Question How do I connect my Headphones with my turntable?

Discussion in 'Hi-Fi Stereo Systems & Separates' started by amerbikic, Apr 15, 2019 at 1:53 PM.

  1. amerbikic

    amerbikic
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    I have a Rega RP1 turntable connected to a Rega Elex-R amplifier, and I want know if I can connect my Sennheiser Momentum 2.0 over-ear headphones directly into the amplifier without buying a headphone-amp.

    Is that possible? I have the AudioQuest DragonFly Red portable DAC that I use frequently with my smartphone, but not sure it that is sufficient or even feasible with my hifi-system?

    My initial thought was to connect my 3.5mm headphone cable into a female 3.5mm/RCA adapter, and connect the RCA-end into one of the amplifier’s outputs - would that work?

    Appreciate any advice or helpful information.
     
  2. amerbikic

    amerbikic
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    Elex-r.jpg
    That's the back of the amp
     
  3. gibbsy

    gibbsy
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    No. You will need a standalone headphone amp. You would connect the headphone amp to the 'record out' RCA. This would then allow the headphone amp to control the volume. You would though need to turn the volume right down on the Elex otherwise the speakers would be in use. Using the volume control on the Elex will not influence the audio to the headphone amp at all.

    Although I have a Elicit-R which has a different set of RCAs for the headphone amp to fit into I did audition a Lehmann Linear headphone using the Elex and it was a very simple connection and use. I also took my Marantz SACD player with me and a pair of Oppo PM1s and the Elex didn't colour the sound at all, same as the Elicit.

    It's a bit of a pain having to power on both the Rega amp and the Lehmann but the benefit of better audio is well worth it.
     
  4. dannnielll

    dannnielll
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    I am going to disagree with the venerable Gibbsey. There is a way, its very cheap and it requires a little DIY.
    It involves getting 4 resistors and a little bit of wiring... Soldering is preferable but optional. . The sequence needs to repeated for each channel.. it means getting a head phone extension cable and cutting off the end and stripping the two channels of wiring .. the left and right channels... giving 4 wires in total.
    For each channel you will need two resistors a big value one ,say 68 ohms and a small value one say 2.2 ohms. . .. exact values are not important but should be in this range and ratio. Ideally the 68 ohm resistor will be a power resistor of 5 watts rating. . The rating of the small one is irrelevant.
    Connect one end of the big resistor to the red or + speaker terminal post for the left channel
    Connect one end of the small value resistor to the other terminal post( black or -) for the same channel.
    Join the two free ends of the resistors together.
    Connect one lead of the left channel adaptor to the junction of these two resistors.

    IMPORTANT
    Connect the other lead of the left channel adaptor to the black,or - terminal..the same one as the small value resistance is connected to.
    Repeat for the Right channel .

    This will setup out of the speaker terminals a reduced value voltage about 1/30 that which go to speakers, and should be within the range of any headphones. . The exact value is R2/(R1+R2), where R1 is the large resistor value 68 ohm and R2 is the small value 2.2
    All the quality of the expensive amplifier is preserved.
    While soldering will give a nicer job, it can be done using screw connector strip.
     
  5. gibbsy

    gibbsy
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    If it can't be accomplished somewhere along the line using a sledgehammer I'm out. The tool of choice in my firefighting career.;)
     
  6. BlueWizard

    BlueWizard
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    What Dannnielll is getting at is the Power and Voltage out of the speaker terminals is too high for Headphones, so you need a voltage divider to drop that down to a more manageable level. Though putting resistance in series with the signal is not necessarily the best idea.

    First you need to decide what the maximum range is for your Headphones. Then make a voltage divider to drop the voltage down under the rating of the Headphones.

    A Headphone Amp is not necessarily that much money, though if you want one of a quality similar to your Amp, the cost can be considerably higher.

    Using this example of a SMSL Headphone amp, the Input should be in the range of 400mv to 2v, and it has a max out of 1 Watt -

    Input Level: 400mv to 2V
    Output power: 150mw / 250ohm, 300mW / 120ohm, 1000mw / 32ohm


    There are devices on the market specifically made for reducing Speaker Level down to Line Level, you could consider something like this.

    https://www.amazon.co.uk/s?k=speake...aker+level+to+lin,aps,292&ref=nb_sb_ss_i_1_20

    Because the Rega Elicit-R has Pre-Amp outs, you could use that to drive a Headphone Amp, set the Headphone Amp to a fixed level, then use the Main Amp Volume Control/Remote to control the volume.

    There are also reasonably price Headphone Amps that have Multiple Outputs -

    https://www.amazon.co.uk/Behringer-AMP800-Channel-Headphone-Amplifier/dp/B000KU87SM/

    This one independently supports up to Four Sets of Headphones. Again it would have to be connected to the Record Out of the Amp or the Pre-Amp Out.

    Other Headphone Amps -

    https://www.amazon.co.uk/Sanskrit-Pha-Headphone-Amplifier-Silver/dp/B017VXQ7OG/

    https://www.amazon.co.uk/TPA6120A2-Stereo-Headphone-Amplifier-switch-Black/dp/B06WVBLTZJ/

    Here is one from REGA at a somewhat modest price -

    Rega EAR MK2 Headphone Amplifier

    And a few others -

    Musical Fidelity LX2-HPA Headphone Amplifier

    Marantz HD-DAC1 Headphone Amplifier and DAC

    Naim Headline 2 Headphone Amplifier Black

    Again, if you set the Headphone Amp to a Fixed Level, you can connect to the Amp's Pre-Out and continue to use the Amp's Volume/Remote Control.

