Measuring the power of an amp, with an oscilloscope

[Bow_Wazoo]

That's what I'm trying to figure out right now.
So with EDM the volume control of the FA-10 (medium gain) moves to 4 o'clock...

 

[antcollinet]

My comment was referring to the size of the heatsink you have on the resistor. Probably good for 20W or so

 

[Bow_Wazoo]

I just had that on hand. According to the manufacturer, the FA-10 brings 16W per channel at 32Ohm

 

[antcollinet]

I just had that on hand. According to the manufacturer, the FA-10 brings 16W per channel at 32Ohm

How many times over can that blow out your eardrums? What SPL does 16W generate in a headphone?

(Edit - I find it difficult that headphone sensitivity specs rarely state if it is mW, W or V. This obviously makes a huge difference - your HE6SE simply state 83.5dB)

 

[Bow_Wazoo]

I wonder if the HE6SE V2 really has 50Ohms....
Amir has measured the HE6SE with 64Ohm, as far as I can remember.

 

[HarmonicTHD]

I wonder if the HE6SE V2 really has 50Ohms....
Amir has measured the HE6SE with 64Ohm, as far as I can remember.

… than you are on the conservative side of things as the 50ohm represents are higher load than the HE6SE.
Alternatively you can also get a ca 30ohm resistor if your goal is if the amp meets the manufacturer‘s specs.
(Sure the heatsink is overkill but hey it will do the job).

 

[Bow_Wazoo]

OK, now I know:
To listen to Miles Davis - doop-bob at the desired volume, i need at least 4v rms per channel
I just attached the oscilloscope while listening.

 

[HarmonicTHD]

OK, now I know:
To listen to Miles Davis - doop-bob at the desired volume, i need at least 4v rms per channel
I just attached the oscilloscope while listening.

View attachment 214414

… so ca. 0.3W into 50 ohm. … see no heat sink necessary

 

[Bow_Wazoo]

But how about EDM?

 

[HarmonicTHD]

But how about EDM?

View attachment 214416

What about it? You now know how to measure the power required.

 

[Bow_Wazoo]

We are already somewhere else.
When I listen to EDM, I really step on the gas, and have to turn up the volume control to 100% (gain mid).
Then I need 2.5W per channel.

 

[Bow_Wazoo]

At 21v rms the curve starts to get messy.

At the next volume step, 23v, clear clipping is visible. This corresponds to this position of the volume control.

One more shift later we are at maximum

Measured like this (1khz sine wave), the signal starts to become unclean at about 8.8W.

 

[HarmonicTHD]

At 21v rms the curve starts to get messy.



View attachment 214429

At the next volume step, 23v, clear clipping is visible. This corresponds to this position of the volume control.
View attachment 214430
View attachment 214431

One more shift later we are at maximum
View attachment 214432

Measured like this (1khz sinusoidal wave), the signal starts to become unclean at about 8.8W.

Good.

Just some friendly advice for any future amp measurements. Be careful how you hook up your oscilloscope. The Amp Out Negative is not always equal Earth Ground (negative connect of your oscilloscope probe). Especially for Class D and Bridge Mode Amps this is not the case and when you hook up your oscilloscope the way you did here the magic smoke might escape.

 

[Bow_Wazoo]

All right, I understand.
Thank you.
Probably I also had a thinking error in it.
I don't know what the technical term is in English, but here in Germany this is a protection class 1 device, which means that the housing is connected to earth, so it is not insulated.
And usually, in protection class 1 devices, the earth is connected to the negative out (RCA).
So in my head was total confusion.
But that must have been my mistake, because the negative out of the balance output can not possibly be connected to earth, right?

 

[HarmonicTHD]

All right, I understand.
Thank you.
Probably I also had a thinking error in it.
I don't know what the technical term is in English, but here in Germany this is a protection class 1 device, which means that the housing is connected to earth, so it is not insulated.
But that must have been my mistake, because the ground of the balance output can not possibly be connected to earth, right?

Some are some are not.

Easy to check. Take your multimeter and see if there is a continuity between your Negative Amp Out and Earth Ground (on your outlet or safer on your oscilloscope ground). If there is, it is safe to hook up your negative probe.

Alternatively, check if there is a significant voltage when the amp is idle btw Negative Amp Out and Earth Ground (applies often to Class D, Bridge Mode Amps). If there is a voltage don’t hook up the negative probe of your oscilloscope.

 

[Bow_Wazoo]

I had to correct my post again. That is why your quote is no longer up to date

 

[Bow_Wazoo]

We are already somewhere else.
When I listen to EDM anyway, I really step on the gas and have to turn up the volume control to (gain mid).
Then I need 2.5W per channel.

View attachment 214420View attachment 214421

I also have to correct this statement.

With "Move Ds - Songs from Beehive" album,
the mentioned 11Volt RMS are sometimes not enough for me.
At my personal maximum volume, I get there on 16V RMS.
So I need 5W per channel.
All measurements I made with music were done with EQ (Harman target) and preamp set to -8dB.

In any case, my conclusion is instructive.
Anyone who drives a HE6SE with EQ,
and also likes to listen very loudly,
needs a lot of power.
An FA-10 is exactly the right thing.

I've had a lot of TOTL headphones in my possession, but none delivered as exciting an experience, as the combination of HE6SE and FA-10.
I attribute this to the fact that you can achieve very high volumes, with low distortion levels ,with these devices.

 

[antcollinet]

Just one comment - when listening at high volumes, you need to have at least an idea how high (in SPL terms) they are. Listening loud for long periods of time (or very loud for short periods) can permanently damage your hearing. I'm speaking as a lifelong tinnitus sufferer from a Motorhead concert in 1982. Dangerous volumes are not necessarily painful.

See the chart here:

What Noises Cause Hearing Loss? | NCEH | CDC

Noise is a significant source of hearing loss, but you can protect your hearing. An important first step is to understand how noise causes hearing loss.

www.cdc.gov

 

[Bow_Wazoo]

Yes, I have measured more often, it is a maximum of 95 to 100 dB.
But never over a long period of time. But only individual tracks.
It is important to me to have the possibility to be able to really step on the gas for a short time.

 

[Balle Clorin]

I always use a resistor and pot meter to make a parallel voltage divider across my dummy load. Then I never can short circuit the amp to ground, and do not overload the oscope