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  #1  
Old 09-14-2018, 01:27 AM
Cajunpepe Cajunpepe is online now
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Default Why no 47k ohm setting on c500?

Any reason for nat having a “wide open” or 47k ohm as a selection for MM capacitance setting on the c500 preamp?

I ask because I want to run a low output MC cart (0.25 mV) through a Bob’s Devices step-up transformer into the MM stage. I believe these step-ups are designed to be run into a 47k ohm cap setting, but the c500 has an upper limit of 750 ohms.

The cart is a Denon 103R.

Yes, I know I can run it through the MC, and I have—but the gain was not enough...and I run a second MC cart (Lyra Titan i) through the MC stage as a primary.

The step-up transformer does give the necessary gain (even on the “low” setting) needed for the MM stage, but it doesn’t have some of the low end snap I feel it should have, and the high end sounds restrained.

Any suggestions?

Any insight as to why Mac doesn’t offer a 47k ohm setting for MM?
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Old 09-14-2018, 02:31 AM
uglatto uglatto is online now
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I believe that you are confusing capacitance for input impedance, which, according to the C500 owner's manual, is 47K ohms. Input impedance is expressed in ohms, while capacitance is expressed in pF.

As to why you're not getting what you are looking for, out of your step up transformer, your guess is as good as mine. I'm sure that somebody, a lot more knowledgeable than myself, will come along shortly to offer some insight. Good luck getting it sorted out.
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Old 09-14-2018, 08:55 AM
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Spec's from the manual:
Input Impedance
High Level: 22K ohms
Phono:
MM, 47K ohms; 50 to 750pF, in 50pF steps
MC: 25, 50, 100, 200, 500 or 1,000 ohms; 100pF

Setting the MC to 100 ohms is recommended by some reviewers for the Denon 103R
The C500 MC phono stage has 60db of gain which should be enough. Check your input trim settings which can be adjusted +-6dB.

Ron
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Old 09-14-2018, 11:47 AM
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I run a Denon DL103 mc Cartridge which has .25mv output into my C2500 preamp at 100 ohms and I have plenty of volume. Putting the volume control at 45 is as loud as I would want it and it sounds really excellent. I had a Bobs Devices SUT with the red Cinemag transformers and tried it into the MM input, but liked the MC input without transformer better. It sounded more pure with more body and weight.
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Old 09-14-2018, 04:09 PM
Cajunpepe Cajunpepe is online now
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It is in a second system where I am using Maggies, which are taking every last watt out of the amps—and I listen at high levels, so as I said before, the output is not high enough...and as stated above, I am using the MC stage for a Lyra cart.
The output is a good bit lower than any of the other 5 carts I use.

I would like to use a 47k ohm load setting for the MM stage, but 750 ohm is the max. I have a few stand alone MM/MC phono stages that have a MM load setting option of 47k ohms, but the Mac doesn’t offer one...why not?
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Old 09-14-2018, 04:12 PM
Cajunpepe Cajunpepe is online now
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I also found the Denon 103R to be best at 1000 ohms when using the MC stage...it just needs a bit of a bump in output.

Thanks for the replies.
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Old 09-14-2018, 04:24 PM
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Quote:
Originally Posted by Cajunpepe View Post
I would like to use a 47k ohm load setting for the MM stage, but 750 ohm is the max. I have a few stand alone MM/MC phono stages that have a MM load setting option of 47k ohms, but the Mac doesn’t offer one...why not?
So the spec's I posted above are not correct?

Phono:
MM, 47K ohms; 50 to 750pF, in 50pF steps
MC: 25, 50, 100, 200, 500 or 1,000 ohms; 100pF

Ron
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Old 09-14-2018, 05:31 PM
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Quote:
Originally Posted by Cajunpepe View Post
It is in a second system where I am using Maggies, which are taking every last watt out of the amps—and I listen at high levels, so as I said before, the output is not high enough...and as stated above, I am using the MC stage for a Lyra cart.
The output is a good bit lower than any of the other 5 carts I use.

I would like to use a 47k ohm load setting for the MM stage, but 750 ohm is the max. I have a few stand alone MM/MC phono stages that have a MM load setting option of 47k ohms, but the Mac doesn’t offer one...why not?
See post #2.
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Old 09-14-2018, 05:44 PM
Cajunpepe Cajunpepe is online now
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OK...I got it now.

So the MM stage is set to 47k with variable capacitance settings. That being the case, would changing capacitance setting among the 50pF to 750pF range alter the sound using a step-up with a MC cart? Is there a better setting (mathematically speaking)? The carts internal impedance is 14ohm, and I am using a 20:1 ratio for the step-up.

Thanks again for the replies—appreciate the help and explanations.
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Old 09-14-2018, 10:23 PM
Cajunpepe Cajunpepe is online now
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And yes, I was misreading and confusing the capacitance and ohm figures....my brain was turned to “off”...happens sometimes for some unknown reasons (age maybe?).

Thanks again.
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