What is gain overlap?

[meade916]

here is a good read from the David Navone website (by Richard Clark):

Proper adjustment of an audio system begins with the initial selection of components. Component interface should be considered in regard to signal level, input/output impedance, and wiring and connector types. Failure to consider that some components are just not well suited for use with certain other components can doom a system to poor performance. And just for the record — don’t assume that just because you have decided to go the “everything from one manufacturer” route that you will be spared. If we can assume that attention has been given to these issues we are faced with the basic requirements for level setting.
The real heart of the issue is that every component has a noise floor below which it cannot pass a clean signal. Every component also has a maximum level above which it cannot pass a signal without severe distortion. In operation, it is critical to make sure the signal stays as high above the noise floor as possible without exceeding the maximum undistorted level. This is important no matter what the brand, price, or design the equipment may be. It should be acknowledged that an experienced technician can probably do a quick “tune it by
ear” and get most systems pretty close to optimum, but it is just as true that to achieve 100% of a system’s dynamic performance, the use of test signals and at least basic test equipment is needed.

Optimal Level Setting
As we mentioned before, a system that is not set up properly will have excessive noise or distortion or more likely both. With many systems costing thousands of dollars it is really silly to consider that level matching is not worth at least a few dollars and a little time. If you have a thousand dollars invested in your system and you improve it only 5% with a little tweaking, that’s a value of at least fifty dollars the way I see it. The fact is that in most cases the overall dynamic range of a system can be increased several dB with precision tweaking over what even the best “ears” can do. If you want to consider value, a mere 3dB is like doubling the value of your system.
So how do we go about this important final system tweak? First off forget all those statements such as “set it at 3/4” or “turn such and such to here.” Such comments are the babblings of techno-idiots and should be ignored by anyone serious about quality audio. No doubt you have heard such poor advice, as well as the other extreme, where the process is described in detail that would rival brain surgery. Really it’s not as complicated as its importance would suggest. All we really want to do is insure that when a signal starts out at the beginning of a system that it passes through the entire system as high as each component will allow without adding distortion. When a system is adjusted for absolute best S/N and lowest distortion, all the components will reach overload at the same time.

Begin With a AHB Signal
There are really only a couple things that are needed to do a professional job of level setting in an audio system. A good stable low distortion signal is the first thing required. I suggest you use a frequency of somewhere in the 500 Hz to 1 KHz range. A suitable signal would be what we call recorded at “all high bits” (AHB). This means that the signal outputs the highest voltage that would ever be encountered from an undistorted music source. There are numerous test CDs that contain suitable signals or you can burn your own from one of the numerous web sites that contain test signals.

Using An Oscilloscope
Once we have the signal we need a way to monitor it as it is passed through each stage of the system. There are several ways that work well and I will cover three of them. Naturally the best ways cost the most but either will work with patience. The best way to monitor any electrical signal is to use an oscilloscope. While this may sound rather exotic it really isn’t. Considering that today a scope can be bought for as little as 100-200 dollars (even less on eBay),
it is a good investment for anyone who is serious about a future in audio. Personally I would place its importance right up there with a drill or a DVM.

Once this simple procedure is finished, it is time to adjust the power amp gains. If we lived in a perfect world our systems would always have more power than we could ever use. Unfortunately it’s rarely that way. If we set our gains “textbook perfect,” the musical signal would never be able to produce a clipped signal. That is the good news. The bad news is that since the crest factor (peak to average power factor) of music is relatively high, the average power of most music signals is over ten to one or about ten dB. What this means is that in a perfectly gain matched system; the highest average power we can ever use from our power amps is about one tenth! This means that with a 1000 Watt power amp, the most long term average UNDISTORTED power we can listen to music is about 100 Watts or even less!

Gain Overlap
Fortunately short term music peaks don’t last very long and we can cheat just a little and get away with it with little or no audible downsides. The fix for this is what is known as “gain overlap.” Gain overlap is an intentional mismatch in the final gain adjustment done right at the power amp. This procedure allows for short term music peaks to be clipped and at the same time allowing the average level of signal to be increased. The net result is a large, noticeable increase in how loud the system will play.
Much testing of skilled listeners has shown that the added distortion of a 10 dB gain overlap is extremely difficult to hear. It just so happens that the real bonus of a 10 dB gain overlap is that the system will play at a level that is perceived by listeners to be fully twice as loud. Of course you can choose the amount of overlap you care to incorporate, but less overlap reduces the usable loudness, and more overlap leads to distortion audible.
Several years ago at Autosound 2000 labs we actually produced Test CD#104 “Level Setting.” This disc demonstrates the actual audible effects that result from different degrees of gain overlap. The test disc also demonstrates the differences in loudness that result with each choice of overlap. Those that are new to this concept or are uncertain on just how they want to adjust their respective system might want to audition this disc. Gain settings from 0 to as high as 20 dB of overlap are demonstrated with varying steps in between.
(Note: The Autosound 2000 Test Disc CD#104 “Level Setting” is available from Automedia / Car Sound And Performance for only $15.00 at www.carsound.com)
The gain overlap is achieved by doing the very last amp gain adjustment with a test signal that is reduced in level by the amount that you want to have the gain overlapped. As such, a 10 dB overlap would be done by adjusting the amp gains with a test signal that was 10 dB less than the “O” bit signal that is used for the rest of the system components. In addition to demonstrations of the effect the actual signals necessary to make the needed adjustments are included on the CD#104.

