Ortofon MC10 clipping?

[ericross3]

I recently got a smoking deal on a gentleman's older gear. Amongst the haul was a Pioneer PL-707 turntable with an Ortofon MC 10 installed. The fella who sold me the table had not used the stuff in years and said that everything worked well (which so far has been the case), however, he said that all other cartridges and inputs he had worked fine, but the MC 10 would clip when attached to the preamp, a Hitachi HCA-7500 mkii (which was included in the deal). He had the Ortofon STM-72 step-up transformer (included) still attached to the table and had been using it. I would guess that he was using the transformer and still running it through the MC section of the preamp, which is redundant, right? He admitted to not knowing much about the equipment. Would that possibly make the preamp clip? Isn't a step-up transformer meant to run thru the MM section? Or is it meant to run thru an aux input? Should I just run the table directly through the phono section and turn the switch to the MC 0.1mV setting? This is my first experience with an MC cartridge and don't want to do any damage. So, how would you guys proceed? Any help would be appreciated. Thank you.

 

[Blue Shadow]

The STM-72 plugs into the MM input as you believe.

 

[ericross3]

Do you know if running it through the MC section would cause the clipping?

 

[Blue Shadow]

The signal would be close to all that a MC input would want to see and may have overloaded that part of the unit. Don't know if that would be clipping but it might not have sounded too good.

The MC-10 has an output of 1.0mV and the MC input is looking for 1.0mV so you could try that input directly or the STM-72 into the MM phono input and see what you prefer.

 

[jeffjeremy]

Vinylengine.com: Mass 7g, Output 0.1 mV, Frequency 10Hz - 20kHz, Separation 25dB, Balance 1.5dB, Output Impedance 3 ohms, Stylus elliptical 18/8 um, Tip mass: 0.5mg, VTF: 2.0g (1.7 to 2.4g).

Load Impedance
10-20 ohms This is lwr then most MC input load settings of 100 ohms or 1000 ohms. Because the MC-10 has the old school 0.1mV output it may need a step up designed to bump it to 0.3 prior to some (later) MC designed pre sections. Also Ortofon MCA-10 step-up was made for the MC10 cart (it has a fixed 10Ω input impedance).


LOMC(0.1 -1.75 mv) HOMC >2.0mV Output will work on MM pre sections...

 

[ETI_5000]

It probably would have overloaded the MC input, which would make it sound very distorted. It’s hard to find much information about the Ortofon STM-72, but it was designed to step up the voltage from a low output MC to MM levels, so putting that into a MC input would overload it.

The STM-72 is designed to plug into a MM input. Plugging it into a MC input will overload the preamp, while plugging into the AUX input will provide very low volume sound without any RIAA equalisation (bass boost, treble cut). You could also run the MC-10 straight into a MC input.

 

[sqlsavior]

The STM-72 seems to have a turn (voltage) ratio of 1:60, so if the output is .1mV, the preamp would see 6 mV, about normal for a MM input. If however the output is .3 mV (that of the MC-10 Super), then the preamp would see 18 mV, a probable (depends on the design) overload. There is also an MC-10 Supreme, apparently (can't find the spec for it) and who knows what other varieties of "MC-10".

Either way, it shouldn't hurt to try it, even if it clips/overloads the preamp. Just keep the volume down at first, and see what it sounds like. If it sounds distorted on louder passages with the transformer into the MM input, try running without the transformer into the MC input. That *should* be fine. If not, you're probably stuck with the MM input, without the transformer, and having to turn the volume up quite a bit.

 

[jeffjeremy]

Don't forget about the need for the input impedance load to be less then a 30 ohms setting or the freq. response will be off.

 

[rothwellaudio]

You are correct that an mc step-up transformer should be fed into a 47k mm phono input.
However, although feeding it into an mc input would appear to give you far too much gain, the reality is a bit more complicated. The transformer you have has a very high turns ratio (1:60 as stated above) and if the mc input of your Hitachi has a typical mc input load of 100 ohms it will load down the transformer significantly and give a lot less overall gain than you might expect. A 1:60 transformer into a 100 ohm load will present a tiny 0.03 ohm impedance to the cartridge (ignoring winding resistance), hence a significant signal loss right at the start of the chain and lower overall gain than expected.

The options you have are to use the transformer and run it into the mm input, or use the cartridge directly into the mc input. Just see which sounds best.

Unfortunately, there have been various models of MC10 from Ortofon and their outputs have covered a wide range so it would be difficult to say exactly what you have.

 

[ericross3]

Ran it thru the MC input directly late last night (.1mV). Holy cow. Why haven't I had an MC cart before? No clipping at any volume. I will try the transformer tonight just to make sure it's not defective, but I'd be fine if I was stuck with this setup. Thanks I'll let you know how it goes.

 

[muovimies]

It's not that complicated with the various MC10 - they say it right on the front of the cartridge what model it is. The basic MC10 was the very lowoutput model, it's a blue cartridge with MC10 on front (gray background). All the other models have output ranging from 0.3mV to 0.5mV if I recall correctly (MC 10 Super, Super mkII, Supreme)

Ortofon makes a nice moving coil and you're right, IMO generally speaking MCs just seem to do certain things better with the trade off of lower output voltage. But if you like the things MCs do well, it's hard to go back to MM, though of course not all carts are the same and I haven't heard the modern TOTL MMs.

 

[rothwellaudio]

It's not that complicated with the various MC10 - they say it right on the front of the cartridge what model it is.

Perhaps I should clarify. It would be difficult for me to say exactly what the OP has because he just said "MC10" and I can't see it.
I'm assuming (possibly wrongly) that the cartridge and transformer were bought at the same time and the cartridge is the very low output model which would work well with the transformer. If it is a later model with 0.3mV-0.5mV output and a higher source impedance, then the transformer's ratio will be too high to work well with the cartridge.

Still, it's only a question of trying it and listening.

 

[iLUVanalog]

I recently got a smoking deal on a gentleman's older gear. Amongst the haul was a Pioneer PL-707 turntable with an Ortofon MC 10 installed. The fella who sold me the table had not used the stuff in years and said that everything worked well (which so far has been the case), however, he said that all other cartridges and inputs he had worked fine, but the MC 10 would clip when attached to the preamp, a Hitachi HCA-7500 mkii (which was included in the deal). He had the Ortofon STM-72 step-up transformer (included) still attached to the table and had been using it. I would guess that he was using the transformer and still running it through the MC section of the preamp, which is redundant, right? He admitted to not knowing much about the equipment. Would that possibly make the preamp clip? Isn't a step-up transformer meant to run thru the MM section? Or is it meant to run thru an aux input? Should I just run the table directly through the phono section and turn the switch to the MC 0.1mV setting? This is my first experience with an MC cartridge and don't want to do any damage. So, how would you guys proceed? Any help would be appreciated. Thank you.

del....

 

[ericross3]

del....

I don't understand.

 

[rothwellaudio]

I don't understand.

No, I didn't understand it either.
Let us know how you get on with/without the transformer - I'd be interested to hear what you think.

 

[ericross3]

Didn't get chance to try the transformer last night. Will definitely be able to tonight.