Audio-Technica AT-LP120 Preamp Removal (Detailed Instructions Video)

Discussion in 'Audio Hardware' started by FrankieP, May 20, 2013.

  1. rich100

    rich100 Well-Known Member

    Location:
    Middle of England
    Thanks chaps - conversion complete (with ground wire - hum is very apparent without it) and very happy with the results.

    Immediately noticeable to me, when listening through headphones - is the utter silence - not even a hint of noise when at a standstill.

    One thing to point out re: the brass spacers on the cover screws - these are thin enough to pass through the hole in the plastic base screw holes - but narrow enough for the head of the screw to hold them - so instead of balancing them or taping in place on the screw posts (which seemed to be the suggestion on the video) - place the lid back in place and then drop the screw in the hole along with the spacer so both drop in at the same time - just be careful not to let go of the spacer too early as it will drop down and be out of line for the screw to pass through - worked for me anyway.

    The table seems to work well with the rubber and felt mat together.

    I've also bought a digital tracking force meter - based on that the counterweight is .2g out, 1.8g on the weight was actually 1.6g on the scale.

    Based on the success of this one - I've also modded the Pioneer PL30K removing the internal pre-amp - also a success - will write a post up at some point in case anyone is interested but let me know if any info required.
     
  2. ZSamuels28

    ZSamuels28 New Member

    Location:
    Los Angeles
    Awesome! Glad it worked out for you. I'm thinking of replacing the cables inside, I did some soldering and shrink wrapping and ended up stripping too much and not having a long enough ground wire, I'm very into making my own cables so I may replace the RCA with a better cable (mogami w2528) and same with the connection to the circuit board inside (also replaced with mogami w2549). For the ground wire I bought a 14awg silver plated copper 19 strand wire from navships (a very well known eBay seller of wires) and purchased some gold plated copper spades from eBay as well. One day I really want to possibly dremel some holes in the back and put some RCA female jacks, but that's just a thought for now.

    As a side note, has anyone figured out how to resolve the anti skate problem on this turntable?
     
  3. rich100

    rich100 Well-Known Member

    Location:
    Middle of England
    The AS seems to be rubbish doesn't it?
    You can see the AS working when the arm is floating - AS applied makes it return to the right - but on test records etc it appears to do nothing.
     
  4. ZSamuels28

    ZSamuels28 New Member

    Location:
    Los Angeles
    Yeah it is rubbish... Is there any way to fix it or just leave it as is? Will it damage my records if I set it at the same as the VTF?
     
  5. Poison_Flour

    Poison_Flour Well-Known Member

    Has anyone experimented with any other mods on this table
    such as KAB TD-1200 tonearm fluid damper etc ?
     
  6. MickAvory

    MickAvory Forum Resident

    Location:
    New Orleans, LA
    I never got the KAB fluid damper, but I seriously looked into it. I don't believe it will work on the Audio Technica. If you look at the tone arm assemblies between the AT and a Technics SL-1200.. they are slightly different. The part of the base where the rest stand is happens to be shaped differently on the AT. It doesn't appear that it will fit the KAB. I looked at different photos on line of the AT & the Technics with the KAB and without. The arm assemblies don't seem to match up exactly to me. Maybe somebody knows better than me though.
     
    Poison_Flour likes this.
  7. picassoson

    picassoson Well-Known Member

    Location:
    New York City
    I'm really tempted to try this soon.

    I have an the AT-LP120 and a Pioneer PL-115D both equipped with a Shure m97xe cartridge running through a Marantz Model 2252B receiver. The Pioneer is running through the Marantz's phono stage, and the Audio Technica is running through the Marantz but using it's own internal preamp.

    Recently I did an A/B comparison needledrop of Gene Clark's No Other using both turntables. I'm not great with audiophile terms, but the AT-LP120 is audibly warmer and much less harsh (or maybe less "detailed" / "open") on the high end. I enjoy how it sounds a little more than the Pioneer maybe, but it's really apples and oranges, especially depending on the recording.

    However, when I looked at the waveforms (and looked back on the wave forms of the hundreds of needle drops I've made on the AT-LP120 over the years) there is a very visible change going on that curbs the frequencies on the high end. This seems like a pretty major EQ issue. Has Audio Technica ever acknowledged or addressed this?

