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Using test tones to set amplifier gain

When the hum turns into a buzz, it's clipping

In the 1950's, I'd take the family television's vacuum tubes down to Willow Grove Radio and TV Repair, check them with the giant tester machine, buy new replacement tubes, and reassemble the repaired television, so my mom and dad could enjoy their precious, respectively, Dean Martin and Red Skelton shows. In the 1960's, I studied radio and electronics at the Franklin Institute in Philadelphia. After college, in the early 70's, I joined a rock 'n roll band as the soundman, learning how to operate the electronics that make music sound good. Then, I worked in a music store in Austin manufacturing, installing, repairing, and operating sound systems and components for recording studios, nightclubs, and touring bands. I moved back to Charlottesville permanently in 1984 and opened a little demo recording studio. I also attempted to put to practical use the creative writing degree I had picked up along the way. In 2006, I finally came to my senses and got this job at Crutchfield where they actually pay me to ramble on, rant, and explain the things I love about music, electronics, and getting good sound.

More from Buck Pomerantz

Buck in the Crutchfield Labs

Buck in the Crutchfield Labs

In an amplified car system, you need to set your amplifier’s gain correctly in order to enjoy your music’s full range of dynamics and frequency response — hearing all the notes clearly, whether loud or soft.

Setting an amp’s gain right results in the highest signal and the lowest noise and distortion. You’ll feel your music’s impact better and hear exciting details that otherwise would get lost in your car.

Setting the gain by playing music

The quick and easy way to set the gain is by ear while playing music.

Most manufacturers recommend playing familiar music with the amp gain low, raising the receiver's volume until the music distorts, then backing it off until the music sounds clean again. Next, you turn up the amp's gain until you hear the distortion again, then back it off slightly, and you're done.

Setting the gain using test tones

The other methods of setting gain involve using test tones. A test tone is a single note played at a specific frequency, and is typically found on a level-setting disc, but can also be found online for downloading. In the Crutchfield Labs, I ran a set of tests and determined that “doing it by ear and music” works, but not quite as accurately or scientifically as using test tones.

1. Test tones and oscilloscope

Each tone creates a reference-level (0 dB) sine wave that you can observe on an oscilloscope screen. Instead of listening for distortion in music. As you adjust the volume and gain, you can see exactly at what point the signal of each frequency distorts and where it plays clean.

Waveform image

An example of a a clean waveform (left) and a distorted, clipped wave (right)

2. Test tones and speakers

But seeing as most people don’t have oscilloscopes, I thought that maybe by listening to the tones through speakers, one could also set an amplifier’s gain correctly. A non-distorted sine wave test tone sounds like a pure hum. When it distorts, you can clearly hear it buzz. By using test tones played through a speaker, I wondered how accurately I could set an amp’s gain as compared to setting it by the other methods. 

Welcome to my Crutchfield Labs project

I went into The Crutchfield Labs and set up an amplifier, wired to a power supply, a car receiver, and a pair of speakers. I also attached two sets of probes to a pair of speaker wires, one going to a voltage meter and the other to an oscilloscope. This way, we could see what the sounds look like and read the resulting power level the amp produced.

Pioneer DEH-3400UB CD receiver

Pioneer DEH-3400UB CD receiver

First set the tone controls to the way you listen

The receiver's and amp’s EQ and crossovers needed to be set to where they normally would be when playing music. This is so the gain would be set under real-world conditions. Adding boost, at any frequency, after setting the gain, can make the amp clip, distorting the sound and endangering speakers and subs.

I let the receiver (a Pioneer DEH-3400UB) stay in its factory preset “Dynamic” EQ setting, which boosts the bass and treble for a fuller sound. That meant certain frequencies would play louder than others. I needed to find out which tone clipped the receiver first, at the lowest volume setting. Then, I needed to use that receiver volume setting at that tone’s frequency to set the amp’s gain.

Part 1: Setting the gain with the oscilloscope

How loud can the receiver play and still play clean?

I started with the amp’s gain set to its minimum, and the speakers disconnected. I played the first tone, 40 Hz, a low bass note, only fit for subwoofers, and set the scope to view the sine wave. Then I turned up the receiver’s volume until I could see something bizarre happening to the wave’s shape. It didn’t “clip” at the top and bottom, it distorted in the middle. But I could see exactly at what volume level the distortion first appeared, and where it disappeared.

