Audio Technica ATLP 1240

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kramer
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Audio Technica ATLP 1240

Post by kramer » 31 Jul 2016 16:58

Just wondering if anyone has had any success in disconnecting/desoldering the female phonos from the preamp PCB and soldering the tonearm wires directly to the phono's. I've attached a guesstimate of how this could be done however I may be over simplifying the task in hand. Hopefully tho this may completely bypass the onboard preamp without the need to remove it completely.
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detune
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Re: Audio Technica ATLP 1240

Post by detune » 31 Jul 2016 17:31

I would leave the RCAs untouched on the PCB.
You could instead remove L607, C632, L606, C631. Then solder the signal wires from the pickup to the former connection points of the removed LC networks. You could also leave all ground wires where they are.
Removing the Ls essentially breaks the connection from the switch/internal preamp to the RCAs.
The capacitors were obviously fitted for RFI reasons and are pointless when going directly to the phono connectors.
In other words, remove the PHL and PHR wire from the board connector and solder them to points where L607 and C632 (left) and L606 and C631(right) met.
This will completely bypass the internal preamp.

cheers,
Georg

kramer
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Re: Audio Technica ATLP 1240

Post by kramer » 31 Jul 2016 18:48

detune wrote:I would leave the RCAs untouched on the PCB.
You could instead remove L607, C632, L606, C631. Then solder the signal wires from the pickup to the former connection points of the removed LC networks. You could also leave all ground wires where they are.
Removing the Ls essentially breaks the connection from the switch/internal preamp to the RCAs.
The capacitors were obviously fitted for RFI reasons and are pointless when going directly to the phono connectors.
In other words, remove the PHL and PHR wire from the board connector and solder them to points where L607 and C632 (left) and L606 and C631(right) met.
This will completely bypass the internal preamp.

cheers,
Georg
Thanks Georg, I did consider removing the capacitors but I was unsure of their purpose. I just need to wait until the warranty runs out before I start my amateur electronics project..

kramer
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Re: Audio Technica ATLP 1240

Post by kramer » 31 Jul 2016 19:36

kramer wrote:
detune wrote:I would leave the RCAs untouched on the PCB.
You could instead remove L607, C632, L606, C631. Then solder the signal wires from the pickup to the former connection points of the removed LC networks. You could also leave all ground wires where they are.
Removing the Ls essentially breaks the connection from the switch/internal preamp to the RCAs.
The capacitors were obviously fitted for RFI reasons and are pointless when going directly to the phono connectors.
In other words, remove the PHL and PHR wire from the board connector and solder them to points where L607 and C632 (left) and L606 and C631(right) met.
This will completely bypass the internal preamp.

cheers,
Georg
Thanks Georg, I did consider removing the capacitors but I was unsure of their purpose. I just need to wait until the warranty runs out before I start my amateur electronics project..
After removing the capacitors, is the following the correct configuration?
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detune
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Re: Audio Technica ATLP 1240

Post by detune » 31 Jul 2016 20:33

You have to remove the inductors (L606/L607) also. This is important as otherwise the output of the internal preamp will stay connected.

I think a made a slight mistake as I cannot tell where the white board connector goes to - maybe from the internal pre to the USB Board? At first I thought it would come from the arm.
Then you can leave it, it won't work no more anyway.
Guess the thin wires on the backside of the PCB are coming from the arm? Then move the white one to the left solder pad of the RCA, the red to the right. This removes the cartridge's output away from the internal pre's input directly to the output jacks.
The green/blue can probably stay where they are, I think they both connect to ground.

Cheers,
Georg

edit: If you can post photos from both complete sides of the PCB I can see it better. But I think I am correct for the moment. :)
Last edited by detune on 31 Jul 2016 21:05, edited 1 time in total.

kramer
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Re: Audio Technica ATLP 1240

Post by kramer » 31 Jul 2016 21:04

detune wrote:You have to remove the inductors (L606/L607) also. This is important as otherwise the output of the internal preamp will stay connected.