Summation:
When it comes right down to it, there is little that one can do or spend on a system that can rival the sonic improvement that comes with proper gain adjustment of the system as a whole. A system adjusted for perfect gain matching is like chain that has equal strength in every link. In such a chain every link will fail at the same instant. A properly adjusted system with gain overlap at the amplifier is like a carefully engineered electrical system that offers maximum performance but has a fusible link.

More here:

http://davidnavone.com/level-setting/

[White Lightning]

Richard Clark ... Haven't heard that name in a while. Good Find Steve !!!

[oldsoundguy]

Thanks Steve. That read made a lot more sense. I have my system set at 0db right now. I tried -5 and -10 with both my front stage and subwoofer. I found that -5 and -10 on the front stage was too much for them and brought in distortion at higher volumes but the subwoofer was able to handle the -5 and -10. So I set the front stage at 0db and the sub at -5 for now.

[neuspeedescort]

18 minutes ago, oldsoundguy said:

Thanks Steve. That read made a lot more sense. I have my system set at 0db right now. I tried -5 and -10 with both my front stage and subwoofer. I found that -5 and -10 on the front stage was too much for them and brought in distortion at higher volumes but the subwoofer was able to handle the -5 and -10. So I set the front stage at 0db and the sub at -5 for now.

same thing i have found in most of my systems.  0 on highs. -5 on subs.  i generally like to drive my mids a little over powered on 4 ohms.  that coupled with the -5 on the sub stage is a nice blend

[DLHgn]

The whole -10, -5, etc, track thing actually makes sense now. Thanks for the read!

[ShadeTreeMechanic]

Good stuff! I always seem to be on the hot side with my gains. Lol

[06RTCharger]

11 hours ago, Karkov said:

Read every post, I understand what overlap is but i will simplify a little.  

Since you have the DD-1+ I will say it like this, pretend your gain on your amplifier actually had marks for EVERY setting...pretending you already set it with DD1 using a 0 db track then it would then go/say 0.1 then 0.2 then 0.3 etc. when turning the gain up

5 being 5.0 obviously so meaning 50x that of 0.1

10 being 10.0 obviously so meaning 100x that of 0.1 and so on to the -15 track being 15.0 being 150x that of 0.1  (using DD1, NOT DD-1+)

 

Disclaimer: DD-1+ shows overlap with a positive (+) symbol not to be confused with -5, like AudioFanaticz explained, you are adding overlap, blah blah, what *IS* -5 or -10 overlap will show on DD-1+ as +5 and +10 respectively.

 

Because I said you already set the gain using 0 DB track on DD1 you could/would then turn gain lower and assume there were marks on amplifier showing -0.1 then -0.2 then -0.3  assuming that you set gain using 0 db track with DD1 (not DD-1+)  so gain is pretend 1/3 of the way up, thus anything ABOVE 1/3 starts at 0.1 and goes up and anything below 1/3 gain would be -0.1 and continue to go lower.  (NOT on DD-1+ but we're pretending there are marks on side of amplifier)

 

When people talk headroom, they have a more powerful amp then need be and set gain at 1/5 gain on my scale above thus much lower then 0 db track (assuming 1/3 is 0) on DD1 (respectively much lower than 0 DB overlap on DD-1+)  the DD-1+ just says "No Overlap" when you go lower then the matching to your HU voltage output, so 1/3 or lower using my scenario will show "No Overlap" on DD-1+

 

Disclaimer: me saying gain is 1/3 or 1/5 is purely fictional for explanation purposes don't think you can set any amplifier at 1/3 or 1/5 and be safe.

 

DD-1 gives you tracks of 0, -5, -10, -15.  People can make their own tracks, such as Snowdrifter on this site made tracks of -2.5 and -7.5 before the DD-1+ was released.  

 

DD-1+ allows you to adjust at ANY inbetween setting going to the nearest tenth ( 10.1, 10.2, 10.3 etc.)

