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Headphone adapter for AFTER the amp?

Discussion in 'Amps and Cabs [BG]' started by LutherHeggs00, May 9, 2010.


  1. LutherHeggs00

    LutherHeggs00

    Apr 11, 2006
    Currently have a Genz-Benz Neo-pak 3.5 which does not have the headphone input like the new Shuttle models do. I already own a Raven Labs headphone practice amp, but the output is pretty sterile.

    Is there any gadget that will reduce the output of the amp to my headphones? :confused:

    Thanks in advance.

    :bassist:
     
  2. 6foot5

    6foot5

    Apr 14, 2010
    Ontario, Canada
    Like this?

    [​IMG]
     
  3. Jim C

    Jim C Is that what you meant to play or is this jazz? Supporting Member

    Nov 29, 2008
    Bethesda, MD
    Had the same idea but with a different amp.
    Bassman Paul had the answer and it's pretty easy to build as shown here:

    http://www.talkbass.com/forum/showthread.php?t=615414&highlight=headphone

    I've tried this box (which reduces power amp output to headphone input via 5 watt resistors) with an SWR and a LMII and thought the sound to also be sterile.
    Always wanted to try / buy a Raven Labs box but think the next time I get the urge I will just buy a small Mackie mixer. Just saw a tiny little thing at Best Buy with 2 bands of EQ and RC inputs with a stereo headphone out for something like $50.

    I've got enough spares to build one of these boxes for cheap if you get the itch but it didn't make me all that happy with the tone.
     
  4. hasbeen

    hasbeen Commercial User

    Sep 23, 2004
    Vice President, KMC Music. Warwick U.S. distribution, Ampeg distribution
    have you tried your headphones in the effects send?

    Or..in the D.I? If you choose "post eq", you can adjust the tone and volume.
     
  5. synaesthesia

    synaesthesia

    Apr 13, 2004
    UK
    Feed the effects out into the input of your Raven labs unit.

    done.
     
  6. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa, Product Support-Genz Benz
    Unfortunately the FX send or DI won't have enough drive capability for any but the very high impedance headphones/buds (not at all common).

    The correct way to do it is the way (on the NeoPak) is the way Bassman Paul said (there are more sophisticated ways but that will work).

    Do NOT do this on any of the class D amps as what is normally assumed to be ground and common are not ground or common. You could end up letting some magic smoke out. The shell of the "headphone adaptor" would also have as much as 100 volts on it, so it's not safe either. Same applies to any amp using a bridged output.
     
  7. Jeff Scott

    Jeff Scott Rickenbacker guru.......... Supporting Member

    Apr 11, 2006
    Really? If it is the PHA-1 I'll buy it off you if you really don't like it.
     
  8. hasbeen

    hasbeen Commercial User

    Sep 23, 2004
    Vice President, KMC Music. Warwick U.S. distribution, Ampeg distribution
    Really? The Raven Labs unit is a powered, headphone "amp".
     
  9. Jim C

    Jim C Is that what you meant to play or is this jazz? Supporting Member

    Nov 29, 2008
    Bethesda, MD
    The sound (with decent Sony MDR-7506 headphones) is quite dry and strident; not just anaylitical like when wearing headphones in the studio
    Very percussive tone with just a fundamental note and very little harmonic richness.
    Was thinking that maybe impedance is coming into play as this doesn't happen when using even a cheap mixer.
    Your thoughts .....
     
  10. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa, Product Support-Genz Benz
    Was referring to direct driving headphones or buds directly from those jacks.

    There are some line drivers that exist that can directly drive some headphones, but not at all common in the MI industry. Some pro audio and recording preamps have this kind of capacity, but again it's a pretty low percentage.

    If driving the headphone amp, then the DI or line ouots would be suitable, but I thought the idea was to use the speaker outs which I would not recommend going into the headphone amp with any speaker out and ESPECIALLY with any of the new class D or bridged amp products as magic smoke emission is a likely result.

    Trying to be cautious as there are many lurkers who see this stuff and try it on their own withouot appreciating all the details and potential pitfalls.
     
  11. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa, Product Support-Genz Benz
    I don't know enough about your headphone amp to know if that's the issue or not. The 7506 is a full range headphone, the response of it is quite wide compared with a bass cabinet. I would expet that you might want to roll off some high end when using cans. This would apply to most situations like this.
     
  12. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa, Product Support-Genz Benz
  13. Bassmec

    Bassmec

    May 9, 2008
    Ipswich UK
    Proprietor Springvale Studios
  14. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa, Product Support-Genz Benz
    Before hooking any class D or bridged amp up to a device like this, verify with the manufacturer that the amp input is fully floating and there is no connection between the speaker "-" or "ground" input and any audio ground anywhere else including the direct out to the PA. If this is overlooked, it's quite possible that you could severely damage either the power amp, the console or both.

    On many new amps, neither speaker output terminal is connected or referenced to audio ground and any inadvertant connection to ground through a device like this, or even a direct box, shorts 1/2 of the bridge and can cause expensive failure. This is becoming more common wiith many manufacturers so beware!!!
     
  15. Bassmec

    Bassmec

    May 9, 2008
    Ipswich UK
    Proprietor Springvale Studios
    I would'nt connect a class D amp to it myself! Its not that the ground isn't fully floating or that it presents any danger to the class d amp at all.
    Its because I have very very good taste.:D
    PS My full original 2U Motherload, reassuringly cost more last century than your most expensive amp costs today.:bassist:
     
  16. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa, Product Support-Genz Benz
    My comment has nothing to do with taste, but was intended to prevent othey folks who might be followingthis thread from doing something that "seems" good on the surface and then damaging their amp. It's being a good steward of accurate information.
     
  17. My little box will also work with a Class D amp however if the amp has a bridged output stage, as I understand some GB products do, then a speakon would be the preferred connector to the amp. A plastic head phone socket would be a good idea too. Sleeve to -1 and common of the resistors to +1.

    Paul
     
  18. agedhorse

    agedhorse Supporting Member Commercial User

    Feb 12, 2006
    Davis, CA (USA)
    Development Engineer-Mesa, Product Support-Genz Benz
    Correct. Many amps that contain class D technology also utilize a bridged output stage. There are some benefits exclusive to class D that justify this.

    Whenever a device that contains ground referenced non-floating electronics is connected to the output of a class D or conventional amp that utilizes any kind of bridged output stage, the speaker "-" is not at ground so when connected to a true ground via the electronics in the box, large currents will flow to ground damaging things on it's way. Expensive things usually.

    This is becoming a big deal in the PA world, people inadvertantly taking a speaker level signal through a DI and with pin 1 connected through suddently the console's grounding system is looking at as much as 10-20 amps of fault current before something opens up. Here, the costs can be astoundingly high depending on the console being used.
     
  19. Jim C

    Jim C Is that what you meant to play or is this jazz? Supporting Member

    Nov 29, 2008
    Bethesda, MD
    Paul,
    You're box attenuated the signal perfectly but the sound was not that rich and very strident with both an SWR SM400 and a LMII
    Could this be a headphone impedance issue or is this as good as it gets?
    Just confused as even an inexpensive PA mixer sounded better
     

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