[Decommo]

Hello. I am keen to purchase Fostex T50RP MK3 and can anyone recommend budget desktop amp? I heard that it is quite hard to drive and might need strong amp to drive in full capacity. Any help would be greatly helpful.  

 

[wild bill]

  Hello. I am keen to purchase Fostex T50RP MK3 and can anyone recommend budget desktop amp? I heard that it is quite hard to drive and might need strong amp to drive in full capacity. Any help would be greatly helpful.  

 
yes, that is the problem - you really need a strong amp like the $425 Lake People/Violectric G109-A to properly drive it, if you want all of the volume and bass that the mk3's are capable of, or a good serious tube amp, and I am talking about REAL tube amps, the ones with high current and big heavy transformers, not those silly things you see for $200 that just light up some tubes for display purposes.
 
if you are bound to $200 or less, the Claro Halo board that fits into a PC or else the O2 amp would at least allow you to get decent volume and bass in the meantime while you increase your amp fund, but there is no low cost choice that can showcase these headphones like a high current amp with some serious iron (transformers) inside.
 
Wish I had better news for you, but this is just not the headphone choice if you are thinking of a lightweight amp and a tight budget, so forget Schiit as well as any of the budget Chinese amps and any other lightweights, save up for an amp to do these justice, they are pretty remarkable, especially with the fantastic ZMF cowhide pads, and you save so much on the headphones, just put that savings into the amp.

 

[Decommo]

 

  Hello. I am keen to purchase Fostex T50RP MK3 and can anyone recommend budget desktop amp? I heard that it is quite hard to drive and might need strong amp to drive in full capacity. Any help would be greatly helpful.  

 
yes, that is the problem - you really need a strong amp like the $425 Lake People/Violectric G109-A to properly drive it, if you want all of the volume and bass that the mk3's are capable of, or a good serious tube amp, and I am talking about REAL tube amps, the ones with high current and big heavy transformers, not those silly things you see for $200 that just light up some tubes for display purposes.
 
if you are bound to $200 or less, the Claro Halo board that fits into a PC or else the O2 amp would at least allow you to get decent volume and bass in the meantime while you increase your amp fund, but there is no low cost choice that can showcase these headphones like a high current amp with some serious iron (transformers) inside.
 
Wish I had better news for you, but this is just not the headphone choice if you are thinking of a lightweight amp and a tight budget, so forget Schiit as well as any of the budget Chinese amps and any other lightweights, save up for an amp to do these justice, they are pretty remarkable, especially with the fantastic ZMF cowhide pads, and you save so much on the headphones, just put that savings into the amp.

 
Wow.... This headphone is very power demanding. Will Chord Mojo drive T50RP MK3 well?

 

[wild bill]

   
Wow.... This headphone is very power demanding. Will Chord Mojo drive T50RP MK3 well?

 
well not really, but it would definitely make a smartphone go from low volume to decent listenable volume, but there would be no serious rockin-out!
 
also, keep in mind that for less than that kind of money, you could get a proper amp for it like the G109-A or a strong tube amp
 
the key to help figure out if an amp is going drive this headphone properly is to look inside of it for a good size transformer, either toroidal (round doughnut) or traditional, and beefy capacitors - the amps will be physically heavy, so let that be your first clue - the weight

 

[Decommo]

 

   
Wow.... This headphone is very power demanding. Will Chord Mojo drive T50RP MK3 well?

 
well not really, but it would definitely make a smartphone go from low volume to decent listenable volume, but there would be no serious rockin-out!
 
also, keep in mind that for less than that kind of money, you could get a proper amp for it like the G109-A or a strong tube amp
 
the key to help figure out if an amp is going drive this headphone properly is to look inside of it for a good size transformer, either toroidal (round doughnut) or traditional, and beefy capacitors - the amps will be physically heavy, so let that be your first clue - the weight

 
I see. Thank you for your feedback. This may be a dumb question and how about old Pioneer VSX-915-K 7.1 receiver which is to be used to build a home theater? Can this be used to drive this headphone by any chance?

 

[wild bill]

   
I see. Thank you for your feedback. This may be a dumb question and how about old Pioneer VSX-915-K 7.1 receiver which is to be used to build a home theater? Can this be used to drive this headphone by any chance?