 

Overlap by a simple definition is the range at which you can set your gain on your amplifier.  Your amplifier prolly says something like 0.2v on the low side and 6.0v on the high side.  Your HU sends out a 4.0v signal (4 volts) so you want that to match your amplifier gain, the DD-1 and DD-1+ allow you to do that precisely, it's just that the DD-1+ allows you to set it anywhere you want (all inbetween voltages rounded to the nearest tenth).  Having your gain on amplifier much higher than it should be has the potential to introduce distortion and clipping.  All clipping is distortion, but not all distortion is clipping.  keep in mind that where your gain is set at is irrelevant compared to anyone else because it's HU reliant, maybe your HU puts out 2v preout, maybe 5v preout, this determines how high your gain will appear on your amplifier if set correctly.  When people say gain is 1/3 or 3/4 or whatever they may or may not have set it correctly but since it's HU based either one COULD be right but no one will know till hooked up to a DD-1, DD-1+, or O-scope.

 

The hard part:  music today is recorded differently, so a 5.5 overlap may work for one song but may distort another, or be really quiet for another, that's the struggle that we all face, especially with so many more devices being able to play music through you car today, all depends how it was recorded from the beginning (the song).  You will see on here people talk about really knowing their system, it's because they stick tons of time into listening and setting and they know what they can and can't play and they know when they are and aren't clipping.  There is no real set it and forget it although some set it a little conservative if they always listen to music from the same source and can in most instances be safe.  Some songs you may not be playing your system to it's full potential (inefficient) but others you may be causing harm to your gear (clipping/distortion).

Yup, the fact i understood what ur saying....means i understand the "gain overlap" topic. Thanks man. Its all about "matching" every component in ur system to achieve maximum safe output. Like matching ur amp gain to ur Headunits/sources output voltage. Then because that perfectly matched gain setting might be a lil weak or lil strong for certain music tracks, you adjust the gain VERY slightly accordingly -or+ so that the song plays at its best. And the DD-1+ allows u to know exactly how slightly ur setting it. And i understand the +db is actually -db. Its because youve moved the starting point, youve moved the "0". If u set the gain first with a -10db then try to do ur overlap, that -10 is actually ur starting point and becomes "0" so any setting above that point will be read as positive and any setting below that point would be negative. 

[06RTCharger]

VERY much appreciated all this info Steve, this car audio noob is learning a few tricks of the trade lol. 

[ALDJ253]

On 1/2/2017 at 9:38 AM, meade916 said:

here is a good read from the David Navone website (by Richard Clark):

Proper adjustment of an audio system begins with the initial selection of components. Component interface should be considered in regard to signal level, input/output impedance, and wiring and connector types. Failure to consider that some components are just not well suited for use with certain other components can doom a system to poor performance. And just for the record — don’t assume that just because you have decided to go the “everything from one manufacturer” route that you will be spared. If we can assume that attention has been given to these issues we are faced with the basic requirements for level setting.
The real heart of the issue is that every component has a noise floor below which it cannot pass a clean signal. Every component also has a maximum level above which it cannot pass a signal without severe distortion. In operation, it is critical to make sure the signal stays as high above the noise floor as possible without exceeding the maximum undistorted level. This is important no matter what the brand, price, or design the equipment may be. It should be acknowledged that an experienced technician can probably do a quick “tune it by
ear” and get most systems pretty close to optimum, but it is just as true that to achieve 100% of a system’s dynamic performance, the use of test signals and at least basic test equipment is needed.

Optimal Level Setting
As we mentioned before, a system that is not set up properly will have excessive noise or distortion or more likely both. With many systems costing thousands of dollars it is really silly to consider that level matching is not worth at least a few dollars and a little time. If you have a thousand dollars invested in your system and you improve it only 5% with a little tweaking, that’s a value of at least fifty dollars the way I see it. The fact is that in most cases the overall dynamic range of a system can be increased several dB with precision tweaking over what even the best “ears” can do. If you want to consider value, a mere 3dB is like doubling the value of your system.
So how do we go about this important final system tweak? First off forget all those statements such as “set it at 3/4” or “turn such and such to here.” Such comments are the babblings of techno-idiots and should be ignored by anyone serious about quality audio. No doubt you have heard such poor advice, as well as the other extreme, where the process is described in detail that would rival brain surgery. Really it’s not as complicated as its importance would suggest. All we really want to do is insure that when a signal starts out at the beginning of a system that it passes through the entire system as high as each component will allow without adding distortion. When a system is adjusted for absolute best S/N and lowest distortion, all the components will reach overload at the same time.

Begin With a AHB Signal
There are really only a couple things that are needed to do a professional job of level setting in an audio system. A good stable low distortion signal is the first thing required. I suggest you use a frequency of somewhere in the 500 Hz to 1 KHz range. A suitable signal would be what we call recorded at “all high bits” (AHB). This means that the signal outputs the highest voltage that would ever be encountered from an undistorted music source. There are numerous test CDs that contain suitable signals or you can burn your own from one of the numerous web sites that contain test signals.

