Audio Technica AT-LP1240-USB under the hood with high resolution photos

Hi everyone, this is my first post here. I noticed that many of you are curious about AT-LP1240-USB and it's inner guts. Before deciding to buy it, I really wish I could have seen some pictures of it's inner parts to ponder it towards AT-LP120-USB. So before inserting the pictures, I'd like to mention a few things that will certainly be handy for those considering buying it:

Myths busted:

-The top is really a metal and plastic combination. You can easily check it with a magnet, it will adhere.
-Some people say it truly bypasses the preamp, but no, this is false. The signal goes through some roundabouts before reaching the rear RCA female connectors.
-A considerable part of it's massive weight (16 kilos) comes from a heavy metal plate attached to the bottom cover.
-The quality of the arm gimbals, counterweight and cue lever is indeed better than those of AT-LP120, made out of metal.
-The platter is rubberized at the bottom.
-The black bottom cover is rubberized plastic.

Ok, now let's head to the pictures. I made an album at Imgur because the pictures are big, so here's the link.

http://imgur.com/a/HXtYB

Now if anybody could help me out sorting these wires, I'd like to know which color goes where at the RCA plugs so I can do my bypass here and share some audio samples with you for comparison. My idea is to unsolder the female connectors from the board and solder the thin wires from the arm assembly directly to the RCA, so there's no interference from the rest of that circuit board. I'll also need to extend the grounding to the ground post screw because it uses the board to conduct.

 

Maybe this would be helpful. I got it from an AT tech (see bold):

The AT-LP120-USB and AT-LP1240-USB Turntables have the same output circuit design. When the switch is set to the phono position, the preamplifier circuitry is totally bypassed. It is literally a direct connection from the tonearm to the output cable or output jacks. However, there are two components that are always in circuit with the outputs, a 100 pF capacitor across the output to ground, and a ferrite bead in line with the output. The 100 pF capacitor will add along with the input capacitance of the external phono pre. For example, our AT-PEQ3 external phono preamplifier has an input capacitance of 220 pF, the 100 pF capacitor internal to the turntables would be in parallel with that and add to a total capacitance of 320 pF. Additional capacitance will have an effect on the high end frequency response. It causes a bit of a presence bump with less extension. Bypassing everything internal to the LP120 or 1240 will have an effect on response linearity. The effect and how great it is will be based on the input capacitance of the particular external phono preamplifier that is used. If you can do it, removing the two 100 pF caps on the PCB will provide a more linear response and greater high frequency extension. Please note that any modification of the turntables voids its warranty.

 

Bump.

OP, have you made any modifications to better utilize the LP1240? I am wanting to remove the preamp of my older LP240 but I am unsure as to going about it. I want to either A) Remove the preamp & keep using the turntable; or B) Somehow sell the turntable & possibly invest in something better. If you have a suggestion post back.

Best regards.

 

I want to try removing the capacitors as ogetsu said here, but it's been a busy year end. I believe the internal pre-amp wiring and layout of the LP240 is exactly the same as the LP1240, but why are you thinking of selling it in first place? Unless you want to shell out some 4 figures, it will be hard to achieve the same quality and durability, unless you want to depart from direct-driven turntables.

 

If I may ask, didn't you like what you hear from your TT? My RP3 does not have such complex circuitry and if I own your TT, I would not touch it until the warranty ends. Use the bypass switch and pick better phono preamp to pair with it. That will be safer IMHO.

 

There's no warranty here where I live. Also, I'm using them with an Allen & Heath mixer, so maybe the highs will get a bit clearer without the capacitors. I'll try and post results, ripping the same record with same stylus and same everything, only changing the presence and absence of the capacitors.

 

I say rip the pre amp out. I did it on a lp120. Really easy, took me 40 minutes. Noticably better sound

 

Yeah, same here. Getting rid of the preamp entirely is the way to go.

 

What you guys have done to take it off? The board does the wiring to the RCA female connectors and also holds the phono/line switch, so I believe you unsoldered the RCAs from that board, took the board out completely, soldered extensions to the phono wires and the grounding. Is that correct? How you've held the RCAs in place, because the board does a structural function there.

 

I cut the rca's going to the board and resoldered (and heat shrink) them to the rca cables the come out of the turntable. I also put some better quality rca cables in. I cabled tied them to something insided so then wouldn't just float around. Then I added a ground wire to go to an external preamp. I crimped a circle connecter to the ground wire to put it with the other ground wires.

