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#1
03-29-2015, 11:30 AM
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Mixer to Soloamp, feedback + confusion
Based on advice from Joseph Hannah here a few years ago (Thanks Joseph!), I have been operating with the following signal chain:
• Instrument(s) + Mic(s) > Behringer Xenyx 1204 USB mixer, Main Out (XLR) > Soloamp, front panel, Ch1 or Ch2 (XLR) This chain has worked well but I am having some feedback issues that I’d like to minimize. I understand the relationship of mic(s) to Soloamp, and moving things around is my first line of defense. Another possible issue… I learned that this signal chain has double pre-amp (mixer + Soloamp), or even triple pre-amp (Fishman guitar pickup with preamp + mixer + Soloamp). Could this be part of my feedback problem? I just can’t get any signal from Mixer to Fishman other than thru the signal chain first described. I have tried the following, result = zero output from Fishman: • Mixer Main Out, XLR (tried both L & R) > Soloamp Monitor In, XLR • Mixer Control Room Out, ¼” (tried both L & R) > Soloamp Effects Return, ¼” (tried both Ch1 & Ch2) • Mixer Control Room Out, ¼” (tried both L & R) > Soloamp Aux-In, ¼” • Mixer Alt Outputs, ¼” (Tried both 3 & 4) > Soloamp Effects Return, and also to Soloamp Aux-in • Mixer, every combination with Stereo Aux Sends, 1/4" That is virtually every combination I could come up with… Am I missing something? Or am I chasing a ghost… multiple pre-amps not an issue in regard to feedback. Last thought... I really love the Soloamp... Portable, easy setup, when set up correctly the sound is crystal clear. We play as many as 3 mics and 2 instruments thru the mixer, in small venues with up to 80 people. Great net sound from the Soloamp!
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_________________________________________ The Tree: I was alive in the forest, I was cut by the cruel axe. In life I was silent, In death I sweetly sing. Now back living in Baja Sur where I started my carbon fiber journey... Bend OR was too cold! 
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#2
03-29-2015, 12:02 PM
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I don't know why you're not getting any output using those alternative schemes (people who know those particular pieces of equipment better can help you troubleshoot that), but having several preamp stages in your signal chain has nothing in-and-of itself to do with feedback, which is caused by one thing and one thing only: particular frequencies being too loud and getting into a mic or a pickup. In other words, it's about the final volume either in the room or on stage, and not about how many gain stages it takes you to get there.
It's true that having more than one preamp in the chain will make it more challenging to get a very low noise signal and to keep something from distorting (there's just more you have to pay attention to, in other words), but it sounds like you're getting a good sound with the volume you need and no distortion, so figure out which mic or instrument is the problem, work on your speaker/mic/pickup placement, and consider exactly what it is that's causing you to have to turn up beyond the feedback threshold. You may need to consider getting the main amplification out front and getting some sort of monitor set up for some gigs. Beyond that, there's applying EQ (various options) or getting a feedback buster. Louis
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#3
03-29-2015, 12:45 PM
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bilder;
First off, google "Gain Staging" and check it out until you understand it and apply it... this will help you in many ways, and may solve part of your problems easily... No, having multiple preamps will not, in itself, "cause" feedback, as Louis just mentioned... I would suggest that you "start" with having ALL the tone controls on "flat" or middle settings, to begin with... I have always wanted to hear what my audience is hearing; as such, I detest using monitors! They always sound thin and wimpy and weird, and frequently have zero fx... Even before I got my Bose L1 system, I would get my two EV speakers far enough away from me that I could angle them to cover, both the room and the spot I was sitting/playing... never had feedback issues to speak of... with the Bose, I get nothing problematic, except for the occasional low-mid "moan" from an acoustic guitar with a pickup... and that's easy enough to get rid of... Try to get the Soloamp a bit away from you, but angled so you can hear it... I would probably opt for using "line out" from the mixer and run that (your Soloamp is mono, so a stereo output will do nothing good for you) into the "line in" on your Soloamp. If you have a stereo mixer, just set all the balance knobs to one side and then use THAT side's output or line-out to the Soloamp... Again, read up on gain-staging and put that into practise... it's not an "exact" thing, but if you get close, it will sound really nice!