    I've attached an image of the waveforms of the first three songs below:
    • Top = AT-LP120 > Internal Preamp > Marantz 2252B > MacBook Pro
    • Bottom = Pioneer PL-115D > Marantz 2252B Phono Stage > MacBook Pro

    [​IMG]
     
    SpeedMorris likes this.
  8. SpeedMorris

    SpeedMorris Well-Known Member

    Location:
    Iowa
    Like given for Gene Clark mention.:)
     
    picassoson likes this.
  9. Poison_Flour

    Poison_Flour Well-Known Member

    The preamp in the LP120 is rubbish this just proves why so many people have removed them - I did read that in the new Audio Technica turntable LP5 they have stressed great improvements with the preamp
     
    picassoson likes this.
  10. P2CH

    P2CH Well-Known Member

    I have one of these TT's but I don't plan on doing this mod. What I wonder though, why do they show taking the entire board out? If I were to do the mod., I see no reason ripping the board out of it. There may be a time when you might want to connect it back up for some reason? I like having the option of running it USB. And there might be a time the internal preamp can come in handy too. I could hook it up to my JVC boom box if I wanted or any other similar system.

    I seen one guy remove the steel plate out of his. To me, the plate is there to add weight which helps to eliminate feedback.

    Either way, if the switch is by-passing the board I don't see a value add in doing this. Just my 2 cents worth.
     
  11. OcdMan

    OcdMan Forum Resident

    Location:
    Maryland
    From what I've read, the switch doesn't completely bypass the preamp. There are still some electronics in the signal path coloring the sound.
     
    patient_ot likes this.
  12. Marshman96

    Marshman96 Well-Known Member

    Location:
    harrisburg, PA
    I tried the preamp bypassed by switch into my external preamp then did the major surgery and removed the whole internal and the difference was night and day. it was the best thing I have done and made my turntable into a whole new beast.
     
    patient_ot likes this.
  13. rich100

    rich100 Well-Known Member

    Location:
    Middle of England
    The signal wires from the tonearm go via the circuitry, and not just the switch but other components on the board also. I decided to pull the board out completely as I wouldn't be using it again, I would prefer to capture the analog signal via a sound card instead.
     
    patient_ot likes this.
  14. Marshman96

    Marshman96 Well-Known Member

    Location:
    harrisburg, PA
    Also there are plenty of external preamps with USB support it that is a concern.
     
    patient_ot likes this.
  15. P2CH

    P2CH Well-Known Member

    In regard to pulling the preamp, I suppose if it actually makes that big of a difference taking it out of the circuit, that is a good thing. Personally, even if I disconnected it, I'd still leave it in there though. It's not doing any harm sitting there. Thanks for the added info.
     
  16. navydiver

    navydiver Member

    Location:
    Victoria, BC
    Sold my AT-LP120 and bought this one and modded the snot out of it - best thing I ever did. Not even on the same playing field (or galaxy) for sound quality IMHO (certainly not a DJ Table to be sure):

    Before
    [​IMG]


    After
    [​IMG]
     
    MikeInFla likes this.
  17. marcob1963

    marcob1963 Forum Resident

    The AT LP120 wave looks like its a bit shaved/declipped at the top end compared to the Pioneer, resulting in a less detailed or open sound. I assure you that the culprit is the preamp in the AT LP120.

    Rip it out, its a cancer! I assure you you'll be blown away by the improvement, particularly a more detailed wider sound, including tighter bottom end. Any subsequent wave file will look at lot more like the Pioneer's wave.
     
    picassoson likes this.
  18. picassoson

    picassoson Well-Known Member

    Location:
    New York City
    Surgery is scheduled for tomorrow morning - wish me luck! :) Now if I could just figure out how to properly align my cartridge so I can get rid of that pesky IGD...
     
  19. picassoson

    picassoson Well-Known Member

    Location:
    New York City
    Welp... I just ruined my turntable I think. :(

    I have the non-USB version of the AT-PL 120 and I didn't realize how different the guts would be from the USB version. After splicing and soldering the RCA out from the switch board I connected it to what I thought were the ground/right/left channel outs from the tone arm board... but I'm not getting any signal out now. I also foolishly snipped what I thought was one of the other outs from the tone arm board to the phono pre-amp - but I'm not so sure now.

