I think I will have a seat here to build one. Reading it seems to be a really good proyect (thanks PMA) and easy as my first DIY item.
I see best option is OPA627 but expensive and as low cost alternative is recommended OPA134.
But, ommiting DIP encapsulation, between OPA827 and OPA134 which of them will give you better result?
I see best option is OPA627 but expensive and as low cost alternative is recommended OPA134.
But, ommiting DIP encapsulation, between OPA827 and OPA134 which of them will give you better result?
I built my Opanamp1 using Craigtone's board. I used the ADA4627-1 for the gain stage and have had hundreds of hours of listening happiness. I used an LME49600 for the buffer (swapped pins around and deleted the bandwidth resistor) because I like it and had some on hand. I did not install the input diodes.
I tried the OPA 827 but it did not sound right. I since bought a couple OPA 828s but right now I just want to leave the Openamp1 like it is.
Some day when I feel more affluent, I might buy a couple OPA 627s to try.
I tried the OPA 827 but it did not sound right. I since bought a couple OPA 828s but right now I just want to leave the Openamp1 like it is.
Some day when I feel more affluent, I might buy a couple OPA 627s to try.
Just finished building Opanamp1 using pcb from craigtone. Using Jung/Didden Superreg for the PS. Will listen for a few days and post my findings.
Question:
In reference to post#60
"above 1kHz the noise in MM preamp is dominated by the 47k standardized load resistor"
The following phono preamp uses what they call "electronic termination" or "“Electronic Cooling” and according to this whitepaper it reduces the input noise by (in the limit) 13.28 dB
whitepaper:
www.akitika.com/documents/ElectronicCooling.pdf
schematic:
www.akitika.com/documents/SchematicPhonoPreampRevB4.pdf
Does this technique reduce the noise caused by the loading resistor? Has anyone tried this?
Question:
In reference to post#60
"above 1kHz the noise in MM preamp is dominated by the 47k standardized load resistor"
The following phono preamp uses what they call "electronic termination" or "“Electronic Cooling” and according to this whitepaper it reduces the input noise by (in the limit) 13.28 dB
whitepaper:
www.akitika.com/documents/ElectronicCooling.pdf
schematic:
www.akitika.com/documents/SchematicPhonoPreampRevB4.pdf
Does this technique reduce the noise caused by the loading resistor? Has anyone tried this?
Probably because most MM phono stages are already several db quieter than the surface noise of records and the noise from cartridges. There is a National semiconductor app note that calculates the noise from typical MM cartridge. If you measure the noise from a MM preamp with the inputs shorted it will be lower than when a cartridge is connected. Cue a record and the noise goes up again. It's one of those diminishing return things.
Just curious: did you use old vintage OPA827 or newer vintage? A TI engineer has posted on this board that a mask change was made to the OPA827 that improved it's performance. The later ones are measureably better than the earlier ones.
mlloyd1
The OPA 827s were purchased approximately December 2020 from Mouser. I have since gone to the OPA 1656 with the adapter wired for single channel, and like it a little more than the ADA-4627-1. For my MC cartridge, I put OPA-1656's in my Emerald in the second stage (AD797 input stage) with great success as well.
I don't remember. Best to find johnc124 post on the topics. i'll search too but not right now ...
OK, i found it:
https://www.diyaudio.com/community/...jfet-input-op-amps.264797/page-3#post-6972689
post #49 in the thread in case the link doesn't work. the post prior gives some test data that prompted john's reply.
https://www.diyaudio.com/community/...jfet-input-op-amps.264797/page-3#post-6972689
post #49 in the thread in case the link doesn't work. the post prior gives some test data that prompted john's reply.
I used this technique professionally in a tape head preamplifier. Like a Phono cart, a tape head is primarily inductive and very low noise by itself. And like a phono cart, a tape head needs a damping resistor to control the resonance that occurs due to the amplifier's input capacitance. This technique works very well and I recommend it.
Hello Pavel,
I decided to build your mm preamp as a complement to the digital source. Which of these modern ICs would you recommend for my first position?
Here are my candidates:
1, opa827aidr + socket
Input voltage noise density (1khz @4 nV/√Hz), Input offset voltage (75 μV)
2, opa828id + socket
Input voltage noise density (1khz @4 nV/√Hz), Input offset voltage (50 μV)
3, opa627au + socket
Input voltage noise density (1khz @5,6 nV/√Hz), Input offset voltage (280 μV)
Thank You
I decided to build your mm preamp as a complement to the digital source. Which of these modern ICs would you recommend for my first position?
Here are my candidates:
1, opa827aidr + socket
Input voltage noise density (1khz @4 nV/√Hz), Input offset voltage (75 μV)
2, opa828id + socket
Input voltage noise density (1khz @4 nV/√Hz), Input offset voltage (50 μV)
3, opa627au + socket
Input voltage noise density (1khz @5,6 nV/√Hz), Input offset voltage (280 μV)
Thank You
Well almost done, I was a bit scared of smd soldering but in the end it turned out pretty good. On the first position I used the excellent ADA4610-1 and the servo is in charge of the OP177GPZ. I'm just waiting for the LT1010 and it will be done.
Capacitors and resistors which are responsible for the RIAA curve I tried to select within 1% tolerance.
The OPENAMP1 power supply is finally taken care of by a shunt regulator from Dadod. PCB shunt regulator in smd version are on their way.
Capacitors and resistors which are responsible for the RIAA curve I tried to select within 1% tolerance.
The OPENAMP1 power supply is finally taken care of by a shunt regulator from Dadod. PCB shunt regulator in smd version are on their way.