I took note of what the receiver’s volume reading was: 52. (The receiver’s top volume number was 62.) That meant the receiver played 40 Hz clean and at its loudest at its “52” volume.

Test Tone CD Track 7 40 Hz Maximum Clean Volume = 52
Test Tone CD Track 8 100 Hz Maximum Clean Volume = 51
Test Tone CD Track 9 400 Hz Maximum Clean Volume = 57
Test Tone CD Track 10 1K Hz Maximum Clean Volume = 59
Test Tone CD  Track 11 4K Hz Maximum Clean Volume = 56
Test Tone CD Track 12 8K Hz Maximum Clean Volume = 55
This receiver plays loudest at volume 51, otherwise 100 Hz notes would clip

I measured the receiver’s distortion-free top volumes for the other test tones on the disc. The 100 Hz tone stood out as the strongest — I had to turn the volume to its lowest setting to get it to play clean. Because that volume represented the level that all the tones would play cleanly through the receiver, I used the 51 setting for the receiver’s volume for the next step. Because the 100 Hz tone was the strongest, and would clip the amp first, I used the 100 Hz test tone to set the amp's gain.

Sound Ordnance amplifier

Sound Ordnance M-4050 4-channel amplifier

The amplifier’s turn

I played the tone and looked at the sine wave while turning up the amplifier’s gain knob. Any waveform distortion I then saw came from the amp, not the receiver. Turning the gain back down until the distortion disappeared, I set the gain exactly where the amp and receiver were both at their maximum clean output levels: perfectly gain-matched.

Setting the gain right optimizes the amp’s output

I turned up the gain to the amp’s top clean-playing point and read the volt meter. The volt meter read AC (alternating current) voltage, and the amp I used (a Sound Ordnance M-4050 4-channel) showed a top clean output for 100 Hz of 17.6 VAC. That translated to about 77 watts. Not bad for an amp rated at 50 watts RMS per channel.

Bench testing results in higher power readings

What was going on was the power supply the receiver and amp used was 13.5 volts DC, about the same as a running car’s system usually provides, but the amp wasn't connected to the speakers and so wasn't loading down the power supply with the increased current demand of the speakers. That explained some of the “extra” power. But the amp definitely performed above its specified rating. If I had wanted to, I could have set the amp’s output to exactly 50 watts, by turning the gain down until the voltage read a targeted number, in this case 14.14 volts AC.

Math formulas — skip this paragraph

The wattage equals the voltage squared divided by the speaker’s impedance in ohms, 4 ohms in most cases. The voltage equals the square-root of the product of the wattage times the speaker’s impedance (also usually 4). 50 watts times 4 ohms equals 200; the square-root of which is 14.14 volts AC. 14.14 volts through 4 ohms of impedance creates 50 watts of power. These formulae are based on Ohm’s and Joule’s Laws and you can’t break them if you tried.

A note on multimeter accuracy

To accurately measure your amplifier’s output power with a multimeter, use a 60 Hz tone for a subwoofer amp, and a 100 Hz tone for a full-range amp with its high-pass filter turned off.

  • This is because most meters are made to measure AC voltage accurately at 50-60 Hz (the common frequency of all power systems around the world). Using a standard hand-held multimeter to measure the voltage of a higher-frequency signal results in readings that are much lower and leads to inaccurate power calculations.
  • For instance, the Amprobe 15XP-B multimeter I used in this Labs demonstration reads the voltage of a 0 dB 1 KHz signal about one-fifth the level that it reads at 40 Hz or 100 Hz. This would result in a calculated wattage about one-twentieth of the correct output power.
  • Different meters will have different degrees of deviation.

Kenwood KFC-6984PS 6"x9" 4-way speakers

Kenwood KFC-6984PS 6"x9" 4-way speakers

Part 2: Setting the gain using speakers and my ears

The noisy part of the test

I then repeated the whole performance with one speaker connected — a Kenwood KFC-6984PS 6"x9" 4-way. I want to say, in advance, that this was not a pleasant experience. Two hours later, my ears were still painfully ringing from the very high 8K Hz tone. Jordan, also in the Labs area at the time, complained that the 4K Hz tone was still ringing in his. This method can produce high-pitched, annoying, ear-drilling sounds that could hurt your hearing if you expose yourself for too long, and definitely will bother everyone within listening distance.

