AliExpress / eBay JL Hood 1969 Class A Amp

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

  1. ruinevil

    ruinevil Rando

    Contributor
    Joined:
    Nov 17, 2019
    Likes Received:
    11
    Dislikes Received:
    0
    Trophy Points:
    3
    Location:
    Capital District, NY
    Home Page:
    How much does this weight. I'm getting a 7 pound box from California from the US Nobsound Warehouse.
     
  2. Vtory

    Vtory Illogical Spock

    Friend MZR
    Joined:
    Sep 12, 2016
    Likes Received:
    4,827
    Dislikes Received:
    37
    Trophy Points:
    113
    Location:
    Greater Philadelphia Area, PA
    @ruinevil It highly depends on which metal chassis is used, as essentially being a semi-DIY assembly (circuit/parts kit + general chassis). The one pictured in the first page weighs around 14-16 lbs as l remember.
     
  3. Vtory

    Vtory Illogical Spock

    Friend MZR
    Joined:
    Sep 12, 2016
    Likes Received:
    4,827
    Dislikes Received:
    37
    Trophy Points:
    113
    Location:
    Greater Philadelphia Area, PA
    As a two-year long user, I can't understand why this JLH69 amp isn't recommended frequently. It should not be automatically dismissed for those who are on a budget but still want a high performance -- conditioned by high-sensitivy speakers or not-too-low sensitivity speakers in the near field. At least I don't think this loses much against Aegir (Aegir being a little more refined and better balanced .. but more similar than different).

    Pros
    • Surprisingly resolving. This combined with decent budget bookshelf speakers smokes well-received active monitors. I can choose jbl 4408 (quite vintage passive monitor) + jlh69 over lsr305/8 any day (had both for years) in terms of scalability, transparency, micro ability, and clarity.
    • Lovely harmonics and tones -- you can regard this as a semi-tubes. Shares benefits to some extent.
    • BQ, part qualities are well above what we can expect with $100-ish amps.
    • CAP modification is pretty easy and cheap. Well established in earlier pages of this thread. It can slightly address bass weakness and help more neutral presentation.
    • Base circuit is well explained by John, the original developer. Refer to http://www.keith-snook.info/wireless-world-magazine/Wireless-World-1969/Simple Class A Amplifier - .pdf
    • Insane, insane value. I can't help emphasizing this more. $100(+shipping) new for an integrated amp this good? Ridiculous in a good way.
      • Why ridiculous? Let's look this way. $100 magni 3 is an insane value headphone amp. "Quality" class-AB or even D integrated amps don't sell this cheap (e.g., crown xls1002 for $350 new) -- not to mention class-A.
    Cons
    • Runs fairly hot. Class-A + relatively small chassis -- Physics rules.
    • <50hz bass is mostly muted .. loose at best. So for this reason, it's not very suitable for full range applications (including low sensitivity headphones such as HE6)
    • Its insanely low price makes shipping costs feel too much.
    • Low gain (22db) and low power (10Wpc). So walk away if you use low sensitivity speakers at large room-filling volume. Had no problem with 85-88 dbSPL/Wm speakers at close distance (< 6ft) though.
    • I don't like two red leds on the front.
    • ... and as usual with my favorite products, objectivists must avoid this. Pretty sure it won't measure well from today's standard.
     
    Last edited: Apr 23, 2020
    Lyander, ampguy, Priidik and 8 others like this.
  4. ruinevil

    ruinevil Rando

    Contributor
    Joined:
    Nov 17, 2019
    Likes Received:
    11
    Dislikes Received:
    0
    Trophy Points:
    3
    Location:
    Capital District, NY
    Home Page:
    I wonder what Nobsound is sending to me that UPS is saying weighs 7 pounds...

    I ordered: https://www.ebay.com/itm/273008586195
     
    Noldir likes this.
  5. Vtory

    Vtory Illogical Spock

    Friend MZR
    Joined:
    Sep 12, 2016
    Likes Received:
    4,827
    Dislikes Received:
    37
    Trophy Points:
    113
    Location:
    Greater Philadelphia Area, PA
    Weird. In the ebay description..

    That's aournd 14 lbs.
     
    fraggler likes this.
  6. bengo

    bengo Friend

    Friend
    Joined:
    Apr 17, 2017
    Likes Received:
    1,346
    Dislikes Received:
    6
    Trophy Points:
    93
    Location:
    Divisive Kingdom
    Home Page:
    Monoblocks :D
     
    ruinevil and Vtory like this.
  7. Inoculator

    Inoculator Almost "Made"

    Contributor
    Joined:
    Dec 5, 2018
    Likes Received:
    194
    Dislikes Received:
    0
    Trophy Points:
    33
    Location:
    Tacoma, WA
    Thanks for the impressions, I wish I had paid attention to this before I chased an Aegir for my very humble nearfield home office setup, which is mainly setup for headphone listening. Just driving some Ascend Acoustic CBM-170 SE for now, which are not super sensitive, but get plenty loud nearfield with one Aegir and sound really lively with Freya S on 4x. Feels silly to be driving $300 speakers with thousands in gear, but decided to treat myself to a Verite this quarantine.

