HELP - Digital piano headphones output signal is low and noisy when connected as line

Discussion in 'Tech Talk - Electronic Repair Modifications DIY' started by Garygo, Apr 18, 2018.

  1. Garygo

    Garygo Active Member

    Apr 18, 2018
    Hi all,
    Looking for some help here...

    I have a digital piano Yamaha YDP-163 which has 2 headphone jacks as audio outputs. Sadly, no AUX OUT or LINE OUT jacks so only headphones.
    When plugging a single pair of headphones to either of the headphone jacks, the audio signal is clean, clear and loud with very good signal to noise ratio.
    Now, i wish to be able to record audio from this piano into my PC using RME Fireface 400 inputs.

    Since the headphone jacks are 1/4 TRSF i need a breakout cable to split L and R signals - means a split from 1/4 TRSF to dual 1/4 TS (Unbalanced) connectors
    I have tried to search over the internet for a high quality cable for that matter (low noise, good shield, good plugs) and came across with this one and decided to buy it:

    Mogami GOLD INSERT TS-12 Insert Cable, 1/4" Straight TRS Male Plug to Dual 1/4" Straight TS Male Plug Send/Receive Connectors, Gold Contacts, 12 Foot Mogami GOLD INSERT TS-12 Insert Cable, 1/4" Straight TRS Male Plug to Dual 1/4" Straight TS Male Plug Send/Receive Connectors, Gold Contacts, 12 Foot: Musical Instruments

    Pretty expansive cable if you ask me, but i figured - Mogami audio wire and Neutrik connectors - Looks like a great high quality cable to capture the great sound of my piano.

    So the cable arrived and i connected it but sadly I’m having 2 issues with it:
    1. Audio signal is too low
    2. Very audible noise floor

    Audio signal is too low when monitoring inputs in RME Fireface 400 - even if i crank up the piano master volume to MAX, the signal is still too low.
    I tried increasing the LINE IN volume, and also tried activating the LINE IN inputs as INSTRUMENT IN mode to have more gain – Ok so the signal is louder now but now such increase involve noise.
    Sp all possible gain increase alternatives via RME Fireface 400 lead to increase of the noise floor which is not acceptable.
    The noise is somewhat not a typical hiss or hum but rather soft rapid “clicks” (for the lack of a better term) that are audible especially when increasing the volume in my audio interface.
    Decreasing the piano master volume to MIN has no effect on the noise. Also, when powering off the but leaving the cables connected still introduces the same noise.

    As for the noise - I’m beginning to think it might be an issue with the cable. I didn’t pay too much attention to the purpose of the cable - Insert cable for send/receive loop effects, but rather thought that the wiring and the connectors is exactly what I need.
    Is there a possibility that the cable is not compatible for stereo breakout duties ? Maybe that audio noise is a result of using the cable in different direction as opposed to what the cable intentionally was meant for ?

    If the audio signal level capture would have been very high to begin with I guess that lowering the Fireface line inputs or even using the built-in PADs to attenuate the signal would improve the signal to noise ratio.

    I just made a quick check:
    My headphones are AKG K240 Studio (Not MKII) – Rated impedance – 55 Ohm
    RME Fireface 400 Line Ins jacks – Rated impedance – When used as “LINE IN” inputs – rated as 10 kOhm, When activated as “INSTRUMENT IN” inputs – rated at 470 kOhm.

    So my main concerns:
    Is the low audio signal captured in RME is due to impedance mismatch ?
    Is there an issue with my audio interface ?
    Is there an issue with the mogami audio cable ?
    Is the mogami audio cable I purchased may not be intended for such use ?

    I tried to search google for similar issues.. most left unanswered ultimately…

    Such a shame that I can’e record my piano in this current situation…Will be glad to hear opinions and suggestions

  2. Garygo

    Garygo Active Member

    Apr 18, 2018

    I just tested another cheapo Y-cable that i managed to grab.
    It introduced the exact same issue.

    So i can rule out the cable issue.

    One interesting point - I just noticed that if i minimize RME Fireface mixer, the soft clicking noise is almost eliminated but there is still a noise floor and the signal is still low (hence bad signal-to-noise ratio).
    Also harddrive seeks seem to introduce some noise.

    Looks like shielding issue; the cable picks up interference from the surrounding electronics (flash elements on screen, harddrive seeks)

    I was quite sure the Mogami cable i use "should" be built of high quality materials, including the shield inside.
    But maybe that's pure limitation of the unbalanced connectivity. Go figure...
    The Mogami cable i use now is 12 feet long. Not too long but not extremely short either.

    One more thing - regarding the low signal volume:

    I read somewhere:
    "..Balanced connections reduce noise but the signal level WILL be less if the recording interface is balanced and you use an unbalanced signal.."