For using tones and your ears to set an amp’s gain, I recommend sticking with only the 40, 100, 400, or 1K Hz tones. They don't hurt at all. The 100 Hz tone alone will do for both subwoofer and full-range speaker amps.

Humm
Buzz
When a hum starts to buzz

A sine wave sounds like a hum. When it distorts, you can clearly hear it buzz. Again, the 100 Hz tone was the first to buzz, and at the exact same 51 volume setting. With the receiver at that top distortion-free level, I played the tone again and turned up the amp’s gain until I could hear the tone buzz again. Then I backed it off until the hum alone remained. The place the gain knob was set and the voltage readings were exactly the same as it had been using the scope.

I did this test after working hours so no one else would be disturbed. But I proved to myself, at least, that the ear-and-tone method worked just as well and as accurately as using a scope. The 40 Hz tone couldn't really be reproduced by the speakers, so was useless. The 100 Hz tone rattled everything on the desk, so it was a little difficult to pick the buzz-point out of the crowd of reverberations. The 400 Hz tone was the best tone to detect clip-points, with a very clearly defined hum-to-buzz point. 

I hear music

Finally, I tried music and my ears alone. I performed this test twice, days apart, and also afterhours. Not everyone wants to hear my songs played loudly over and over again. At first, I played a favorite R&B-type song full of percussion, bass, horns, and lots of production — but I couldn’t hear it distort, only get loud. So I switched to a clear-voiced female vocalist singing swing. I also played a male singer, to see if it would be any different — it wasn’t.

Your hearing gets more acute when you close your eyes

I closed my eyes when I did this test, so no numbers were used to set the receiver’s top volume. I turned it up until I heard something go wrong with the vocal — it seemed thinner, not as bell-like, and harsher. The male singer's voice suddenly developed a rasp. After turning the receiver down a little, restoring the fine quality of the singer’s voice, I turned up the amp gain until I heard the same thing.

The two times I did this test, I got two different results. The first time, the receiver's maximum volume setting ended up one notch below the tones and scope setting. The second time, it was one notch higher than the tones and scope setting. But both times, the amp gain setting was exactly the same as the other methods.

The differences can’t be heard

On the first day, setting it by ear and music alone, I ended up thinking I should never turn the receiver higher than 50, and the gain was set so that at that 50 volume, the amp put out 15.7 VAC at 100 Hz, or 62 watts. On the second day, it ended up that I could turn it up to 52, and get 18.8 VAC at 100 Hz, or 88 watts. That 100 Hz tone was indeed slightly distorted visually, but it wasn't audible in the music. Plus, I don't usually listen to music full-blast for very long periods of time, so in real use, I would likely never be able to hear the difference.

It’s all about the music

I think either I was a little more or less sensitive to the singers’ voices on different days, and noticed changes at different levels than I could see in the waveforms’ shapes, or the music CDs I used were recorded at a different reference levels. I certainly cranked some swing those evenings in the Crutchfield Lab.

Whatever the differences between the methods were, they all resulted in having the receiver and amp properly gain-matched, and loud, distortion-free music ensued. Using the test tones disc was easier than listening to music. even without the oscilloscope, the tones made it possible for me accurately set the gain. It was very easy to discern when the hum distorted into a buzz.

Download some test tone files or pick up a test tone disc and try if for yourself! To make it easier, I've summarized the process below.

Instructions for gain-setting using test tones
  1. Set the receiver’s EQ presets and the amp’s bass boost to the way you normally listen to your music.
  2. With the amp gain at minimum, play a tone from the disc (we recommend 40 or 100 Hz) and turn up the receiver’s volume until you hear it buzz. Back off the volume until the hum returns, and write down or mark the volume setting.
  3. Repeat Step 2, noting the top clean volume settings, using the 400, 800, and 1K Hz tones.
  4. Pick the tone with the lowest clean volume setting and play it again at that setting.
  5. Raise the amp’s gain until you hear it buzz, back off until it hums, and you’re done.
  • dominicmonastra from Clifton heights pa

    Posted on 7/1/2015

    This really helped me in so many ways !!!

