Kenwood Basic C1 Preamplifier Restoration/Upgrade

Discussion in 'Kenwood-Trio/Kensonic-Accuphase' started by Leestereo, Aug 14, 2014.

  1. vsat88

    vsat88 Like my Bluetooth ?

    Messages:
    555
    Location:
    Phenix City, AL.
    Yep, there is most definitely a problem with my C2..I know this is a C1 thread ...hope no one minds.... The volume level has to be turned up way too far for it to get as loud as it should and I bought a 40.00 tube 12V pre amp off ePay and it sounds much better that the C2...Something is wrong, very wrong. I have tried everything I know to figure it out and still no luck. I know this pre amp should run circles around a dOUK aUDIO 40.00 Pre. I wish it would be something like change two caps...I am sick of going into it so I have all but decided to just leave it alone...Lee Audio..Aurex.. Can I send it to you so you can check it out for me or can you guys at least point me in the right direction..
     

     

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  2. Karl vd Berg

    Karl vd Berg Super Member

    Messages:
    1,953
    I tried two "NOS" Panasonic M of 2200uF/50V in the PSU and the sound improved a lot over the KMF's. Probably worth put newer FC's. Caps feeding the opamps (C45, C46) are now fresh Nichicon's PW...
     
    Last edited: Apr 20, 2017
  3. vsat88

    vsat88 Like my Bluetooth ?

    Messages:
    555
    Location:
    Phenix City, AL.
    Installed new Nichicon's (electrolytic) in those positions during re cap. New Op Amps and diodes..None of this helped..Still does not sound right, still have to turn the volume control up to high. It was this way before the restore as well..Hold that thought..Are you speaking of ceramics ?? (" Caps feeding the opamps (C45, C46) are now fresh Nichicon's PW"). My numbers are different because it is a C2 not a C1. I have some stacked caps...Just FYI.
     
  4. Karl vd Berg

    Karl vd Berg Super Member

    Messages:
    1,953
    I had to do the same with the previous Nippon Chemicon's KMF at PSU, turning the volume up high and there was no bass and weak sound. Now it's different, the sound is much more present, full, nicer. I think that may be room for further improvement, with C0G multi layer ceramic caps, soft recovery rectifiers and a couple of fresh Panasonic FC caps in the PSU...

    I have the Basic C1 unit, the C45 and C46 follow the new 16V Zeners, before the opamps, and I'm using here PW's 390uF/35V (stock ones were Elna 330uF/25V).

    I have to see the schematic of C2, and will help you for sure :)

    Edit: do you have a thread for your C2 unit?
     
  5. vsat88

    vsat88 Like my Bluetooth ?

    Messages:
    555
    Location:
    Phenix City, AL.
    I did not see the edit till now "do you have a thread for your C2 unit?" I am starting one now. Kenwood Basic C2 Preamplifier Restoration/Upgrade

    Done :http://www.audiokarma.org/forums/in...c-c2-preamplifier-restoration-upgrade.767344/
     
    Last edited: Apr 20, 2017
    Karl vd Berg likes this.
  6. 24Vboost

    24Vboost Active Member

    Messages:
    311
    Hello guys,

    I wanted to ask if the Basic C1 is close to the Yamaha CX 600U for specs...I just bought on eBay but the seller went and shoved a 'won't be back until May. 10th...then a few minutes later I check back and it is May.11th" unfair to us who paid right away and there were no indicators on being out on the yacht!

    I missed out on the Yamaha today as I thought I could use a Yamaha AX 630 or 900 for a preamp but they did not get back to me so I just went and purchased something close (I hope)...

    I just caught the end of your posts for this pre and may find it worth the check from page 1 to see how they fix these, the photos the guy took for eBay looked so fake like the amp just came off the line, but he said they are his so I will see...whenever he ships it now...looks like I will not see it for 1 month, just nice after I paid in seconds!

    I thank you in advance to anyone who has owned these and what to watch out for...the amp that goes with this has 'unreal' spec, 1000 for a damping factor...really possible??
     

     

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  7. 24Vboost

    24Vboost Active Member

    Messages:
    311
    Thank you for this thread I am getting one in soon and I never owned any Kenwood before but I will be using this with a Nikko Alpha II amp and a DACmagic 100 in the link...music from my computer...
     
  8. Karl vd Berg

    Karl vd Berg Super Member

    Messages:
    1,953
    I did a few combinations, including an OPA2604 at flat amp and an LM4562 at tone amp. In the end, I found that OPA2134 at flat amp and stock 2043DD at tone amp suited best here. I don't have an LME49720 (yet).
     
  9. vsat88

    vsat88 Like my Bluetooth ?

    Messages:
    555
    Location:
    Phenix City, AL.
    Karl, you said "and I'm using here PW's 390uF/35V" what is a PW ? A brand name I am not aware of ???
     
  10. Karl vd Berg

    Karl vd Berg Super Member

    Messages:
    1,953
  11. vsat88

    vsat88 Like my Bluetooth ?

    Messages:
    555
    Location:
    Phenix City, AL.
    Placed the order for two Panasonic FC Caps along with the rest to finish my Phase Linear PL 400. Thanks Karl/
     
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  12. LinhTrade

    LinhTrade New Member

    Messages:
    19
    Hi There. I hope everyone is doing good. I know this is an old thread but I need help on my C1. It only plays with 1 channel and other channel is totally out. If you crank up the max volume on the preamp and my power amp, you can hear it a little. I checked the voltage for a non working channel, there is no voltage. My question is: How can you tell if it's a balance control problem or it actually the preamp board issue? I test all of the inputs and same result. Should I spray the cleaner to input switch before anything else? Please help me. Thank you.
     
  13. Anti_Skate

    Anti_Skate Well-Known Member

    Messages:
    543
    Location:
    Somewhere in Mid Michigan
    I would start by cleaning all of the switches with cleaner and see what happens. I would suspect the relay located toward back of the unit. Theres a link for a replacement above in this thread.
     
  14. LinhTrade

    LinhTrade New Member

    Messages:
    19
    Thank you. I measured the voltage of output line before going to the relay and it has 0 volt (the other line has almost 4 volts). I suspect the IC chip that power the output signal but I am not sure anyone else having this problem?
     

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