Yes, that would be better than most choices, although the G109-A would be much better (class A), the Pioneer VSX-915-K is a good idea for a low cost choice.

 

[peter123]

These "doughnuts" works pretty amazing with my two modded pairs of the T50RP MK2's 

 

 

[wild bill]

Another idea is to use the rear speaker outputs of the Pioneer amp and take four good quality resistors and build a small voltage divider network in order to better match the impedance to the cans (damping factor), this would sound even better than the front panel headphone jack, possibly a huge amount better.
 

 

[MarcoGV]

  Hello. I am keen to purchase Fostex T50RP MK3 and can anyone recommend budget desktop amp? I heard that it is quite hard to drive and might need strong amp to drive in full capacity. Any help would be greatly helpful.  

I find that the O2 drives the MK2 well, certainly to levels that are well beyond comfortable for me!  Mayflower Electronics, which sells modified MK2s and the O2s to drive them, evidently agrees.

 

[silvrr]

 
I find that the O2 drives the MK2 well, certainly to levels that are well beyond comfortable for me!  Mayflower Electronics, which sells modified MK2s and the O2s to drive them, evidently agrees.

I recently had the chance to review the Chord Mojo as part of a loaner program form Todd the Vinyl Junkie and it has similar specs power wise as the 02.
 
Mojo:
Output Power @ 1kHz (600 ohms 35mW) (8 ohms 720mW)
 
O2:
Max Output (33 Ohms) 613 mW (150 Ohms)  355 mW (600 Ohms) 88 mW
 
Compared to my Schiit Lyr2 the Mojo ran out of gas on songs with a low recording level.   The bass fell away and things got a bit harsh on the Mojo while the Lyr was hitting its stride.  My only caution from this is that while both were producing the same volume the character of what was played back was very different.  

 

[cpt000]

Fostex is currently offering a $50 rebate on all rp m3s...
 
http://www.americanmusicandsound.com/en/pages/promos/promo_fostex_50_rebate_RPMK3_2016.html

 

[Armaegis]

  Another idea is to use the rear speaker outputs of the Pioneer amp and take four good quality resistors and build a small voltage divider network in order to better match the impedance to the cans (damping factor), this would sound even better than the front panel headphone jack, possibly a huge amount better.
 

 
The resistor divider (aka L-pad) is for reducing the amount of power sent to the headphones, not for impedance matching. You're actually making the damping factor worse by doing this.
 
The front panel jack is already a divider network of sorts, except missing the R2 (assuming a typical configuration).

 

[wild bill]

   
The resistor divider (aka L-pad) is for reducing the amount of power sent to the headphones, not for impedance matching. You're actually making the damping factor worse by doing this.
 
The front panel jack is already a divider network of sorts, except missing the R2 (assuming a typical configuration).

 
To quote John Woodgate, from the The Loudspeaker and Headphone Handbook (1988) -
 
"Headphone transducers are resistance-controlled, not mass-controlled like loudspeaker drivers above the main resonance. In any case 'damping factor' is largely nonsense - most of the resistance in the circuit is the voice-coil resistance and reducing the amplifier source impedance to infinitesimal proportions has an exactly corresponding effect on damping - infinitesimal.
 
However, the source impedance affects the *frequency response* of a loudspeaker because the motional impedance varies with frequency, and thus so does the voltage drop across the source impedance. This means that the source impedance (including the cable) should be less than about one-twentieth (not one two-hundredth or less!) of the rated impedance of the loudspeaker, to give a *worst-possible change* in frequency response from true voltage-drive of 0.5 dB.
 
The motional impedance of headphone transducers varies very little (or should vary very little - someone can always do it wrong!) with frequency, so the source impedance can be high with no ill effect."
 
------------------------------------------------------------------------------------------------------------------
 
Chu Moy explains it this way:
 
"With loudspeakers, the lower the amplifier's output impedance, the higher the damping factor into the rated load. Damping factor is given as the ratio of loudspeaker impedance to the amplifier's output impedance. As the theory goes, the higher the damping factor, the better the amplifier's ability to control a loudspeaker's low frequency response (when the motional reactance of the system is at maximum), because the low output impedance of the amplifier allows any back-emf generated by the loudspeaker to be absorbed by the amplifier. That theory has been discharged by members of the audio community as unsubstantiated.
 
