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RIAA preamp into my sony gx69es
RIAA preamp into my sony gx69es
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Old 26th December 2017, 01:47 PM   #1
pat allen is offline pat allen  Canada
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Default RIAA preamp into my sony gx69es

Hi, its been a while last time i posted on this forum....

I do have this Sony GX69Es integrated amplifier that i like a lot, mated to a Technics Sl2000 turntable on a fresh needle setup.

i always found its sound to be "dry" no matter what.

i was wondering if any experienced electronics guru would dare to look at the schematic of the riaa preamp itself and pinpoints potential "improvements" to give more hump to this set-up.
yes i am thinking about altering the riaa curve or whatever that could improve its sound rendering.

fwiw the whole amp got a capacitor refresh with some nichicon fg and elna silmics (i know there are other choices, better than nothing there), no noticeable improvements once done.

thanks.
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Old 26th December 2017, 03:15 PM   #2
ALPUY is offline ALPUY  Uruguay
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RIAA preamp into my sony gx69es


Modified (560k to 680k)

RIAA preamp into my sony gx69es
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Old 26th December 2017, 03:45 PM   #3
pat allen is offline pat allen  Canada
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so you mean by changing the 560k to a 680k makes a difference in the low end response ?
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Old 26th December 2017, 04:30 PM   #4
ALPUY is offline ALPUY  Uruguay
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Yes. We are modifying the values of the RIAA equalization components.
In this case, by increasing from 560k to 680k, you increase the low frequencies and decrease the average lows a bit, which are what give the sensation of "dry blow".
In the forum there are people who know a lot about the subject (AndrewT, Calvin, RJM, Vulejov, etc)
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Old 26th December 2017, 04:45 PM   #5
rayma is online now rayma  United States
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Quote:
Originally Posted by pat allen View Post
so you mean by changing the 560k to a 680k makes a difference in the low end response ?
A better value for C505 seems to be 1.57nF, so add a parallel 68pF across it.
All the other component values (including R526) are close enough as-is.

Last edited by rayma; 26th December 2017 at 04:50 PM.
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Old 26th December 2017, 05:40 PM   #6
ALPUY is offline ALPUY  Uruguay
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RIAA preamp into my sony gx69es


I have simulated replacing the capacitor C505 with value of 1.57nF.

It is closer to a flat response. But what you want is to decrease the "dry" sound and give more warmth to the low frequencies.
You choose.
I'll tell you, I have a Marantz PM6006 integrated amplifier with a phono preamp with excellent sound, but I'm using an external phono preamp (Kit VSPS 400 from RJM) connected to the auxiliary.
Result: superior sound; more details; broader soud stage.
I repeat your choices from changing a resistor, a capacitor or using a good external phono pre.

Last edited by ALPUY; 26th December 2017 at 05:42 PM.
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Old 26th December 2017, 05:53 PM   #7
rayma is online now rayma  United States
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Originally Posted by ALPUY View Post
I'm using an external phono preamp (Kit VSPS 400 from RJM) connected to the auxiliary.
Result: superior sound; more details; broader soud stage.
I suspect he should just buy a new and better design external RIAA preamp.

Last edited by rayma; 26th December 2017 at 06:03 PM.
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Old 27th December 2017, 01:22 PM   #8
pat allen is offline pat allen  Canada
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fow now i want to keep the modifications as simple as possible. i will try to change the resistor and maybe the cap too and will let you know how it goes.
thanks a lot guys !!
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Old 27th December 2017, 02:18 PM   #9
MarcelvdG is offline MarcelvdG  Netherlands
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Increase R523 to 82 kohm; assuming an ideal op-amp, right now the input shunt resistance at audio frequencies is (R523 // R524) + R501 ~= 32.3 kohm, while all normal MM cartridges are designed for 47 kohm. This makes a difference for the treble, not for the bass.

Last edited by MarcelvdG; 27th December 2017 at 02:22 PM.
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Old 27th December 2017, 07:56 PM   #10
pat allen is offline pat allen  Canada
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Quote:
Originally Posted by ALPUY View Post
Yes. We are modifying the values of the RIAA equalization components.
In this case, by increasing from 560k to 680k, you increase the low frequencies and decrease the average lows a bit, which are what give the sensation of "dry blow".
In the forum there are people who know a lot about the subject (AndrewT, Calvin, RJM, Vulejov, etc)
i made a search and didnt realy found anything about the dry blow sensation.
id like to read read more about it, if you could point me to some threads about it i would appreciate
regards,
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