  • Chad Barkla from Australia

    Posted on 8/4/2015

    Great detailed article. Now i realise why my system sounded like rubbish when i set amp gains with receiver full tilt and no test tone Cd. Cheers

  • Ken Lacy from Baxter

    Posted on 8/24/2015

    Please help? I have installed a Pyle 5 channel amp 6800 watts into a chevy cruze.. Powering an alpine 12" sub rated for 1000 rms. Power from Batt measures 14.2 at the amp. ground is good from the amp to the frame. 17ft rca's from the stock head unit with a pac AAGM-44 adapter to give me the rca outputs. Everything is brand new. All settings on hu and amp set to minimum or 0 - volume at 75%. I play the 50hz sounds and my multimeter starts at 6 volts and i turn the gain all the way up and the highest voltage i get is 44. I have two other gain adjusters for the other 4 channels and the highest reading i get on either of them is 42. My 2 ohm sub calls for 48 watts. Everything I read from others doing it, they can get the readings up over 60 watts and gain not even turned up all the way. Any ideas why I am getting less than normal wattage readings?

  • Buck Pomerantz from Crutchfield

    Posted on 8/25/2015

    Ken, You might have your voltage and wattage a bit confused. Wattage equals the voltage squared divided by the sub's impedance in ohms. If you read that your amplifier's putting out 44 volts AC RMS, it means that it's outputting 968 watts into that 2-ohm subwoofer.

  • Jack S.

    Posted on 10/19/2015

    Thank you so much for all the great information. I have read that I'm okay with headroom on an amp's RMS output being higher than the speakers' RMS handling. But should I always set the amplifier's output to the proper voltage for my speakers using Ohm's/Joule's Laws?

  • Buck Pomerantz from Crutchfield

    Posted on 10/21/2015

    Jack, Setting an amplifier's gain with test tones and a multimeter is one of the three methods delineated in this article, and not necessarily the most accurate. It does not take into account whether the source signal is clipped or not. Personally, I think using test tones and listening for the buzz is an easier and more accurate method for setting an amp's gain.

  • thomas from Garden Grove

    Posted on 11/20/2015

    My head unit preout is 4V and my 4-ch amp gain setting is 4V at full counter-clockwise and 150mV at full clockwise. Does this mean I leave my amp gain at the lowest setting (4V)? Also, I have an EQ on the head unit, do I set this to my preference before I set my gain?

  • Buck Pomerantz from Crutchfield

    Posted on 11/20/2015

    Thomas, Just because a receiver's spec states it can put out a 4-volt preamp signal doesn't mean the signal is clean at that level. That's why I recommend using your ears to set an amplifier's gain, so you can hear distortion when it occurs. And yes, like the article says: "Set the receiver's EQ presets and the amp's bass boost to the way you normally listen to your music" before setting the gain.

  • Hayden

    Posted on 11/27/2015

    Can't find the test tone disc. Is it at 0db or -10db?

  • Jake from Phoenix, AZ

    Posted on 12/7/2015

    Extremely helpful!

  • Douglas menchu from Austin

    Posted on 1/9/2016

    I have a question, To set the gain properly after I have set eq and bass. Do I do each speaker individually by going to front left, FR,RL,RR? Or as a pair, front then rear or all together? My front speakers are component with crossover.100 rms Rear speaker is full range. 100 rms One single sub in back.100 rms

  • Buck Pomerantz from Crutchfield

    Posted on 1/11/2016

    Douglas, You should adjust and set every gain control that your amplifiers have. If a gain controls the input sensitivity of a single subwoofer channel, then you've set gain for one device. But most car amplifier gains control pairs of channels - like left-right or front-rear - so you adjust the gains for two speakers at once.

  • Ray from Phoenix

    Posted on 4/3/2016

    If i turn my gain all the way up and the voltage is only half of my target number, what can be the problem? I get up to 7 but ohms law calls for 14.14. Its a 50Wx4 RMS. Great article by the way!

  • Buck Pomerantz from Crutchfield

    Posted on 4/3/2016

    Ray, There are a few short-falls to using multimeter readings to set gain, instead of your ears. 1) The receiver's output may not be set to its maximum level short of distortion. 2) Your amplifier may not really put out 50 watts RMS into a 4-ohm load. 3) The speakers may be presenting 8-ohm loads to the amp. 4) Your multimeter's AC volts RMS readings may not be accurate at the frequency tone you're using.