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"Home is where I hang my hat, but home is so much more than that. Home is where the ones and the things I hold dear are near... And I always find my way back home." "Home" (working title) J.S, Sherman
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#4
03-29-2015, 02:36 PM
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YMMV but here's how I run an Allen & Heath ZED-10FX mixer into my SA-220:
o Set FX as needed per channel. o I leave Pan @ Noon for whatever. o Set levels as needed per channel. I have not had issues with feedback using this approach. Don't be shy about contacting Fishman tech support. They're great.
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It's all one big note. - Frank Zappa Ain't Nobody's Business: https://soundcloud.com/vern-equinox/...usiness-but-my
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#5
03-30-2015, 07:41 PM
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Quote:
You are a good guy, always taking the time to respond to questions from inexperienced folks. Thank you.
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_________________________________________ The Tree: I was alive in the forest, I was cut by the cruel axe. In life I was silent, In death I sweetly sing. Now back living in Baja Sur where I started my carbon fiber journey... Bend OR was too cold!
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#6
03-30-2015, 07:50 PM
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Quote:
Quote:
I think I have a problem with the mixer. If you look at the connections I tried I think I did try your approach, but no signal output from the amp with the exception of direct from mixer mono-out into one of the front panel channel inputs. Good suggestion to call Fishman, and I will also call Behringer... something isn't right. BD
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_________________________________________ The Tree: I was alive in the forest, I was cut by the cruel axe. In life I was silent, In death I sweetly sing. Now back living in Baja Sur where I started my carbon fiber journey... Bend OR was too cold!
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#7
03-30-2015, 08:40 PM
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Quote:
Louis
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#8
03-31-2015, 11:20 AM
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Billder99, Trying to address and answer this particular issue, is next to impossible without more specific details. It's like throwing darts while blind-folded.
First off, Louis is bang-on about certain frequencies being too loud. Stated more precisely, certain frequencies are too loud "at" the offending mics' capsule. This is the "only" cause of feedback. Understanding "why and how" those offending frequencies are too loud will lead to a solution. Proper gain-staging is one element, but you also have to be aware of direct and indirect (reflected) sound-waves, as well as phase issues caused by running FX through your monitor.(in this case, I assume your SA200 is your "monitor", as well as your FOH.) Now, you've made no mention of what "mics" you're referring to. Does your guitar pick-up have a built-in mic?(blender pick-up/ mic and UST, etc). What vocal mics are you using? Do you know which mic is causing the issue? (I'm assuming the guitars' mic for the moment). Now, let's look at some basics, starting with electronic gain-staging. Basically, this is all about setting proper gain-level at all the various stages.(guitar pre-amp,,,mixer input gain (sensitivity),,,,channel output gain,,,,mixer output level,,,,, speaker input level,,,, speaker output level. It's quite a balancing act,,, and it's relatively easy to overload a circuit if it's not done properly. Many basic manuals suggest "turn up the gain 'til the peak indicator light comes on, then back off gain 'til the peak indicator light goes out". This is utter nonsense, and only works in the simplest of signal chains, and situations. What you really want is, to set gain at a point where it provides a clean yet strong signal to the next stage. In many instances, once that peak indicator light comes on, you can back off that gain by as much as 6-9db (or even more), and still have plenty of clean gain. Obviously, you don't want to set gain too low, otherwise, you'll start hearing the noise-floor of the circuit (hiss). Now, let's look at the loud-speaker, and its' relationship to feedback. Let's assume you're outdoors, and the speaker is facing away from you, with no walls to reflect and bounce sound-waves back toward you. You can crank that loud-speaker 'til she blows,,, and you'll get zero feedback. Now, start turning that loudspeaker around slightly, so you can hear it better,,,, and to no surprise, it sounds louder to