    Will probably pair this amp with some Omega Speakers (very sensitive and gorgeous) for my at work office setup. Had been eyeing another Aegir or Rag 2.
     
    Last edited: Apr 23, 2020
    ohshitgorillas and Vtory like this.
  8. ohshitgorillas

    ohshitgorillas Friend

    Friend
    Joined:
    Nov 27, 2015
    Likes Received:
    313
    Dislikes Received:
    2
    Trophy Points:
    63
    Location:
    Purgatory, Connecticut
    Speaking to someone on Facebook who has a similar build (from scratch), apparently changing out the output caps for Nichicon FGs at 4700uF helps the bass issue by a lot. N Perhaps the stock 2000uF isn't enough? Next time I order from DigiKey or etc, I'll snag a pair and give it a shot. Personally I run a pair of powered subs so have never really noticed a lack of bass power.

    Also, a quick follow up, this amp is EXTREMELY impressive with my cap upgrades. Again, I don't have a good amount of reference points with high end speaker amps, but from my experience with headphones, I would say the levels of detail and depth and clarity that I'm getting make the $100 price tag mind boggling. I am loving this little guy. My only real 'complaint' is that I wish it had been silver to match my Bifrost Multibit/Saga OG.

    edit: also, to those other owners out there, for safety purposes I suggest opening your case to make sure the chassis is grounded to earth mains. Mine was not....there was nothing on the earth mains actually. Totally unused. Took all of a minute to run a wire from the earth mains tab on the IEC inlet to one of the trafo housing nuts, using a spade. The chassis is grounded to the signal ground via the pot, at least on mine, but the chassis should also definitely be connected to earth mains at SOME point...
     
    Last edited: Apr 25, 2020
  9. purr1n

    purr1n Finding his inner redneck

    Staff Member Friend BWC
    Joined:
    Sep 24, 2015
    Likes Received:
    58,933
    Dislikes Received:
    101
    Trophy Points:
    113
    Location:
    Antarctica
    Probably less the value rather than the quality of the cap. I was lazy so I just paralleled with a smaller value high quality cap to get rid of that haze in the bass.
     
  10. dmckean44

    dmckean44 In a Sherwood S6040CP relationship

    Friend
    Joined:
    Nov 17, 2016
    Likes Received:
    1,326
    Dislikes Received:
    12
    Trophy Points:
    93
    Location:
    San Diego
    I noticed that when I owned it. It's never been something I've worried about too much. Until like 5 years ago I lived in a house that still had knob and tube wiring.
     
  11. msommers

    msommers High on Epipens

    Friend
    Joined:
    Nov 6, 2016
    Likes Received:
    2,663
    Dislikes Received:
    35
    Trophy Points:
    113
    Location:
    Calgary, Alberta
    Home Page:
    Wait....this is a $350 CAD shipped integrated Class A amp and it doesn't suck?

    [​IMG]
     
  12. ruinevil

    ruinevil Rando

    Contributor
    Joined:
    Nov 17, 2019
    Likes Received:
    11
    Dislikes Received:
    0
    Trophy Points:
    3
    Location:
    Capital District, NY
    Home Page:
    So I received the amplifier. I've run it for a few hours today through my Fibhorn 2 in my bedroom. They sound very smooth compared to Panasonic SA-XR55 I had running them before. A lot less harshness and graininess in the treble region.

    Cons: Higher noise, especially in the left channel. There is also less sparkle to the cymbals, so while it sounds cleaner in treble, it does not extend as far.

    When I opened it, I noticed that the ground is connected to the rear chassis. I also noticed that the transformer is buzzing a bit.

    [​IMG]

    [​IMG]

    I'll give it a month before I start modding it. What do you have the test circuit running at other people who own this? I went from test to ground at 25.1VDC following JELabs write up on the Hood 1969.
     
    ohshitgorillas likes this.
  13. ruinevil

    ruinevil Rando

    Contributor
    Joined:
    Nov 17, 2019
    Likes Received:
    11
    Dislikes Received:
    0
    Trophy Points:
    3
    Location:
    Capital District, NY
    Home Page:
    I brought the test circuits bias to 24V. Though JELabs states lower sounds better, the transformer starts humming loudly if I go any lower than 24V. The bias also falls as the circuit heats up. I'll need to wait for the local Makerspace to open so I use their oscilloscope to match the wave forms.
     
  14. ohshitgorillas

    ohshitgorillas Friend

    Friend
    Joined:
    Nov 27, 2015
    Likes Received:
    313
    Dislikes Received:
    2
    Trophy Points:
    63
    Location:
    Purgatory, Connecticut
    Having given the new caps time to burn in, I am really surprised with the level of subtlety and detail and depth and soundstage precision that this amplifier is capable of presenting.I have a few final mods that I want to do before I 'finalize' it by removing those screw post connectors and soldering the trafo and signal wires directly to the board:

    * Nichicon 2200 uF output cap to replace 2x1000 uF stock
    * Add second bypass to output caps: 0.22uF Russian FT-3 Teflon caps (if they fit... if not I have some Audyn True Copper Max 0.1uF caps that would definitely fit)
    * Replace all output wiring with Duelund DCA16GA tin-plated OFC in cotton/oil (haven't decided whether to use twisted pair or a 4x braid yet)
    * KLEI bare copper 'naked harmony' binding posts (surprisingly affordable compared to other copper options)

    ...and I'm giving some consideration to...