  • Zack from Euless

    Posted on 4/8/2016

    I plan on setting my gain using a multimeter and calculating the max volts I should see for my sub. The reason is that I have a 12" DVC sub wired in parallel that can handle 300 watts RMS, but the Alpine amp powering it can put out 500 watts RMS in 2-ohm mode. So I need to calculate how many volts 300 watts RMS is, then set the gain to that level. In doing my math, should I first test the positive/negative speaker lead to the sub to get the exact ohms for my calculation? Or is just going with 2-ohms okay? I'm just concerned that different subs/speaker runs may introduce resistance variation, and I'm trying to be accurate.

  • Buck Pomerantz from Crutchfield

    Posted on 4/8/2016

    Zack, A subwoofer voice coil presents an inductive load, not a resistive load, to an amplifier's output - so measuring a coil's DC resistance with a multimeter won't accurately tell you its impedance. A coil's impedance actually changes according to the frequency of the signal played. Using the manufacturer's "nominal" impedance rating will bring the best results. Just be sure, when setting the gain, that your source is at its highest level with no clipping and your multimeter is accurate at the frequency of the tone you use. Most meters only read accurate AC RMS voltage around 60 Hz. (PS: producing 300 watts through a 2-ohm load takes 24.5 volts.)

  • Tiny from Charlotte

    Posted on 4/30/2016

    Where can I buy a test tone cd?

  • Buck Pomerantz from Crutchfield

    Posted on 5/2/2016

    Tiny, You can download test tones for free from the internet - a web search will turn up a vast selection. After downloading, you can burn them to a CD or store them onto a thumb drive for playing later.

  • Roger from Chicago

    Posted on 6/3/2016

    Some confusion. How can you get 17.2V RMS on 13.5 DC power supply? Were you measuring peak-to peak? Does your amp has boost power supply to get 17.2 V RMS?

  • Buck Pomerantz from Crutchfield

    Posted on 6/7/2016

    Roger, The circuitry of an amplifier uses its power supply's DC (direct current) voltage as the primary building block of its output. Along the way, power flows through the circuit's transisters, inductors, and capacitors that have the ability to boost the subsequent AC (alternating current) output. It's through the magic of each manufacturer's design that it's done.

  • nazri from malaysia

    Posted on 7/20/2016

    Do we need to change the gain level setting each time we change the speaker or we can just used the current that we already set?

  • Buck Pomerantz from Crutchfield

    Posted on 7/20/2016

    Nazri, Once the amplifier gain is set, in a system, it should remain untouched, no matter what volume your speakers play. When a speaker gets replaced, then the gain should be re-set to ensure that the new speaker doesn't distort.

  • donavon locklear from raleigh

    Posted on 7/24/2016

    Hello just purchased a jl audio w6v3, been trying to get the gain set right for a week now using a multimeter. When using a multimeter do I need to set the gain with you eq being how I listen to it? Or turn everything off?

  • Buck Pomerantz from Crutchfield

    Posted on 7/25/2016

    Donavon, You should set your amp's gain with all EQs and boosts set as you would normally listen to music. Applying some bass boost after setting the gain, for example, will result in clipping. Using test tones and a multimeter to set amp gain will only work if the meter is accurate at the test tone's frequency - that's why I recommend using speakers and your ears.

  • Kenyon Cody from TX

    Posted on 8/2/2016

    So using a oscilloscope what type of cd should I I use to set EQs line drivers processors etc, also what would I look for while setting them? And if I use a oscilloscope to test tone the crossovers should I test the amps along with it first so the amps are at their full potentional before the crossovers? Thank you!

  • Buck Pomerantz from Crutchfield

    Posted on 8/2/2016

    Kenyon, Test tones and oscilloscopes are commonly used to set gains in audio equipment - a device's input sensitivity to the output of a preceding device in a system. You can download "0-dB" test tones for free from the internet - a web search will turn up a vast selection. After downloading, you can burn them to a CD or store them onto a thumb drive for playing later. You then use the oscilloscope to visualize the tone as a sine wave - when the sine wave distorts, it means the signal's clipping and the gain needs to be reduced. I can't think of any reason to use test tones and an oscilloscope to set an equalizer or a crossover, however. For those, people often use pink noise and an RTA (real-time analyzer).