The IEC 61938 international standard specifies that headphones should be driven by a 120 ohm source - regardless of the impedance of the headphones themselves. If the headphones were designed to this standard, then an amplifier's high output impedance should have little effect on the sound of the headphones. In general, headphones with a flat impedance curve over the audio range will not be affected by high output impedance. For example, in May 1995, Stereo Review published a review of the Grado SR125 headphones. The impedance curve of the SR125s, which have a nominal impedance of 32 ohms, varied from 31 to 36 ohms over the entire 20Hz to 20kHz spectrum. Not all headphones may be as well behaved as the Grados, but neither do they usually have the roller-coaster impedance runs of a loudspeaker. Tube amplifiers (with their high output impedances), it should be noted, have very low damping factors."
 
Current-limiting resistors will increase the output impedance of the amplifier as seen by the headphones. Whether the higher impedance affects the sound of the headphones depends on the design of the headphones. The IEC 61938 international standard recommends that headphones should expect a 120 ohm source (5V rms max.) - regardless of the headphone's own impedance. If the manufacturer followed this standard, the 100 ohm resistor will not affect sound. 
 
A slightly more elaborate scheme (circuit shown below) is to use two resistors as a voltage divider across each channel. Here, the output impedance of the amplifier is lower (essentially the resistance of the two resistors in parallel) and the output voltage is less dependent on the impedance of the headphones. Although the effective output impedance is lower, the amplifier itself sees the voltage divider as a series load (which is good). Begin with R2 = 10 ohms (1/2W) and scale R2 up or down to adjust volume."
 

 

[Armaegis]

   
To quote John Woodgate, from the The Loudspeaker and Headphone Handbook (1988) -
------------------------------------------------------------------------------------------------------------------ Chu Moy explains it this way:

 
The effects of damping factor on headphones is minimal, but are in fact measurable.
 
More critically however, is the effect of headphone impedance when the amp output impedance is too high. With planars like the T50rp which are mostly resistive (ie: the impedance is flat across the spectrum) then this is moot. With dynamics or balanced armature designs however, a fluctuating impedance curve results in an altered frequency response because the headphone load itself acts as a voltage divider. If your source impedance is high, then your frequency response will almost literally follow your impedance curve. The most classic case is with the Sennheiser HD5xx or 6xx family or the Beyerdynamic DTxx0 family who all have impedance humps in the midbass around 100-120Hz (in the case of the Senn HD5xx family, the impedance bump is almost 5x which is rather extreme). Running these headphones off a high output impedance amp (say 10ohm or so) will result in a midbass bloom and a murkier sound. IEMs with multiple drivers/crossovers and whatnots present very strange impedance curves, often with sharp peaks in several areas and rising impedance in the treble. Running those off an amp with a couple ohms output impedance will sound muddy and shrill simultaneously; just a hot mess.
 
Ironically, an output impedance that is very high skews the voltage divider equations enough that your frequency response is actually not as bad as when it is only moderately high*. However, in these cases then the effect of damping on dynamic drivers becomes more apparent.
 
*edit: actually I misspoke, the effects will keep increasing but asymptotically approach a curvature matching the load impedance. Also, you are becoming more and more inefficient since you're dissipating all your power through the dividers rather than the headphone.
 
The IEC standards are incredibly antiquated and originally stem from long distance transmission protocols. You will also find standards dictating 600 ohms as proper headphone loads stemming from old broadcasting/etc requirements where running many loads in parallel without blowing the distribution board was the primary concern. These are all well outdated and serve no place in a modern headphone viewpoint.
 
Also the needs for power are grossly overstated... but I'm tired and don't want to get into that right now.

 

[ExDementia]

For what it's worth, I just picked up a set of MK3 T40RPs and an AudioQuest Dragonfly v1.2 for my work computer, and the teeny little Dragonfly drives them just fine. Max volume is too loud for comfort, and they sound great.
 
I also think the needs for power are very much being overstated.