SL-10 with Plinius M7 Pre-Amp

[ksbadri]

Hi Guys - Need some help.

I bought an SL-10 in good condition recently. I connected it to my Plinius M7 Pre-amp through the phono connection. The cartridge is the original EPS-310MC. The person who sold it to me hasnt played this in years as he sold his pre-amp many years ago.

When I started playing the Vinyls, I can hear that the vinyl is playing if I place my ear close to the the turntable, but nothing can be heard from the speakers.

I am not able to figure out if the issue is with the pre-amp or the turntable. BTW the pre-amp works with other sources such as Onkyo SACD/CD player.

If anyone knows how to rectify, please respond.

Thanks
Badri

 

[Saket]

First of all congrats on your purchase. Its a pretty nice model which featured the first direct drive among the linear tracking TTs.
Coming to your problem, let me tell you that the faint sound you are hearing is just the sound reproduction at the point of contact b/w needle & disc.
In case you have a multitester, place one probe lead to the centre pin of RCA connector & one probe pin to the outer connecter RCA. Polarities dont matter here. YOu should ideally get a reading (value not important) on both left & right RCA out channels. In case, it reads 0, then you probably have a dry soldering/bad connection/bad cable or at the worst an open circuit in the cartridge. I sincerely pray that you dont fall to the last category else you will need to replace the cartridge. This much on the TT side.
You also need to check your preamp if it works fine. You said that your other source plays well through the amp but the phonostage may be bad too. You can check with some other sources...or just as a 'desi' method what you can do is to insert a small screw driver carefully in the centre hole (positive) of the preamp & touch the metal part of screw driver while the preamp is on. It should give out a loud static noise. Make sure the volume is not too high while using this method else you can damage your speakers.
By now, you should be able to trace the source of your problem. Try these, in case you need more help, I would be glad to help.

Regards,
Saket

 

[jls001]

Going by this ad, your preamp doesn't seem to have a phono stage:

Plinius M7 preamp plus P7 power amp | Trade Me

When you say "through the phono connection", do you mean to say there is an input R and L which is specifically marked "Phono"?

To explain a bit, the output of your turntable's cartridge is a very low signal. It needs to be amplified by a phono preamplifier (also known as phono stage). The phono stage also performs the reverse of RIAA equalization.

The output of the phono stage becomes a line level signal - same level as other line level sources like CD player output, Tuner output, etc. And can be plugged into inputs marked CD, Tuner, Aux, etc.

Now, this phono stage can be built into your preamp, or it can be external. If it is inbuilt, then the phono stage to preamplifier connections are internal and you don't have to worry about that part.

Further, assuming that you have inbuilt phono stage in your Plinius, you NEED to check if it supports MM type cartridge (whose output is usually high -- 2.5 mV or higher), or if it also supports MC type of cartridge (whose output is typically much, much lower).

Your cartridge seems to be MC type.

So to get sound from your turntable, check whether your Plinius pre has phono stage which supports MC cartridges.

If it is MM only, then you have a problem. There are solutions but will cost money.

 

[Saket]

Also please check what jls said...It has a MC cart which needs a phonostage different from MM type. In case your plinius has a phonostage, you also need to check if its compatible/switchable to MC carts. In case of doubt, you can check with some other TT as a source, preferably MM cart type. If it plays, then you will have to find other ways to play your MC cart at cost of some money of course.

 

[ksbadri]

Saket & Jls001 - thanks for your excellent suggestions.

Saket - First I used my old multimeter for this (the min DC Amp it can detect is 0.5 mA and min voltage is 10 V DC). I didnt get any reading or needle movement. I am now not sure if this is due to the tester or TT. Anyways I'll look for slightly accurate tester before responding with my final results.

One question though, since this TT hasnt been used in ages, should I try removing the cartride and refixing to see if there is any issues there?

jls001 - The user M7 user manual says that it has a phono stage but is optimized for CD Audio. Here's the user manual info:

"The M7 has been designed to operate with medium to high output moving coil
cartridges, although it will accept the output of lower level moving magnets as well.
If required there is a small jumper located on the Phono Board that can be moved to
provide an extra 2dB of gain."

