Understanding signal levels?

Is there some mathematical way to make sense of db levels? EG- Let's say I buss 5 signals that are all set to -4db (none of which come close to clipping) to a common aux channel. Is there a way to predict what the peak level of the aux channel will be based on mathematically adding together what the signals are in some way?
I ask this question because I'm always confused why I can have a bunch of signals that aren't clipping but when I combine all of them into a submix they will clip... I'd love to make better sense of all this.
Thanks for any help!!

Here's a good reference:
http://www.engineeringtoolbox.com/adding-decibel-d_63.html
There's a nice chart in there showing how sources sum in dB. For instance, given your five bus example, you'll get a 7 dB increase in level. So, if all your sources are close to clipping, you need to pull them all down -7dB to ensure the bus doesn't clip.
Then again, keep in mind that Logic mixes floating-point, so it really doesn't matter if your bus input clips--just pull down the bus fader, and you won't get any distortion at the bus output. I'm with you, though--I tend to keep the red lights away... more superstition than anything else
-James

Similar Messages

Ipad vga signal levels

3 out of 5 attempts to present Keynote (and other video enabled apps) presentations have failed. After some investigation I discovered that the failed talks (ipad could not drive video projector - iapd couldn't find project, and projector couldn't find ipad) were result of long cable lengths between projector and VGA connector that I plugged into dock-to-VGA adapter. These were 50' long cables in conference centers. I rustled up some more standard length cables after these very embarrassing failed attempts to give public presentations, and with shorter cables everything worked properly. I should also mentioned that numerous MacBook, MacBookPro and PC-types laptops all had no problem whatsoever driving VGA through a 50' cable.
Anyone else experience this problem? It makes it impossible to trust the iPad as a conference presentation device if iPad video signal levels are too low. Perhaps I have a defective iPad, or is this a systematic problem?
If I have to buy a VGA signal booster to carry along with an iPad, its absurd since these devices are nearly the size of the iPad itself!

I am not sure of what the official limit is, but a google search brought up 50' as the "practical" limit. Another site said 9 meters. I have seen some long vga cables in various conference rooms.
You may have an iPad with a reduced output. You could either try another ipad, if you know of one available, or take your ipad to the Apple store and see if an expert can test the output strength.

Signal Level Meter

Signal Level Meter
CATV Signal Level Meter GAO2002 is specially designed for CATV system maintenance. Signal Level Meter GAO2002 features small size (160mm x 130mm x 65mm) , light weight (368g including battery), long operating time (more than 6 hours), and well-built from appearance to architecture. Signal Level Meter GAO2002 combines the most practical functions and makes them easy to use. What is even better about this piece of equipment is that its added aseismatic design makes it more durable than you can expect. Tests show that it can continue to work well after being dropped from 5 meters high. It supports Level, V/A, Tilt and Trunk Level testing as well as testing two channels at the same time.
CATV Signal Level Meter GAO2002 Specifications:
Frequency
Frequency range: 46MHz ~ 860MHz
Frequency step: 50kHz, 1MHz, 10MHz and 100MHz
Level Measurement
Range: 20dBuV ~ 50dBuV
Accuracy: ±20dB (20ºC ± 5ºC)
Resolution: 0.5dB
Carrier to Noise (C/N)
Option Range: 20dBuV ~ 50dBuV
Input signal range: ≥ 85dB
Measure accuracy: ± 2.5dB (20ºC ± 5ºC) shut off the carrier
Resolution: 0.5dB
Voltage
Input range: 1~100V (AC/DC)
Measured accuracy: ±2V
Resolution: 1V
Miscellaneous
Size: 160mm x 130mm x 65mm
Weight: 368g (including battery)
Working: -10ºC ~ 40ºC
Audio: Built-in speaker (Auto on in single frequency mode)
Battery
Built-in battery: 3.6V/2.1AH Ni-MH
Working time: More than 6 hours (Shut off the audio and LCD backlight)
Charging time: 10 ~ 12 hours (power off)
Gao Tek Inc.