And yes, I took the board out completely. You could get more creative and add a switch if you wanna still use the usb output

Check out this post (with video instructions). It's about the lp120 but the internal components should be somewhat similar.

http://forums.stevehoffman.tv/threa...p-removal-detailed-instructions-video.318596/

 

Excuse my bump of this thread.

I've attempted to perform the actions of the video instructions for the LP-120 on my LP-240 but I believe I killed my turntable; the circuitry is different and I accidentally plucked out a blue tonearm wire. I'm going to look around for possible repair places but I'm not getting my hopes up.

If worse comes for worse, RIP to my LP-240 (2011 - 2015).

 

These Hanpin TTs are a mess electronically. Just compare to a Technics SL1200 under the hood (Platter in fact). The whole design looks botched together and it also has to accommodate internal crappy phono amp and USB. All stuff that is detrimental to SQ. Just hope the Japanese start designing and building proper decks again.

 

Has anyone successfully removed the preamp or two 100 pF caps on this yet? Any comments or instructions would be greatly appreciated!

 

Hi, I have been doing some research with some help from my friends on Vinylengine. If anyone has some thoughts on the attached link I will be grateful.

Audio Technica ATLP 1240 - Vinyl Engine »

 

I have this table and I'm totally fine with the sound on the built-in preamp.

 

I think you may be right, but I did notice a slight difference sound quality when I completely removed the preamp from my LP 120.

 

Hello Ogetsu,

I was comparing the two and just discovered this is true. I used my Audio Precision to plot the audio response and input overload of a 12o and then proceeded to a 1240 in my home lab. They were the identical. However, I noticed a problem. One channel of the 1240 was AOK, but the other channel had no high frequency deemphasis. So, a capacitor is bad, wrong, or not on the PCB. Do you have schematic or any other information to help me repair the preamp.

Best,
Radioarchivist

 

Sorry I'm late to the discussion. I just made this mod to my AT-LP240 and can vouch for the improvement, at least in my case. I'm running an AT440MLB cartridge, which is rated for a 100-200pf load capacitance. As stated before, simply using the table's switch to bypass the internal preamp does not remove a 100 pf load capacitor. Measurement of the AT-LP240's tonearm/cable capacitance with said capacitor in place was 275 pf, which was well above the recommended load capacitance for my AT440MLB. Removing the internal 100 pf capacitance would put me in range at 175 pf (I'd already removed the load capacitance from my phono stage input). However, once I got inside the unit I quickly discovered it would be easy to remove the preamp and connector board, add RCA jacks, and run the tonearm cables directly to the RCAs. I even used a short run of copper tubing to shield the internal tonearm wires to the RCAs. The improvement in sound was definitely discernible (more linear frequency response), which was most likely due to getting the load capacitance in range. Long story short, I would highly recommend this mod to anyone running a moving magnet type cartridge that requires a lower load capacitance, but probably not as important if you're running a cart less sensitive to load capacitance.

 

Hi Telefunkin, I successfully removed the preamp from my ATLP 120 as per YouTube instructions and it sounded a lot better.

The ATLP 1240 does not look as straightforward, did you take any step by step pictures of the modifications as they would be a big help to me.

Thanks.

 

Hi, all after 2 years of should I, shouldn't I, finally got up the courage to open up my AT LP 1240. Had an idiotic eureka moment when I went over some old posts on vinyl engine and realised I had been stressing about nothing.

Stupidly (well I have zero electronics ability) I realised that I mistaken the PCB board adjacent to the RCA's for the preamp when in fact it was the tan PCB just just above it.

Playing safe, I removed the connectors from the preamp board and reassembled to check that everything still worked.... it did. Next stage is to take out the preamp and unsolder the tone arm wires from the other PCB and the resolder them to some new female RCA's... what possibly go wrong? see attached idiots (me) guide...

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I wish someone had a video and more detailed explanation on how to do this. Whethet ripping out the preamp or unsolder the caps.

 

Hi bru87, I will post some step by step pictures next week, assuming I haven't bricked it with my basic tech skills (?)

 

Preamp mod at the end of this thread Audio Technica ATLP 1240 - Page 2- Vinyl Engine

Be careful, I take no responsibility for any damage caused
In fact check with someone with more technical knowledge before attempting mod in case I've made any errors.