AliExpress / eBay JL Hood 1969 Class A Amp

Discussion in 'Power Amps' started by purr1n, Apr 25, 2017.

  1. Philipp F.

    Philipp F. Rando

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    Hey guys,

    I'm somewhat inexperienced and planing to upgrade my desk audio setup (DAC, headphone amp and stereo amp). I will be going with Schiit Modi 3, Magni 3, SYS (switching between Modi 3 and Phono) and a stereo amplifier for some small desk speakers that I will also look into DIYing. I was looking for a low cost amp that will fit in nicely with the Schiit stack, it doesn't have to be very powerful as I mainly use it for studying and casual music enjoyment. I stumbled across this amp and I think it might fit the bill, I wanted something simple, chunky and analog.

    Now, I've found 2 different variants on Aliexpress and Taobao that seem to have different PCB's and cases:

    The usual one with logo on the case and rectifier at the back (ignore the 2018 1969 version).

    And an "upgraded version" without a logo, slightly different case and rectifiers at the front.

    What do you think? Should I get one, if yes what do you think about the two variants?

    Also, will it be fine if I hook it up to the rear preamp output of the Magni 3?

    PS: Google site translation and image translation gets some useful information out of the Chinese texts.
     
  2. ergopower

    ergopower Almost "Made"

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    It seems extraordinary you would pass up the one with 'true-class gallbladder sound quality'

    Just so this reply isn't entirely noise - Sys is passive, so needs line level input. Phono output is normally much lower and needs a phono pre-amp to boost signal to line level, or do you have one of those turntables with built-in phono pre-amp (Audio Technica, for example)
     
  3. purr1n

    purr1n Finding his inner redneck

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    Could still use Sys, but feed from Mani phonostage (or any other) for TT.
     
  4. Philipp F.

    Philipp F. Rando

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    Sorry, should have clarified that phono goes to my Azur 640P preamp and the output of that goes into the SYS.

    "true-class gallbladder sound quality"?

    EDIT: Oh haha, I just noticed the translation. Imagine that as a quote in a hifi magazine advert...
     
    Last edited: Oct 10, 2018
  5. Decomo

    Decomo Almost "Made"

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    Here is my humble opinion. I had both units and I could not tell much difference between the two in terms of sound quality. However, improved version (as they claimed) generate much less heat when I touch the chassis compare with original. I opened the top plate and touched the black cylinder cover that protects torroidal transformer and it is very hot. Somehow it manages heat more efficiently.

    In terms of power, I drove my mini floorstander (90db sensitivity) with it and listen in near field (3 foot distance) and I could listen loud at 11 o'clock volume knob. I do not think that I can crank the volume more than 1 o'clock position and it becomes way too loud and do not recommend because it starts sounding grainy after that.

    Hope it helps.
     
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  6. Philipp F.

    Philipp F. Rando

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    Thank you very much! This is exactly the information I am looking for. Is there anything else that might help me to decide? components, enclosure, etc.? I think I prefer the new one without the logo, but on the photos the finish of the original looks better, the top cover of the new one looks kinda weird.
     
  7. spwath

    spwath Collegiate hijinks master

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    Pretty sure the enclosure is exactly the same between the two, I think its just the photos that are different.
     
  8. restrav3

    restrav3 Likes Audio-GD

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  9. purr1n

    purr1n Finding his inner redneck

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    That actually might be pretty decent. I think I might have heard those OPTs*. They are very good considering the insanely low price for the pair of amps. I don't like how the choke and OPT are oriented and placed so closely together, but it might not be an issue. Looks like the WIMA are the interstage caps which are pretty good - can always swap them out later.

    LOL, the pair might be better sounding than the Woo WA234.

    * The better Chinese OPTs are extremely good. Some of the guys really know their shit or have reversed engineered 1950s designs, experimented, and added flair of their own. Because the Chinese suck at branding, copy the shit out of each other and mispresent themselves, we really have no idea what is what. The way to get the good stuff is to find a "good" supplier, don't ask questions and hope he doesn't scam you six months later by replacing the good shit with cheap cloned stuff.
     
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  10. zerodeefex

    zerodeefex Grumpiest admin

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    You should order one and send it in for a review .
     
  11. Thenewerguy009

    Thenewerguy009 Friend

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    ...eh when I PMed you, you said it's too busy to do any reviews or measurements if sent in.
     
  12. zerodeefex

    zerodeefex Grumpiest admin

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    Because you PMed me with things he wouldn't care about. I'm sure he and a few of the other senior members would review this.
     
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  13. restrav3

    restrav3 Likes Audio-GD

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    Every single unit of this on ebay and amazon sold out since I posted it. [​IMG]
     
  14. OJneg

    OJneg The Most Insufferable

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    Not PP. Top device is behaving as emitter follower, bottom is behaving as common emitter. Both driven by 2N697 which is also acting as a phase splitter. This is actually an interestingly simple circuit. I wouldn't call it a "simple" circuit actually, since there's a few different feedback paths. Would be more apt to say it's an interestingly low-part-count circuit.
     
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  15. Zampotech

    Zampotech Wow, I made it this far without being a friend?

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    purr1n, you lit me up with this theme.

    I know this amplifier. Assembly of this amplifier was included in the program of children's radio school.
    I collected it back in 1978. I was 13-14 years old.:rolleyes:

    We built it on germanium transistors. We didn't have silicon transistors, but there were plenty of germanium transistors.

    [​IMG]


    We didn't have good sound sources back then and couldn't appreciate the excellent quality of this genius amplifier.

    Nostalgia.....:rolleyes:

    You lit me. I will assemble this amplifier according to my drawings. Maybe I'll give more money than the price from China. But I'll try to do it myself.

    Amplifier with aliexpress I do not know and I have not seen it live. I can only reason on the photo.

    I noticed a few points that IMHO need to improve

    1. High thermal resistance of the cooler. The heat from the transistors goes on a thin aluminum corner.
    2. Small cooling area. During operation of the amplifier cooler probably very hot.
    3. It is difficult to estimate the scale, but I think the toroidal transformer is not very high power. Approximately 60-70 watts.
    Should be hot, too

    I may be wrong, these are my impressions of the photo.
     

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