All very good advice. -----Original Message----- From: ddots-l-bounce@xxxxxxxxxxxxx [mailto:ddots-l-bounce@xxxxxxxxxxxxx] On Behalf Of Dave Carlson Sent: Saturday, May 22, 2010 1:41 PM To: ddots-l@xxxxxxxxxxxxx Subject: [ddots-l] Re: Ground Lift Annabel, Red the following that I got from somewhere. It may help. Dave quote--The War on Hum How to Maintain a Hum Free Audio System By Tweak The "war on hum" is a major battle every home studio has to wage. I have been battling it since I started recording, sometimes winning, sometimes losing. Currently, I am winning the war. The more gear you have, the more likely you are to encounter hum. Like it or not, it's a war you have to fight. Fortunately, observing a few principles can fix many situations. This is deliberately a non technical article. You probably don't want a lecture on the nature of ground loops and electrical systems. So I won't get too deep into it, but I will link you to some excellent sources of material at the end. Basically, the hum you hear is typically a bass tone at 60Hz (or 50Hz, if you are across the pond), along with its harmonics at higher frequencies, which may sound like a buzz. Because this hum and buzz creates noise throughout the audio spectrum, its almost impossible to filter it out without totally wrecking the audio signal. Causes can be many: ground loops, often caused by different electrical pathways to the house ground, TV cable lines, bad or shorted audio cables, old equipment with damaged power supplies, equipment with poor or broken internal grounds, and cables that travel near magnetic fields. There are plenty of other sources of noise too--electric motors, radio stations, even your neighbor using power tools. In some cases, the electricity supplied by the power company may be erratic. 1. Make sure your audio gear and all devices that connect to audio gear are on the same house circuit , observing the specified limits of the circuit. That is your audio interface, monitors, mixer, and gear connected to the mixer. Trouble shoot your house circuit breaker so you know which switches go to which outlets in your house and most importantly, your studio. You want all the gear to use the same path to ground. Before you touch your home's electrical equipment, Beware! Messing with electricity can be dangerous, even fatal. If you don't know what you are doing, don't do it. While this is not a magic formula to cure all ground loops, it can get rid of many preventable ones. 2. Use balanced gear with balanced TRS and XLR cables . If you have to use unbalanced gear, keep the cables short, under 10 feet if possible. Long RCA and TS (two wire) cables are highly susceptible to picking up hum. For those of you using mixers , this is really important. One poorly grounded device or poorly situated unbalanced cable can infect the whole mixer with hum. Those with a lot of vintage synths (which are nearly always unbalanced) will certainly run into this problem. I've had real good luck with Behringer direct boxes plugged into and powered by the board's mic preamps. You can input TS line level and output a hefty XLR balanced signal. Touch it up with the gain and you have a clean sounding vintage synth. You can't just use TRS cables and expect your unbalanced gear to be balanced. It does not work that way. You can use a line level shifter to do the job though. 3. Keep audio cables away from wall warts , those power supply adapters that so many pieces of studio gear use. A cable resting on a wall-wart on the floor can pick up hum. Also don't let the AC cables run parallel to audio cables. If they cross, do it at 90 degree angles. This happens because of magnetic fields that form around the the power cables and adapter. Electrons don't always stay inside the cable jacket. Don't look now, but are they jumping all over the place in that mess under your desk? Back in my 8 bus mixer days, whenever the hum started to rear its ugly head I would go under the desk and fix the cable paths. Result: Less Hum. It can help significantly. If you do all the above and you still have hum, it could be that a particular unit is causing the problem. This happens a lot with old gear , whose power supplies may be weakened from years of use. Troubleshoot by disconnecting everything and plugging in items one by one until the culprit reveals itself. Note that for some gear, ground loops can persist even when equipment is not turned on. This is important to know when troubleshooting. You may have to disconnect the power cable from the wall as well as removing audio cables to ensure that a piece is not causing trouble. That piece may need separate treatment if you need to continue using it. I've had good luck with the Ebtech hum eliminator and with direct boxes that have ground lifts. Hard Questions and Answers Q) When I pan my synth to the left, its clean. When I pan to the right I get HUM. What is wrong with my mixer? A) Nearly always that is a cable problem. Swap them to see if the problem is reversed. If it is that confirms it is the cable or the gear connected to the mixer, not the mixer. You then might try connecting the gear with different cables. If the problem continues, it is likely that the problem is in the gear itself. Q) Here's a