Author Topic: Patch levels (Read 239 times)

mike1762 · « **on:** November 04, 2012, 05:32:26 AM »

Haven't posted in a long time, but I figured this would be the best place to get an answer/explanation to a question/observation. My signal path is a BOSS GT10B into a QSC PLX 3402 into an ElWhappo Jr. I have 5 patches in the GT10B that I routinely use and I send the L balanced output to my rig and the R balanced output I send to the FOH (if we're running everything thru the PA). I have attempted to normalize the patches by setting the levels to the same output (based on the input meters on the board). I've tried this running direct and also micing the cabinet. The problem is that some patches are (at least subjectively) quieter than other. The patches each have unique tonal character and I've noticed that the bassier ones just don't cut thru the mix. However, if I raise the levels on those patches I start clipping the board. Any ideas???

jzstephan · « **Reply #1 on:** November 04, 2012, 05:47:27 AM »

Sure, lower the louder ones.

sonicus · « **Reply #2 on:** November 04, 2012, 06:29:05 AM »

There are two line level references in use today: Balanced pro gear (XLR) runs at around +4 dBm (1.23 volts), while unbalanced semi-pro consumer gear (RCA/Phono Jacks) and some 1/4 inch jacks operate at approximately .316 volts (-10 dBV). The two operating levels must not be interconnected directly. The important thing is to match the levels of the gear you are using so that -10 equipment isn't directly feeding +4 equipment, and vice versa. If you use gear of both levels, there are various level matching devices on the market to properly interface the items. What you can do to get the job done in a pinch is send all signals at equal level if possible and pad them down at the mixing desk at the input pads to get your optimum levels with minimum peaks of over modulation (clipping). If you want to get really picky you might want to calibrate the whole enchilada prior to the performance with a test tone for a consistent level set up and set up your room as well with a 1/3 octave EQ using pink noise and an RTA, (real time analyzer).

sonicus · « **Reply #3 on:** November 04, 2012, 09:08:53 AM »

As a reference for 0 VU ; generally 0 VU= .775 volts

mike1762 · « **Reply #4 on:** November 04, 2012, 10:03:54 AM »

I'm balanced all the way thru the chain. Based on the VU meters on my board, I'm confident that the input signal from all my patches were nearly the same. Yet my perception of the volume is that they were not the same. I even had audience members asking me to turn up when I would switch to one of my bassier patches (I was happy to oblige!!!). My main patch is very... neutral. Probably less low end and more midrange than most bassist use. But I have a scooped patch I use for slapping and a few specialty patches that are heavier on the low end. I made a few adjustments as we were playing so that my (perception of) stage volume stayed constant. But if I had been running thru the board I would have clipped the hell out of it with all but my main patch. Going forward, I suppose if I leave my patches as I now have them set (I perceive them to be of the same volume at this point) and adjust the trim on the board using my loudest patch rather than my main patch... I should be OK. But I'm still curious about the phenomena my audience and I are experiencing. Do we perceive volume differently depending upon the dominant frequencies??? Am I making any sense at all?!?!?!?!

sonicus · « **Reply #5 on:** November 04, 2012, 10:47:12 AM »

Yes, you are making sense. Everyone ones ears are different. Few people have what is known in audio engineering circles as 'Golden Ears .http://en.wikipedia.org/wiki/Golden_ear

As well there my be capacitance and inductance issues on the electronics in some of your patches that will effect the timbrel aspects as well as actual frequency response. Standing wave ratio in the listening room will also effect the perception of low frequencies and comb filtering effects in the room will also offer variations to the puzzle.

(Message edited by sonicus on November 04, 2012)

sonicus · « **Reply #6 on:** November 04, 2012, 11:21:08 AM »

There is also the Fletcher-Munson Curve http://en.wikipedia.org/wiki/Fletcher%E2%80%93Munson_curves

This is why consumer audio equipment has had a loudness button.

(Message edited by sonicus on November 04, 2012)

mike1762 · « **Reply #7 on:** November 04, 2012, 12:29:54 PM »

Interesting. I had a little trouble deciphering the graph at first, but I now see that it reflects my observation. If I want to hear myself at 60 phons (I'd never heard of this unit before... no pun intended), I need more dBs for the lower frequencies... at least for the somewhat linear portion of the curve from 10-1000Hz. One of my patches was an octaver (an octave below) and it was the most affected. I appreciate the info and can quit ruminating over it.

sonicus · « **Reply #8 on:** November 04, 2012, 12:42:59 PM »

I am happy to help. The octave below type of patch can be a tricky beast for multible reasons.

stout71 · « **Reply #9 on:** November 04, 2012, 02:58:06 PM »

I own the same pedalboard, and I concur with the comments about the vastly different output levels on the individual patches. I agree that the human ear and hearing perception do play a role. After all, humans evolved to hear mid-range frequencies better than highs and lows, but that can't explain away all the output level differences. In fact, I used an SPL meter to measure the output and the volume varied ridiculously. Basically, I had to create duplicate patches based on the presets and adjust the levels, and then use those. Kinda dumb. Makes me want to go analog again...

mike1762 · « **Reply #10 on:** November 04, 2012, 03:37:26 PM »

I actually started from scratch on my patches. I figured I was being clever using the VU meter to be sure that the outputs were the same... as usual it's not quite that simple. I had sort-of noticed this phenomena at a few prior gigs, but I was going thru the FOH and monitors. As such, the difference wasn't as pronounced as this WE when I was just counting on my stage volume. For years all I ever did was find a tone and go with it... so this was never an issue. Now that I'm using different tones for different songs, I just have to be sure that I can be heard while NOT clipping the board. Now that I have a better understanding of what was happening, I think I know how to handle it.

David Houck · « **Reply #11 on:** November 04, 2012, 05:55:26 PM »

Just thought I would throw out that if the bassier patches are the ones that don't seem as loud in the FOH, you might want to check that the FOH isn't rolling off the low frequencies either on the board or on the power amps.

mike1762 · « **Reply #12 on:** November 05, 2012, 10:41:53 AM »

Dave: I hadn't considered that. I think the PLX does have a low-end filter and I always roll-off the lows thru the mains. At this point I'm going to leave everything alone since I had a decent balance by the end of the gig.