  • Anthony from Lake elmo

    Posted on 8/14/2016

    When I'm setting the amp gain for my sub's?, what test tone frequency should I use to most easily distinguish clipping and distortion? I have trouble hearing clipping and distortion playing music, there doesn't seem to be much even with gain at 3/4 and db at half

  • Buck Pomerantz from Crutchfield

    Posted on 8/15/2016

    Anthony, Any test tone will very clearly change its sound from a hum to a buzz when it clips. You can hear it even when wearing ear plugs for protection. For setting a subwoofer amplifier's gain, you can use a 40 or a 60 Hz tone.

  • Tendai from Derby, UK

    Posted on 9/10/2016

    Hi Buck Great article. Still a bit confused. I have a Mosconi 130.4 DSP amp rated at 130RMS per channel at 4 ohms or 175RMS at 2 ohms. My speakers are Gladen 201 3 way with 4x150/100 rating at 3 ohms in a BMW E60 UK spec with 2 channels being 8 inch subs and 2 channels feeding doorcard midbases plus tweeters via a crossover. I take the 100 to be the nominal rating in that? What target voltage would you recommend if I were to use a DMM? I've tried setting by ear but the E60 BMW does not have a visual for the volume so it's difficult to tell when one has hit 3/4 volume etc etc plus the buttons can be pressed til time immemorial without one having the foggiest whether you've hit the top, mid-top, somewhere-top, not-so-top etc

  • Buck Pomerantz from Crutchfield

    Posted on 9/12/2016

    Tendai, I don't recommend using a multi-meter to set an amp's gain because it'll only read voltage accurately around 60 Hz and can't tell you if the signal's clipped or not. Using test tones and your ears means it doesn't matter what an amp or receiver's visual display or markings show while setting gains. But the answer to your question is that to put out 100 watts RMS through a 3-ohm load takes 17.3 AC volts RMS.

  • Tendai from Derby

    Posted on 9/19/2016

    Hi again Buck Thanks for that. I'd purchased a DSO 112 O'scope which was en route when I asked. I've since hooked it up to the amp and set the gain using 1000Hz tone for the mids and 40/50 tones for the 8 inch woofers cutting the gain to about 10% before clipping. That said I then went on to check the output voltages after all had been set with lovely sine waves on the scope. Strangely channels 1 and 2 show voltages of 17.5 and 16.5 even though I set them both to high pass at the same level (180 as per mfr). Stranger still channels 3 and 4 which are for the woofers low passed at (100Hz as per Mosconi) show voltages of 20-21 without any sign of distortion. Is there a family of gremlins in the amp?

  • Buck Pomerantz from Crutchfield

    Posted on 9/19/2016

    Tendai, The gremlin's in your multi-meter - it's only accurate at 60 Hz. And you didn't say what the impedance of your subs are. 20 volts AC through a 2-ohm sub, for instance, generates 200 watts RMS. Another complication that you might not be aware of is that the impedance of a speaker or sub changes with different frequencies, and its output power does as well. Trying to set amp gain using an inaccurate meter reading the voltage of different frequencies through an unknown impedance will not work very well. If you have an oscilloscope, use that to set your amp gains, it will result in a more accurate setting.

  • Brent from Denver

    Posted on 10/16/2016

    When looking at the tones of the Amp with an Oscilloscope do I hook up the Scope to the speaker output with no speaker attached?

  • Buck Pomerantz from Crutchfield

    Posted on 10/17/2016

    Brent, It'll work either way, but most people prefer setting amp gain quietly, with the speakers disconnected, if possible. If you do set gain via test tones and an oscilloscope with the speakers connected, you will be able to hear as well as see when the amp clips.

  • Adam from Gothenburg

    Posted on 11/17/2016

    I cant use cd's on my stereo, so im going to download some tones and play them via usb and the use a oscillioscope. But i wonder what level the tones should be, -0db, -5db and so on. I've done some searching on the web but everyone says different

  • Buck Pomerantz from Crutchfield

    Posted on 11/17/2016

    Adam, If you want to squeeze every last watt you can out of your system and don't mind a little distortion, use -5dB test tones. Using the lower-level signal means you'll set the amp gain a bit higher than you would with 0dB tones. However, it's safer using 0dB tones to set gain.