really strange problem. When I raise the fader on my mixer, hum disappears! When I lower it, it comes back. WT heck is going on? A) That's a tough one. You have to go into advanced troubleshooting mode. It's quite possible that the problem is on a different channel than the one you are boosting. Start disconnecting audio cables on other channels. When the problem stops, you have found the villain. Now peek under the desk to see if any cables are touching wall warts. Also check for an impedance mismatch where a +4 output is going into a -10 input. Q) I hear "digital hash" in my audio. It's not hum, but almost sounds like shortwave radio interference. A) Here's a cool experiment to make you more aware of magnetic fields. Connect a TS cable to the input of your mixer or audio interface. Turn up the volume. Don't plug in the other end, but use it as a sensor and point it towards each piece of gear. As you get closer to the gear, within 1 inch, you will hear the digital clock signals bleed into your audio, especially when you get near the LCD. That's digital clock noise. Now look for a cable that strayed too close to one of these electronic fields. Many times, if the gear is balanced, using balanced cables will knock this right out. Q) I put a hum eliminator on the outputs of my mixer but the hum is unchanged! I thought these items always worked! A) They do work if you know their limitations. First you have to find the device causing the ground loop and put the hum eliminator on that device. You can't use it "downstream" as hum has already become part of the audio signal earlier in the chain. You must apply the hum eliminator to the source of the problem, before the ground loop becomes a hum problem. Q) When I connect the audio outs from my TV cable box to my audio interface it hums so bad I can barely hear the program. A) Common problem. The TV cable itself may use a different ground path than your studio equipment, especially if you have a lot of TVs in the house. For me, a Hum Eliminator completely fixes the problem. Q) What types of rigs are best for avoiding issues with hum? A) Avoid cheap unbalanced mixers. Those with large mixers and a lot of gear know that ground loop hygiene is crucial to keeping the board hum free. Those folks have to be especially vigilant to win the war. Going mixerless can help. Plugging direct into an audio interface gets rid of a lot of cables, and as we have seen, cables can cause problems. Don't plug in gear that you know is problematic. Instead, connect it only when you want to record it, and run through helper devices like noise gates and the ones mentioned earlier in the article. Audio interfaces like the Tascam FW1884 and Project Mix can help because they incorporate what would be several separate pieces into one box with one ground. I'd also avoid using cheap laptops for audio. We have had several problems documented at studio-central where ground loops could not be corrected. Likewise, adapting an audio chain to an unbalanced 1/8" stereo line input is just begging for trouble. Q) Does one ever actually win the war? Can you truly ever totally eliminate ground loop hum in a home studio? A) Technically, the answer is a matter of degree. The ground differential potential that creates ground loops is always present, but you can succeed in getting rid of its artifact, the hum. The enemy is still there, waiting for you to let your guard down. The way homes send current to ground will always have the potential for ground loops, but with good gear and following a few simple practices, you won't hear it. When you turn up your monitors all the way (without playing anything but with all your gear connected) and all you hear is sweet white hiss, you know you are, for now, winning the war. You can leave feedback and discuss this topic here: http://studio-central.com/phpbb/viewtopic.php?p=286223#286223 Links Ground loop problems and how to get rid of them Ground Loops, or 'Let Me Hum A Few Bars' [SMR] Ground loop (electricity) - Wikipedia, the free encyclopedia Everything you were Afraid to Ask about Cables Threads FAQ- Difference Between Balanced and Unbalanced How to- Unbalanced => balanced wiring Laptop Hummmmmmmmmm Grounding & RFI Question Why does my Guitar amp hum Review of the EbTech Hum ... Hum Eliminator, Unbal to Balanced Converter Go to the Next Class home_studio_construction.htm unquote. improve the sound of your studio Studio Gear at zZounds Ebtech HE8 8-Channel Hum Eliminator Rack a--3745/item--EBTHE8/sid--feed3 Do you hear hum or buzz in your audio signal? Are long, unbalanced lines across stage creating problems? Get the Hum Eliminator! Just plug the Hum Eliminator into the signal lines between offending pieces of equipment and you're done. Quick and easy! Priced from 219.95 Ebtech HE2PKG Hum Eliminator (2-Channel) a--3745/item--EBTHE2PKG/sid--feed3 Silence AC hum forever! Almost all AC hum (60Hz in the U.S.) is caused by groundloops. Rather than filtering, the Hum Eliminator prevents groundloops from forming in the first place. Just plug the Hum Eliminator into the signal lines between offending pieces of equipment and you're done. Quick and easy. Priced from 59.95 Ebtech HUMX Voltage Hum Filter a--3745/item--EBTHUMX/sid--feed3 The Hum X