Asus Essence One Headphone Amp/DAC (CeBIT 2011) - Page 81

jabbilabbi,

That assumes that you have a perfect circuit. However, the voltage peak to peak may be 7 volts but I would also assume that that is not under load. The base equation for power is voltage x current so the question really is: how much current can the amplifier supply without distorting? You also have to consider that there is a certain amount of resistance applied by the resistors after the opamp in the circuit. If I actually had the schematics I could probably get pretty close to that measured values with equations.

Quote:

Originally Posted by jabbilabbi 

 

Hi Tim,

 

According to Asus webpage http://www.asus.com/Sound_Cards_and_DigitaltoAnalog_Converters/Xonar_Essence_One/#specifications

 

They say "Headphone : 7 Vrms ( Vp-p)"

 

and so @ 32 ohms   that would be   P = V^2/R      ( P = 7^2/32 )  ( P = ~1.53 Watts)

 

 

-Alex

Well Alex, i only went off by 6moons since at most times, they're reliable.

6moons supposedly sent those questions to ASUS in which they answered.

You're saying it can do 1.5W at 32Ω? Have you measured this yourself?

I would be glad to try, but i have no idea if it could be done using by using a multimeter.

Tim

cssarrow,

The only way I could think of doing it with a mutlimeter is to put it in line with 32 ohm headphones and measure current. Then I^2xR=W. Just to note though, with one multimeter you're going to be measuring either right or left. I personally don't think this is a good idea unless you also hook up the other channel to keep it running. Not saying that anything bad would happen. I just don't like the idea of running one channel all out while the other is disconnected.

Quote:

Originally Posted by Sk1n5 

cssarrow,

The only way I could think of doing it with a mutlimeter is to put it in line with 32 ohm headphones and measure current. Then I^2xR=W. Just to note though, with one multimeter you're going to be measuring either right or left. I personally don't think this is a good idea unless you also hook up the other channel to keep it running. Not saying that anything bad would happen. I just don't like the idea of running one channel all out while the other is disconnected.

I'm confused already.

Where should i measure from? underneath the 4 pin headphone surface mount?

Left + Ground and Right + Ground?

Which setting should be used on the multimeter? V~ or V--

I have two multimeters so it shouldn't be a problem measuring both at the same time.
 

I can put in a 35Ω (HE-400) or 32Ω (Razer Orca) and give it a measure.

Tim

Quote:

Originally Posted by Sk1n5 

Added 0.1uF/50V capacitors to my AD797Bs in the I/V stage. My jaw dropped at the difference. I knew they had a minor oscillation without, I'd verified it myself, but i didn't think an oscillation up in the MHz range would actually have an effect on sound quality. Guess I was wrong. Now I wish I still had my o-scope to check it for sure.

Where did you put the capacitor, did you solder it on the 4-8 pins of the op? I am also using the ad797br but with 49720ha-s in lpf and buffer. Did you use some standard electrolytic or film capacitors. I experimented with some cheap electrolyt 100mF capacitors as bypass and it made quite a difference on the 2132 in the lpf that i used before but i would get some wima film capacitors for the ad797 if it is a noticeable upgrade.

Quote:

Originally Posted by cssarrow 

I'm confused already.

 

Where should i measure from? underneath the 4 pin headphone surface mount?

Left + Ground and Right + Ground?

Which setting should be used on the multimeter? V~ or V--

 

I have two multimeters so it shouldn't be a problem measuring both at the same time.
 

I can put in a 35Ω (HE-400) or 32Ω (Razer Orca) and give it a measure.

 

Tim

For measuring you should use a resistor since the headphones have different impedances depending on the frequency. So it is best to use 5w or 10w resistors for the measurement. You can measure the AC Voltage between grund and one channel and the current on the same channel. Then you can calculate the power.

