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Ortofon MC-20

Been reading this thread with interest. I have an MC 20 won in a sales contest way back when by a salesman friend of mine who never used it. It came with the Ortofon transformer mounted in a well shielded tube affair. A few years back I mounted it to my Dual 1245, then to my Denon and used it for a while... then put it away. I liked the sound of it but the transformer was hum sensitive... tried everything, all the usual fixes and it remained placement sensitive, with the right orientation it was quiet but move anything and by some degree the hum would return. Tried different amps with all possible ground situations and they were all the same... even replaced the cables with connectronics cable, everything soldered, no difference. The output to the amp was the same as the Shure V-15 three that I had, by same I mean matched the level with the volume control. I never tried the MC 20 with an active MC preamp so don't have anything to offer about that. It was described as being low output, this was at a time MC cartridges were somewhat rare.
 
@spicer do you have the stm-72 from ortofon? Or do you have the MCA-76? You’re not happy with it?
these Mc-20 are a very specific affair. But do sound so good.
 
toby7362 said:
@spicer do you have the stm-72 from ortofon? Or do you have the MCA-76? You’re not happy with it?
these Mc-20 are a very specific affair. But do sound so good.
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I have the STM-72 moving coil transformer that was with the cartridge as delivered. Looks like this:
s-l225.jpg
It worked fine just hum sensitive by proximity to other devices, like amplifiers, but you could orient it to be quiet. I liked the cartridge but to honest always wondered if there might not have been a better match with tone arms... sometimes it was everything one had heard about MC cartridges... transparent, etc., other times not certain I didn't like the Shure V-15 III better. I liked it though... it was won in a sales contest so I didn't have to pay for it.
 
spicer said:
I liked the sound of it but the transformer was hum sensitive... tried everything, all the usual fixes and it remained placement sensitive, with the right orientation it was quiet but move anything and by some degree the hum would return.
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spicer said:
s-l225.jpg
It worked fine just hum sensitive by proximity to other devices, like amplifiers, but you could orient it to be quiet.
Click to expand...
Yes, to a greater or lesser extent, all step-up transformers are prone to being hum sensitive, but it is possible to get them extremely quiet. The following phonostage with its RIAA eq usually has about 40dB gain, which is a lot, but due to the eq curve there's more like 60dB gain at 50/60Hz. That's a huge amount of gain, so any tiny bit of hum picked up by the transformer gets amplified by 60dB and becomes audible. Good screening and clever winding techniques can be employed to minimise the hum picked up from stray magnetic fields, and some transformers are better than others in this regard. You can't simply plonk a transformer down anywhere and expect it to be hum free, and if you place it on top of, for example, a power amp with a large mains transformer, you'll get hum. However, it's possible to site the transformer away from strong magnetic fields and get very low hum indeed.
 
rothwellaudio said:
Yes, to a greater or lesser extent, all step-up transformers are prone to being hum sensitive, but it is possible to get them extremely quiet. The following phonostage with its RIAA eq usually has about 40dB gain, which is a lot, but due to the eq curve there's more like 60dB gain at 50/60Hz. That's a huge amount of gain, so any tiny bit of hum picked up by the transformer gets amplified by 60dB and becomes audible. Good screening and clever winding techniques can be employed to minimise the hum picked up from stray magnetic fields, and some transformers are better than others in this regard. You can't simply plonk a transformer down anywhere and expect it to be hum free, and if you place it on top of, for example, a power amp with a large mains transformer, you'll get hum. However, it's possible to site the transformer away from strong magnetic fields and get very low hum indeed.
Click to expand...
Yes... all true. It was/is definitely being induced into the Ortofon transformer, not generated by a grounding issues. I assumed when I first used it that Ortofon would have provided sufficient shielding for the intended working environment but that does not appear to be the case. Longer cables for relocation away from everything including power cords would eliminate the hum but since I could orient it that is what I ended up doing. At the time... mid 70s, sometime around there... active MC pre preamps were expensive and most components did not have it built in otherwise even Ortofon might have supplied one... at least that is my thinking looking back. The transformer did provide the necessary impedance and voltage conversion though and the cartridge worked well with the amp.
 
Where did you get the TT? Did it come with the cartridge? Did the seller use it and if so with what? Maybe they had the device you need.
 
I wish. It was a contractor clearing out a house. The person left the gear. He also told me he through out all of the other stereo stuff. He kept the tt because he thought it looked cool. I can’t even imagine what he threw out.
 
Hey all
Thank you so much. @HalfApt helped me to realize that my PP2e will output enough for me. I was worried that it wasn’t good to crank it past halfway on the volume knob but it seems ok.

with that said, I am turning my interest over to a different receiver that might have more output and better control over sound. For ex, I have seen that Marantz have a mid control. Is that the only receiver that offered that? If not what other receivers would be a good choice? If I need to change posting spot, I will. Not familiar with all of the ins and outs of the forum rules.
 
toby7362 said:
@HalfApt helped me to realize that my PP2e will output enough for me. I was worried that it wasn’t good to crank it past halfway on the volume knob but it seems ok.
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:dunno: You didn't seem to believe me when I said it.
rothwellaudio said:
If you have to turn up the volume a lot more than you would do for other sources, it isn't really a major problem.
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rothwellaudio said:
My recommendation is to just turn up the volume. If it's as loud as it ever needs to be when flat out, just live with it.
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The volume control is really just an attenuator. It turns things down not up. So using it wide open is just fine if needed. You will hear more noise but you aren't going to break anything if you need that much signal to get the volume as in this case.

You should have told folks you were not going past half way and we could have had you listening in aural bliss a week ago. Glad we got this cleared up.
 
I bought a STM-72 off of the bay years ago -was ready to try it with a Linn Troika -when Rothwell set me straight (really appreciated that) - so- since these were specifically designed for these Ortofon very low output carts ,,,,,,, and that's how I ended up owning 2 MC-10 .a MC-20 ,a MC-100 and a MC-200 - I REALLY like this series of Ortofon carts. STM-72's show up fairly often -prices are all over the place , My guess is that lots of folks try these with either or both : higher output carts or higher gain phono stages -experience overload as a result and sell them on. BUT-if you want a very nice match for these VERY low ouput Ortofon carts - the STM-72 will get you there.
 
Another Ortofon SUT option is the T-20. 32dB gain and a 1:43 winding ratio, it was meant to match cartridges with 3 ohm output impedance, ie. the MC-20.
 
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