filters out unwanted voltage and current in the ground line that cause ground loop hum while simultaneously maintaining a solid, safe ground. Priced from 59.95 Ebtech LLS2 Line Level Shifter (2 channel) a--3745/item--EBTLLS2PKG/sid--feed3 The Line Level Shifter uses the physics of inductance and impedance matching to increase or decrease the signal voltage without the added noise of active electronics. The Line Level Shifter also converts back and forth between balanced and unbalanced signals automatically. It also contains Hum Eliminator technology to prevent groundloops that cause AC hum. Priced from 69.95 Ebtech HEXLR XLR Hum Eliminator (2-channel) a--3745/item--EBTHEXLR/sid--feed3 The Ebtech HEXLR Hum Eliminator is designed to eliminate 60 cycle hum (60Hz AC signal) caused by Ground Loops. It is also designed to convert unbalanced lines to a true balanced lines (and vice versa). Why? Unbalanced lines are more susceptible to picking up electrical noise and RF interference. Priced from 79.95 Ebtech LLSXLR Line Level Shifter (2-Channel) a--3745/item--EBTLLSXLR/sid--feed3 The Ebtech Line Level Shifter is designed to increase or decrease signal voltage (-10dBV and +4dBu) without adding noise. The Line Level Shifter also converts back and forth between balanced (+4dBu) and unbalanced (-10dBV) signals automatically. The Line Level Shifter also contains Ebtechs' Hum Eliminator technology to break ground loops that cause AC hum. Priced from 89.95 Ebtech Swizz Army 6 in 1 Cable Tester a--3745/item--EBTSWIZZCT/sid--feed3 Checks XLR, 1/4 in., RCA, 1/8 in., TT, and MIDI cables for continuity and/or intermittent connections. Also detects opens and shorts for each pin. Other features include test tone generator (+4, -10, Mic), phantom power detector, grounded XLR shield detector and cable wiring display. Priced from 89.95 Gear Finder a--3745 Furman AR15 Series II 15-Amp Voltage Regulator a--3745/item--FURAR15II/sid--hum The 15 amp AR-15 II delivers a stable 120 volts of AC power to protect equipment from problems caused by AC line voltage irregularities such as sags, brownouts, or overvoltages -- all of which can cause sensitive electronic equipment to malfunction or sustain damage. AR-15 II accepts any input voltage from 97V to 137V and transforms it to a constant 120V, +/-5V. Voltages beyond that range may also be converted to usable levels, depending on the range variance. Monster Cable Pro 5100 Power Conditioner Behringer DI4000 Ultra DI Pro 4-Channel Direct Box a--3745/item--BEHDI4000/sid--hum MXR M135 Smart Gate Pedal a--3745/item--MXRM135/sid--hum If you're addicted to the indispensable juice of a high gain amp or a string of stomp boxes, you need this pedal. Because along with your hot-wired tones, you're probably getting a generous helping of noise. Equipped with 3 selectable types of noise reduction, Hiss, Mid, and Full, the Smart Gate bites down on sizzle and hum but lets the smallest detail of your playing through. Mogami Gold Studio Microphone Cable a--3745/item--MOGGSTU/sid--hum Virtually every major recording facility in the world is wired with Mogami cable. This means that just about any music you choose has been recorded using Mogami in the audio chain. This cable is famous for unmatched accuracy, extremely low noise and remarkable flexibility. Top engineers rave about its amazing clarity and silent background. If accuracy in reproduction is your goal, this is the cable for you. CBI BLUA Ultimate Series 1/4 in. TRS-TRS Cable a--3745/item--CBIBLUA/sid--hum Belden/CBI MLU "Ultimate" 20-gauge cable with braided shield. Neutrik Nickel 1/4 in. connectors; TRS - TRS male. Neutrik NYSSPPL 48-Point TRS Balanced Patchbay a--3745/item--NTKNYSSPPL/sid--hum New, economic, and versatile describes the 1/4 in. modular Patch Panel. 48 balanced channels in one rack space and just 1U high. CBI 8-Channel TRS to TRS Snake a--3745/item--CBIMT8/sid--hum CBI cables give you quality connections without hissing or cut-outs. Without the high price of other big named cable brands, CBI cables will provide you with clean, crisp sound. And with a variety of colors and connections, you can pick up the perfect cable for your individual needs and looks. Ebtech HUMX Voltage Hum Filter a--3745/item--EBTHUMX/sid--hum Behringer HD400 2-Channel Hum Destroyer a--3745/item--BEHHD400/sid--hum Ebtech HE2PKG Hum Eliminator (2-Channel) ----- Original Message ----- From: Annabelle Susan Morison <mailto:foristnights@xxxxxxxxxxx> To: ddots-l@xxxxxxxxxxxxx Cc: 'NFBnet Music Talk Mailing List' <mailto:musictlk@xxxxxxxxxx> Sent: Saturday, May 22, 2010 09:17 Subject: [ddots-l] Ground Lift Hi, it's Annabelle. I tried flipping the switch for the ground lift on my EQ Machine, but it didn't work. The 60 Cycle hum is still there. What do I do next? PLEASE READ THIS FOOTER AT LEAST ONCE! To leave the list, click on the immediately following link: ddots-l-request@xxxxxxxxxxxxx?subject=unsubscribe If this link doesn't work then send a message to: ddots-l-request@xxxxxxxxxxxxx and in the Subject line type unsubscribe For other list commands such as vacation mode, click on the immediately following link: ddots-l-request@xxxxxxxxxxxxx?subjectúq or send a message, to ddots-l-request@xxxxxxxxxxxxx and in the Subject line type faq