My project "JLH-69"

Discussion in 'DIY' started by Zampotech, Feb 8, 2019.

  1. denny_dow

    denny_dow Acquaintance

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    Hello Sir. Been lurking here on the forum for a while, following your posts, and got so tempted by the power amp project that I finally came around to signing up. Please put my name on the list for the power amp, I have in mind KEF LS50 or Klipsch RP600M, so a 8-16 Ohm version please.

    The 'Germanium' headamp also looks intriguing, but i understand that is still in its early stages?

    Thank you and godspeed!
     
  2. Zampotech

    Zampotech Friend

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    One of the important reasons for the delay in the start of production of the JLH-69 was the lack of logarithmic drivers for UV meters.The developed driver was good only for the first half hour of the amplifier's operation, while the amplifier is cold. After heating the amplifier to the operating temperature ( JLH 69 is a hot amplifier), the UV meter needle moved very lazily and slightly, like in the morning after a stormy night with alcohol and girls.

    Of course, it was possible to use specialized logarithmic amplifiers for drivers, but they are rare and quite expensive.

    Now I want to brag. I still managed to make a thermally independent driver from radio components almost from the trash can.
    The display range of the VU meter turned out to be 37dB, the driver is very cheap and easy to configure.
    In addition, drawings of several case variants were prepared. Cases for the desktop arrangement of the amplifier and a case for placing on a bookshelf (for example, next to monitors). The case for placing on the bookshelf was born at the request of my friend, he lives in a small studio apartment in the winter and he has little space for placing the amplifier.
     
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  3. Zampotech

    Zampotech Friend

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    Continuation of the topic about JLH. This time JLH is for planar headphones.

    I made a chassis for the layout of the amplifier circuit and design.

    [​IMG]

    [​IMG]

    Assembled a test amplifier

    [​IMG]

    The inputs and outputs of the amplifier were made from the front panel so that it was convenient for measurements

    The scale of the VU meter will have to be changed. In the original VU meter, the scale is 23 dB and it is nonlinear. In my case, the scale should be linear with a range of 40 dB. The developed driver for VU meter has such a range.

    For comparison, different output transistors are installed in the channels. In the right channel there is a transistor P605

    [​IMG]

    In the left channel of the transistor GT906

    [​IMG]

    What did the initial measurement and testing show:
    - It is not realistic to make a universal JLH amplifier on germanium transistors for all types of planar headphones. High-resistance planar headphones require high voltage and low current, low-resistance planar headphones require low voltage and high current. It is almost impossible to combine high voltage and high current without loss of quality.
    - On silicon transistors, a universal amplifier can be made without problems
    - The JLH amplifier for low-sensitivity planar headphones may require forced air cooling or the use of high-power germanium output transistors

    For example on takieh

    [​IMG]

    The main reason for this limitation is temperature. Germanium transistors are prone to self-heating and at temperatures above +75 go to the "land of eternal hunting".

    I don't know what a planar headphone amplifier sounds like yet, since I don't have such headphones. To evaluate the sound, I made a JLH power amplifier with germanium transistors for speakers.

    For the first 10-15 minutes, this amplifier sounded great, excellent and comfortable sound. Then he died, despite the fact that radiators for transistors dominated a large area.
    then I made another amplifier, also on germanium transistors, also at 10 watts, but the transistors worked in AB mode. This amplifier is still alive.

    From all this, I concluded that in mode A, it is impossible to load germanium transistors by more than 10-20% of its maximum power

    That is why for different types of planar headphones there should be different modes in terms of voltage and current of the output transistors.

    So I want to ask the community what are the most popular planar headphones right now.
     
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    Last edited: Nov 7, 2021
  4. Koth Ganesh

    Koth Ganesh Friend

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    @Zampotech, I’ll kick off the responses by stating my planar preferences - the Abyss TC 1266, the HE 6 and the Susvara ( in that order).
     
  5. dBel84

    dBel84 Friend

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    This is what @rhythmdevils has been hoping for.

    I will let others comment about other Planars but Hifiman and Audeze are going to be the most popular generally
     
  6. Pancakes

    Pancakes Friend

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    @Zampotech what is your definition of high vs low resistance relatively speaking? Roughly where (impedance rating) would you draw the line between the two?
     
