Monoprice Monolith Liquid Platinum Headphone Amplifier by Alex Cavalli

Discussion in 'Headphone Amplifiers and Combo (DAC/Amp) Units' started by Vtory, Apr 4, 2018.

  1. jmpsmash

    jmpsmash Acquaintance

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    Alex, thanks for a great amp and detailed reply. If you don't mind can you reveal what's the typology used in the Liquid Platinum?
     
  2. runeight

    runeight MOT: Alex Cavalli

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    The topology is a differential amp with tubes embedded (no caps) into the gain stages. It uses current feedback instead of voltage feedback (voltage feedback being more common, so far as I know, in diff amps).

    Output devices are mosfets, as in all of my amps except the CTH.
     
  3. SPAZ

    SPAZ New

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    Is it safe to use 396A / 2C51 tubes with an adapter on this amp?
     
  4. runeight

    runeight MOT: Alex Cavalli

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    Well....we have to keep in mind that these are really Monoprice products and they are responsible for warranties and the circumstances under which they honor those.

    In general I think you guys should stick with 6922s and the exact equivalents, like 6dj8 (slightly lower heater current, but otherwise the same). Other tubes might work so long as they have the same heater characteristics and come to roughly the same operating point (exceeding 330mA heater current could do damage). But, basicallly, when you roll tubes you are kind of on your own. :)

    The 2C51 appears to take the same heater current as 6dj8 (300mA). You can always try. I am not a fan of socket adapters or extenders because using them is often like adding a giant antenna right in the middle of the highest gain portions of the circuit thus amplifying any noise picked up by the new antenna loops.

    OTOH, since I am as crazy as you are, I know you guys are going to do it anyway. :D
     
  5. jmpsmash

    jmpsmash Acquaintance

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    Swapped in some Russian 6H23P-EB for some quick listen this morning. They are ever slightly fatter but still managed to fit in the opening.

    Love the 20cm form factor.

    [​IMG]

    [​IMG]
     
  6. Ash1412

    Ash1412 Friend

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    Do you have any opinion on local vs global feedback, current vs voltage feedback and mosfet vs bjt output stages?
     
  7. runeight

    runeight MOT: Alex Cavalli

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    I do....

    A very high percentage of amps have both local and global feedback. For example, an amp with a complementary output (BJT or Mosfet) has emitter/source resistors on the output devices. These provide some amount of local NFB. If the output is also fed back into the earlier stages of the amp then it has both global and local NFB. Local NFB also appears in other places depending on what the designer is trying to accomplish.

    I prefer current feedback, but it's not a hard and fast rule and depends on the goal. The Liquid Gold, Liquid Glass (buffer), Liquid Carbon, Liquid Gold, Liquid Platinum are current feedback amps. The Liquid Crimson, Liquid Fire, Liquid Spark, CTH are voltage feedback amps.

    I prefer mosfets as the power output devices.

    The larger issue is, IMHO, that, for analog amps, there is a small number of basic circuit elements that are used in nearly every amp, probably every amp. Most of these have been around for decades and much of what an amp designer does is determine which of these, where they go, and what components are configured inside these circuit blocks.
     
  8. Thaitao

    Thaitao New

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    Isn't Liquid Platinum is the same as Liquid Crimson? so why one is VFB another is CFB?
     
  9. Walderstorn

    Walderstorn Friend

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    He already stated that they are similar but they are, obviously, different amps. You wouldn't be able to pick the crimson, with it's transformers and chassis and turn it into something in this price bracket.
     
  10. Thaitao

    Thaitao New

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    Not different in topology https://www.head-fi.org/threads/mon...-by-alex-cavalli.876406/page-30#post-14577481, both use the same circuit, just one balanced , one se, so if one is CFA or VFA another must be the same.
     
  11. Walderstorn

    Walderstorn Friend

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    Good point but he also mentioned:

    "They should be similar, but only those who have both can do the direct comparison to hear the differences. Keep in mind that the Crimson was a $3k amp. The Platinum does make those engineering choices I described above to achieve its size and price point.

    I just want to be clear that you all are not getting a full Liquid Crimson, but perhaps something that is within reach of it."

    So i'm expecting those changes to also happen on that department, although he also used the word "exactly" i am guessing it's not 100% same topology. Maybe it's in the way he worded it or i am thinking too much. He'll probably explain a little better soon.
     
  12. Thaitao

    Thaitao New

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    Pls read this post https://www.head-fi.org/threads/mon...-by-alex-cavalli.876406/page-29#post-14576892
     
  13. atomicbob

    atomicbob dScope Yoda

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    While everyone is nitpicking how similar or different Liquid Platinum is from Liquid Crimson, the simple fact that Liquid Platinum is a damn fine amplifier at a great price point seems to be taking a back seat.
     
  14. msommers

    msommers High on Epipens

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    @Thaitao Have you heard Liquid Platinum yet?
     
  15. runeight

    runeight MOT: Alex Cavalli

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    I was expecting this question. :)

    The circuit topology is the same except that Platinum is balanced. With the change to balanced also was the opportunity to use current feedback with the differential front end. I liked this better for this new amp.

    I think the Platinum stands on its own as an amp regardless of its predecessor and would be the same amp if the Crimson had never existed bc this is how I would have done it.
     
  16. Jozurr

    Jozurr Facebook Friend

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    Would love to read your impressions comparing the two amps please.
     
  17. atomicbob

    atomicbob dScope Yoda

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  18. Skyline

    Skyline Double-blindly done with this hobby

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    I'm far more interested in Lyr 3 comparisons if anyone has them.
     
  19. Hands

    Hands Overzealous Auto Flusher - Measurbator

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    Hmm, going off memory, they are kind of similar. Both hit that fairly balanced sound, slight warm tilt. LP seems more sensitive to tube rolling. I slapped in some A-frame Amperex tubes and was surprised how much thicker it sounded. I think I found the LP with stock tubes a little more tonally coherent and normal than Lyr 3 with the NOS Russian tube. Hard to explain on memory...

    The LP, to me, doesn't have the stage depth and layering weaknesses that the Lyr 3 had. That's not to say LP is a super expansive sounding amp, but not weak in this area. LP is probably a little more laid-back, slightly smoother timbre (actually pairs well with new production tubes), yet seems to improve on most technical areas over the Lyr 3.

    The Lyr 3 to me was a really balanced sounding amp. A good do-it-all at a good price. Nonetheless, even though the ZDT Jr. has more trade offs over the Lyr 3 (namely bass quality), it also excels and has a certain magic to it that the Lyr 3 did not. Lyr 3 did most things well, and as such is an easy recommendation for most people, but didn't captivate me given my tastes and needs.

    LP has me a little more enthusiastic in that it tends to do most things a little better than Lyr 3. This has so far kept me more engaged with it and less prone to just want to switch back to the ZDT Jr.

    I see the LP as sort of the next step in what the Lyr 3 brought to the table. In this case, you actually get a fair step up by spending more money.
     
  20. Za Warudo

    Za Warudo Acquaintance

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    So how does LP compare to the ZDT Jr for the HD650?
     

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