I saw this link and alot of audiophiles speaking about unable to drive a 600ohm headphone with a an ipod?
Got this info from the link.. NwAvGuy: Headphone Impedance Explained
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WHY IMPEDANCE MATTERS: Headphone sources generally put out very different amounts of power into different headphone impedances. For example the Clip+ portable player can put out 16 mW into 16 ohms but only 0.8 mW into 300 ohms. The FiiO E7 can put out over 100 mW into 16 ohms but only 2.8 mW into 600 ohms. And some sources are not as compatible with low impedances such as the Mini3 and FiiO E9.
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so why does this happen or the reply above states only regarding the power output in 600ohm but what is not getting sufficient is it voltage or current or both.
Can the wire amp drive the 600 ohm with ease?
Got this info from the link.. NwAvGuy: Headphone Impedance Explained
_______________________________________________________________________
WHY IMPEDANCE MATTERS: Headphone sources generally put out very different amounts of power into different headphone impedances. For example the Clip+ portable player can put out 16 mW into 16 ohms but only 0.8 mW into 300 ohms. The FiiO E7 can put out over 100 mW into 16 ohms but only 2.8 mW into 600 ohms. And some sources are not as compatible with low impedances such as the Mini3 and FiiO E9.
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so why does this happen or the reply above states only regarding the power output in 600ohm but what is not getting sufficient is it voltage or current or both.
Can the wire amp drive the 600 ohm with ease?
Power = U^2/R
for a given voltage the higher the R the lower the P.
600-ohm is greater than 16-ohm by 37.5 times, therefor you get 1/37.5 as much power from a player designed to drive 16-ohm phones.
because the sound pressure level is directly related with power the headphones get the higher impedance phones generally speaking sound weak driven by a player designed to drive low impedance phones.
in order to obtain the same power on high impedance phones, obviously one has to hit them with higher voltage.
for a given voltage the higher the R the lower the P.
600-ohm is greater than 16-ohm by 37.5 times, therefor you get 1/37.5 as much power from a player designed to drive 16-ohm phones.
because the sound pressure level is directly related with power the headphones get the higher impedance phones generally speaking sound weak driven by a player designed to drive low impedance phones.
in order to obtain the same power on high impedance phones, obviously one has to hit them with higher voltage.
You also need to know the sensitivity rating of the headphone in either dB/mW or dB/V from the headphone's specification sheet. Then you can plug the numbers into this handy spreadsheet at the link in the top of this posting by Rob Robinette over on Head-Fi:
Headphone Power Calculator Spreadsheet - Head-Fi.org Community
to see what voltage and currents you will need to hit 120dB, 90dB, or other sound pressure level. Compare that vs. whatever power rails you are using, or plan to use, with opc's Wire.
If the headphone's spec sheet sensitivity is given as dB/mW then put a zero in the spreadsheet's input box for dB/V sensitivity, or vice versa. If the manufacturer doesn't specify units on the sensitivity (happens a lot it seems) try assuming dB/mW for older models and dB/V for newer ones.
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yes right said so if we take a 600ohm imp headphone with .5W of power input.
Here the math goes so 0.5 = V^2 / 600 = 17.32V to drive it with full potential.
but the SE or BAL version of wire amp can do that output voltage?
Isn't impedance of HD 800 300 Ohms? Thus 12.25Vrms for max. input power as per data sheet.
With it's sensitivity of 102dB/1Vrms 12.25Vrms would be 123dB sound pressure level. Not sure you really want to listen to this
Impedance raises to 600 ohms at certain frequencies..
ok according to the Final schematic...
http://www.diyaudio.com/forums/atta...e-headphone-amplifier-pcbs-wire-final-sch.pdf
Few doubts
1. What values in the balanced out version in page 1 and in page 3 sets the gain?
Page1: is it 1+ (R2/R1)?
Page3: is it 1+ (R21/R22)?
2. At the input does OPA627 performs as good as 49990? to drive a 600 ohm headphone?
3. I need an output of +/-14V for the input of 0.5V of input so gain of 22 will be amp be stable? This is just to drive the high impedance headphones with full slam. Or the 4x gain is sufficient enough?
FYI!
The 25VA, 12V AnTek toroids are back in stock and going fast:
AN-0212 - 25VA 12V Transformer - AnTek Products Corp
The 25VA, 12V AnTek toroids are back in stock and going fast:
AN-0212 - 25VA 12V Transformer - AnTek Products Corp
It is not a schematic error... those are definitely the correct values for a unity gain amplifier. R15 and R19 were not originally the correct value and need to be 10k for unity gain.
This breaks down as follows:
R13 and R14 form an L-pad that gives a gain of 0.909
The gain of the amplifier section is 1+(R16/R15) which is 1+(1k/10k) or 1.1
The two together mean you have 0.909*1.1 = ~1
The amp was measured with a gain of 1 using exactly what is show in the schematic, but would be perfectly fine with a higher gain if needed. The noise floor might go up slightly, but what's show in the measurements is just the AP noise floor, so it might not even be a measurable difference if the gain is kept around 2x or 3x.
After using this amp and measuring it, I would actually agree that it's the only one of the amps you could really make a case for having more gain with. Many SE sources don't have much drive, and it might be reasonable to up the gain to 2x in some cases. For example, the AP measurements stop at 7.2VRMS since that's the highest voltage the generators can do in SE mode. This amp is good for roughly 9.2VRMS which might be more attainable with a gain of 4x if you really need all that voltage swing.
For a gain of 2x change R15 and R19 to 833 ohms
For a gain of 3x change R15 and R19 to 435 ohms
For a gain of 4x change R15 and R19 to 295 ohms
Cheers,
Owen
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Hello Owen,
Guess I missed something. Believe the SE-SE pcb does not have a R19 resistor. Unless topic switched to one other than SE-SE pcb. What resistors
need to be changed to get 2x & 3x gain for the SE-SE version?
Thanks,
Greg
This breaks down as follows:
R13 and R14 form an L-pad that gives a gain of 0.909
The gain of the amplifier section is 1+(R16/R15) which is 1+(1k/10k) or 1.1
The two together mean you have 0.909*1.1 = ~1
The amp was measured with a gain of 1 using exactly what is show in the schematic, but would be perfectly fine with a higher gain if needed. The noise floor might go up slightly, but what's show in the measurements is just the AP noise floor, so it might not even be a measurable difference if the gain is kept around 2x or 3x.
After using this amp and measuring it, I would actually agree that it's the only one of the amps you could really make a case for having more gain with. Many SE sources don't have much drive, and it might be reasonable to up the gain to 2x in some cases. For example, the AP measurements stop at 7.2VRMS since that's the highest voltage the generators can do in SE mode. This amp is good for roughly 9.2VRMS which might be more attainable with a gain of 4x if you really need all that voltage swing.
For a gain of 2x change R15 and R19 to 833 ohms
For a gain of 3x change R15 and R19 to 435 ohms
For a gain of 4x change R15 and R19 to 295 ohms
Cheers,
Owen
------------------------------
Hello Owen,
Guess I missed something. Believe the SE-SE pcb does not have a R19 resistor. Unless topic switched to one other than SE-SE pcb. What resistors
need to be changed to get 2x & 3x gain for the SE-SE version?
Thanks,
Greg