It can reduce treble to make it sound more laid back when you crank it up.
Limiters can be useful at home. I use it to protect my main amp which is a bit lacking in power. It tames the peaks and reduces concern when I push things.
Forget those graphic eq units, I would go ultracurve, it is very powerful. It can do quite a bit more than I've mentioned here.
The EP2500 amp is a great buy. I would not consider another amp for subs. Excellent value. |
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| CARTRulz |
Ok so I'm about ready to give up.
I just purchased 3 of the RCA to 1/4 inch cables becasue i heard they would solve my problems. Not only is the audio quality much lower, but the humming is even worse. So theres another 50 bucks wasted. If this is the case, how does anybody use pro audion stuff in the home? I've tried both xlr to rca and 1/4 inch to rca and nothing has worked.
Somebody help me please! |
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| paulspencer |
| You should not need to use balanced cables for home use since the runs would be short. Using those adaptors won't fix hum issues. You will have to do some trouble shooting, make lots of changes until you isolate where it is coming from. Don't give up just yet. |
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| BlackCatSound |
| quote: | Originally posted by paulspencer
I would not run balanced unless you need to since there is a circuit involved and more components added in the signal path.
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The signal passes through the same electronics no matter if its ballanced or not. You don't bypass anything by feeding an unballanced signal into a ballanced input.
Running ballanced DOES help with ground loop induced noise as you can earth lift one of the ends. Its why pro audio is all ballanced as you can never rely on the earth in a venue being any good. |
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| CARTRulz |
| Well its definetly coming from the cables as the noise changes when i slide the 1/4 inch jacks in and out of their outlets. I cant imagine how its a grounding issue because before I introduced the pro audio components i had just standars RCA's everywhere and I never had a problem. Then i added the ep2500 and the ultragraph pro and everything went to hell. |
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| BlackCatSound |
| Use ballanced between the ultragraph and the amp and flick the earth lift switch on the amp. |
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| CARTRulz |
Ok let me explain the setup. Ive got 2 technics amps that are pushing 4 floor standing technics speakers (one pair per amp), and i then have the signal split to a paradigm crossover to the ep2500 to power the subs. So basically, I have 6 connection points (equalizer ins and outs, and the 2 ins for the ep2500) that need to be adapted from either rca to xlr, or rca to 1/4 inch. Also, the ultragraph equalizer is the main eq for the 2 technics amps. So basically, the humming is not only for the 2 subs, but its for the entire system through all floorstanding speakers as well. So there isnt a chance to run balanced between eq and sub because there isnt a connection. ALSO, i just checked the amp and there isnt an earth lift switch, and even so then im still stuck with the problem of the EQ humming.
Thanks so much guys! |
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| Nigel Goodwin |
It's ESSENTIAL! to only have ONE earth connection for the entire system, this isn't just for pro gear, it's for domestic gear as well. If you have more than one earth, then current passing through the ground connections induces hum into the audio - it's a well known effect.
Pro-gear often overcomes it by using 'ground lift' switches, which disconnect the ground on the input socket, effectively disconnecting the screen at one end. Domestic gear is often made as 'class II' with no earth connection at all. |
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| paulspencer |
| quote: | Originally posted by BlackCatSound
The signal passes through the same electronics no matter if its ballanced or not. You don't bypass anything by feeding an unballanced signal into a ballanced input.
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As I understand, balanced outputs mean that additional circuits are added in the signal path to the balanced output jacks. If the unbalanced outputs are used from a unit, then surely these circuits would be bypassed and not in the signal path.
I don't have any special knowledge on this, however, it seems logical that it would be done this way. If you can back up that statement, then please do fill me in. |
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| CARTRulz |
| Ok last question for you guys. I cant seem to find an earth or ground lift switch on either the ep2500 or the ultragraph pro. Does this mean i need to drop another 50 bucks on one of these "clean boxes" or DI boxes to be able to use an earth lift switch? |
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| Nigel Goodwin |
| No, simply remove the screen connection from one end of the interconnecting cables (which is basically what a 'ground lift' switch does). |
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| CARTRulz |
| thanks a bunch Nigel, your certainly very knowledgable and extremely helpful. Now, I know this will seem very silly to you, but Im new to this stuff, and I don't exactly know how remove the screen connection from a cable. |
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| BlackCatSound |
| quote: | Originally posted by paulspencer
As I understand, balanced outputs mean that additional circuits are added in the signal path to the balanced output jacks. If the unbalanced outputs are used from a unit, then surely these circuits would be bypassed and not in the signal path. |
Its the same circuit that feeds both. Its just the ballanced connector has the normal signal plus an inverted version of it.
A DI box is used to feed a line level signal into a microphone input on a mixing desk, not what you need.
You need a ballanced cable between the ultragraph and the amp but do not connect the earth, just connect hot and cold.