    * Still interested in removing the volume pot but unsure what to do with the leftover hole in the front panel, may settle for replacing it with a stepped attenuator.
    * Replace IEC input w/ fuse with Furutech

    One last point of note: These use 2N3055 and MJ2955, which are apparently cheaper alternatives that are often sold as counterfeit MJ15003/4 (https://sound-au.com/counterfeit.htm). I talked to a guy on a DIY Audio facebook group who is considering swapping out the stock MOSFETs with the the MJ1500x, and I'm eagerly awaiting his results.
     
    ruinevil and Inoculator like this.
  15. ruinevil

    ruinevil Rando

    Contributor
    Joined:
    Nov 17, 2019
    Likes Received:
    11
    Dislikes Received:
    0
    Trophy Points:
    3
    Location:
    Capital District, NY
    Home Page:
    The left channel noise was annoying me too much, so I sent it back. I tried to buy another one, but Doukmall blocked me.
     
  16. Priidik

    Priidik Friend

    Friend BWC
    Joined:
    Sep 27, 2015
    Likes Received:
    1,558
    Dislikes Received:
    3
    Trophy Points:
    93
    Location:
    Estonia
    From cap properties, what I have found that helps in this setup.
    • Enough capacitance to not allow for phase issues in bass --> more is better, but after about 4 mF the improvement is probably not worth it. 8 ohms load, 4 mF (4000 uF):
    • upload_2020-5-11_12-15-47.png
    • With 2 mF the phase response at 30 Hz is up by meager 5 deg, so it's not that much, and by itself probably not audible (speakers also distort phase in bass region)
    • Low ESR and low leakage are the quality factors that probably help the sound quality the most in this setup. The ESR adds to the already not very good source resistance of the amp, ie the damping ratio is not excellent, still better than most tube amps. Leakage and dielectric memory effects muck up the highs and probably have adverse effect on soundstage and plankton. There are good cap choices from Nichicon, Panasonic, Kemet etc that have these boxes ticked.
     
    ohshitgorillas likes this.
  17. ampguy

    ampguy Rando

    Joined:
    May 12, 2020
    Likes Received:
    3
    Dislikes Received:
    0
    Trophy Points:
    3
    Location:
    Seattle
    Newb here, first post. I'm curious if going this route with an unmodded one, would give about the same sound as an Aegir. For me, the cost would likely be about half for the Nobsound or Douk ones on ebay, as the aliexpress ones have high shipping, putting them about the same as us ebay sellers. If there are big advantages to paying twice for the Aegir, I could probably do that, but if they're about the same, unmodded, the Nobsound, Douk might be worth trying. I have several types of speakers including LS-50s, but don't expect this level of power to be quite sufficient. The standard amp I'm using is a Marantz PM7005 which is 60 watts @8 ohms, 80 watts @4 ohms. Don't really care about resale value, as if it will probably go to a 2nd or 3rd setup, if it's not optimal, mostly a thing to try.
     
  18. Mystic

    Mystic Mystique's Spiritual Advisor

    Friend
    Joined:
    Jan 28, 2016
    Likes Received:
    2,303
    Dislikes Received:
    2
    Trophy Points:
    93
    Location:
    U.S.
    Received my amp from the same seller as @ruinevil. Huge upgrade from the Yamaha av receiver I was using. I also got a Rythmik L12 sub since my Heresys don't go very low. This is overall a massive improvement from my barebones setup before.

    Unfortunately my amp also has buzzing in both speakers. It's very faint in my right speaker but noticeable at my listening position in the left speaker. I'm not handy with electronics and their inner workings, is this something I can fix. Is this common for this amp design and I should look for a different amp altogether or just try a different seller/builder?
     
  19. dmckean44

    dmckean44 In a Sherwood S6040CP relationship

    Friend
    Joined:
    Nov 17, 2016
    Likes Received:
    1,326
    Dislikes Received:
    12
    Trophy Points:
    93
    Location:
    San Diego
    The Aegir is significantly better than the unmodded Nobsound. Both of these amps sound more alike than different and share the same strengths and weaknesses. The Aegir sounds clearer and larger when compared A-B. The Aegir is also 4x the price and significantly more powerful.

    I wouldn't use either of these amps with LS-50s though.
     
    ampguy and Vtory like this.
  20. Vtory

    Vtory Illogical Spock

    Friend MZR
    Joined:
    Sep 12, 2016
    Likes Received:
    4,827
    Dislikes Received:
    37
    Trophy Points:
    113
    Location:
    Greater Philadelphia Area, PA
    Mine (ordered via Ali) doesn't have that problem, but I assume the nature of this amp (semi-diy) is very subjective to product to product variation (QC is nearly minimal). It might be also worth checking grounding issues.
     

Share This Page