Max output from amp !

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[ThxOne Premium Member]

Hello,
is it possible to detect max output from amp without the clamp or meade tool ?

E=P×R

I have a 500 watt amp, (youtube dyno 560 at 2 ohms)

I then took 500 × 2 ohms = 1,000
square root ov 1000 is 31.62

I then ran a 50 hz 0db but amp reads 29.8 at max gain, using DMM.

then it also would read 29.0 from the halfway line on gain knob. from halfway to max it stays at 29, u til 29.8.

is there something I missed ? what else can I do ?

my HU distorts at 38, so I set my gain at vol 31. at the place it read 29 volts.

I use one of these. It is cheap and allows you to see the waveform to see if it is clipping or not. Easy way to find the max gain level of the amp. Once you get it to just before clipping it will also display the voltage at the same time. Then you can do your math to find out what the wattage is.

https://www.amazon.com/dp/B07RN5J9YT/?tag=caraudiocom-20

 

[winkychevelle 10+ year member]

Hello,
is it possible to detect max output from amp without the clamp or meade tool ?

E=P×R

I have a 500 watt amp, (youtube dyno 560 at 2 ohms)

I then took 500 × 2 ohms = 1,000
square root ov 1000 is 31.62

I then ran a 50 hz 0db but amp reads 29.8 at max gain, using DMM.

then it also would read 29.0 from the halfway line on gain knob. from halfway to max it stays at 29, u til 29.8.

is there something I missed ? what else can I do ?

my HU distorts at 38, so I set my gain at vol 31. at the place it read 29 volts.

Just set to to 500w the extra 60w won't make a difference and who knows if the QC is so struck that your amp also make 560w maybe it only make 505w as long as it makes the 500w youre golden and the manufacturer didn't lie

 

[nauc 10+ year member]

try it like this, with HU at 3/4, whether distorting or not. and id try with their test tones too (theyre at the very bottom)

also, set your sub volume (if your deck has that) to 3/4 too

also, list all the gear youre using . deck, speakers, sub, amp etc

Amplifier Level Setting Guide

Note:The following article describes the Amplifier Level Setting process for most car audio amplifiers, regardless of brand. Specific target voltages for applicable JL Audio amplifiers are included...

jlaudio.zendesk.com

 

[Water Bear]

Is there any EQ active on the HU?

my HU distorts at 38, so I set my gain at vol 31. at the place it read 29 volts.

The amp can only multiply the voltage it receives. If your head unit is not putting out sufficient voltage at 31 out of 38, then the amp physically can't reach the voltage you're looking for. Say at max gain your amp multiples the voltage by 10. If your head unit outputs 2.98 volts at volume level 31, then your amp is going to output 29.8 volts at that level, max gain.

In other words, turn up your unit. The right place to test is at 1 volume level below distortion. So if you distort at 38 then set gains at 37.

 

[mat3833 10+ year member]

Is there any EQ active on the HU?



The amp can only multiply the voltage it receives. If your head unit is not putting out sufficient voltage at 31 out of 38, then the amp physically can't reach the voltage you're looking for. Say at max gain your amp multiples the voltage by 10. If your head unit outputs 2.98 volts at volume level 31, then your amp is going to output 29.8 volts at that level, max gain.

In other words, turn up your unit. The right place to test is at 1 volume level below distortion. So if you distort at 38 then set gains at 37.

That's really not how that works... In its simplest form, Yea. But in reality, alot of amps don't want an input voltage above 5v. Hell, my Smart 5 doesn't like anything above 4v.

The point of setting your headunit volume to 3/4 full is you reduce the likelihood of feeding an already distorted or clipped signal to the amp.

Matt

 

[Water Bear]

That's really not how that works... In its simplest form, Yea. But in reality, alot of amps don't want an input voltage above 5v. Hell, my Smart 5 doesn't like anything above 4v.

The point of setting your headunit volume to 3/4 full is you reduce the likelihood of feeding an already distorted or clipped signal to the amp.

Matt

That is exactly how that works. Gain is usually expressed in decibels. For example if your gain is some number = 20 * log(V_out / V_in), then V_out = 10^[(some number) / 20] * V_in or, stated a little cleaner, V_out = (some other number) times V_in.

If you have your head unit at volume level 10, that's probably less than 1 volt and you will never get your amp's rated power by just maxing your gain. You have to pick an appropriate input level. If you don't know what it is and you're just setting it at 3/4 and praying that's right, you end up in OP's position where you really need to be going higher. Just take out your multimeter and read the AC voltage that your head unit is outputting. Turn up the volume until either 1) you hit 4V or 2) your signal distorts. Or buy an SMD-DD1.

...It should be obvious that you shouldn't exceed your amps input limits. Most head units (obviously not all - but we're having to state the obvious now) go up to 4 volts and most amps (again - not all) accept 4 volt inputs. Yes, some go up to 5 and some amps take less than 4 (or a good bit more). Read your spec sheets before YOLOing with gain knobs.

 

[audiobaun 5,000+ posts]

 

[metalheadjoe 10+ year member]

You can't measure actual output unless you can measure voltage and current simultaneously.

 

[Water Bear]

You can't measure actual output unless you can measure voltage and current simultaneously.

What about Ohm's law? And moreover, what does this have to do with answering OP's question? I feel like we've slipped into some other kind of debate.

 

[metalheadjoe 10+ year member]

What about Ohm's law? And moreover, what does this have to do with answering OP's question? I feel like we've slipped into some other kind of debate.