Also on the feed to the ultragraph wire the centre pin of the RCA to hot on the ballanced jack/XLR and the shield of the RCA to cold on the jack/XLR. |
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| Nigel Goodwin |
If you're using XLR leads, then there will be three wires inside the plugs, two are normal insulated wires, the third is the screen (or shield) and has no insulation on it. It's this uninsulated wire which should be disconnected.
If you're using 1/4 inch mono jack plugs (there's no reason for you to be using XLR's), there's only two wires, an insulated one to the tip, and the screen to the sleeve - again, disconnect the screen. |
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| BlackCatSound |
Disconnecting the earth on a mono jack won't do the same job.
You can only do that with XLRs or TRS (stereo) jacks. |
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| CARTRulz |
| Thanks for all the help guys, I really appreciate it. |
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| Nigel Goodwin |
| quote: | Originally posted by BlackCatSound
Disconnecting the earth on a mono jack won't do the same job.
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Of course it will, what makes you think it won't?. |
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| rdf |
Hi CARTRulz, these days most everyone in the West wires balanced XLR connectors:
Pin 1 - ground, either circuit, chassis or switchable
Pin 2 - signal positive
Pin 3 - signal negative (not ground!, signal negative has audio on it out-of-phase with Pin 2)
Interfacing from balanced to unbalanced gets complicated because there are so many variables on the balanced side. Unbalanced is easy, centre pin carries the signal, outer 'pin' is system reference or ground. The balanced side has three common types - transformer-coupled passive balancing, instrumentation-type active balancing, and 'generic' active balancing. The first two are true isolated balancing in that impedance between either balanced leg and circuit ground is extremely high, on the order of mega ohms. An instrumentation amp is an active circuit designed to emulate a transformer. For both these types using only Pin 1 (ground) and one of either signal pins won't work. To visualize why, consider connecting an unbalanced source to a transformer input using only pins 1 and 2. Pin 3, the other end of the transformer primary, isn't connected to anything so no current flows (in reality almost no current, physical imperfections like winding capacitance allows a little signal through.) Generic active is sometimes called 'pseudo balancing', both inputs are referenced to ground. It's the equivalent of two unbalanced inputs/outputs, each independent of the other handling a different phase. These factors limit how ground is handled.
Examining unbalanced output to balanced input connections first:
Transformer coupled in - RCA centre pin to XLR pin 2, RCA ground to XLR pin 3, optionally (and likely) connect XLR pin 3 to XLR pin 1 to reduce hum
Instrumentation amp in - Generally same as above
Generic Active in - RCA centre pin to XLR pin 2, RCA ground to XLR pin 1, optionally tie XLR pin 1 to XLR pin 3 to reduce noise
Now the output side, balanced to RCA unbalanced:
Transformer coupled output - XLR pin 2 to RCA centre pin, XLR pin 3 to RCA ground, optionally connect XLR pin 3 to XLR pin 1 to reduce hum, often not required
Instrumentation amp output - Generally same as above
Generic Active output - XLR pin 2 to RCA centre pin, RCA ground to XLR pin 1, do not tie XLR pin 1 to XLR pin 3. Doing so shorts one leg of the output to ground.
The first two output connections preserve the full output voltage swing, the latter loses 6 dB since only one leg is available for use. In reality there is no true 'balanced' connection to unbalanced equipment, you're really just messing around with grounds. My suggestion for unbalanced out to balanced in is: RCA centre pin to XLR pin 2, RCA ground to XLR Pin 1, tie XLR Pin 1 to XLR Pin 3. For balanced output to unbalanced input: XLR Pin 2 to RCA centre pin, XLR pin 1 to RCA ground. Only tie XLR pin 3 to XLR pin 1 only if the output completely lacks bass if left unconnected. And by that I really mean sounds like a telephone, or is very low in level. |
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| CARTRulz |
Ok now heres where I'm very confused. I purchased these the other day"
http://www.amazon.com/gp/product/B0...5Fencoding=UTF8
However, I'm still getting hum. Is that becasue its going from ballanced to unballanced? So basically when I follow those directions I'll be making a cable thats staying unballanced to unballanced, which will eliminate humming, correct? |
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| BlackCatSound |
| quote: | Originally posted by Nigel Goodwin
Of course it will, what makes you think it won't?. |
Because a mono jack in a ballanced jack socket shorts cold and earth together, no matter what the wiring. |
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| CARTRulz |
| Ok so heres what I got now. I bought 6 RCA to XLR cables. On the RCA side there is one insulated wire from the pin and one straight piece of metal that goes from the ring and has a wire soldered to that, which then comes in contact with the metal sleve that screws into the head. On the XLR side there are 3 wires. One insulated thats in pin 3, and 2 uninsulated that go to pins 1 and 2. However, this seems to go against what Nigel said, as the insulated wire on the XLR side goes to the pin on the RCA side, which carries the signal, correct? Im so lost, someone please send help! |
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| burnedfingers |
Very simple....
