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. purr1n

    purr1n Finding his inner redneck

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    I've noted that some new production 6922 tubes die an early death, becoming noisy.

    As far as tube rolling, this should be a sticky (or redone into a one of my blog posts for easy reference: https://www.superbestaudiofriends.o...-other-glowing-delights.486/page-8#post-21818

    Assuming everything works and specs won't cause long term damage, some things such as bias and voltages are left up to the designer. This will be dependent upon the tube type, the circuit, and could even be something subjective (oh how horrible, am amp designer also using ears to design an amp!). When we change tube types, we throw that out the window.

    ...

    1. One day, the GE JAN5670s will be rare.
    2. While some new production 6922s die early, there is no guarantee old stock 5670s will perform up to par. I bought a bunch of WE396a, and one-third of them I would not resell to anyone here on SBAF. They either have extreme gain mismatches between the triodes or have unacceptably low omissions. Basically, trash can or relegated to Vali 2 use. 10% are total trash can.
     
  2. ChaChaRealSmooth

    ChaChaRealSmooth SBAF Gearmaster

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    Despite my better judgment, and knowing what a rabbit hole tube rolling can be, my curiosity won over my reason and I ended up buying some Telefunken PCC88 tubes to roll in the Liquid Platinum (was inspired by @Ice-man rolling similar Telefunkens in his LP). I was a bit nervous due to the difference in spec, but the tubes run fine, the amp is still its normal temperature, and sonically.....

    It's going to take a little bit to get my head around exactly what I'm hearing, but insofar it's been fabulous. The stage seems to have moved a bit forward, staging gained some depth (not sure, but maybe at the expense of a slight bit of width), bass seems to be better in body and pitch, and treble seems a bit more extended and less rolled. I like this last part the best honestly; it doesn't take away the somewhat polite nature of the LP, but it does help bring cymbals forward and does help in the space/air part of classical piano pieces. Mids are still good old Cavalli (nothing seems to have changed, but that's okay with me)

    I will not be rolling any more tubes, and I'm not sure I can recommend this for every person who owns a Liquid Platinum, but my experience has been pretty positive on my ears and negative on the wallet.
     
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  3. dBel84

    dBel84 Friend

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    Not diesel....

    But, the heater is under voltage thus the tube is at risk of not operating at its spec. Possible effects sonically are a little more tube compression, meaning a little warmer possibly a little more harmonic distortion often perceived as air and space.

    I for one like a little second harmonic mixed in, and the platinum in stock form should have a smidge.

    The 7DJ8 / PC 88 will not damage the amp, it just won't have the tube operating optimally and thus the circuit as designed will not operate per Atomic Bob's measurements.

    The sound anyone prefers is their own, thus I say live and let live (as long as we do so with knowledge and intent)

    .. dB
     
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  4. nickwin

    nickwin Facebook Friend

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    I just hooked up a new-stock LP and thought Id share a couple observations compared to the original batch. The PS is different, presumably the same specs but from a different supplier. This one looks slightly different and uses a standard IEC power cord which is kind of nice.

    I had some minor tube socket alignment/tightness issues with both of the original batch LPs, I didn't have any of that with this one. The tube cutouts look like they might even be slightly bigger but I can't say for sure without having the old one on hand.

    This one has me perplexed, but the gain seems lower. I used to listen to most music around 8:30-9:30 o'clock with my HE500s, but right off the bat I'm listening to the same music at around 10-11 o'clock on this one. Im going off memory, but on my old LPs the difference between 9 and 11 o'clock would be HUGE. This seems really odd to me since my understanding is that the high gain was a necessary design choice on this amp. I really hope Monoprice didn't demand changes to the design that would potentially effect the performance of the amp based on complaints of the gain being too high. That said, I'm not hearing anything alarming, its sounding great right out of the box. Maybe my ears are just plugged up or something, but Im really curious to hear if anyone else notices the same thing.
     
    Last edited: May 19, 2019
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  5. jazztherapist

    jazztherapist analrapist

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    Yeah, I’d love to hear more about any gain differences. That and reliability were my only issues. Question: Are you on your third Platinum or are you referring to loaner experiences?
     