  • James

    Posted on 1/3/2017

    A lot on online videos about setting amp gain reference using 40Hz and 1kHz test tones with your everyday multimeter. Does the statement about using a 100Hz test tone for setting the gain on full-range amps still apply? Is it more accurate than using a 1kHz test tone? Thnx

  • Buck Pomerantz from Crutchfield

    Posted on 1/3/2017

    James, I don't recommend using a multi-meter to set an amplifier's gain because it'll only read voltage accurately around 60 Hz (maybe 40-100 Hz) and can't tell you if the signal's clipped or not. This is why I do recommend using test tones and your ears to set gain accurately.

  • Shannon

    Posted on 1/3/2017

    Hey Buck are you tired yet of giving the same answer over and over? Maybe I am abnormal but I actually read the article before questions or comments...ha ha...smh

  • Buck Pomerantz from Crutchfield

    Posted on 1/4/2017

    Shannon, Thank you - it's heartening to hear that there are actual readers out there. I'll let you in on a little writer's secret. I keep a document with a bunch of stock answers to those frequently repeated questions saved, so all I have to do is copy and paste them when needed. Especially for those who leave comments on multiple articles I wrote.

  • Pascal from Boston

    Posted on 1/11/2017

    If I don't wish to use my ears to set an amp gain -- sensitivity issue -- and I don't have the funds for an oscilloscope, would it make a difference if I bought a True RMS multimeter (such as the Fluke 115 or Amprobe AM-530) vs a regular cheap multimeter to set my amp gains for accuracy?

  • Buck Pomerantz from Crutchfield

    Posted on 1/11/2017

    Pascal, I don't recommend using a multi-meter to set an amplifier's gain because it'll only read voltage accurately around 60 Hz and can't tell you if the signal's clipped or not. For instance, that Amprobe meter's specs claim 1% AC voltage accuracy only from 45 to 400 Hz. A less expensive solution would be to get a pair of noise-reducing earplugs that'll protect your hearing while still allowing you to hear test tones humming and buzzing.

  • cory from long beach

    Posted on 2/14/2017

    I have read some tutorials stating that you should only use the scope and test tone to set the gain up to the voltage calculated by the units actual power and the 4 ohms, and not the clipping point. the difference being that the former is the manufacturers recommended limit for "stable" power, and though there may be headroom between that number and the clipping point (your extra found power), it was not necessarily stable there... do you have any insight on that?

  • Buck Pomerantz from Crutchfield

    Posted on 2/15/2017

    Cory, Using a manufacturer's claimed ratings to set amp gain by voltage sometimes results in a mis-set situation which could endanger speakers. Setting gain to just below the clipping point, whether ascertained audibly or visually, ensures maximum signal headroom and minimum noise floor. A lot of people set their amp gains to just above clipping, to achieve higher levels of sound.

  • Cody from Scott AFB

    Posted on 5/2/2017

    Sir/Ma'am, So I have an Orion Step to 122d 12" sub rated 1500 RMS and an Orion amp 1500 RMS and i fried a sub after it was professuonally tuned.... So basically to tune properly the LPF needs to be all the way up along with the volume at the proper level then adjust the gain till it clips/distorts/buzzes right? So what's the purpose of having bass boost? Basically I want to push all 1500 RMS or close to it but not sure you could do that without bass boost. Also, I have a yellow top batt ran to my primary and my amp ran to the yellow top so it has a standalone battery all for itself.

  • Buck Pomerantz from Crutchfield

    Posted on 5/3/2017

    Cody, The misuse of low-pas filters (HPF) and bass boosts lead to the destruction of many subwoofers. Both are equalizers used to optimize the tone of the bass sound. A low-pass filter gets engaged to remove the high-frequency notes you don't want the sub to play. Turning it "all the way up" is not the proper way to set it. Check out Tuning your subs for that. A bass boost gets engaged when you want to emphasize the lowest bass notes, around the low E of a bass guitar or piano. If you like the tone when using a bass boost, you must readjust the amp's gain control to compensate for the boost in over-all volume and ensure that no dangerous distortion ever plays. Achieving full power in an amplifier depends on setting the gain correctly, not on the tone of the bass signal.