Do you have drivers for LabVIEW?
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"It’s the questions that drive us.”
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Setup help - low signal level in Logic

I'm getting low input signal levels when recording in Logic (-17db to about -10db, on average), and am hoping someone here can point out an obvious oversight on my part.
I'm recording mic'd guitars and vocals (one track at a time), with the mic(s)running into a Mackie 1402 mixer via XLR. Signals are strong and fine when I solo on the Mackie.
The signal runs out of the Mackie via the Alt 3-4 bus into the first and second 1/4" inputs on the back of a Motu 828 mkII, then into Logic.
Even if I drive the signal to near clipping on the Mackie, I get these low levels when recording in Logic. This is true whether I'm using a condenser mic with phantom power for vocals, or a dynamic mic on a guitar amp. I've also tried swithcing XLR mic cables.
I'm running Logic Pro 7.2.3 and OS X (10.4.9) on a G5 2.5 DP.
Is my signal path in need of some tweaking, or perhaps it's a setting I'm overlooking on the Motu 828?
Any help greatly appreciated to get this rookie back on track!
G5 2.5 DP Mac OS X (10.4.9)

Hi,
You wrote:
I'm recording mic'd guitars and vocals (one track at
a time), with the mic(s)running into a Mackie 1402
mixer via XLR. Signals are strong and fine when I
solo on the Mackie.
The solo on the Mackie is probably louder,check to see if you have it AFL(after fader listen or PFL(pre fader level or "level set").
The signal runs out of the Mackie via the Alt 3-4 bus
into the first and second 1/4" inputs on the back of
a Motu 828 mkII, then into Logic.
The first thing to check is to see what kind of cables you are running into the Motu mkii.
A. Unbalanced (ie "guitar-type" with two wires)
B.Balanced (ie "stereo-type" with three wires)
The second thing is to check what your inputs on your Motu are,there are two choices: +4dBu("pro") or -10dBV("consumer")
Here's the catch:
You MUST MATCH the correct cables for the correct levels.If the Mackie is outputting -10dBV but your Motu is thinking it is +4 you see less level no matter how loud you make the Mackie outputs.
The Mackie can output AUTOMATICALLY either -10dBV or +4dBu depending on what cable is hooked up to it.
Even if I drive the signal to near clipping on the
Mackie, I get these low levels when recording in
Logic. This is true whether I'm using a condenser mic
with phantom power for vocals, or a dynamic mic on a
guitar amp. I've also tried swithcing XLR mic cables.
This is not where the problem lies.It lieas between the output of the Mackie and the input to Logic.
I'm running Logic Pro 7.2.3 and OS X (10.4.9) on a G5
2.5 DP.
Is my signal path in need of some tweaking, or
perhaps it's a setting I'm overlooking on the Motu
828?
Yes,a setting somewhere in the Motu is not set correctly.Check above for how to do that.
Any help greatly appreciated to get this rookie back
on track!
G5 2.5 DP
Mac OS X (10.4.9)
Cheers

Signal level lights don't light up even when wifi is connected

I have a new MBP (the Core 2 Duo one). When I'm connected to a wifi access point, the Signal Level lights in the Internet Connect window never light up. Anyone else seen anything like this? I suppose it's not a huge deal, since I'm getting a connection OK. It's just that I'm curious how good my connection is. And it seems strange they'd make these nice little fake LEDs but then not use them.