  6. nickwin

    nickwin Facebook Friend

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    Yup this is my third, but not because there were any major reliability issues. I got two different tubes with the first one and Monoprice wanted me to return the whole thing instead of just replacing one of the tubes. I actually thought there was something weird with the sound of this one too, but it's possible the mismatched tubes just bothered me. The second one had a couple minor issues, some play in the volume knob and the tube sockets didn't lineup correctly with the tube cutouts. Based on what Im seeing it seems like they have stepped up the QC/fit and finish with this batch but obviously you cant infer a whole lot based on one or two samples of each version.

    EDIT: The more I'm listening to this LP, the more Im thinking the gain really is lower. Not only is the overall level lower, but changes in the volume setting seem to make smaller differences on the volume than before. Id love to see a measurement to know if this is actually the case.
     
    Last edited: May 19, 2019
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  7. Luckbad

    Luckbad Traded in a unicorn for a Corolla

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    Mind taking some pics of the tube cutouts and power supply?
     
  8. nickwin

    nickwin Facebook Friend

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    Sure, but how the hell do I attach an image here lol?
     
  9. Walderstorn

    Walderstorn Friend

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    Can use something like imgur, for example, upload them there and use the provided "share link" here. Just press the 6th icon from the right (reply toolbar).
     
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  10. Ksaurav402

    Ksaurav402 Acquaintance

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    I also see the warranty is only 1 year now.
    I remember when I got mine it was 5 years or am I confusing with Schiit products.
     
  11. RatSalad

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    It's 5 years or it was... Says was updated may 1 probably be the last big ticket item I buy from monoprice this is like the 3rd time they changed it.
     
  12. nickwin

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    Got it, I will try to do this tonight.

    So I just looked in the manual and it still says the gain is 5x, but it also says "these specs are subject to change at any time". Ive been looking through the Midi, audio and iTunes settings on my Mac to see If I can find anything on that side that would explain the reduced level but I haven't found anything. Weird.

    The warranty went from 5 years to 1 year? Thats quite a difference. This is too expensive of an amp to not have good longevity IMO. Has anyone here had any reliability issues with their LP thus far?
     
  13. msommers

    msommers High on Epipens

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    Wow that's absolutely brutal of Monoprice to chop their warranty like that. Clearly not built for the long term and they don't want to deal with it.

    Hate to say but glad I gave up obtaining this amp, especially as a Canuck. Too many foreseeable PITAs
     
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  14. nickwin

    nickwin Facebook Friend

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    Alright these pics aren't great but they are the best I can do at the moment.

    Its hard to really see the cutouts in the pictures. Im planning on swapping tubes sometime in the near future, when I do I will get a better pic and measurement of the cutouts. Its possible they just seem bigger to me because the sockets are actually centered on this one so there is decent space all the way around the tube. on my last LP one of the tubes was actually hitting the cutout in one spot.

    It looks like the PS input went from 1.1A to 1.5A and the output went from 1.5A to 1.4A.

    EDIT: Hmm, I'm not sure why the images aren't showing up. I uploaded them to Imgur and then pasted the link into the "image" text box here. Why in gods name can I not just attach and image here like I can on every other forum???

    Here is a link, let me know if this doesn't work https://imgur.com/a/w6TJTmT
    [​IMG]
     
    Last edited: May 20, 2019
  15. lcmusiclover

    lcmusiclover Almost "Made"

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    HF user Wes S has been chatting with Monoprice and got them to change their minds -- they say 5 years warranty and say they will correct the website.

    Fingers crossed :)
     
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  16. Luckbad

    Luckbad Traded in a unicorn for a Corolla

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    Power brick is definitely different.

    Tube slots look the same.

    The clips shown in the XLR input have always been in the pics on Monoprice and never been in the real amp.

    Not sure on the warranty. I see one mention of 5 years from a forum member and many more mentions of 1 year.
     
  17. Ash1412

    Ash1412 Friend

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    You're right about the power supply. About the cutouts, mine has angled (tapered?) edges. It doesn't look like yours do, which could've been a change made to make the openings larger, which otherwise looks about the same size from the top.

    http://imgur.com/gallery/UBvzQgI

    [​IMG]
     
  18. lcmusiclover

    lcmusiclover Almost "Made"

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  19. ChaChaRealSmooth

    ChaChaRealSmooth SBAF Gearmaster

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    I didn't want to believe this, but this information seems correct. Some sleuthing on the Monoprice site says 1 year. Shame.

    Agree with the statement that the amp is too expensive not to expect longevity.
     
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  20. AllanMarcus

    AllanMarcus Friend

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    Just make sure your mac's volume and iTunes volume is set to max, then use the volume control on the amp.
     

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