Calculating inductor based passive RIAA

[davidsrsb]

I have used MM cartridge inductance as one of the poles of a RIAA preamp with a series resistor into a virtual earth ie inductance values of around 1H
This realistically will always need high permeability core and a lot of fine turns. This results in all of the resistance, capacitance and core material loss issues that stop MM cartridges managing flat response to 20 kHz and beyond

 

[kaputt]

Then you were using really crappy inductors.

 

[kaputt]

Those who seek to minimise the number of wound components. These people form a clear majority of circuit designers so it is in order to describe them as "most".

Ok, talking about circuit designers is useful information. Especially as I am sure that a global "most people" don't know what an inductor is anyways.

Btw, I looked for the best selling piece of audio gear on Amazon, which also seems to have little inductors and therefore is chosen by people:
http://www.amazon.com/Amazon-SK705DI-Echo/dp/B00X4WHP5E/ref=zg_bs_667846011_1

 

[billshurv]

you are now trolling.

 

[DF96]

I have used MM cartridge inductance as one of the poles of a RIAA preamp with a series resistor into a virtual earth ie inductance values of around 1H

That might create problems as most MM manufacturers use the normal LCR peak to offset mechanical issues. Change the loading and the result may be electrically 'correct' but no longer compensate for the mechanical issues. Unless, of course, it was a homemade MM so everything was under your control.

 

[billshurv]

That might create problems as most MM manufacturers use the normal LCR peak to offset mechanical issues. Change the loading and the result may be electrically 'correct' but no longer compensate for the mechanical issues. Unless, of course, it was a homemade MM so everything was under your control.

It can work very well. Look at the Cordell vinyltrak design where he calls it damped eq. But you do have to know if you cartridge has a resonant boost or not. Newer MMs seem to suffer from this more than the best of the late 70s and early 80s.

 

[Conrad Hoffman]

Inductors are sufficiently flawed as to make them very interesting to play with. I've no idea how well it will work, and the values are bound to be inconvenient, but I'd say go for it! I'd make up a winding jig with a crank, counter and drill chuck and wind them yourself.

 

[SY]

Btw, I looked for the best selling piece of audio gear on Amazon, which also seems to have little inductors

This also sells well, has very positive reviews, and uses inductors.

Better than RIAA

 

[kaputt]

you are now trolling.

No. I am not. It's sometimes hard to make out a tone in written. And why I value DF96's contributions to the forum and see him as one of the few who seem to know what they are talking about I felt he is trying to spit on a circuit concept because he disregards it because he uses some other concepts.
Building an LRnoC pre in my book is a respectable approach and I find trying different circuits way more interesting than rolling of components, be it tubes, capacitors or even resistors.

Just wait until I post about my signal transformer core rolling adventures

 

[billshurv]

He said 'minimum wound components'. Which makes total sense. Use them where you have to and not where you don't. You have to use wound components in transformers for example, and speaker crossovers. Most other places you would only use them for

A) marketing mystique
B) For fun, or more accurately the academic exercise of trying to get them to work well.

http://www.pmillett.com/file_downloads/LR Phono Preamps.pdf is a very good read on why inductor based RIAA is challenging. Pete's stuff is always worth reading.

 

[billshurv]

I should also add that I was only talking about audio frequencies. As we head in the RF band inductors end up being necessary as well as appearing in all sorts of places you don't want them.

 

[Pulatom]

Looks like LR vs RC equalization is a pretty hot topic, just like CD vs Vinyl

A) marketing mystique

And THAT is the main reason for various odd materials and circuits being used in commercial audio equipment.

Of course I will have to wind my own inductors for this circuit, but I made a few output trannys for guitar amps and it isn't as scary as it looks like.

 

[DF96]

I felt he is trying to spit on a circuit concept because he disregards it because he uses some other concepts.

You misjudge me. I do not "disregard" LR networks because I do things a different way; I warn against them because they do not work very well. I am warning someone who appears to be inexperienced (his opening question implies this) that the path he is contemplating is likely to lead to frustration. At best he will achieve results somewhat inferior to a CR circuit; more likely is that he will not even get that far.

It will be a useful learning exercise. At the end of it he will better understand why few people use LR for RIAA - except for those who are trying to write a good story to sell some product.

Building an LRnoC pre in my book is a respectable approach and I find trying different circuits way more interesting than rolling of components, be it tubes, capacitors or even resistors.

Rolling of components could only be of interest to people who know little of circuits. Trying to maximise the performance of an inappropriate circuit may be a "respectable" approach for a hobby, provided that the hobby in question is building circuits rather than listening to music.

Looks like LR vs RC equalization is a pretty hot topic, just like CD vs Vinyl

No. CD vs vinyl is a hot topic for some. LR vs RC is more a matter of common sense vs eccentricity.

 

[Pulatom]

That's right. LR preamp, especially with tubes (Op Amps would be easier to use because of their low output impedance), is quite an eccentric thing. But even using analog equipment is considered odd/eccentric by a lot of people. I think I can live with that .