Quote:

Originally Posted by Sk1n5 

jabbilabbi,

That assumes that you have a perfect circuit. However, the voltage peak to peak may be 7 volts but I would also assume that that is not under load. The base equation for power is voltage x current so the question really is: how much current can the amplifier supply without distorting? You also have to consider that there is a certain amount of resistance applied by the resistors after the opamp in the circuit. If I actually had the schematics I could probably get pretty close to that measured values with equations.

The output impedance of the Essence One has already been measured by someone, it is slightly more than 10 Ω. So, that by itself limits the power into low impedance loads. The output resistors may also be small surface mount ones that cannot handle very high power dissipation. The headphone buffer IC is the LME49600, so the specifications of that can also be useful when estimating the maximum power output into low impedance loads (assuming that the power supply does not become the limiting factor).

Quote:

Originally Posted by Whit3Rav3n 

For measuring you should use a resistor since the headphones have different impedances depending on the frequency. So it is best to use 5w or 10w resistors for the measurement. You can measure the AC Voltage between grund and one channel and the current on the same channel. Then you can calculate the power.

It is unlikely that the maximum undistorted output into 32 Ω is not less than 1 W (the 7 Vrms maximum voltage and 10 Ω output impedance already limit it to ~0.9 W), so 10 W resistors might not be needed.

When using a DMM to measure AC, make sure first that it is accurate at the frequency used for testing. Some DMMs work poorly at audio frequencies.

Quote:

Originally Posted by Whit3Rav3n 

Where did you put the capacitor, did you solder it on the 4-8 pins of the op? I am also using the ad797br but with 49720ha-s in lpf and buffer. Did you use some standard electrolytic or film capacitors. I experimented with some cheap electrolyt 100mF capacitors as bypass and it made quite a difference on the 2132 in the lpf that i used before but i would get some wima film capacitors for the ad797 if it is a noticeable upgrade.

I just soldered it on to pins 4 and 8 on the adapter. I used film capacitors.

Quote:

Originally Posted by Sk1n5 

 

I just soldered it on to pins 4 and 8 on the adapter. I used film capacitors.

I am going to try film capacitors tomorrow, tried to use the cheap electolytic 100mF capacitors today but it sounds exactly the same and heats up exactly the same so it didn´t do anything.

Quote:

Originally Posted by Sk1n5 

 

I just soldered it on to pins 4 and 8 on the adapter. I used film capacitors.

Wima FKP2 Film should be okay right? 

Tim

Quote:

Originally Posted by Whit3Rav3n 

I am going to try film capacitors tomorrow, tried to use the cheap electolytic 100mF capacitors today but it sounds exactly the same and heats up exactly the same so it didn´t do anything.

That's a big difference in capacitance from what I used. Mine are only 0.22uF that magnitude of difference may have an effect.

Quote:

Originally Posted by cssarrow 

Wima FKP2 Film should be okay right? 

 

Tim

I just used polyester film caps I picked up at Radio Shack. Looking into picking up some polypropylene caps to see if it improves performance further, so let me know how that works out for you.

Quote:

Originally Posted by Sk1n5 

 

That's a big difference in capacitance from what I used. Mine are only 0.22uF that magnitude of difference may have an effect.

 

 

I just used polyester film caps I picked up at Radio Shack. Looking into picking up some polypropylene caps to see if it improves performance further, so let me know how that works out for you.

I only used 100uF instead of 100mF but theoretically a big capacitance should not have a negative effect since it only works in this case as a low pass filter for ripple so a bigger capacitor filters out lower frequency ripples witch is pointless after a certain point. I am going to go for 0.22uF film capacitors for the next test.

Apparently ebay only has MKS for 0.22 values.

Time to search for FKP2. Mouser would have some, but shipping is rather expensive.

Tim

Quote:

Originally Posted by cssarrow 

Apparently ebay only has MKS for 0.22 values.

 

Time to search for FKP2. Mouser would have some, but shipping is rather expensive.

 

Tim

But then since it is only for power supply bypassing there is no need to go crazy on the quality because the capacitor is not in the signal path anyway. I think the lme49720/10 could also use some bypassing, i am going to test it later.