The only way to accurately calculate power is to simultaneously measure voltage and current. Look up "inductive reactance" before you reply.

Here is how it pertains to OP's question:

is it possible to detect max output from amp without the clamp or meade tool ?

 

[mat3833 10+ year member]

That is exactly how that works. Gain is usually expressed in decibels. For example if your gain is some number = 20 * log(V_out / V_in), then V_out = 10^[(some number) / 20] * V_in or, stated a little cleaner, V_out = (some other number) times V_in.

If you have your head unit at volume level 10, that's probably less than 1 volt and you will never get your amp's rated power by just maxing your gain. You have to pick an appropriate input level. If you don't know what it is and you're just setting it at 3/4 and praying that's right, you end up in OP's position where you really need to be going higher. Just take out your multimeter and read the AC voltage that your head unit is outputting. Turn up the volume until either 1) you hit 4V or 2) your signal distorts. Or buy an SMD-DD1.

...It should be obvious that you shouldn't exceed your amps input limits. Most head units (obviously not all - but we're having to state the obvious now) go up to 4 volts and most amps (again - not all) accept 4 volt inputs. Yes, some go up to 5 and some amps take less than 4 (or a good bit more). Read your spec sheets before YOLOing with gain knobs.

For a purely analog amp, Yea you have it spot on. But not many amps now, even the most basic ones use a purely analog input section. Headunit output is usually not linear, neither is amp gain. Any decent quality amp will make full power with as little as 0.2v.

The point in using 3/4 of the max is to have a clean signal if you don't have some means of checking your RCA signals.

I'll use my current headunits "2v" rca outs as an example since I actually measured the voltage at intervals of 5 from 5-35, and then 36, the max. Readings were taken while playing pink noise, with EQ flat.

5 - 0.15v
10 - 0.42v
15 - 0.86v
20 - 1.29v
25 - 1.94v
30 - 2.52v
35 - 3.01v
36 - 3.22v

If I had a Scope I would have checked the signal to see if it was even remotely clean, but I only ran RCA level for about a week before I switched to Optical.

The input voltage range for my Audison amp is 0.2v-8v. It's a digital amp/DSP with an input calibration process, so the amp automatically adjusts the "max" gain to unclipped. The input voltage range for my previous Helix Msix was 0.2v-6v(i beleive, I can look it up if you would like). I set the gain like I always have, set the headunit to 3/4 of max, and then adjust the gain on the amp until I'm satisfied with the volume.

Matt

 

[Water Bear]

The only way to accurately calculate power is to simultaneously measure voltage and current. Look up "inductive reactance" before you reply.

Here is how it pertains to OP's question:

Impedance Z is resistance plus reactance and depends on signal frequency. Ohm's law for Impedance is V = I |Z|. Know the impedance and the voltage and you don't need to measure the current - you know it. I get what you're saying, though. The simple RLC model is probably not totally accurate and measuring V and I to get P is the only "true" way to do it.

For a purely analog amp, Yea you have it spot on. But not many amps now, even the most basic ones use a purely analog input section. Headunit output is usually not linear, neither is amp gain. Any decent quality amp will make full power with as little as 0.2v.

The point in using 3/4 of the max is to have a clean signal if you don't have some means of checking your RCA signals.

I'll use my current headunits "2v" rca outs as an example since I actually measured the voltage at intervals of 5 from 5-35, and then 36, the max. Readings were taken while playing pink noise, with EQ flat.

5 - 0.15v
10 - 0.42v
15 - 0.86v
20 - 1.29v
25 - 1.94v
30 - 2.52v
35 - 3.01v
36 - 3.22v

If I had a Scope I would have checked the signal to see if it was even remotely clean, but I only ran RCA level for about a week before I switched to Optical.

The input voltage range for my Audison amp is 0.2v-8v. It's a digital amp/DSP with an input calibration process, so the amp automatically adjusts the "max" gain to unclipped. The input voltage range for my previous Helix Msix was 0.2v-6v(i beleive, I can look it up if you would like). I set the gain like I always have, set the headunit to 3/4 of max, and then adjust the gain on the amp until I'm satisfied with the volume.

Matt

An amp is definitely not going to "make full power at 0.2V". Turn your amp gain to max and tell me if it's outputting more voltage at volume 2 than at volume 1. I can max the gain on my SFB-5k and it won't clip until HU volume 45/60.

So. What do you @mat3833 and @metalheadjoe actually suggest that @OP do to solve his problem?

 

[mat3833 10+ year member]

Impedance Z is resistance plus reactance and depends on signal frequency. Ohm's law for Impedance is V = I |Z|. Know the impedance and the voltage and you don't need to measure the current - you know it. I get what you're saying, though. The simple RLC model is probably not totally accurate and measuring V and I to get P is the only "true" way to do it.



An amp is definitely not going to "make full power at 0.2V". Turn your amp gain to max and tell me if it's outputting more voltage at volume 2 than at volume 1. I can max the gain on my SFB-5k and it won't clip until HU volume 45/60.

So. What do you @mat3833 and @metalheadjoe actually suggest that @OP do to solve his problem?

Joe already gave him a solution. I popped in to correct a misleading "fact" about how amp gain works.

If I were running my amp that close to rated power I would want to verify it's a clean signal. There's a reason I currently run a 5k amp and only use 2k.

Matt

 

[hispls 5,000+ posts]

Know the impedance and the voltage and you don't need to measure the current

So what method will you use to plot the impedance of your woofer in the box in your vehicle? How will you account for impedance changes due to compression if you need to determine power at maximum output?