I think a made a slight mistake as I cannot tell where the white board connector goes to - maybe from the internal pre to the USB Board?
Then you can leave it, it won't work no more anyway.
Guess the thin wires on the backside of the PCB are coming from the arm? Then move the white one to the left solder pad of the RCA, the red to the right. This removes the cartridge's output away from the internal pre's input directly to the output jacks.
The green/blue can probably stay where they are, I think they both connect to ground.

Cheers,
Georg

edit: If you can post photos from both complete sides of the PCB I can see it better. But I think I am correct for the moment. :)
Yes the thin wires are from the tonearm. Do I still need to remove L606 and L607 (C631 and C632 too?) if I just connect the red and white tonearm wires to the undersideleft and right solder joints?
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detune
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Re: Audio Technica ATLP 1240

Post by detune » 31 Jul 2016 21:12

kramer wrote: Yes the thin wires are from the tonearm. Do I still need to remove L606 and L607 (C631 and C632 too?) if I just connect the red and white tonearm wires to the undersideleft and right solder joints?
Ok, the preamp is not on the board. This does not change the procedure anyway.
Yes, you have to remove the Ls. As I said, they take the signal from the preamp to the jacks. Leaving them inside would make the preamp short the output of your cartridge as soon as you wire it directly to the jacks, leaving you in silence :)

Don't forget, the USB will also be disabled as the internal preamp will receive no input anymore.

Georg

edit: removing the Cs is even not that important - but they unnecessarily load the output of your cartridge. I would ditch them.

detune
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Re: Audio Technica ATLP 1240

Post by detune » 31 Jul 2016 21:31

One more thought: You can give it a simple warranty-friendly try by just pulling off the board connector and leaving the selector switch to "phono". As far as i can see this this should disconnect both the In and Out of the internal pre - but the switch and the two L/Cs will still be in the signal path.

Should be a first improvement anyway.

The only problem may be the grounding, as I don't know where the ground wire of the board connector goes. But I think it's worth a try.

Good luck,
Georg

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Re: Audio Technica ATLP 1240

Post by kramer » 31 Jul 2016 21:48

detune wrote:One more thought: You can give it a simple warranty-friendly try by just pulling off the board connector and leaving the selector switch to "phono". As far as i can see this this should disconnect both the In and Out of the internal pre - but the switch and the two L/Cs will still be in the signal path.

Should be a first improvement anyway.

The only problem may be the grounding, as I don't know where the ground wire of the board connector goes. But I think it's worth a try.

Good luck,
Georg
Thanks for your help, I will try your suggestions.

kramer
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Re: Audio Technica ATLP 1240

Post by kramer » 14 Aug 2016 16:21

kramer wrote:
detune wrote:One more thought: You can give it a simple warranty-friendly try by just pulling off the board connector and leaving the selector switch to "phono". As far as i can see this this should disconnect both the In and Out of the internal pre - but the switch and the two L/Cs will still be in the signal path.

Should be a first improvement anyway.

The only problem may be the grounding, as I don't know where the ground wire of the board connector goes. But I think it's worth a try.

Good luck,
Georg

Thanks for your help, I will try your suggestions.
Hi George

Would it be possible to solder the tonearm wires to these points? Would this bypass the capacitors? Also I could perhaps trace the tonearm directly to the ground post?
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detune
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Re: Audio Technica ATLP 1240

Post by detune » 15 Aug 2016 23:12

What about the preamp? Did it work out by pulling off the connector and now you want to kick out the caps too?
The short answer is no, the caps are wired in parallel to the pickup/connectors. This means they are not being bypassed by changing the points where the arm wires are connected. If you want to get rid of them you have to remove them.
The inductors are wired in series, so they basically would be bypassed but you have to make sure that they are open on the other side, i.e. no preamp output feeding its signal in there. (therefore my idea with the board connector).

Changing the point where the GND wires are connected won't give you a signifacent improvenemt IMHO as long as yos do not isolate them from the rest of the board(by cutting traces). And even then I doubt it would make an audible difference.

