Puresound P10 RIAA

[merlin el mago]

I'm open this new thread to fine tune my Puresound P10 phono RIAA, also I would like to know output impedance of first stage? schematics & real unsoldered components values as follows:

Left channel
R1 329K CADDOCK TF020R
R19 998K CADDOCK TF020R
C9+C8 .00270 paralleled .000106 = 2.806nF teflon film & aluminium foil
R17 38K9 CADDOCK TF020R
C7 .006 paralleled .0022 = 8,2nF teflon film & aluminium foil
R18 99R9 SHINKOH

Right channel
R1 329K CADDOCK TF020R
R19 999k CADDOCK TF020R
C9+C8 .00270 paralleled .000106 = 2.806nF teflon film & aluminium foil
R17 38K9 CADDOCK TF020R
C7 .006 paralleled .0022 = 8,2nF teflon film & aluminium foil
R18 99R9 SHINKOH





Any help will welcome.

[RCruz]

Based on the info here: On 'RIAAEqualization Networks´ and following Lipshitz calc I devised a simple simulator. http://forums.melaudia.net/attachment.php?aid=1301

Excluding the effect of first stage output impedance and also the miller of the second stage, my initial test would be to use:

R17 = 38K9 // 478K = 35973 r

C9//C8 = 2.7nF // 106pF // 220pF = 3.026nF

C7 = 6nF // 2.2nF // 640pF = 8.84nF

Let me know what real values you can get so we can choose the best options.

Of course, all must be recalculated if there is significant output impedance on the first stage and we should also consider miller effect of second stage (I do not know if there is any "forward" miller from the first stage also).

I hope we can get enough input here to come to a consensual result.

Regards
Ricardo

[RCruz]

My assumptions are based on the results of enumerous experiments with Salas Simplistic.

IMO, the 500,5Hz "zero" pole is of fundamental importance to the correct reproduction of the instruments timbre.

> 500,5 Produces less attack
< 500,5 Results in more nasal sound with more attack
= 500,5 Provides perfect Instrument Timbre

According to the simple formula f = 1 / 2pT
500.5Hz corresponds to 318uS time constant

This 318uS is what I am aiming to.

In this case we have R17 = 35973 ohm and C7 = 0.00884uF

R17 x C7 = 318.0013 Very close to 318.

The low frequency pole 50.05Hz and the high frequency 2122Hz are also corrected by my simulator but these depend on the impedance and miller effect on the amplifying stages.

[RCruz]

Similarly to the Simplistic, these SE no NGF designs are much more difficult to implement than the active riaa using feedback as is very well explained here : Audio Gadgets: RIAA Equalization

>>Quote:
Active EqualizationThe advantage of the feedback approach is consistency. Each channel will track the other to a very great degree in spite of aging parts or circuit wiring dissimilarities, as the feedback tends to iron everything out. The disadvantage is that because it is active, it can suffer from voltage overload and instability. Additionally, the varying amount of frequency dependent feedback can result in looser bass reproduction because of smaller amount of feedback at low frequencies and possibly a pinched, compressed high frequency playback due to excessive feedback ratios.

Passive EqualizationPassive RIAA equalization means brute force equalization: the frequency response is tailored to fit that of the RIAA curve by varying the amount of attenuation at different frequencies through a complex RC network. The advantages: no voltage overload, no feed-back, no instability problems. The disadvantages: no gain, insertion loss, impedance matching problems.

End of quote<<

IMO, opamp based Riaa preamps always sound compressed in the high frequencies (due to high feedback ratio)

The simpler SE designs let the sound flow very naturally. Of course, due to the absence of global NFB, these are much more difficult to implement with the same low distortion levels.

Anyway, in a jfet SE input, distortion is mainly 2nd, presenting much lower 3rd than an equivalent differential input.

Also, as there is no global NFB, psrr is quite high so the psu is also very important here.

These SE designs respond very well to psu output impedance tuning.

[merlin el mago]

Wow Ricardo I'm enjoying with your RIAA knowledge.

[RCruz]

I learned a lot because I wanted to understand the differences between the several EQ available (RIAA, IEQ, Columbia, EMI, etc...)

I followed some good threads in this Forum

Parasound JC3 Phono

Which DIY phono-stage gives great results?

RIAA Equalization Standard...

[merlin el mago]

"Excluding the effect of first stage output impedance and also the miller of the second stage

Of course, all must be recalculated if there is significant output impedance on the first stage and we should also consider miller effect of second stage (I do not know if there is any "forward" miller from the first stage also)."

I asked all your questions to the Mr. Gay designer/manufacture Pure Sound P10.

[merlin el mago]

I posted this thread in Analogue Source but I want to post here because it's a tube phono preamp, link to thread:

http://www.diyaudio.com/forums/analo...-p10-riaa.html

[merlin el mago]

please help

[merlin el mago]

bump