Using An Oscilloscope
Once we have the signal we need a way to monitor it as it is passed through each stage of the system. There are several ways that work well and I will cover three of them. Naturally the best ways cost the most but either will work with patience. The best way to monitor any electrical signal is to use an oscilloscope. While this may sound rather exotic it really isn’t. Considering that today a scope can be bought for as little as 100-200 dollars (even less on eBay),
it is a good investment for anyone who is serious about a future in audio. Personally I would place its importance right up there with a drill or a DVM.

Once this simple procedure is finished, it is time to adjust the power amp gains. If we lived in a perfect world our systems would always have more power than we could ever use. Unfortunately it’s rarely that way. If we set our gains “textbook perfect,” the musical signal would never be able to produce a clipped signal. That is the good news. The bad news is that since the crest factor (peak to average power factor) of music is relatively high, the average power of most music signals is over ten to one or about ten dB. What this means is that in a perfectly gain matched system; the highest average power we can ever use from our power amps is about one tenth! This means that with a 1000 Watt power amp, the most long term average UNDISTORTED power we can listen to music is about 100 Watts or even less!

Gain Overlap
Fortunately short term music peaks don’t last very long and we can cheat just a little and get away with it with little or no audible downsides. The fix for this is what is known as “gain overlap.” Gain overlap is an intentional mismatch in the final gain adjustment done right at the power amp. This procedure allows for short term music peaks to be clipped and at the same time allowing the average level of signal to be increased. The net result is a large, noticeable increase in how loud the system will play.
Much testing of skilled listeners has shown that the added distortion of a 10 dB gain overlap is extremely difficult to hear. It just so happens that the real bonus of a 10 dB gain overlap is that the system will play at a level that is perceived by listeners to be fully twice as loud. Of course you can choose the amount of overlap you care to incorporate, but less overlap reduces the usable loudness, and more overlap leads to distortion audible.
Several years ago at Autosound 2000 labs we actually produced Test CD#104 “Level Setting.” This disc demonstrates the actual audible effects that result from different degrees of gain overlap. The test disc also demonstrates the differences in loudness that result with each choice of overlap. Those that are new to this concept or are uncertain on just how they want to adjust their respective system might want to audition this disc. Gain settings from 0 to as high as 20 dB of overlap are demonstrated with varying steps in between.
(Note: The Autosound 2000 Test Disc CD#104 “Level Setting” is available from Automedia / Car Sound And Performance for only $15.00 at www.carsound.com)
The gain overlap is achieved by doing the very last amp gain adjustment with a test signal that is reduced in level by the amount that you want to have the gain overlapped. As such, a 10 dB overlap would be done by adjusting the amp gains with a test signal that was 10 dB less than the “O” bit signal that is used for the rest of the system components. In addition to demonstrations of the effect the actual signals necessary to make the needed adjustments are included on the CD#104.

Summation:
When it comes right down to it, there is little that one can do or spend on a system that can rival the sonic improvement that comes with proper gain adjustment of the system as a whole. A system adjusted for perfect gain matching is like chain that has equal strength in every link. In such a chain every link will fail at the same instant. A properly adjusted system with gain overlap at the amplifier is like a carefully engineered electrical system that offers maximum performance but has a fusible link.

More here:

http://davidnavone.com/level-setting/

 

http://davidnavone.com/level-setting/

 

Good read! I had this question too and decided to look it up. The more I go into car audio, the more I want to spend on things like the DD1+, lol. I already made my original budget of $500 for a sub, amp, and box extend to now I am spending more than $750. Got $240 on the amp, $200 on sub, $180 on the box,  either $70 on the LC2i or $115 on the LC7i, and $120 on a 0 gauge Knuconceptz o gauge to dual 4 gauge amp install kit (May change. I have no idea if I want 2 amps. But the kit is only $25 more than a single 0 gauge kit by them for the fleks model).

 

[06RTCharger]

3 hours ago, ALDJ253 said:

Good read! I had this question too and decided to look it up. The more I go into car audio, the more I want to spend on things like the DD1+, lol. I already made my original budget of $500 for a sub, amp, and box extend to now I am spending more than $750. Got $240 on the amp, $200 on sub, $180 on the box,  either $70 on the LC2i or $115 on the LC7i, and $120 on a 0 gauge Knuconceptz o gauge to dual 4 gauge amp install kit (May change. I have no idea if I want 2 amps. But the kit is only $25 more than a single 0 gauge kit by them for the fleks model).

 

 

This shit can snow ball quick lol specially when new to this stuff.