MM RIAA noise

A resource for technical documentation. Datasheets, application notes, instruction manuals, books and links to resources are found in the Document Library.
ricardo
Posts: 262
Joined: Sun Apr 10, 2011 7:24 am

MM RIAA noise

Post by ricardo »

http://www.ti.com/lit/an/snva515c/snva515c.pdf

Not sure if I posted this before. It's the article with a detailed study of MM noise in RIAA amps taking into account the cartridge, RIAA EQ and noise weighting. I thought it was from AD but my senile memory was wrong.

Now converted by TI from the original National AN
emrr
Posts: 570
Joined: Sun Mar 02, 2008 10:27 pm
Location: NC, USA
Contact:

Re: MM RIAA noise

Post by emrr »

Great! That clarifies some of my brain mush. Not ready for the test yet....
Best,

Doug Williams
Electromagnetic Radiation Recorders
User avatar
JR.
Posts: 3700
Joined: Sat May 24, 2008 7:21 pm
Contact:

Re: MM RIAA noise

Post by JR. »

That looks like some of the old national app notes material. I recall using that in the early days with their LM381 and LM387 bipolar phono preamp chips. OK technology for the '70s and my first preamp design (I used two LM387 inside a DJ mixer kit in 1978). This was written before very low noise JFET opamps like we have today.

JR
Cancel the "cancel culture", do not support mob hatred.
ricardo
Posts: 262
Joined: Sun Apr 10, 2011 7:24 am

Re: MM RIAA noise

Post by ricardo »

JR. wrote:That looks like some of the old national app notes material. I recall using that in the early days with their LM381 and LM387 bipolar phono preamp chips. OK technology for the '70s and my first preamp design (I used two LM387 inside a DJ mixer kit in 1978). This was written before very low noise JFET opamps like we have today.
It IS an old National AN.

Dem Texans attemptin' to erase all evidence of NS :o

You get slightly better numbers from da new supa dupa FET OPAs but the important take from that is the inductance of the MM cartridge makes the 47k noise predominant even with 'perfect' OPAs .. especially in the sensitive 4kHz region.

The noise curves I posted some time ago for my MC headamp shows this clearly. Most MCs don't have enough inductance to matter so if the electronics is quiet enough, some MCs can be quieter than the best MMs.
User avatar
JR.
Posts: 3700
Joined: Sat May 24, 2008 7:21 pm
Contact:

Re: MM RIAA noise

Post by JR. »

ricardo wrote:
JR. wrote:That looks like some of the old national app notes material. I recall using that in the early days with their LM381 and LM387 bipolar phono preamp chips. OK technology for the '70s and my first preamp design (I used two LM387 inside a DJ mixer kit in 1978). This was written before very low noise JFET opamps like we have today.
It IS an old National AN.
yup,,,
Dem Texans attemptin' to erase all evidence of NS :o
The victor gets to write the history,,, I learned a lot from those old National Semi design notes. They were an early player with bi-fet op amps but I did not care for their asymmetrical slew rate even though >> than typical bipolars du-juor ignoreing the 5534.
You get slightly better numbers from da new supa dupa FET OPAs but the important take from that is the inductance of the MM cartridge makes the 47k noise predominant even with 'perfect' OPAs .. especially in the sensitive 4kHz region.
There is also a few hundred pF of capacitance in parallel with that 47k while not very low Z at 4kHz, significant for the top audio octave.
The noise curves I posted some time ago for my MC headamp shows this clearly. Most MCs don't have enough inductance to matter so if the electronics is quiet enough, some MCs can be quieter than the best MMs.
My experience was that surface noise for most vinyl pressings would swamp decent pre-amp executions. I appreciate the exercise of optimizing every aspect we have control over, I just gave up on phono preamps a few decades ago, due to non-linear customers. :lol:

JR
Cancel the "cancel culture", do not support mob hatred.
User avatar
mediatechnology
Posts: 5442
Joined: Sat Aug 11, 2007 2:34 pm
Location: Oak Cliff, Texas
Contact:

Re: MM RIAA noise

Post by mediatechnology »

Thanks for posting that ricardo.

I found the original National AN-104 and was surprised to see that it was not in the later "Audio Handbook."
AN-104 dates back to 1974; the Audio Handbook was published in '76 IIRC.
There's no author credited on the original - TI scrubbed a lot of the authors from National's work.
They removed Dobkin and Widlar from some of the early stuff.
emrr
Posts: 570
Joined: Sun Mar 02, 2008 10:27 pm
Location: NC, USA
Contact:

Re: MM RIAA noise

Post by emrr »

I feel certain I'd never seen it. The subjects get discussed plenty of places, but not with such focus.
Best,

Doug Williams
Electromagnetic Radiation Recorders
User avatar
JR.
Posts: 3700
Joined: Sat May 24, 2008 7:21 pm
Contact:

Re: MM RIAA noise

Post by JR. »

I can swear that I remember that exact note, and I've cleared out all my old applications literature. National was pretty good back in those days with support documentation that went above and beyond typical app notes.

I recall very similar noise related documentation published in support of their low noise (for back then) phono preamp ICs (LM381/387) and the LM394 low noise dual transistor. IIRC they had numerous documents assembled into several collections, one or two targeted to audio apps and others more general purpose. They were a great resource for a self taught guy like me. Some of my old bound paperback collections were dog eared from referring to some sections over and over. They managed to convey important concepts while keeping the math (and science) accessible.

Some of the authors for those early app notes went on to important careers in the semiconductor or audio industry.

JR
Cancel the "cancel culture", do not support mob hatred.
User avatar
mediatechnology
Posts: 5442
Joined: Sat Aug 11, 2007 2:34 pm
Location: Oak Cliff, Texas
Contact:

Re: MM RIAA noise

Post by mediatechnology »

I can swear that I remember that exact note, and I've cleared out all my old applications literature.
OK, mystery solved!

It was in the National Semiconductor Audio Handbook in the Appendix § 5.0 pg 6-13 in the 1977 edition.

I looked earlier in the section on phono preamps but didn't see it.
Today, before putting it back away, I leafed through the whole book and found it near the very back.

I'm pretty sure that you're not going to find it John: You sent me your 1976 copy.
User avatar
JR.
Posts: 3700
Joined: Sat May 24, 2008 7:21 pm
Contact:

Re: MM RIAA noise

Post by JR. »

mediatechnology wrote:
I can swear that I remember that exact note, and I've cleared out all my old applications literature.
OK, mystery solved!

It was in the National Semiconductor Audio Handbook in the Appendix § 5.0 pg 6-13 in the 1977 edition.

I looked earlier in the section on phono preamps but didn't see it.
Today, before putting it back away, I leafed through the whole book and found it near the very back.

I'm pretty sure that you're not going to find it John: You sent me your 1976 copy.
I meant to say I CAN'T swear that I've read it before, but it looked familiar... Don't worry I wasn't looking for it... :lol:

JR
Cancel the "cancel culture", do not support mob hatred.
Post Reply