So seems like it should work. Probably its a cartridge issue or something else.

Thanks
Badri

 

[Saket]

If you are DIY types, then remove the cart & place the probes directly on the leads of the cart to check. All points should read some value, none should read zero. If its okay, then check the connectors & wires.
What you have quoted from your manual, looks like it can accept MC carts. First I would check the TT , then go to the amp.

 

[reubensm]

The Technics EPS-310MC is one of Technics' moving coil cartridge offerings. Rated by many as one of the best Technics standard fit cartridges. The great thing about this
TT is that is comes with an in-built Moving coil cartridge preamp. So all you have to do is ensure that the internal preamp is on (set the switch for this) and connect your TT to your regular phono input. If no sound comes with this internal preamp switch in on mode, the following can be the issue:

1) break in the circuit between the cartridge and preamp (faulty contacts, break in the tone arm wires, faulty cartridge
2) your internal MC preamp may not be working

keep the volume on your amp at the lowest possible, hold the metallic part of a small screw driver and attempt to touch the cartridge connectors with it, if you hear a loud buzz, separate for each channel with different pins, you'd be sure that your amp and your inbuilt MC phonostage are working. Then you can narrow down to the cart and the tonearm wiring. If you don't hear the buzz, your inbuilt MC phonostage may not be working.

The stylus of this cart cannot be replaced as the cart and stylus is a single unit. You'll have to replace the entire cart if its not working. However any standard p-mount cart (like the audio technica AT93) will fit.

 

[sachu888]

Hi Ksbadri Plinius M7 Pre-Amp only has phono input for MM carts.You will need a MM cart for this preamp or MC pre for your existing cart.
I can offer my 6 month's old Ortofon OM-10 MM cart in exchange with your Techbics MC cartridge
Pl don't take above line seriously as EPS-310 is a P mount cart which won't fit my TT without adapter.
BTW:this cart is discontinued and worth keeping .It was the top of the line cart from Techincs with Boron cantilever.Technics Sl-10 is also a decent liner tracker TT.My suggestion is buy an MC pre and you will be more than happy.
Regards,
Sachin

 

[sachu888]

Hi Badri,
just saw the specifications of Sl-10 it used to come with builtin MC phonostage so you can directly connect it to your amp.Never measure MC cart with multimeter it will destroy coils of cart.

Regards,
Sachin

 

[ksbadri]

Sachin - Thanks for the response. I was about to mention that SL-10 has a pre-pre-amp MC circuit.

Anyways, looks like my problem is related to cart after I removed it and checked. I need to confirm it one last time before making any other move. Planning to hook up a different pre-amp with phono stage & check.

Will keep you guys posted on the updates.

Badri

 

[reubensm]

looks like my problem is related to cart after I removed it and checked.

Hope there's no physical damage to the cart. It is always a cardinal sin to open up something which is working, causing it to fail. :sad: There's an old Russian saying, "If it its'nt broken, don't fix it"

Assuming that everything is fine, p-mounts are generally plugged in so there is no possibility of the connectors getting messed up. However, are you sure that the p-mount cart connectors are making proper contact with the p-mount socket? P-mount sockets (especially the old ones) tend to be have issues with contacts.

 

[ksbadri]

Thanks reubensm.

You're absolutely right about "dont fix if it aint broken".

I was checking to see if there was a contact issue but doesnt seem like one. But here's my hypothesis:

The issue seems to be between the cart and the RCA output (no brainer there).

1. It could be the Cart and I am suspecting this now. I am trying to hook it to
2. or it could be the MC circuit.
3. Or even the MC switch in the rear (maybe its not engaging the circuit).

My only issue with this hypothesis is that, when I checked with multimeter, the expected output from RCA is around 2.5 mV DC whereas the minimum range of the multimeter was 10 V DC, so the reading would be very small. So how am I to take this as a determining factor that cart isnt working or even the MC circuit.

