New Net City - JAMMA speaker wiring (help)

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    • New Net City - JAMMA speaker wiring (help)

      Hi - does anyone know the best/safest way to wire a JVS New Net City for JAMMA, specifically the sound? I have a RiverService JAMMA conversation harness (rs2006.co.jp/e/jamma_harness/index.html) but the sound goes to RCA connectors that are meant to go into the NNC amp, then to the speakers.

      I believe this might create issues because sound is already amplified on the JAMMA board, and it would then be amplified again by the NNC amp.

      I have read that an audio line out converter / high-low converter could work (by lowering sound power into the NNC amp) (ms-line.co.jp/original_hi_low_21hl_20gl.html) but would there be any risk to the JAMMA board (e.g. Somehow the converter stresses the JAMMA board amp)?

      Another option could be to create a connector that takes the RCA connectors from the JAMMA harness and connects directly to the NNC speakers. This would bypass the NNC amp. Is this an option/advisable?

      Any expert advice would be appreciated.

      Thanks
    • Use a line level converter, works just fine and is what I use with all my boards that have amplified stereo (like MVS etc).

      for Jamma (mono) wire the speaker connection from the Jamma edge to both L/R of the Line level, or just wire it to one channel and use a RCA splitter to feed both L/R to your NNC amp
    • PascalP wrote:

      Use a line level converter, works just fine and is what I use with all my boards that have amplified stereo (like MVS etc).

      for Jamma (mono) wire the speaker connection from the Jamma edge to both L/R of the Line level, or just wire it to one channel and use a RCA splitter to feed both L/R to your NNC amp
      Use a line level converter, works just fine and is what I use with all my boards that have amplified stereo (like MVS etc).

      PascalP wrote:


      for Jamma (mono) wire the speaker connection from the Jamma edge to both L/R of the Line level, or just wire it to one channel and use a RCA splitter to feed both L/R to your NNC amp
      Pascal - thanks for the quick reply! Appreciated. Is there anything that can go wrong in the wiring process (e.g. What should i be careful about - particularly if i am wiring both things together for JAMMA)? Is there anything to consider about the type of line level converter itself that might be unique to a NNC/arcade system?

      Thanks
    • nem wrote:

      Personally I would just wire the audio straight to the speakers. Although you do then lose the option to change volume from the control panel.
      + you lose the ability to quickly plug in the line level converter to boards with stereo out like Konami and MVS.
      But also for CPS2/3 it makes sense to keep the amp with RCA in place imo :)
    • Thanks for the advice. I like the idea of wiring directly for JAMMA as this is how JAMMA boards were intended apparently. And the line level converter can be used for stereo boards if i usem in the future.

      I assume RCA female connectors to AMP UP female connectors would be sufficient to bridge the gap between the harness RCA plugs and the speaker plugs? Unless i am mistaken (not the first time)! :)
    • Joe wrote:

      I assume RCA female connectors to AMP UP female connectors would be sufficient to bridge the gap between the harness RCA plugs and the speaker plugs?

      That's right. However, you will want to double check that combined impedance is 8 ohms or over.

      Are you sure the audio output on the RCA connectors isn't attenuated? Check that too.
    • How do you intend to wire Jamma and the amp in parallel?
      Otherwise if you use your amp the speakers are bridged and you can short it out.
      So if you go that route, make sure to completely disconnect the speakers from the Jamma harness before using the amp
    • Nem / Pascal - thanks for the follow-up. It was probably my unclear explanation/lack of coffee. I don't intend to have both mono and stereo set ups wired together, but interchange them with relevant boards. Most boards i own are normal JAMMA so think the most elegant solution is to take the two harness RCA connectors and join them to each respective speaker cable (if i can find the right connectors). That way it will bypass any complexities of the cabinet amp. I lose the cabinet volume control as you say, but this seems more in line with the JAMMA intention. I would assume conbined impedance would not matter in this case as it would be like JAMMA edge going direct to each speaker?

