john curl said:
Well, I don't know and honestly I don't care. I'll leave the MC/MM user market in your trustful hands and stick myself with the Linn studio digital recordings. If one would use the new generation of dirty sand extra contaminated with germanium high speed ICs from TI then I guess it would be quiet enough for me. Which doesn't mean much for you or anybody else.
Low noise design is a specialized topic of which I am an expert. Your interests may vary.
P.S. Do you know Ivor? We have been good friends for 1/3 century. I own a Linn Sondek turntable, which is my 3'rd. I purchased the first in 1974. Ever been to the factory? Had a beer or two with Ivor? He exports great Scotch!
P.S. Do you know Ivor? We have been good friends for 1/3 century. I own a Linn Sondek turntable, which is my 3'rd. I purchased the first in 1974. Ever been to the factory? Had a beer or two with Ivor? He exports great Scotch!
john curl said:Out of nothing else to do, let us take apart SE's question. How quiet is good enough? What is good enough for me, an old man? What about a young woman? What about a really low output MC cartridge like the original Ortofon cartridges, that this design was originally made for?
Why do you think that I chose 2 ohms as the input? That is the DCR of the Ortofon cartridge. Yes, it is the cartridge itself that sets the gain. What is the noise figure of this preamp with an Ortofon cartridge? Is it 3dB, 6dB, 10dB? Something else? Hint: With a 10 ohm cartridge, it is 3dB.
3dB?
Not bad.
And what was it you said? "NOISE is EVERYTHING," right?
I just calculated the noise figure for one of Jensen's dedicated MC step-up transformers.
It'll give you about 30dB of voltage gain and with a 10 ohm cartridge and loaded by a MM input's 47.5k ohms, has a noise figure of...
1.6dB.
So, if as John says, "NOISE is EVERYTHING with MC input," you can do better with a transformer.
se
john curl said:What is the DCR of the transformer referred to the input? You have to add that in, you know!
Wow, no mention of the referred DCR of the transformers on the spec sheet? They must run in liquid nitrogen, or use superconductiong wire, or both! Bill, shame on you.
The DCR for both the primary and secondary are in the datasheets, John.
For this particular transformer, the primary DCR is .302 ohms and the secondary DCR is 953 ohms.
se
Sorry Bill!: 
Now that I have the complete data sheet, I notice some low frequency distortion at low frequencies. Would you like to comment on that SE?
For everyone, have you ever tried to photograph the direct output of a phono cartridge directly to an oscilloscope? You will find it VERY BOUNCY. In fact, it is almost impossible to do it without serious hi pass filtering. This is due to minor record warp. This is what makes transformers go crazy. They hate this stuff. Prove me wrong, SE!
Now that I have the complete data sheet, I notice some low frequency distortion at low frequencies. Would you like to comment on that SE?For everyone, have you ever tried to photograph the direct output of a phono cartridge directly to an oscilloscope? You will find it VERY BOUNCY. In fact, it is almost impossible to do it without serious hi pass filtering. This is due to minor record warp. This is what makes transformers go crazy. They hate this stuff. Prove me wrong, SE!
dimitri said:
So what? I was just trying to respond to a challenge. At least I'm not pretending I have reinvented the wheel. Or try to sell a classic, almost textbook, feedback circuit as Wow! something special.
I'm looking into EL2125/27 as buffer with gain or OPA827 as follower. Good enough for me. But then, it might not be good for others. In particular as John is now out-of-the-blue looking at ppm low frequency distortion levels.
john curl said:
Well, yes. Low frequencies is where one would likely expect to find low frequency distortion.
Sure.
"NOISE is EVERYTHING with MC input" --John Curl
For everyone, have you ever tried to photograph the direct output of a phono cartridge directly to an oscilloscope? You will find it VERY BOUNCY. In fact, it is almost impossible to do it without serious hi pass filtering. This is due to minor record warp. This is what makes transformers go crazy. They hate this stuff. Prove me wrong, SE!
Prove that it matters.
se
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