your ear, and it's more intelligible. Well, simply put, your mics are just like your ears, and those mics will start hearing better too. Now, let's look at the mic inside your guitar, and what it "hears" once that loud-speaker has been turned around. It hears the sound of the plucked string, and its' effect within the guitars sound-chamber, but,,,,, it's now, also hearing the loudspeaker. Now, the guitar mic is sending two combined signal-sources to the amplifier/loud-speaker, where it's re-amplified, and re-arrives at the guitar mic once again, and is further re-amplified,,, and on, and on,,,. and now you have a Feedback Loop!!!!! Turn that loudspeaker away again, and it's gone. Let's go indoors. Now, even with the loud-speaker facing away from you, there are limits to how loud that loudspeaker can be within a given reflective space. Certain frequencies will be absorbed by curtains, carpeting, human water-bags, etc. Other frequencies may bounce back off reflective walls, floors, windows, ceilings, etc. Once your guitar-mic starts "hearing" those reflected sound-waves, and combines those waves with the instruments own sound-waves, and sends them out again to be continuously re-amplified, you'll start flirting with feedback. Now, let's look at FX's contribution to feedback, and this subject will touch on why pro's tend to use dedicated floor-monitors, as well as FOH boxes, rather than relying solely on their mains for combined FOH and monitor duties. Adding FX to the monitor introduces additional sound-waves,(or louder sound-waves) to what the mic "hears". Some of those frequencies will arrive at the mic-capsule in-phase, and some will arrive out-of-phase. Those that arrive in-phase, will combine with the instruments' own sound, and once again, the re-amplification occurs, and presto,,, feedback loop. Reverb and compression are especially notorious for this, and for this reason, dedicated floor-monitor mixes are generally kept reasonably "dry". So how does this all relate to that single speaker set-up, doing double-duty as a FOH main, and monitor duty? Well it all boils down to doing a proper pre-show sound-check, and that includes EQ'ing the stage sound, as well as the room sound. A decent 31-band EQ can resolve a lot of monitoring issues. Also, a rooms' acoustics can change considerably as the room fills with patrons. Single source/dual-duty loud-speaker set-ups, often means unacceptable compromise.
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#9
04-04-2015, 12:44 PM
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HAH! And now I'm going to make it worse. Thanks so much for this response. Clearly you spent a lot of time on this, very kind of you. I just read your response, slowly and in detail, for the 2nd time. You have explained some things that never occurred to me in regard to feedback, and you're right, understanding will help me with better setups going forward. We are doing shows in 3 different venues (2 outdoors, 1 indoors), and I've had feedback at each venue. We call our events "Open Mic", but it's always the same small rotating group, between 4-10 people. We try to change up our music at every event, so it's always evolving. Each of us does 3-4 songs, then we rotate... sometimes we do songs as duos, trios, etc... you would laugh if you saw the snake-tangle of cords at the end of each evening. We are filling the venues with standing-room only crowds, people seem to like the mix of music and performance-personalities. Gear: As you can imagine, it gets a bit complicated. My Fishman Soloamp is the primary vocal amp, with 3-4 mics thru the Xenyx mixer. I also run my guitar thru the Xenyx. There are always 2 or 3 more amps up there for guitars (mostly acoustic), mandolins, etc, but the feedback seems to always come from my Soloamp. The vocal mics are SM58 and Heil PR122... sometimes we mic an instrument using an SM57 (even a percussion instrument like a cajon)... it's usually not obvious which mic is giving the feedback, we just turn-down & turn-away the amp(s). I use all Planet Waves cables... no one uses pedals, but some of the small guitar amps have effects... sheesh, it sounds more complicated when I start writing it all down....chaos! Reading back on all of this, it's amazing we are pulling this off as well as we are. It is clear to me that I just have to keep experimenting, but your comments above really do help in understanding causation of feedback.
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_________________________________________ The Tree: I was alive in the forest, I was cut by the cruel axe. In life I was silent, In death I sweetly sing. Now back living in Baja Sur where I started my carbon fiber journey... Bend OR was too cold! Last edited by billder99; 04-04-2015 at 12:51 PM.
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