      I dont think the RCA are attenuated on the RS harness - i read on another thread someone looked - but not opened to check myself.

      I have summoned all my artistic might to show this (obviously this would not be wired on the amp, just showing the connection path):
      Images
      • _20200224_115627.JPG

        364.74 kB, 1,918×1,440, viewed 66 times

      The post was edited 1 time, last by Joe ().

    • Another thing to consider is that you need to wire the speakers in series (2x 4ohm = 8ohm).
      If you wire them in parallel it would equal 2 ohms which is not good for your Jamma board’s amp!

      so it would consider a significant rewiring and I would just use a line level like suggested so it is safe, easy, plug n play for both Jamma mono and stereo and you keep volume control :)
      So a win-win if you ask me ;)
    • PascalP wrote:

      Another thing to consider is that you need to wire the speakers in series (2x 4ohm = 8ohm).
      If you wire them in parallel it would equal 2 ohms which is not good for your Jamma board’s amp!

      so it would consider a significant rewiring and I would just use a line level like suggested so it is safe, easy, plug n play for both Jamma mono and stereo and you keep volume control :)
      So a win-win if you ask me ;)
      Thanks Pascal - really appreciate your advice. Something i didn't think of, and a testament to me wasting time at school coloring in maps in geography or reading 17th century poetry, when this is what i should have been studying!

      I am sold on the line converter, but now doubt my wiring prowess. Might tap you for a second opinion on my wiring once i get round to it in a few weeks 'if you don't mind).

      Now you have me thinking of another cabinet i have that might be wired in parallel (was converted from JVS but amp bypassed by this board...). So complex for such a seemingly small issue :) what symptoms would it display? The jamma amp gets a little hot but not much, and the sound seems fine.
    • Well it works till it works :)

      depends a bit on the amp on the Jamma board and how much it can take, heat will be the biggest concern indeed.
      Also depends on the cab, if it has 2x 8ohm speakers that equals 4ohm total, so not that bad as dual 4ohm speaker (= 2ohm total)

      hope that makes sense :)
    • You'll eventually blow your amps on the boards if the impedance is too low.

      PascalP wrote:

      so it would consider a significant rewiring

      However, I'll disagree here. It's not significant rewiring at all. It's super easy to wire the speakers in series. You need two female AMP UP 2-pin connectors to mate with the speaker connectors that normally go to the amp. You wire speaker (+) to the positive terminal of the left speaker. You wire the negative terminal of the left speaker to the positive terminal of the right speaker. You wire the negative terminal of the right speaker to speaker (-). Done.

      Two connectors will need to unplugged and swapped when you want to go from jamma mono to cab amplified stereo. Easy peasy.
    • nem wrote:

      You'll eventually blow your amps on the boards if the impedance is too low.

      PascalP wrote:

      so it would consider a significant rewiring
      However, I'll disagree here. It's not significant rewiring at all. It's super easy to wire the speakers in series. You need two female AMP UP 2-pin connectors to mate with the speaker connectors that normally go to the amp. You wire speaker (+) to the positive terminal of the left speaker. You wire the negative terminal of the left speaker to the positive terminal of the right speaker. You wire the negative terminal of the right speaker to speaker (-). Done.

      Two connectors will need to unplugged and swapped when you want to go from jamma mono to cab amplified stereo. Easy peasy.
      Thanks Nem/Pascal - i am standing on the shoulders of giants(youe technical prowess) hen it comes to this, so I appreciate your help. When i get time maybe this weekend or next i will mock up the wiring diagram before i take the plunge with one or other options and share.

      One bizarre thought that crossed my mind (amongst many!) is whether having just one channel (one RCA input) into the line converter would stress its components - is it not designed to have load into both inputs? I might be worrying unduly, but thought i would ask. If i understood, the suggestion would be feeding one mono RCA into it (from the JAMMA loom) , and then splitting from one RCA output to two RCAs to feed the cabinet amp.