    I'm resigned to failure (I was prepared for the risk of this not working going in), but does anyone more knowledgeable about these things have any idea where I may have screwed up, and if it might still be fixable?

    [​IMG]
     
  20. ghostmerlott

    ghostmerlott New Member

    Location:
    australia
    Hi guys,

    Just finished reading through, great stuff!

    Just curious, say if
    - Without pre-amp surgery using Line out, sound is a 2/10
    - With pre-amp surgery, sound say 9/10

    What will the sound x/10 be like for
    - Without pre-amp surgery using ART-DJ external pre- amp? Will it be exactly 2/10 don't bother category .... or maybe a slight improvement to 4/10?

    Thanks guys.
     
  21. ghostmerlott

    ghostmerlott New Member

    Location:
    australia
    using an at-lp60.
     
  22. AppleCorp3

    AppleCorp3 Forum Resident

    Have we ever determined if the PL-120 has the same issue and needs the mod too or just the USB LP-120?
     
  23. yarvelling

    yarvelling Active Member

    Hi folks :)
    Thought I'd join in here, as I too had been wondering, having read so much about removing the pre-amp, about whether it's worth it.
    I've just taken delivery today of a brand-new AT-LP120 USB, after reading so much about it over the past few years.... it seemed a 'table that I kept coming back to!
    I tried a new one last November but that arrived D.O.A... no power, and so it was returned. However, it's been itch that couldn't be scratched ever since, and so I finally hit the Buy Now button yesterday with an Ebay retailer, and took delivery today :)
    I have it with the as-fitted AT-95E in the newer HS-10 headshell, running through a Rega Mini Phono USB pre-amp, and really cannot hear any of "veiled" sound that people talk of.... And this is in comparison with an older Technics SL-BD22 and a Rega RP1 turntable through the same pre-amp.... The sound to me is more 'open' and 'spacious' sounding.
    OK, The Technics is a P-Mount deck and has a Shure M92E mounted, and sounds great, and the Rega has the original Carbon cartridge, which also surprised me with just how much it could resolve :)
    I guess my point is, with this new turntable, and the AT95E cartridge in the new headshell, is that the sound doesn't seem "grey", or veiled, as others have described it. It seems open, wide, with a clear and well defined treble... so maybe AT have have had some work done on the built-in pre-amp (haven't tried that yet!), and it has removed the extra capacitance in the signal path?
    Thing to note is that the Rega pre-amp has a very low capacitance of only 110mh (however it's called!!) - half of what many others that I've seen, and owned, and so maybe could account for the lack of 'veiling' seen by others with pre-amps in the higher 200+? A few months ago I changed from using a NAD PP2 pre-amp with 200mh to the Rega, and noted that the sound opened-up, became cleaner and clearer using Sure cartridges ( it gave some 'life' and sparkle to an old M75-6!) for instance, so I wonder if maybe this could a reason also..?
    If the turntable is putting capacitance into the signal path even though the internal pre-amp is switched out, maybe the very low input capacitance of the Rega pre-amp is helping? Or has AT done some work on it?
    Whatever.... it's sounding very good, clear, and clean :) I get the impression that I'm hearing extra detail in the tracks played so far - and some that the Rega RP1 never managed to pick-out too!
    My record collection is from both new records, and records I collected way back in the 60's and 70's :) Mainly rock, swing and jazz.
    So with the newest versions of this 'table, is really necessary to remove the built-in pre-amp?
    Thanks :)
     
    MikeInFla likes this.
  24. rich100

    rich100 Well-Known Member

    Location:
    Middle of England
    Is it the one with the square holes in the headshell? I bought mine a few months back now, I removed the amp and the main thing I noticed was when on headphones I could previously hear noise when nothing playing - after the mod it's absolutely silent until the needle hits the record.
     
  25. yarvelling

    yarvelling Active Member

    Yeah... it's the new one with the "square holes" in the headshell.... Haven't tried headphones yet, but certainly through speakers, there is no other 'noise' that shouldn't be be there!
    Just the fact that seems so clean and clear, compared to other turntables used (turntables that have no pre-amps built-in)... I wondered if maybe AT had finally done something to 'fix' that problem, or whether my Rega pre-amp, having such a low capacitance input, is nullifying the problem seen by others ;)
     
    MikeInFla likes this.

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