    As an Alternative, though perhaps less than ideal, there are MANY MANY Bluetooth Headphones on the market today. Thousands to choose from. Put a Bluetooth Transmitter on the Amp, and listen using Bluetooth Headphones.

    The above REGA Headphone Amp should be of similar quality to your Amp, and cost a somewhat modest - £199.

    Steve/bluewizard
     
  7. BlueWizard

    BlueWizard
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    Regarding the Voltage Divider. The peak voltage output of a 72w amp is about 34v. That means to reduce that to under 2v per the SMSL Headphone Amp, you need to divide the signal down by a factor of 17 or greater. Likely something like 20x to 25x would be functional.

    The resulting load has to be high enough that it doesn't appreciably load the amp, but low enough to be practical.

    If it possible to make a L-Pad, level reducer, that is impedance matched. That is, for example if you have 32 ohm headphones, the amp will see 32 ohms even though your have resistors in the path. Here is a link to a calculator for Impedance Matched Attentuator.

    Crossover Design Chart and Inductance vs. Frequency Calculator(Low-pass)

    Unfortunately the reduction is in dB, which is not impossible but difficult to convert to Voltage Ratios. Scroll to the bottom until you see this title - L-pad (Speaker Attenuation) - enter the Impedance you want to match, and the amount of attenuation you want, and it will give you the resistor values. It also shows a diagram of how the resistors should be wired - one in Series, one in Parallel.

    For what it is worth, this is how Power and Voltage Ratios are converted into dB values -

    dB = 20 log(Vo/Vi)

    dB = 10 log(Po/Pi)

    Steve/bluewizard
     
  8. dannnielll

    dannnielll
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    I could agree that normally using resistances could be a poor idea, however in this case, and with the values I have suggested, there will be no problem. The source impedance driving current into the headphone is 2.2 ohm ,which is much smaller than the 32 ohms of the headphone. So it looks like a voltage source
    One does not want a matched impedance load, for this type of circuit as we want the voltage source to control the movement of the diaphragm for good DF.
     
    Last edited: Apr 15, 2019 at 10:35 PM
  9. BlueWizard

    BlueWizard
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    An impedance matched voltage divider, assuming 32 ohm headphones and a 20dB reduction would require -

    Crossover Design Chart and Inductance vs. Frequency Calculator(Low-pass)

    R1 (series) = 28.8 ohms
    R2 (parallel) = 3.6 ohms

    Typically with these odd values, you simply use the closest standard resistor value.

    If we want to reduce 34v down to say 1.5 volts, then we can apply the formula to determine the dB of reduction.

    For Voltage -

    dB = 20 Log(Vo/Vi) = 20 Log(1v/34v) = -31dB

    dB = 20 Log(Vo/Vi) = 20 Log(1.5v/34v) = -27dB

    dB = 20 Log(Vo/Vi) = 20 Log(2v/34v) = -25dB

    If we use Power -

    dB = 10 Log(Po/Pi) = 10 Log(1w/72w) = -18.6dB

    So, if nothing else that gives you a working range for Impedance Matched Voltage Dividers (L-PADS).

    Steve/bluewizard
     
    Last edited: Apr 16, 2019 at 7:00 PM
  10. dannnielll

    dannnielll
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    Steve, if you were concerned about loading the amplifier... Which realistically might possibly matter only if the output was transformer coupled, one would simply get a 8ohm 100watt resistor in series with a 0.1 ohm resistor. And feed the headphone from across the 0.1ohm resistance. Getting a 0.1ohm resistance is difficult ,but just a length of thin wire will do...
    Likewise getting 100 watt resistors are uncommon outside auto shops and lighting . But since amplifiers are rarely at full power, a 5watt 8.2ohm or 6.8ohm will probably be o k.
     
  11. BlueWizard

    BlueWizard
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    If you are going to do it, it doesn't cost any more to impedance match the L-Pad Resistors.

    R1 (series) = 28.8 ohms
    R2 (parallel) = 3.6 ohms

    The nearest standard values are either 27 ohm or 30 ohms - R2 - 10w, 5%, Wirewound -

    Jantzen Audio 002-0238 Jantzen 27,00 Ohm superes resistor 10W 1% | Loudspeaker freaks

    Europe Audio EA-L10W-30R Ceramic 30,00 Ohm resistor 10W 5% | Loudspeaker freaks

    The nearest to R2 would be - 3.6 ohms, 10w, 1% -

    Jantzen Audio 002-0190 Jantzen 3,60 Ohm superes resistor 10W 1% | Loudspeaker freaks

    Total cost for the 2 resistors = €4.04.

    But a Speaker Level to Line Converter and a Headphone Amp probably make the most sense. Save a lot of wiring.

    Keep in mind for the Resistive Dividers, you are probably going to need the Resistors, Wire, Electrical Solder, a Soldering Iron, a Box, and assorted Connectors to attach to the Box. Then the time and effort to build it.

    But in principle you are right, it doesn't necessarily need to be impedance matched.

    Steve/bluewizard
     

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