With XLR connectors short 3 to 1 in other words the inverted signal known as cold to the shield or ground. This will unbalance a balanced connection.
If dealing with a terminal strip make a short jumper to go from ground/shield to the minus or cold.
I suggest that attention be paid to proper grounding. As stated prior...there needs to be only ONE ground for the system otherwise the nasty gtound loop monster comes out to play.
There a a number of us with pro audio experience under our belts and I can say that we have all dealt with the noise issues have provided the solution based on experience and textbook knowledge. |
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| CARTRulz |
| Ok so I just did exactly what you guys told me and now the problem is even worse. I think I'm giving up, I'll just return the stuff and stick to home audio with all RCA's. |
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| burnedfingers |
Send a picture or two of what you have done so we are clear on it
I'm sure we can resolve the problem. |
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| jleaman |
| Hey never give up. We are all here to help. Im running the same type of cable with aleph mini's into a passive pot and well no hum. I tried it with the op-amp Bufer too. I agree with the picture. Can you post any pics ? |
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| BlackCatSound |
| CARTRulz, disconnect the wire from pin 1 on the XLR end. |
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| burnedfingers |
| Picture of terminal strip unbalance |
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| burnedfingers |
| Home made unbalance cables |
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| burnedfingers |
| One could also use standard XLR cables and leave the 1-3 jumpers on the terminal strip for unbalanced. |
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| burnedfingers |
| quote: | | CARTRulz, disconnect the wire from pin 1 on the XLR end. |
I believe that BlackCatSound is pointing out that it is sometimes necessary to float the shield on one end of the equipment to eliminate the hum.
This practice will and does vary from consultant to consultant. Some favor lifting the shield on the input and some on the output. |
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| BlackCatSound |
| As he is going from RCA to XLR the only option is to earth lift the XLR end. |
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| burnedfingers |
I'm not clear and need a picture of what he has done.
This isn't all that difficult. :( :( |
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| Nigel Goodwin |
| quote: | Originally posted by burnedfingers
This practice will and does vary from consultant to consultant. Some favor lifting the shield on the input and some on the output. |
Makes no difference which end really, as long as you break the earth loop.
But it's very hard to diagnose and give a complete answer on a forum, I'm sure most of us here could cure it in a couple of minutes if we were there?. |
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| burnedfingers |
| quote: | | But it's very hard to diagnose and give a complete answer on a forum, I'm sure most of us here could cure it in a couple of minutes if we were there?. |
We have done it so many times that we don't give it a second thought anymore. |
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| CARTRulz |
well the part that I dont understand is that these cables are low noise RCA to XLR cables, so haven't they already done what I would have to do anyway? Like I said before, On the RCA side there is one shielded wire that connects to the pin, and then another 2 that connect to the sleve, and then on the XLR side the shielded wire goes into pin 3 and the other 2 wires go into 1 and 2 respectively. So I left the shielded one alone becasue thats the signal wire, and since the other 2 were soldered to the sleve on the RCA side, I tied those together and soldered them to pin 1 on the XLR side, and ran a jumper wire between 1 and 2. I thought this was how its done, however I guess not becasue the hum is even worse. Is there a different procedure for using male and female XLR's? Becasue since its a equalizer its got 2 male inputs from the amp and then 2 female outputs back to the amp. So I guess its going from RCA to XLR with the males and from XLR to RCA for the females.
Thanks again for having the patience to work with me guys, you don't know how much I appreciate it. |
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| BlackCatSound |
Centre pin of the RCA to XLR pin 3.
Shield of the RCA to XLR pin 2.
Nothing to XLR pin 1.
Give it a go. |
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| CARTRulz |
| Here are 2 EXTREMELY low quality pictures, if you can discern anything from them I'll be surprised, but heres the deal. On the RCa side, the signal wire is the shielded one, and then theres that piece of flat metal which has 2 wires soldered to it at the bottom. Then on the XLR side theres the same signal wire, and the other 2 thinner wires go to pins 1 and 2. Isnt this procedure essentially the same exact thing as running the signal wire from one pin to another, and then running the shield to another pin and then having a jumper between them? Either way the signal wire takes one pin and the shield take the other 2, they just made it look nicer. |
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| burnedfingers |
| Maybe this will help |
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| burnedfingers |
This was scanned from a typical amplifier manual. In this case its an Altec Lansing model 9442. Its a commercial piece. Don't pay any attention to the voltage wiring chart at the top.
Figure #2
This is standard wiring practice for unbalanced and balanced in's and outs.
It clearly shows an unbalanced source going to the 9442 input and how to wire it. |
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