[jessietigres]

I have some fostex t50rp mk3 (50 ohms) and i have a 30 ohm output impedence amp how do they work i have heard before that you get distortion if you don't use headphones that are 8x the impedence number of your amp

 

[PurpleAngel]

From my understanding (not an expert), Planar Magnetic have less issues when it comes to dealing with a headphone amplifier's output impedance.
How do your headphones sound plugged into the source?

 

[GRUMPYOLDGUY]

I have some fostex t50rp mk3 (50 ohms) and i have a 30 ohm output impedence amp how do they work i have heard before that you get distortion if you don't use headphones that are 8x the impedence number of your amp

 
 
Higher output impedance on the amp means more power is used to drive the output circuitry instead of the drivers in your headphones. 
 
As long as the amp is powerful enough to still drive the headphones at adequate volume, who cares? Maybe if it's for a portable setup, you might have reason to worry about battery life. 

 

[jessietigres]

ok i'm trying it right now and hear no distortion everything sounds right but it just gets to a listenable volume no more

 

[GRUMPYOLDGUY]

  ok i'm trying it right now and hear no distortion everything sounds right but it just gets to a listenable volume no more

 
 
So you need an amp with more gain... maybe.
 
What is your source, and do you have unity gain through the digital side? What is the preamp output level and can it be gained up? 

 

[PurpleAngel]

  ok i'm trying it right now and hear no distortion everything sounds right but it just gets to a listenable volume no more

 
What amplifier are you using and what sources are connected to the amp?

 

[buke9]

ok i'm trying it right now and hear no distortion everything sounds right but it just gets to a listenable volume no more

Had a pair of Alpha Dogs (based off of the T50's ) and out of a Fiio X-1 was barely loud enough adding a Fiio E 12 to the mix was a holy crap moment for me. They just needed more power.

 

[jessietigres]

It's a serenade pro dsd amp/dac combo i'm planning on buying a k5

 

[PurpleAngel]

It's a serenade pro dsd amp/dac combo i'm planning on buying a k5

 
Have you maxed out the volume setting on whatever computer the Serenade Pro is plugged into?

 

[jessietigres]

Yeah full volume on everything

 

[GRUMPYOLDGUY]

Yeah full volume on everything

 
 
I think the DAC/amp is the problem... Check my math please...
 
Headphone impedance is 50Ohm
DAC/amp output impedance is 30Ohm
Loss from driving the output is about 4dB
Max output of DAC/amp is 0.3Vrms (from spec)
Padded down 4dB is ~0.189Vrms
Headphone sensitivity is 92 dB SPL / mW, again impedance is 50Ohm... That's 105 dB SPL / 1Vrms
So you should expect no more than ~90.5 dB SPL
 
And that is what is *mathematically achievable* based on some nominal values, which may or may not have been measured under the same conditions. Assuming the test conditions are at least consistent, you could expect a little less than that.
 
It's not quiet, but by no means is that extraordinarily loud either. Try a different DAC/amp... I would suggest one with a gain switch. In case you pick up some sensitive IEMs or something in the future.

 

[jessietigres]

I have more amps actually what i like about the serenade is the dac the amp just outputs 300mv so... i think ill buy a fiio k5