  7. rhythmdevils

    rhythmdevils MOT: rhythmdevils audio

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    Please make it for high efficiency orthos! I will buy one right now! :)

    Audeze headphones have so much more potential than Hifimans the drivers are just better.
     
  8. Cspirou

    Cspirou They call me Sparky

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    Audeze is everywhere in terms of impedance. LCD-4 is 200Ω while LCD-5 is 14Ω.
     
  9. rhythmdevils

    rhythmdevils MOT: rhythmdevils audio

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    but both love current

    I should clarify that the Susvara is too expensive for many to own. The most popular hifiman is the HE6 and Thsts where I say Audeze drivers have so much more potential. I believe more than any Hifiman but I haven’t heard the Susvara so can’t comment with certainty.

    generally Hifiman throws shit together haphazardly while Audeze does tons of research.
     
    Last edited: Nov 7, 2021
  10. Cspirou

    Cspirou They call me Sparky

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    Sure. But both have a rated max of 5W which results is different requirements

    Max power:
    LCD-5, +/-12V, 0.85A
    LCD-4, +/-44V(WTF!), 0.22A
     
  11. CEE TEE

    CEE TEE MOT: NITSCH

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    @Zampotech I could send you an older, well-regarded double-sided magnet driver HiFiMAN HE-500 to test with alongside a newer HIFIMAN single-sided magnet driver HE-4XX to test. That would be a good range of popular HFM headphones to start with.

    Audeze is still producing some of the best planars so it would make sense to test with a pair of those as well. LCD-4 are very expensive. Maybe someone can send a pair of LCD-2C? If the same version of the amp could work well across new/old HFM + Audeze, that might be the biggest range of popular planars for a single amp version.

    (Let me know in PM if you would like me to ship.)

    Older and newer HiFiMAN HE-6/HE-6SE have different requirements but a real cult following and some of the highest performance when driven well. This is an option but probably a specific niche to develop for.
     
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  12. CEE TEE

    CEE TEE MOT: NITSCH

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    ^Anybody else please chime in to advise whether it would be a good representative sample (or not) to help development!
     
  13. Cspirou

    Cspirou They call me Sparky

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    This is what I think is a good selection:

    t50rp and variants
    LCD-2C
    LCD-X
    HiFiman HE-400se
    Hifiman HE-6 (kinda extreme requirements)
     
  14. rhythmdevils

    rhythmdevils MOT: rhythmdevils audio

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    There are a lot of amps on the market that supply tons of voltage. And three are tons of amp on the market that can drive the HE6 well.

    There are very few amps that provide tons of current.

    that’s what would make this amp stand out from everything else out there.
     
  15. Pancakes

    Pancakes Friend

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    It really seems that way doesn't it? There are so many models and constant changes that it seems like there's no engineering methodology. If you throw a bunch of shit at the wall, inevitably something will stick.
     
  16. lagadu

    lagadu Facebook Friend

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    I get the impression that the three most popular planars would be the LCD-X, LCD-2C and the HE6. Sundara also seems to be pretty popular on reddit but I doubt many owners would be interested in this amp for it, given their entry-level price point.

    Personally I'd love to get this to try with my HE6 and to have a high current amp for other planars in the future.
     
    Last edited: Nov 7, 2021
  17. rhythmdevils

    rhythmdevils MOT: rhythmdevils audio

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    I don’t think an amp should be designed with the unobtanium HE-500. And cheap Hifinans are crap. So I don’t think that’s a great representation.

    and like I said there’s already so many amps that will drive the HE6 well. We have so few high current amps.

    I can send an LCD-2F for the cause if needed.
     
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  18. Gazny

    Gazny Friend

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    I will say anything to drive my vintage ortho 120Ω
     
  19. Walderstorn

    Walderstorn Friend

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    Didn't a bunch of people here buy Verums as well? Maybe in enough number to justify a listening as well?
     
  20. Cspirou

    Cspirou They call me Sparky

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    Verum is also crazy low impedance. 8Ω
     

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