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Thread: The brute has landed: NEC A820E integrated amp

  1. #11
    Join Date: Dec 2011

    Location: South downs

    Posts: 3,477
    I'm James.

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    Quote Originally Posted by Firebottle View Post
    I've had to bite the bullet and buy (cough) a service manual. It's a scanned copy and almost impossible to make out component values, but the circuit arrangement is well shown.

    I'ts a sophisticated circuit with dual FETs on the inputs of the different gain blocks and it appears there is only 1 electrolytic in the signal path, on the output of the phono stage.
    Those will have to get changed.

    If anyone would like a copy of the manual please shout up. It's a PDF of 1.2MB.

    Alan
    Sounds like a nicer design than a couple of very well regarded amps I've got here which having now worked on them I must say I wouldn't touch them with a barge pole... It has in fact put me off the brand. I wont name name's but let's just say they were made in Japan but owned by the Dutch

    Enjoy your bargain !

  2. #12
    Join Date: Oct 2012

    Location: The Black Country

    Posts: 6,089
    I'm Alan.

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    They wouldn't happen to be Ph****s would they?

    It looks like the one electrolytic is probably there just so that the response does not go down to dc.
    It's a non polar 4.7uF with no voltage across it, so I've added a 1uF foil cap across each one.

    The regulator transistors feeding the phono board run really hot, that's the job of valves not semis, so I've also increased the series dropper resistors to cool them down a bit.

    This amp is a seriously good performer, and cheap

    Alan
    I love Hendrix for so many reasons. He was so much more than just a blues guitarist - he played damn well any kind of guitar he wanted. In fact I'm not sure if he even played the guitar - he played music. - Stevie Ray Vaughan

  3. #13
    Join Date: Oct 2011

    Location: Charente, France

    Posts: 3,531
    I'm Nodrog.

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    Quote Originally Posted by Firebottle View Post
    This amp is a seriously good performer, and cheap
    Alan
    Wadya mean cheap?? You've already had to spend almost £20 what with the manual and all. You are up to the amount I usually spend

  4. #14
    Join Date: Dec 2011

    Location: South downs

    Posts: 3,477
    I'm James.

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    No, Marantz

    Got a couple of their higher end models from the early 90's here... Let me count the 'lytic coupling caps: on the phono input, on the phono output, on the buffer input, on the buffer output oh yes and on the power amplifier input as well !!!

    As you say they were commonly used as high pass filters keeping out any sub 30hz grunge. Is the phono stage discrete or IC ? I couldn't make much of the SM... The schematics were pretty much illegible to me

  5. #15
    MartinT Guest

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    I used to work for NEC, but from 1985 onwards. Their hi-fi division soldiered on until just after 1990, when they pulled out of the market. It's a shame as they made some good kit, especially a very high end 'statement' CD player that's as rare as hen's teeth. To think I could have bought one at staff discount

    EDIT: here it is, the NEC CD-10
    http://audio-database.com/NEC-AUTHEN...r/cd-10-e.html

    ...and this earlier beast, the CD-903 (love the remote)
    http://audio-database.com/NEC-AUTHEN.../cd-903-e.html
    Last edited by MartinT; 25-01-2014 at 17:09.

  6. #16
    Join Date: Aug 2009

    Location: Staffordshire, England

    Posts: 37,786
    I'm Martin.

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    Quote Originally Posted by MartinT View Post

    ...and this earlier beast, the CD-903 (love the remote)
    http://audio-database.com/NEC-AUTHEN.../cd-903-e.html
    Yeah that is tasty.
    Current Lash Up:

    TEAC VRDS 701T > Sony TAE1000ESD > Krell KSA50S > JM Labs Focal Electra 926.

  7. #17
    Join Date: Oct 2012

    Location: The Black Country

    Posts: 6,089
    I'm Alan.

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    Quote Originally Posted by istari_knight View Post
    Is the phono stage discrete or IC ?(
    It's discrete, with an IC based servo around it for dc control.
    I love Hendrix for so many reasons. He was so much more than just a blues guitarist - he played damn well any kind of guitar he wanted. In fact I'm not sure if he even played the guitar - he played music. - Stevie Ray Vaughan

  8. #18
    Join Date: Dec 2011

    Location: South downs

    Posts: 3,477
    I'm James.

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    Quote Originally Posted by Firebottle View Post
    It's discrete, with an IC based servo around it for dc control.
    Ooh, this amp really is a nice surprise ! It must have been their top of the range or something ? I shall have to keep an eye out

  9. #19
    Join Date: Aug 2009

    Location: Staffordshire, England

    Posts: 37,786
    I'm Martin.

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    Quote Originally Posted by istari_knight View Post
    Ooh, this amp really is a nice surprise ! It must have been their top of the range or something ? I shall have to keep an eye out
    Yep see my post no2 I linked to a bit of info. According to that it is the amplifier from their 'Flagship Combo system' from 1980 - I wonder what the Combo speakers were like?
    Current Lash Up:

    TEAC VRDS 701T > Sony TAE1000ESD > Krell KSA50S > JM Labs Focal Electra 926.

  10. #20
    Join Date: Dec 2011

    Location: South downs

    Posts: 3,477
    I'm James.

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    Quote Originally Posted by Macca View Post
    Yep see my post no2 I linked to a bit of info. According to that it is the amplifier from their 'Flagship Combo system' from 1980 - I wonder what the Combo speakers were like?
    Completely missed that

    According to "wizargoz" on the link "Sound quality with original NEC Authentic Series Combo speakers is louder than A520E system, better definition but a sound quality far below 80 watt Technics 'New Class A'." ... Whatever that means.

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