Quote: Glad to help out in some way. Related to audio level, I recently have built some basic gear to verify audio specs (typically "A-Weighted in a 20 kHz BW" noise and S/N) of some audio equipment I have. This is a very interesting area and opinions are strong (as you can see from the...

Quote: Assuming roughly that at 60 ohm load, we have ~ max output voltage of 3.3Vrms, then here are some results:   A 2 dB step per volume increment means the output voltage factor is reduced by a FACTOR of 0.794  (or the POWER is reduced by a factor of 0.631).  So, these are the output...

Quote: Yes I agree with that. I think the only useful comparison (and it is only at one frequenc so is really of limited practical use and give a very rough idea of overall "loudness") is the spec'd dbSPL at 1 kHz for either 1 mW or 1Vrms. Being a Physicist, I like to "assume it's a sphere"...

Quote:   Thanks for the useful comments and reference. I'll check it out. dBL as in: "Unweighted sound pressure level is called "linear sound pressure level" and is often written as dBL or just L"  (wiki info). I didn't measure the rms voltage with a voltmeter. I wrote an...

My understanding is that the dBSPL ratings of headphones/iems are ALWAYS given as either dBSPL / 1Vrms (at 1 kHz)  or dBSPL / 1mW (at 1kHz) irrespective of how ear damage threshold values are specified (i.e. if they are A-weighed or not). Is this true?   Also, I was interested in comparing...

According to my HD598 box, the spl is stated as being 112 dB @ 1kHz and 1Vrms. However in several places including a review, I see the spl rated as 112 dB /mW for the HD598. Obviously they can't both be correct with the nominal 1kHz impedance being ~ 50ohm. If 112 dB/1Vrms is correct that...

The main ADC on the X-Fi Elite Pro sound card I use is the AK5394 (123 dB 192kHz/24bit) which is very good for a sound card. At any rate, using a simple loop-back (sound card line-out to line-in) this is my measurement capability (at least based on RMAA which i realize overstates the Xtalk)...

A more detailed frequency response plots comparing E17 and E12:  http://www.jensign.com/FiiOE17/BodePlots Note that the low frequency peak with Bass enabled for the E12 has been moved to higher frequency (~ 50Hz) compared to earlier version.

Quote: I haven't tried that but the L7 line-out adapter for the E7/E17 probably won't work with the E12 since the E12 doesn't have a DAC.  That Creative sound card has a very good line-in A/D which I have characterized and used extensively (although the line-out of that sound card limits...

You can really notice the E12s uneven frequency response, with a slight grade at ~ 1 kHz. Measurements are with 33 ohm loads and with line-in level ~ 1.0Vp and gain adjusted to get ~ 2.5Vpeak headphone output:   http://www.jensign.com/FiiOE17/RMAA/CompareE17E12/Compare_E17_E12.htm

another tidbit ... tested the coax SPDIF input and it is (probably not surprisingly) identical to the optical SPDIF input. This just verifies that there is nothing odd occuring between optical/electrical digital conversion. The RCA/phone-plug adapter provided with the E17 sits with about 1mm+ ...

Quote: Here are some more tests of my E17 for the line-in connection comparing 16bit/44.1kHz with 24bit/96kHz:    http://www.jensign.com/FiiOE17/RMAA/LineIn/ComparisonE17_LineIn.htm Loaded into 33 ohm and at a headphone output level of 1.8Vrms. Unless I misunderstand the InnerFidelity...

I understand about the ground loop. However I'd expect ground loops to only affect the noise floor. However both the SPDIF and USB inputs show much higher distortion levels so that sounds like the DAC part to me. Just a thought.   I should ad that I am not an audiophile by any stretch (as...

Quote: Are the InnerFidelity measurements for the line-in connection?  Are there audio measurements with USB digital input demonstrating difference between no-isolation and isolator for say a "typical" laptop computer? I noticed that FiiO in their product specs (they use Audio Precision...

Thanks for the link to the InnerFidelity measurements and comment on RMAA xtalk lie. Yes I thought that the USB might cause some extra noise. BTW there is no difference in the noise/distortion for the USB case with/without USB charging enabled on the E17. Also, with optical SPDIF input, there...

Some RMAA audio performance measurements comparing line-in, optical S/PDIF and USB modes using headphone loading of 33 ohm:   http://www.jensign.com/FiiOE17/RMAA/ComparisonFiiOInputs.htm Results are discussed at bottom of this page:   http://www.jensign.com/FiiOE17

here is a script calculator I wrote to help calculate dbSPL given either efficiency or sensitivity. It also includes a simple circuit to include any added series and/or shunt resistance (useful for some applications):     http://www.jensign.com/S4/calc.html I originally wrote this to help...

Here is a script headphone dB calculator. Use it to calculate how much volume (for a given impedance headphones) you will loose if you add a series resistor: http://www.jensign.com/Phonesdb/

I think Samsung really missed the boat on this S4 headphone audio output design. If you think about it, had they done proper testing with low impedance buds down to say 12 ohm, they could have done the following easy fix:  - simply add a 10 ohm chip resistor (one per channel) in series with...

Quote: Depending on your headphone impedance, you may be able to go down to 10ohm series resistor and get more volume.  For example if you headset is nominally 12 ohm and you use 20ohm series resistor, you will loose ~ 7.5 dB of level compared to whats available with a direct (problematic)...

Interesting about the noise. I have listened very carefully (but only with 32ohm earbuds and 50ohm Sennheiser) to background noise on my S4 SGH-I337 and it is absolutely quiet at 15/15 volume (paused or playing a digital silence track). This is confirmed by the noise floor in my RMAA...

Quote: It isn't "clipping" which is usually a sign of an output current limiting thing. It is an oscillation (often called a "fuzzie"). For pure sine waves like I tested, it shows at a particular playback volume level but playback of music at a higher "volume level" with different frequency...