iStumbler will give you better information
http://www.istumbler.net/

Understanding isolation levels

I'm having a difficult time understanding isolation levels. I know what problems each isolation level solves (i.e. dirty reads, nonrepeatable reads, phantom reads) and the classic textbook description of each level, but I simply cannot understand how it works. Let me explain my understanding of the various isolation levels:
READ_UNCOMMITTED:
The data read by TX 1 is held in a read lock, correct? TX 1 modifies the data. TX 2 therefore can read that data (but cannot write to it, due to the read lock). TX 2 can therefore read uncommitted data.
READ_COMMITTED:
The data read by TX 1 is held in a write lock, correct? TX 1 modifies the data. TX 2 cannot read the data because of the write lock, hence solving the dirty read problem. It cannot read the data TX 1 has so much as read during the course of its transaction (true?).
REPEATABLE_READ:
This is the biggest source of my confusion. How is it that the nonrepeatable read problem is not solved by READ_COMMITTED? TX 1 reads some data, TX 2 cannot read that data due to the read lock...but somehow it manages to modify TX 1's data so that when TX 1 repeats its query, it gets different results? How is this possible? And apart from the read and write lock of the two previous isolation levels, what does the database do to enforce this new isolation level on top of the other two?
SERIALIZABLE:
TX 2 cannot do anything without TX 1 finishing. (But isn't this similar to READ_COMMITTED, whereby TX 2 cannot even read TX 1's data until it has committed.) What is being meant by sequential execution here?
I think a source of confusion is that I am unaware of whether isolation levels are applied to an entire database, to a transaction, to a query, or some other category. Can one transaction have one isolation level while another transaction has another isolation level?
Any insight into isolation levels would be appreciated. Thanks.

It depends upon the database implementation - there are various different ways to solve the problem.
I think a source of confusion is that I am unaware of whether isolation levels are applied to an entire database, to a transaction, to a query, or some other category.
By definition the isolation levels are applied to the transaction. Other transactions can have other isolation levels.

Signal Level Varies

I don't know if this is related or not but ever since we had several brief power outages the signal level from my Airport Extreme Base Station throughout the house is very low. The base has an antenna connected and is in the room with my main G5 computer. There is also a G5 imac and a G4 ibook in other parts of the house. All 3 receive the signal via Airport. What I notice is that when first connecting (when the computer starts up), the signal strength is very strong and then it slowly backs down until it's only at level one or two on the meter. This even happens in my office which is only about three feet from the base station. I have tried moving the antenna and base station around but it doesn't seem to make a difference. Rebooting the computer often helps, but not permanently. Any suggestions?
Mac OS X (10.4.6)

I don't have an answer but I'd like one - I have exactly the same problem. Except we didn't have any power failures... the signal's just consistently getting worse, and I haven't changed any settings. For a long time it worked fine... anyone?

Signal Level for 2wire

The signal level on my wireless network connection does not work when I go to one specific room in my house - it works upstairs, but not 50 feet away. The signal is either very low or does not work at all in just the one room. I am using a 2wire home portal. Do I need to get an adapter? And where do I place the adapter?
Thank you,
Janice

If you get no wireless signal in one room of your house, then most likely one of the following has happened (in order of most to least likely)
- you are too far away from the wireless router
- there are too many walls, or walls with concrete and/or metal construction located between the iBook and the wireless router
- the room you are in is closer to a source of radiofrequency interference (2.4 GHz portable phones, neighbor's wireless networks)
Try reorienting the wireless router. Turn it, point it in a different direction, put it up higher - any of these tricks just might fix the problem.
What did you have in mind when you asked about an "adapter"?

"No service 3G" displayed without any signal level displayed

I just upgraded to IOS 6 and after re-entering my APN info and restarting my iPad 2 my iPad 2 tried searching for a carrier the displayed:
"No Service 3G"without any signal level displayed.
The Carrier shows correctly in Settings-Carrier and my iPad 2 seems to be fully operational. Data flow (web browsing/e-mail/etc) on the 3G and Wi-Fi networks are good.
How do I get the carrier and signal level to display correctly?