I could draw you a basic schematic if it helps to make it clearer.

Cheers, Georg

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Re: Audio Technica ATLP 1240

Post by taw_rex » 27 Sep 2016 09:36

Hi there,

I know it's been a while since this thread was active, but I thought I would share my experience.

After looking carefully inside the AT-LP1240 I came to the conclusion that modifying or removing the Pre-Amp, as can easily be done on the LP120, is not much of an option here.

So instead I invested in a much better External Pre-Amp that provides for a number of selectable capacitance loads. These were 47pF, 147pF, 267pF and 367pF.

With this range I have been able to ensure that the overall capacitance loading for my Ortofon cartridge is not too high. It sounds very, very good, and the questionable internal circuitry which adds 100pF has no audible effect on the sound.

So a Pre-Amp with selectable capacitances may be a better way than potentially damaging, and voiding warranty, of the LP1240.

Cheers.

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Re: Audio Technica ATLP 1240

Post by espresso1967 » 11 Oct 2016 23:09

Hi, I just talked to a tech about ripping out the amp, but saw your post and might just consider this route. What pre-amp with selectable capacitance loads would you recommend? I have an Ortofon 2M Blue on the way as well.

Thanks
taw_rex wrote:Hi there,

I know it's been a while since this thread was active, but I thought I would share my experience.

After looking carefully inside the AT-LP1240 I came to the conclusion that modifying or removing the Pre-Amp, as can easily be done on the LP120, is not much of an option here.

So instead I invested in a much better External Pre-Amp that provides for a number of selectable capacitance loads. These were 47pF, 147pF, 267pF and 367pF.

With this range I have been able to ensure that the overall capacitance loading for my Ortofon cartridge is not too high. It sounds very, very good, and the questionable internal circuitry which adds 100pF has no audible effect on the sound.

So a Pre-Amp with selectable capacitances may be a better way than potentially damaging, and voiding warranty, of the LP1240.

Cheers.

taw_rex
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Re: Audio Technica ATLP 1240

Post by taw_rex » 11 Oct 2016 23:45

espresso1967 wrote:Hi, I just talked to a tech about ripping out the amp, but saw your post and might just consider this route. What pre-amp with selectable capacitance loads would you recommend? I have an Ortofon 2M Blue on the way as well.

Thanks
Hi there,

I chose a Pro-Ject Tube Box DS, which I am very happy with. Pro-Ject make other completely solid state Phono Preamps that also offer selectable capacitance and impedance (for those with Moving Coil carts).

I am running an Ortofon Super OM 30, and I like the sound via the Tube Box DS. The circuitry in the AT LP1240 adds about 100pF when switched to Phono. With this in mind I set the cpacitance of the Tube Box to 147pF, which allowing for cables etc seems to match the Ortofon nicely.

Cheers.

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Re: Audio Technica ATLP 1240

Post by spazige » 21 Feb 2018 10:54

espresso1967 wrote:Hi, I just talked to a tech about ripping out the amp, but saw your post and might just consider this route. What pre-amp with selectable capacitance loads would you recommend? I have an Ortofon 2M Blue on the way as well.

Thanks
Hi did your Ortofon Blue work ok with the supplied AT LP1240 tonearm counterweight. Just got a 2M Red and it seems to heavy. think I need a heavier counterweight.

taw_rex wrote:Hi there,

I know it's been a while since this thread was active, but I thought I would share my experience.

After looking carefully inside the AT-LP1240 I came to the conclusion that modifying or removing the Pre-Amp, as can easily be done on the LP120, is not much of an option here.

So instead I invested in a much better External Pre-Amp that provides for a number of selectable capacitance loads. These were 47pF, 147pF, 267pF and 367pF.

With this range I have been able to ensure that the overall capacitance loading for my Ortofon cartridge is not too high. It sounds very, very good, and the questionable internal circuitry which adds 100pF has no audible effect on the sound.

So a Pre-Amp with selectable capacitances may be a better way than potentially damaging, and voiding warranty, of the LP1240.

Cheers.

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