So now I am looking at alternate ways of checking by empirical methods.

Badri

 

[reubensm]

Although it it not generally openly talked about, a MC cartridge can be checked by a digital multimeter (dont use the old electrical one with a needled meter). You'd need a 1K resistor in series with your digital multimeter test probes and use the 2k range. The resultant current across the circuit (while testing the cart) will be too small to cause any damage. Never use the continuity test (the one with the beep) on carts. If your cart tests ok, then

1) your tonearm wiring would need to be checked for continuity
2) the internal MC preamp by-pass switch would need to be checked
3) the MC preamp itself would need to be checked
4) take a look at the wiring from the preamp to its powersupply and output wiring to the RCAs

Assuming that your cart is ok, its got to be one of the above 4 points.

 

[sachu888]

Thanks reubensm.

You're absolutely right about "dont fix if it aint broken".

I was checking to see if there was a contact issue but doesnt seem like one. But here's my hypothesis:

The issue seems to be between the cart and the RCA output (no brainer there).

1. It could be the Cart and I am suspecting this now. I am trying to hook it to
2. or it could be the MC circuit.
3. Or even the MC switch in the rear (maybe its not engaging the circuit).

My only issue with this hypothesis is that, when I checked with multimeter, the expected output from RCA is around 2.5 mV DC whereas the minimum range of the multimeter was 10 V DC, so the reading would be very small. So how am I to take this as a determining factor that cart isnt working or even the MC circuit.

So now I am looking at alternate ways of checking by empirical methods.

Badri

Hi Badri,
Please don't measure your MC cart with DMM.It will ruin your MC cart forever.

Regards,
Sachin

 

[ksbadri]

Hi Sachin

Can you say more about it? As reubensm said if its connected with a 1k resistor the current should be low enough not to cause an issue.

Have you had any experience with DMM? In fact I am about to buy a Fluke DMM. Please let me know if you've had a negative experience with this method.

 

[ksbadri]

Hi Sachin - Can you say more about why DMM should not be used with Cart?

Please let us know of your experience. Would you not recommend this method even if the circuit had a 1k resistor.

 

[reubensm]

Hi Sachin - Can you say more about why DMM should not be used with Cart?

Please let us know of your experience. Would you not recommend this method even if the circuit had a 1k resistor.

1k is not a benchmarked value or threshold, you can increase it to even 10k, all you'll have to do is reduce 10k from the reading you get an open circuit will give you no reading. However I would agree with Sachu and avoid doing it if I am not sure with what I am doing. Suggest you check the other aspects discussed and leave the cart for the very end.

 

[sachu888]

Hi Sachin - Can you say more about why DMM should not be used with Cart?

Please let us know of your experience. Would you not recommend this method even if the circuit had a 1k resistor.

Hi Badri,
I have not personally experienced it as I never had an MC cart.It was suggested somewhere in Audiokarma and Diy Audio.

Regards,
Sachin

 

[gopib]

Hi Sachin - Can you say more about why DMM should not be used with Cart?

Please let us know of your experience. Would you not recommend this method even if the circuit had a 1k resistor.

The current handling capacity of the coil is very low. Hence current that is normally generated by the DMM to measure resistance can burn it out. Just like high current can fuse the coil of a bulb. Using an high resistance range of the DMM should be fine (in the M ohm range). I have recently done this with a Denon cart (I think it was dl103 or something). Of course I was checking for continuity only. The other reason why there is hesitance is because of the
quality of some DMM's and the risk of damage to a costly cartridge.

 

[reubensm]

I have tried it on my father's vintage Shure M81MC cart with the 1k resistor, without any damage whatsoever. This cart is currently doing duty at my cousin's place in Adelaide. This idea was from my father's notes which we hand-wrote from some British audio magazine back in the day. The cross-probe voltages on digital multimeters tend to be lower (may be questionable on the el-cheapo ones available in India) when compared to the old electrical needle-multi meters.

Nevertheless, suggest not to try it as damage is irreversable. Stand by Sachu and Gopib on this count. Try the other alternatives first.