That's kind of what i was wondering i live in Apartment Building as well top floor We have a Tower 2 miles to the North a Tower 1 mile or less to our South and 1 that's close to 2 miles to our West and is on Another apartment building and the Signal i'm getting is 3 to 4 bars and the 4G the bars indicate CDMA signal only why as the 4G is your Data.. Our apartment is maid out of Brick with Metal Windows the Roof is a Normal flat Roof with a High Grade Roof shingle..
You might Check and see what is in the Building Materials in your Apartment and if you Live in the bottom part of it that might Hamper the Signal somewhat..

Quadrature Input and RS422 Signal Levels

I have a quadrature signal coming from a motion control drive that is in RS422 levels. What would the easiest solution be to get those signals into the quadrature encoder module (cFP)?
Thanks,
Michael Wise

http://www.baldor.com/products/motioncontrol/microflex.asp?product.asp?1=1&product=Servo+Controls&fa...
It has a simulated (actual signal to drive is a resolver) quadrature signal coming out. I'm only concerned with A+B since I'm just using it to determine speed. In the spec it says the signal levels of the encoder output conform to RS422 Levels.
I was planning on using the NI cFP-QUAD-510 for reading the encoder A/B signals back into the cFP system.

M-Audio FastTrack USB - very low signal level (line/guitar)

I've used FastTrack USB for a couple of years with a microphone through the XLR input with no problems. Now I am trying to connect a line output of a synthesizer to the line input of the FastTrack and the signal level is very low. There is no noise, it's just quiet, even with the track volume all the way up it's still no match for the rest of the tracks.
Any suggestions, except for trying all the knobs and switches on the face and back of the unit (tried that already)? Anybody has similar setup?
I use FastTrack for audio input, and built-in audio for output, it's connected through a hub (no problems for two years). In GB microphone is going to the Channel 1 (mono), and still works fine. Synthesizer goes to Channel 2 (mono) and is really quiet. I tried the syn with two different 1/4 cables with no difference. The headphones jack on the front of the FastTrack works fine with the normal level adjustment range, and if I plug in the headphones directly into the line out of my syn, I have sound, quiet (like you would get by connecting headphones to any line out, turntable even) but steady, so the syn must be fine.
Any thoughts?

No takers. Hm. OK. After some more research on the Net it appears to be that all the Fast Tracks suffer from the same problem, which makes me believe that it's not a bug, but a feature of an unexplainable kind. Oh, well, back to my old iMic noisemaker (this one works, it's just screened very poorly, so it picks up all the possible interference, and also makes its own little nasty hiss--this is why I switched to the Fast Track a while ago--so I will need to cut it out with an EQ, again). Hopefully, the EQ surgery will not affect the synthesizer's sound consistency as severely as it use to do with a microphone.

Airport Signal Level

Hi all,
I have a wireless router in my office and things were going great until recently I notice a drop in speed. I checked my airport info and the signal level has dropped three bars. I don't recall making any changes to the router or to any settings.
My question is, what could trigger a drop in signal level? The router is right on my desk so I am pretty sure the distance is not the issue.
Any help on this issue would be greatly appreciated.
Respectfully,
Eric

They should be tunables on your wireless router. For Linksys routers, they are usually under the "advanced" settings of the wireless page.
xmit power is the power level in milliwatts output by your antennas so your airport card can receive transmissions.
the frag threshold is the max packet size used on the wireless network before it is fragmented and split apart, causing network drops and re-transmissions
the beacon is the emission from your wireless router to wireles network cards, sort of like: "who's out there", sometimes, more frequency can mean more reliable transmission, especially if you have neighbors.
You can find lots of info at dslreports.com in their various forums. I have had 0 issues with my settings, and I live in apartment with 15 other ESSIDs surrounding me.

Wildly fluctuating signal level

After years of trouble-free wifi, last night the airport signal level suddenly started fluctuating wildly - varying over a few minutes from full signal to no signal and losing connection, then re-connecting. We have one computer upstairs and one down, and both showed the same problem, so presumably the origin of it was in the airport, not in the computers. The lights on the airport seemed to be flickering OK. Later on, all seemed to have returned to normal, and this morning the signal level is (so far) an unwavering maximum. Anyone have any ideas what could cause this?
Thanks!

