Balanced input all DC coupled RIAA preamp

[Joachim Gerhard]

I think the only way is to listen. I found that also the type of resistor is important.
The best sound i got so far is with DaleRN65E. I the case of a conventional input i landed between 150 and 300 Ohm in parallel to the cartridge with Lyra Titan i.
If i understand your circuit right you have not the same impedance in both legs. Taking my variety of your circuit the positive leg whould see 5 ohm and 150 Ohm in series when i ignore the ( high ) input impedance of the positive input of your opamp. The negative leg goes to a 5 Ohm resistor and then to virtual ground so your Koetu whould be loaded with 160 Ohm because both inputs are in seies. Do i see that correctly ?

[FdW]

Originally Posted by Joachim Gerhard

I think the only way is to listen. I found that also the type of resistor is important.
The best sound i got so far is with DaleRN65E. I the case of a conventional input i landed between 150 and 300 Ohm in parallel to the cartridge with Lyra Titan i.
If i understand your circuit right you have not the same impedance in both legs. Taking my variety of your circuit the positive leg whould see 5 ohm and 150 Ohm in series when i ignore the ( high ) input impedance of the positive input of your opamp. The negative leg goes to a 5 Ohm resistor and then to virtual ground so your Koetu whould be loaded with 160 Ohm because both inputs are in seies. Do i see that correctly ?

The 5ohm resistor is the internal series resistance of the cartridge, and not part of the circuit (sorry I forgot to take it out before publishing).

In my opinion the input impedance is 102.2ohms (51.1+51.1). As the voltage difference between +in and -in is virtually zero, it may be seen as a shortcut, and thus the feedback resistor and ground resistor are no part of the input impedance equation. Mmm… (I think).

Regards,
Frans.

[FdW]

Originally Posted by FdW

The 5ohm resistor is the internal series resistance of the cartridge, and not part of the circuit (sorry I forgot to take it out before publishing).

In my opinion the input impedance is 102.2ohms (51.1+51.1). As the voltage difference between +in and -in is virtually zero, it may be seen as a shortcut, and thus the feedback resistor and ground resistor are no part of the input impedance equation. Mmm… (I think).

Regards,
Frans.

And I checked (due to the Mmm... ) and found:
Operational amplifier applications - Wikipedia, the free encyclopedia
Near the header: Differential amplifier

Regards,
Frans.

Or am I way out of line here, and did I read your post wrongly?

[Joachim Gerhard]

You are right.
Differential Zin (between the two input pins) = R1 + R2 (Note: this is approximate)

[Joachim Gerhard]

Yes, the internal impedance beteen Pin2 and Pin3 can be interpreted as a short circuit.

[merlin el mago]

Originally Posted by Joachim Gerhard

Sofar i did not have the luxury to try C core. How does your build sound ? I asume great.

Is the best digital sound ever heard till today, now I'm upgrading with film cap in VRef by Salas advice, Salas v1.0 reg with Rs feeding the Buffalo II DAC + passive resistor + coupling cap as suggested me Erno Borbely for I/V (only penalty low gain)while I wait for the modification in his I/V that I own, so the final setup will be Buffalo II DAC + Erno Borbely I/V.

[kannan_s]

Originally Posted by merlin el mago

Is the best digital sound ever heard till today, now I'm upgrading with film cap in VRef by Salas advice, Salas v1.0 reg with Rs feeding the Buffalo II DAC + passive resistor + coupling cap as suggested me Erno Borbely for I/V (only penalty low gain)while I wait for the modification in his I/V that I own, so the final setup will be Buffalo II DAC + Erno Borbely I/V.

what IV model of Borbley you use here ?
can you show the complete functional connections of Salas shunts ( how many - how do you connect to Buffalo ) etc

Is there a photo?
thanks as I am interested to build one
kannan

[FdW]

Originally Posted by Allen Wright

I consider series regs, such as you are using, are as outdated for good sounding audio as paper in oil caps.

Constant current fed shunt regs are very little more complex to build, but offer huge sonic benefits. There are numerous CCS/Shunt circuits here on DIYAudio.

And I agree with the other poster - your input R's are WAY too large for SOTA noise levels - especially on the MM inputs.

Regards, Allen

Any ideas on this one:

The question remaining, and that I would like to see answered, is this; is using lower value resistors a tradeoff between noise and impedance matching? And to what effect? The bottom line is; what am I paying for the lowered noise floor?

Regards,
Frans.

[merlin el mago]

Originally Posted by kannan_s

what IV model of Borbley you use here ?
can you show the complete functional connections of Salas shunts ( how many - how do you connect to Buffalo ) etc

Is there a photo?
thanks as I am interested to build one
kannan

Actually I'm not using the Borbely I/V till Erno modifie the filter for Buffalo II.

The photo with passive I/V (resistor+coupling cap) few post ago.

The Buffalo II only needs a single +5.5V rail supply so only you need to do a Salas reg. p2p like mine photo or buy a Hipnotyze PCB in the GB.

[FdW]

Originally Posted by FdW

Any ideas on this one:

The question remaining, and that I would like to see answered, is this; is using lower value resistors a tradeoff between noise and impedance matching? And to what effect? The bottom line is; what am I paying for the lowered noise floor?

Regards,
Frans.

Any one, any one... please...