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Old 13th October 2012, 05:15 PM   #7581
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I think also the cooling profiles are missing for the power tansistors in the shunt.
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Old 13th October 2012, 08:32 PM   #7582
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Quote:
Originally Posted by mkoerner View Post
Hi,

I currently have the choice of two Phono-Preamp Projects waiting to be soldered over Winter. I would like to base my choice with which to start on the fact which one handles my current favorite Cartridge better.

It's a a "Low-Z" MM Cartridge with 100R recommended loading, 3R DC Resistance, 1mH Inductivity and ultra-low (0,06mv Edit:@1cm/s) output. The output in fact is so low, that the Trigon Advance in full MC Amplification will not handle it properly.

Will the Paradise be able to work well with such a rare beast?

Any hints welcome

Mike
If you don't mind: what cartridge is that?
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Old 13th October 2012, 08:38 PM   #7583
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Just saw the other comment about the Pickering...
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Old 13th October 2012, 10:26 PM   #7584
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Quote:
Originally Posted by RCruz View Post
I did use lower EL cap values but did not reach a definitive math solution for the relation between its values and the 73.5k bass resistor... Maybe someone can give me a hint.

IMO modding EL cap values affects mostly the infrasonic response.

Modifying the bass resistor really affects the riaa curve in the audible range from 20 to 200hz with a peak between 30 and 50hz.

Anyway it is easy to experiment with and I found that we can adjust bass just by slightly mod the bass resistor.

What I really find important is that with the stock values for the riaa:
9100 ohm and 33.3nF that should form the 318us time constant I get a slightly distorted riaa curve as in the pic below.

I do agree that using 9910 ohm and 32.09nF is a much better aproximation. (9910 x 0.03209 = 318)
Ricardo, use the values I reccomended you and you will havea RIAA precision below 0.1dB among the audio band.
As far as the mathematical relationship goes, like I mentioned some time ago, you will have to calculate the transfer function.
As we all know, it affects the very low frequencies, so I would say as long as you have optimum precision down to 20Hz it means that you extend for at least another decade, which is what my simulation shows as well.

You mentioned you tried the lower ELCAP: how did you find it in comparison with the 2X 6.8mF's?
Did you give it a listen to it?

I would be curious to know.

Last question: how did you extract this measurement with? What instruments do you use?
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Last edited by Stefanoo; 13th October 2012 at 10:46 PM.
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Old 14th October 2012, 10:45 AM   #7585
RCruz is offline RCruz  Switzerland
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The values I got from simulating helped by my riaa calculator (spreadsheet).

There are variables that I am not totally sure about and that I believe can be different from build to build... Namely first stage output impedance and buffer input impedance.

So it is difficult to predict "exact values", but mine are very near yours.
I always measure the components and do adjustments to reach a "probable" precision.

I mainly use a listening panel to evaluate the results and compare with other builds.

Anyway, based on the reports from other builders that used "stock" riaa and caps values, it sounds very good also so I believe it might be system dependent.

Regarding the EL caps, after discussing the subject with JG, I used lower values because I did not have the indicated values, so I do not have the means to compare... but in my case it works wonderfully.... Paradise bass is outstanding IMO.

I am really glad this turned out to be a very flexible design that responds well to tuning.... We will learn a lot from the numerous builders subjective input to come soon
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Last edited by RCruz; 14th October 2012 at 10:52 AM.
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Old 14th October 2012, 12:27 PM   #7586
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Well said, Ricardo.
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Old 14th October 2012, 02:28 PM   #7587
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Yes, I know, the cooling profile is on order, but I need to install the transistors first

Speaking of transistor any need to match the J310 and/or the SK170?
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Old 14th October 2012, 02:53 PM   #7588
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Matching the J-Fets helps to get the initial offset in the buffer down.
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Old 14th October 2012, 02:55 PM   #7589
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Go to post 7482 for advice.
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Old 14th October 2012, 03:31 PM   #7590
pdul is offline pdul  Denmark
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Joachim. How are you keeping track of what has been said in which post?
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