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Old 10th December 2015, 09:01 AM   #1
Pulatom is offline Pulatom  Poland
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Question Calculating inductor based passive RIAA

I was thinking about making a phono preamp without caps in RIAA circuit.

Will this topology be good?

Click the image to open in full size.

If so, how to calculate the inductors and resistor values? (knowing the preceding stage output impedance and following stage grid resistor value).
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Old 10th December 2015, 09:34 AM   #2
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Just because something is possible does not make it sensible. Realistic values of grid and output impedance will require very high inductance values
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Old 10th December 2015, 09:51 AM   #3
jcx is offline jcx  United States
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the right material, construction caps are some of the most linear, near ideal components in electronics for audio frequency

the best inductors are usually poor to very bad in nonlinearities, parasitics, frequency dependent losses...

Last edited by jcx; 10th December 2015 at 10:04 AM.
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Old 10th December 2015, 10:01 AM   #4
DF96 is online now DF96  England
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Those who wish to use an unusual topology should understand it enough to know why they want to use it instead of the more common better topologies. As a side effect of this, they will know how to calculate it.

There are good reasons why people generally use C and R for RIAA networks.
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Old 10th December 2015, 08:01 PM   #5
Pulatom is offline Pulatom  Poland
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I am fully aware of all limitations and difficulties related with this type of RIAA correction. But I'm willing to try it anyway, just for fun.

To be honest, I don't "understand" why I want to use it. But I also don't understand why I'm using turntables and single ended triode amplifiers in 2015 when there's class D amplification and high end digital audio equipment all around :P. From what I know, there ARE some commercial RIAA preamps using L filters, so there are some people who might be preferring them.
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Old 10th December 2015, 08:44 PM   #6
kaputt is offline kaputt  Germany
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The good reasons for building phono correction networks from rc networks is that it requires little thought, little space, little money and little courage.
The sound quality you get out of network copied from the RCA manual is the same: little.
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Old 10th December 2015, 08:46 PM   #7
kaputt is offline kaputt  Germany
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Pulatom, check this: European Triode Festival - ETF.13 Competition
A "No C" RIAA Preamp

https://www.google.de/url?sa=t&rct=j...yVbH9TzQeBWXGQ
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Old 11th December 2015, 08:35 AM   #8
Pulatom is offline Pulatom  Poland
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Thanks for the links, a very interesting read. Though I don't consider RC preamps bad sounding (for now), I got bored of making them and LR seems a nice alternative .
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Old 11th December 2015, 09:55 AM   #9
DF96 is online now DF96  England
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Quote:
Originally Posted by kaputt
The good reasons for building phono correction networks from rc networks is that it requires little thought, little space, little money and little courage.
Does "courage" improve audio reproduction?

Quote:
The sound quality you get out of network copied from the RCA manual is the same: little.
It could still be better than an LR network.

Quote:
Originally Posted by Pulatom
I got bored of making them and LR seems a nice alternative
"Nice" in what sense? More hum pickup, more expensive, more distortion, lower Q (so requiring circuit compensation) - all 'nice' features to have in a circuit.
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Old 11th December 2015, 10:30 AM   #10
SY is offline SY  United States
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Quote:
Originally Posted by DF96 View Post
"Nice" in what sense? More hum pickup, more expensive, more distortion, lower Q (so requiring circuit compensation) - all 'nice' features to have in a circuit.
Let's be fair- one could easily argue that using a tube amp is similarly crazy, yet you and I both do. Why? It's entertaining to use a (now) uncommon technology, and with proper design and construction, we get performance good enough to be "hi fi."

Now, if one claims that an LR preamp will outperform a competent RC circuit, I would want to see some good data backing up that remarkable claim (or an analogous claim about a tube amplifier outperforming a competent solid state design).
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