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Yamaha A1 integrated amp (phono issue)

Discussion in 'Yamaha' started by MadcapLaughs, Mar 20, 2017.

  1. MadcapLaughs

    MadcapLaughs New Member

    Messages:
    31
    Hello,

    I just purchased a Yamaha A1 integrated amp. While the line stages sound great I'm noticing some problems in the phono stage.

    1. The gain levels to achieve slightly loud sound output means I am turning the knob past 12 o'clock each time. (High output MM cart used). I have efficient altec bolero horn speakers too, so I know they can get very loud with 70wpc amps.

    2. The oscillations in the woofer cones look terrible, heavy shaking in the woofer cones. Other receivers I have used with the same turntable, arm, cart have not produced this level of shaking, it looks like my speakers might pop out of the cabinet, and the volume is not that loud. Engaging the subsonic filter does not help much at all.

    3. The left speaker eventually mutes if I turn it up past decently normal volumes, as in the bass and treble output is almost gone, and the speaker shaking stops completely.

    It just seems like this amp has no control or authority over the speakers when engaged in phono. Apparently this amp was throughly recapped and serviced in 2011.

    Any input would be greatly appreciated!
     
  2. avionic

    avionic " Black Knights" Subscriber

    Messages:
    33,768
    Location:
    Fort Dodge, Iowa cornfield
    First I'd try cleaning the phono select switch.
     
  3. avionic

    avionic " Black Knights" Subscriber

    Messages:
    33,768
    Location:
    Fort Dodge, Iowa cornfield
    Do you have the correct load plugs installed on the rear panel?
     
  4. avionic

    avionic " Black Knights" Subscriber

    Messages:
    33,768
    Location:
    Fort Dodge, Iowa cornfield
    Do you have the phono hooked up to the correct input jacks ? Not the load plug jacks.
     
  5. MadcapLaughs

    MadcapLaughs New Member

    Messages:
    31
    Yes I do have the 47k plugs for the moving magnet cart (nagaoka mp 110 rated at 47k). Would cleaning the phono switch account for the alarming amount of woofer movement and low volume output though? It may help the cutout in the left channel, I could see that.
     
  6. MadcapLaughs

    MadcapLaughs New Member

    Messages:
    31
    And yes all the inputs are correctly installed I didn't mix up the mm with the mc or anything like that. I have switched speaker cables and all too.
     
  7. avionic

    avionic " Black Knights" Subscriber

    Messages:
    33,768
    Location:
    Fort Dodge, Iowa cornfield
  8. MadcapLaughs

    MadcapLaughs New Member

    Messages:
    31
    Hey thanks for your help troubleshooting so far. I do have the original manual in my possession and have read up on the loading stage. The one item I do not have is the loading plugs for the MC stage. I have a pair of 47k plugs in the cart loading input, and the turntable phono cables hooked up to the mm phono inputs. Do you have to have those shorter MC plugs as well? The manual implies it but doesn't state it specifically
     
  9. avionic

    avionic " Black Knights" Subscriber

    Messages:
    33,768
    Location:
    Fort Dodge, Iowa cornfield
    Yes. May also have a problem with the low filter (subsonic) switch or circuit.
     
  10. avionic

    avionic " Black Knights" Subscriber

    Messages:
    33,768
    Location:
    Fort Dodge, Iowa cornfield
    I believe those are just shorting plugs.To my knowledge, the loading plugs are only for MM carts.
     
    Nashou66 likes this.
  11. clinic-audio

    clinic-audio all on YAMAHA untill 1990

    Messages:
    1,473
    Location:
    France
    Hello MadcapLaugs

    I know your problem very well
    You have to know that it is really rare to improve the sound of these very old YAMAHA gear BUT there is one big improvement to do on A1 :
    (I see all the A1 owners open big eyes)
    the phono input of this very nice amplifier is too much microphonic !
    Try to change the both black cables going from the rear of the unit to go to the PCB inside the unit (they have cinch connectors at each end ) . TRY , you will be surprised !
    If you want to control what I said , do this :
    - put the A1 upside down
    - delete the bottom cover
    - switch the power on
    - listen in PHONO input (with nothing connected to it )
    -choose high volume position
    -touch the both black wires and you will hear your fingers "touching" these wires

    Once you have replace them by a good quality (non microphonic) wires , your trouble will desappear .
    As Avionic said the solution would be to use the subsonic filter only because there is low frequencies loop because of these microphonics cables

    Do it ! and come back to us with report
     
    zaibatsu likes this.
  12. dksp

    dksp Active Member

    Messages:
    340
    Location:
    France
    Interesting… do you mean those ones?

    download.jpg
     
  13. clinic-audio

    clinic-audio all on YAMAHA untill 1990

    Messages:
    1,473
    Location:
    France
    Yes , just try and you will hear ...
     
  14. MadcapLaughs

    MadcapLaughs New Member

    Messages:
    31
    Thanks for the suggestion clinic... I will see if I can request my tech to upgrade the cables pictured above. it seems like that may help with the subsonic rumble and gain potentially, but I still need to figure out why the left channel randomly looses bass. Anyway I'll update when I get the unit back.
     
  15. tensleep

    tensleep AK Subscriber Subscriber

    Messages:
    7,056
    Location:
    Dallas Metroplex
    Watching this thread with avid interest. I am purchasing an A-1 this weekend.
     
  16. Nashou66

    Nashou66 AK Subscriber Subscriber

    Messages:
    765
    Location:
    West Seneca NY

    You'll love it. A bit of a pain to work on some boards and its heavy as hell !
    I have 4 of them. Two are fully working with Re capped power supply boards.

    The other two are waiting for repair, one is a silver Japan model.

    Athanasios
     
    tensleep likes this.
  17. zaibatsu

    zaibatsu Active Member

    Messages:
    285
    You should post up some pics!
    One of Yamaha's most beautiful looking amps in my book.
     
    tensleep likes this.
  18. scoloheros

    scoloheros Active Member

    Messages:
    308
    This was interesting to read, I'm going to refer back to it later as I scroed an A-1 about a week ago with a T-1 sitting on top of it. I don't even know if it works. I'm still a little unclear about exactly what wires are being talked about here but I'll try to figure that out later, thanks for that info!
     

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