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Fostex new RP headphones - T50RPmk3, T40RPmk3 and T20RPmk3

Discussion in 'Headphones (full-size)' started by sopp, Apr 15, 2015.
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  1. IBJamon
    So I have been trying to understand the impact of output impedance on headphones, and from what I am reading, it should have a minimal impact on Planars because of a basically resistive impedence profile. Is that not the case with the Fostex?
    kintsaki likes this.
  2. stellarelephant
    Alright, you all talked me into it. I hacked apart a cheesy 3.5mm/RCA adapter I had lying around and,
    after some trepidation plugging my nicest cans into the 100WPC speaker terminals...
    BEAST MODE!!! :beyersmile:

    Yes... It is waaay better in every way than the same unit's dedicated headphone circuit. Smoooother. Flatter frequency response. The harsh edginess in the treble is just gone. Poof. Soundstage and detail are improved, but in a relaxed and confident way. Distortion has obviously been lowered, to such a degree that I'm sure measurement gear would confirm this. Bass is solid and cleaner. Everthing is cleaner and smoother. Wow. A small amount of audible hum between songs with my Onkyo. Everything else is positively, gloriously transformed. I'll never look back. Time to build a nicer banana->3.5mm adapter!

    Thanks, Kintaski, for encouraging me to try this, and IBJamon for jumping in first!! :beyersmile:

    photo_2018-02-15_23-07-04.jpg photo_2018-02-15_23-07-08.jpg photo_2018-02-15_23-07-13.jpg
  3. IBJamon
    I'm glad it's working so well! The nice thing about the Emotiva (other than the price - only $229!) is that is doesn't require hacking up an adapter - you simply install jumpers inside the case, and it does exactly the same thing - with the benefits of still being able to use it as a speaker amp (it turns off the speakers when you plug it in).

    Here's the product page:


    It's absolutely incredible with my Fostex. I have other headphones so I removed the jumpers for now - but they definitely are going back before long, once I figure out what I'm going to do so I can keep using the amp with other headphones also. :wink:
    trellus and kintsaki like this.
  4. stellarelephant
    I could do jumpers inside the Onkyo monster as well. But I do have speakers to feed too...I like the flexibility of an adapter. The Emotiva is a nicer stereo amp to begin with...I am quite familiar with it ever since Steve Gutenberg and John Darko hyped it up (rightly, I think) a few years ago. Do you get any hum with yours in beast mode?
    kintsaki likes this.
  5. kintsaki
    adapter.jpg 588381-amp_amc_cvt2100a_80wch_lamp_tube.jpg
    trellus and stellarelephant like this.
  6. kintsaki
    Here is an approximation to a constant zero output impedance amplifier with massive transformers and kt88 tubes
    compliments of Hiroaki himself, costed me 400$ many years ago. Another secret is to avoid usb connections at all cost.
    If you have a Mac use the optical connection to your DAC if you have a PC send the signal to your TV via HDMI
    and then take the optical out from the TV to your DAC. Like this
    PC <HDMI> TV <TOSSLINK> DAC(Sony PHA3> ifi Micro DSD > AMC CVT 2100> Fostex Tx0 RP and my " hg.jpg Smeggy thunder pants" Look for the article "Standing Ovation"
    Last edited: Feb 16, 2018
    Stenso and trellus like this.
  7. stellarelephant
    Yeah my Onkyo has an internal Cirrus DAC and accepts digital coax, optical, and HDMI. I have already discovered that HDMI is much noisier than coax. I get coax from my Mac->Echo Audiofire FireWire interface. I just discovered recently that the Mac itself has optical hidden inside the headphone jack. Haven't tried that yet.
    kintsaki likes this.
  8. kintsaki
    It is Lenz's law you cannot get something out of nothing.

    Planar s like Dynamics are still transducers that convert electromagnetic or electrostatic energy to mechanical energy (not thermal energy) and drive the amplifier crazy (someone needs to push that air and push it real hard... at frequencies ranging from 8 Hz to 65Khz for the He-6 to yield punchy true timbre sound unlike Stax Omega 2 with their tin sounding timbre and lifeless punch sound that went out of business two times because they were never able to design a proper amp for them.)
  9. IBJamon
    I can hear a small amount of hum/hiss that I can hear with more efficient headphones, but not with the Fostex unless it's very loud. If I remember right, I believe I tested it with no source plugged in and it went away, so it was mostly source related (though I would have to re-beast it and check again).

    I believe the amp that Steve and friends hyped up was the original A-100, not the new BasX version (also known as v3 of the A100). The new one has beast mode as a supported configuration through the headphone jack, rather than running plugs from the speaker out terminals.
    EDIT: Nevermind, he did review the BasX version

    I am thinking of making a proper voltage dividing adapter for my other headphones, so that I can continue to use 'beast mode on' for these and the voltage divider for everything else. Out of the box they just use 220Ohm resistors, which can't be the best since output impedance takes a huge hit this way.
    Last edited: Feb 16, 2018
    kintsaki and stellarelephant like this.
  10. stellarelephant
    Brilliant feature. I think this amp is on my wish list now... It occurs to me that anyone with basic soldering skills could rig up a "beast switch" to accomplish this. Any amp with both headphone and speaker outputs is a candidate. Just cut the headphone amp circuit leads from the headphone jack and fly leads over from the main amp circuit. Send both sets through a gang switch to toggle.

    I guess if the amp was intended to remain useful for speaker listening, you might have to have a second switch to change whether the main amp circuit output is routed to the switched jack or the speaker taps.

    I wonder if some type of 3-way switch would work more gracefully to select 1) speaker output 2)regular hp output 3)beast mode.

    Most receivers have a switch in the hp jack to defeat the main amp when headphones are plugged in. One would have to bypass this too.

    Fun to think about. But maybe I should just leave the Onkyo stock so I can sell it and put the $ toward an Emotiva and a DAC. :)
    Last edited: Feb 17, 2018
    kintsaki likes this.
  11. IBJamon
    I have rigged up the impedance match adapter and it sounds glorious! I can't do direct comparisons easily, but it seems to drive the Fostex a bit better (though of course direct drive is still best) and my other headphones have the perfect amount of volume play. This is great! I look forward to showing you all more (and sharing it in the A-100 thread also).
    kintsaki and stellarelephant like this.
  12. stellarelephant
    Cool. Please post a schematic and pics.
    kintsaki likes this.
  13. kintsaki
    Well now that you have the required power it is time to move on to JRiver, DSP processing and and above all to Aqua VST Plugins from Acustica trinity.png 2x.png
    Last edited: Feb 17, 2018
  14. kintsaki
    26910492_10209527323213994_7737912166907134960_o.jpg katie_melua_smile-1920x1080.jpg 2423e2b0461148abb6e366415f5ab410.jpg Enjoy, tonight will be Fostex night!
    Last edited: Feb 17, 2018
  15. IBJamon
    What a terrible, terrible day. I was this close - I had everything working, but when I would close the box, the parts would scrunch and cause a short, so I went to fix that.

    Since then everything broke. Both my 1/4" and 1/8" jacks are now worthless, the switch has a broken peg, and I have about had it right now with this project. I need a break...

    Uugh. Nothing like grabbing defeat from the jaws of victory.
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