Jam -
the RIAA in the schematic minus the JFET buffer and minus the servos has already been built about a year ago. Using separate super shunt regulators for each channel, and an R-core transformer. But with the same higher rails for all OPamps (AD745K + some other OPamp).
Instad of a DC servo, I used trim pots to take down the DC offset.
The input impedance following the RIAA was known so the components were decided with this in mind.
Resistors were all TX2352 nude Vishays, and RIAA-caps were all film and foil PS caps. Both Opamps decoupled with BG N and NX HiQ caps.
Sonically, the sound was almost as good as an all-JFET RIAA (with series regulators). Bass was even better but treble not as smooth as the JFET RIAA.
This time, I would like to be able to use any load (= line amplifier), and not have the trim pots but servo(s) instead.
Nothing special about the RIAA, IMO, but it is in the chosen components and powersupply the good sound quality come from.
We used this adapter (designed by me and Per-Anders) for the RIAA:
Sigurd
the RIAA in the schematic minus the JFET buffer and minus the servos has already been built about a year ago. Using separate super shunt regulators for each channel, and an R-core transformer. But with the same higher rails for all OPamps (AD745K + some other OPamp).
Instad of a DC servo, I used trim pots to take down the DC offset.
The input impedance following the RIAA was known so the components were decided with this in mind.
Resistors were all TX2352 nude Vishays, and RIAA-caps were all film and foil PS caps. Both Opamps decoupled with BG N and NX HiQ caps.
Sonically, the sound was almost as good as an all-JFET RIAA (with series regulators). Bass was even better but treble not as smooth as the JFET RIAA.
This time, I would like to be able to use any load (= line amplifier), and not have the trim pots but servo(s) instead.
Nothing special about the RIAA, IMO, but it is in the chosen components and powersupply the good sound quality come from.
We used this adapter (designed by me and Per-Anders) for the RIAA:
Sigurd
jam said:
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Jam -
the adaptor boards are great when one quickly wants to compare different OPamps in DIL8 (we made some SOIC adapter boards aswell with the same possibility to have decoupling caps of most types of caps on the adaptor board together with a GND wire to main ground.)
I do not think that the series regulators were more noisy. On the contrary.
My thought about the difference in bass sonics is due to the use of JFETs. I wonder, can an OPamp have better bass performance than a JFET-buffer?
I do not want to tell what th JFET RIAA amp was.
SIgurd
the adaptor boards are great when one quickly wants to compare different OPamps in DIL8 (we made some SOIC adapter boards aswell with the same possibility to have decoupling caps of most types of caps on the adaptor board together with a GND wire to main ground.)
I do not think that the series regulators were more noisy. On the contrary.
My thought about the difference in bass sonics is due to the use of JFETs. I wonder, can an OPamp have better bass performance than a JFET-buffer?
I do not want to tell what th JFET RIAA amp was.
SIgurd
jam said:
REL capacitors Film and Foil PS caps are available up to 3uF; the RTX series which is film and tin foil. Their RT serie goes up to 470n.
All from Percy Audio.
Attached is a photo of a 226nF and a 100nF RIFA PS cap.
You will aslo see a 2u2 WIMA cap.
SIgurd
All from Percy Audio.
Attached is a photo of a 226nF and a 100nF RIFA PS cap.
You will aslo see a 2u2 WIMA cap.
SIgurd
Lumba Ogir said:
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Not the soundcard, my noise floor for given setup is about -135dB.
You have not added any resistor noise to your LT1028 estimation, have you? You really know how much noise is for 100ohm, I guess .
With the resistors used, the measurement fits quite well, there is a 6dB difference which indicates to some 2.6nV/rt for LT1028 + resistor network.
You have not added any resistor noise to your LT1028 estimation, have you? You really know how much noise is for 100ohm, I guess .
With the resistors used, the measurement fits quite well, there is a 6dB difference which indicates to some 2.6nV/rt for LT1028 + resistor network.
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