Who knows? If it was something of that sort, it was coming from outside; there was certainly nothing new inside the house that could have interfered. As I check now, there are 4 other (password protected) networks detected by the airport; sometimes there are more - can they cause problems?

Digital signal level on d4 screen

This one is probably for the Verizon employees who monitor these boards.....
What's an optimal signal power level for a digital channel on the diagnostic screen (d4)? How's 36dB? Pretty good?
Thanks,
Jeff

What is shown on that screen is SNR (signal to noise ratio) and yes 36 dB is good.
However, you and most people are confusing this with signal level or power. Signal level is in dBm, volts, or watts. SNR is a measure of how clean the signal is not how strong it is. You can have 36 dB SNR and huge or small signal - it is simply a ratio of the signal to the noise floor.
If a forum member gives an answer you like, give them the Kudos they deserve. If a member gives you the answer to your question, mark the answer as Accepted Solution so others can see the solution to the problem.

How to understand Permission level SoD analysis reports?

Hi ,
We would like to confirm whether our understanding is correct in analysing the SoD analysis reports at Permission Level
Below is an example on how functions are configured at permission level
Under Function 0C0004 we have t-code as below
VA01 - Create Sales Order with Auth Objects
B_USER_STAT - ACTVT 01 AND
                            ACTVT 06 AND
K_CKBS_CO-PC - ACTVT 01 AND
                             ACTVT 06 AND
V_VBAK_AAT - ACTVT 01 AND 02 AND 06 etc.,
Similarly we have another Function GA0001 with t-code as below
F-03- Clear G/L Account
F_BKPF_BLA - ACTVT 01 AND
F_BKPF_BUK - ACTVT 01 AND
F_BKPF_KOA - ACTVT 01 AND
We have defined Risk betwee GA0001 & OC0004 with RISK ID 0045.
Does this means that a User / Role which are having t-code VA01 with the above permission values should be thrown as a conflict if the same user/ role is having t-code F-03 with the above permission values.
Do we need to understand the conflicts are only between two transaction codes and their permission values? or
Do we need to understand within the transaction code permission values also there are conflicts i.e. if a user is having 01,02 & 06 for V_VBAK_AAT in VA01 also.
When SoD reports are thrown for a User/ Role it just provides the Rule ID number and the t-codes conflicting followed by the permission values of the t-codes as below
004500101 : Transaction Code Check at Transaction Start Transaction Code     Create Sales Order (VA01)   OC00004
004500101 : Transaction Code Check at Transaction Start Transaction Code      Clear G/L Account (F-03)      OCA00001
004500101: B_USERSTAT : ACTVT : Activity      Delete(06)                          OC00004
004500101: F_BKPF_BLA : ACTVT : Activity      Create or generate(01)      GA00001
004500101: B_USERSTAT : ACTVT : Activity      Create or generate(01)      OC00004
004500101: F_BKPF_KOA : ACTVT : Activity      Create or generate(01)      GA00001
004500101: V_VBAK_VKO : ACTVT : Activity      Create or generate(01)      OC00004
In the above scenario what exactly we need to understand ? Whether the conflicts are between t-codes & their respective permission values or the conflicts are intra conflicts i.e between permission values as well? User should not posses both 01 & 06 for Auth Object B_USERSTAT and remove the access to any of them.
Please provide your suggestions in our understanding.
Thanks and Best Regards,
Srihari.K

Hi Sri,
          In RAR the conflict is always between Actions not permission. Permission level data is only for your info. All permission level details out of the box are not configured you have to activate it and fill in the value in the field. Now based on the value you feed in it will pull out the details.
eg: if you enter * it will show all values, If you enter 01 it will show all values with 01.
       So to summarize the permission level details you need to configure based on needs and are not linked to conflicts they just show AS IS permission level details.
Thanks,
Darshan

Understanding signal levels?

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