    And from my RME FF400 guide:
    "..The Fireface has balanced line inputs as 1/4" TRS jacks on the back of the unit.
    The electronic input stage is built in a servo balanced design which handles unbalanced (mono jacks) and balanced (stereo jacks) correctly, automatically adjusting the level reference.."

    What do you guys think ? Is there any workaround for this issue ?
  3. Boswell

    Boswell Moderator Distinguished Member

    Apr 19, 2006
    Home Page:
    From what you say, you have the correct type of cable and are connecting it up correctly. The line input jacks on the FF400 are true differential inputs, so will handle either balanced or unbalanced signals without quality loss. I'm assuming you have tried connecting something like a portable CD player or a mobile phone (both via a 3.5mm to 6.25mm adaptor), and respectable levels and quality are received at the FF400. It would be normal to have to increase the FF400 line input gain above the default +4dBu setting.

    I've never seen the type of problem you describe with a keyboard, but I was once called in to diagnose something similar on a computer motherboard 3.5mm headphone output. The motherboard would drive headphones without a problem, but gave virtually no signal when feeding a hi-fi stereo input. It turned out that the motherboard monitored the impedance of whatever was connected to its jacks and used the result to make unwanted adjustments to what was sent or received from the connector. I demonstrated that by using a Y-splitter and plugging both the headphones and the hi-fi into it, a strong signal was received at the hi-fi. Rather than leaving headphones squawking on the floor, I made up an adaptor cable with a couple of 33 Ohm 1W resistors soldered from the signal lines to ground, and all was well.

    I'm not saying that this is necessarily your problem with the keyboard, but in order to break the problem down, I do think it's worth experimenting with a 6.25mm TRS Y-piece feeding the headphones and the FF400 inputs at the same time. To ensure that you outwit the keyboard, I would use an external Y-piece for this test rather than use both the keyboard's headphone jacks. If the test makes no difference, we can take it further from there.
  4. pcrecord

    pcrecord Quality recording seeker ! Distinguished Member

    Feb 21, 2013
    Quebec, Canada
    Home Page:
    First, you can't use a TRS on a TR connector. If you have TRS to TR connection to make, use a mono TR cable at both ends.
    Aux out and Line out aren't properly amplified for headphones. So your solution would be to use the realtime mixer of the FF400
    Connect the keyboard line out to the Fireface 400 line-in inputs and in totalmix make sure those inputs are redirected to the FF400 headphone output.
    Just come back with the results and we will see what to do next.

    BTW, if you want to connect more than one headphones to the FF400, use the line outs to a headphone amp and assign it in totalmix acordingly
  5. dvdhawk

    dvdhawk Well-Known Member

    Dec 18, 2008
    Western Pennsylvania, USA
    That is indeed an expensive Insert cable. All other things being equal, I would have also expected that to work as you intended.

    From a quick scan of the manuals it appears the YDP-163 is equipped with a USB port for a variety of uses, including; "as a controller and/or sound source with a variety of music creation applications." And according to the Computer-related Operations guide for the YDP-163, "You can record your keyboard performance as audio data to a Music Production software on your computer", or "you can record your keyboard performance as MIDI data", using the USB port. You may, or may not, need to install the correct drivers for it to work properly.

    Please let us know if there any new developments.

    Good luck!
  6. paulears

    paulears Well-Known Member

    Feb 7, 2014
    Lowestoft - UK
    Home Page:
    The snag here is an impedance mismatch - the keyboard output is design to drive 8-16 Ohm headphones paralleled at a fairly high level - common requirements for sales to schools. The interface is expecting a high impedance load, so your keyboard is seen as an almost short circuit - which lump loads the input circuit drastically reducing the available gain - most of the keys output is lost, so you having to apply too much gain, which lets the very small (usually) hash on the signal line from the keyboard become a problem. First thing I'd try is a proper DI box - where there is a transformer in the circuit. These usually respond better to very low driving impedances than a solid state device.

    Remember - expensive cable is sold under close to false pretences -
    Cable is a passive component, and cheap cable performs just as well as expensive cable. Hence why the cheap insert cable, which is exactly the same as the expensive ones. Try a cheap DI first. One thing to watch out for is that these keyboards rarely record very well. The frequency response is optimised for the small speakers they have and rarely sound convincing in a recording. The noise floor is masked in the headphones and missing from the small speakers - plug into a wider bandwidth device and you start to hear the things you're now discovering made worse by the mismatch.
    pcrecord likes this.
  7. Garygo

    Garygo Active Member

    Apr 18, 2018
    Many useful replies and tips here..
    Thank you all so much for reaching out !
    I will go through each idea you guys pointed out and try it out and will report back.

    Highly appreciated,


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