  • Pete from Woodinville, WA

    Posted on 6/10/2017

    Buck, I have an LC7i in my system taking the stock headunit speaker level outputs to line levels. I'm assuming I would need to set the gain on the LC7i at a very low level as well as my amp gains to a low level to figure out the factory head unit's maximums, then go to the LC7i, set it's maximum and finally go to the amp and set it's gains. Is that correct?

  • Buck Pomerantz from Crutchfield

    Posted on 6/12/2017

    Pete, That sounds right to me. Set the receiver to its maximum distortion-free level, the AudioControl device to its, and then the amp's gain as well. The instructions for the LC7i say that its gain should be set high and the amp's set low.

  • Ashay Borkar from Goa,India

    Posted on 6/22/2017

    Hello Buck ! Very informative article How do I set my 4 channel Scosche LOC gains connected to a 4 channel amp which is connected to 2 speakers and bridged to a sub? My car has a stock head unit . Should I check the whole process on head unit first then the loc and then the amp? Thank you

  • Buck Pomerantz from Crutchfield

    Posted on 6/22/2017

    Ashay, Yes, that's the way to proceed. Find the receiver's highest clean volume, then the LOC's, and then the amp's.

  • Kevin from Bristol

    Posted on 7/9/2017

    One of my amps is 4 x 75w rms but my sub amp is 1 x 550w rms, setting the amps gains by ear with test tones will result in the sub output being a lot louder than the 4 channel amp ? So once gains are set, do you then reduce the sub amp gain until it sounds matched with the lower power amplifier ?

  • Buck Pomerantz from Crutchfield

    Posted on 7/10/2017

    Kevin, You can adjust the subwoofer volume to balance in with the full-range speakers by either lowering the subwoofer level of the receiver or with the sub amp's gain.

  • Brian from Bay Area

    Posted on 9/7/2017

    Hey Buck, fantastic article! I can wait to try all this stuff out next week. Couple things: When you're determining your HU's max clean volume, your gains at that point are at the minimum, right? If you were to have the gain somewhere else but still on the lower end, (say 10% or 20%), would the distortion point on the HU vary in any way? Also, if I want to leave some room to play with for my subs, I'm assuming I should set the HU's sub control to its max or at least whatever number I want to use as my max when setting the gain, correct? And lastly, which is better? Running two 500 RMS subs at 4 Ohms with an amp that puts out a max of 1100 at 4 Ohms, or the same two subs at 2 Ohms where the same amp puts out 2000 at 2 Ohms? Is the amp working harder in the first scenario vs the second? Thanks!

  • Buck Pomerantz from Crutchfield

    Posted on 9/11/2017

    Brian, Finding the maximum clean volume of your receiver is unaffected by the amplifier's gain setting. I don't know which receiver you have, but you should set its subwoofer output as you would the gain - turn it up until it distorts, then lower it until it's clean. Two subwoofers that can get wired together to form a 4-ohm load cannot be rewired to form a 2-ohm load - that's impossible.

  • glennon heinrich from macedon

    Posted on 9/26/2017

    Okay so I've been running 2 Infinity Kappa 100.9 W's in a sealed box with passive radiators tune to 27 Hertz and it sounds phenomenal at 600 RMS each even though they're rated for like 375. I've since switched the speakers to 4 ohm to introduce a 2 ohm load and then I wired in a 12 inch earthquake dbxi in parallel to bring it back to a 1 ohm load. And now it doesn't sound nearly as good but an R&B it's definitely louder and shakes everything more. Could that be because the 12 is in a sealed box would it sound better if I get that box tuned to the same frequency as the other. Thanks P. S. In the pr enclosure those subs take 600 watts RMS all the way down to 12 Hertz then you start to get mechanical noise I've only done it once lol.

  • Buck Pomerantz from Crutchfield

    Posted on 9/27/2017

    Glennon, Not knowing exactly what amplifier you have makes it impossible to give advice on how to wire subs to it. If you want a question answered about a system, you must identify your equipment by brand names and model numbers. Mixing differently voiced subs in a system together often results in less than-ideal-sounding bass.

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