Rolling an op-amp
I received this (pictured below) mystery-to-me op-amp as a gift from @6L6 in my Pearl 3 build kit and I couldn't resist trying it as my first op-amp roll. I still don't know what op-amp this is.
First impressions on a classical record were of mellowness and smoothness, almost slowed down compared to the OPA2604's I started with. That led me to a not-great jazz soundtrack and later some more difficult modern records, as I wanted to challenge the playback a bit. Despite the somewhat recessed sound, I didn't feel like this op-amp called attention to the mastering or recording of the records I'd chosen in any way that bothered me- Jack White's complex orchestrations were plenty separated & balanced. Alabama Shakes sounded quite good, and this is a recording that can sound a little narrow or skewed in places.
Tonight I decided to roll amplifiers, swapping the F6 for a non-lottery lottery Sony p-channel VFET. While the midbass whoosh (I don't know what else to call it, it's a VFET/SIT thing) was there, the treble extension was even more muted now. I'm listening to different stuff tonight, as I do, so it's not an A/B but even still, the mood is there. Just goes to show it's worth playing with amps while also playing with op-amps.
This is a super cool Christmas present, by the way. Happy holidays everybody.
I received this (pictured below) mystery-to-me op-amp as a gift from @6L6 in my Pearl 3 build kit and I couldn't resist trying it as my first op-amp roll. I still don't know what op-amp this is.
First impressions on a classical record were of mellowness and smoothness, almost slowed down compared to the OPA2604's I started with. That led me to a not-great jazz soundtrack and later some more difficult modern records, as I wanted to challenge the playback a bit. Despite the somewhat recessed sound, I didn't feel like this op-amp called attention to the mastering or recording of the records I'd chosen in any way that bothered me- Jack White's complex orchestrations were plenty separated & balanced. Alabama Shakes sounded quite good, and this is a recording that can sound a little narrow or skewed in places.
Tonight I decided to roll amplifiers, swapping the F6 for a non-lottery lottery Sony p-channel VFET. While the midbass whoosh (I don't know what else to call it, it's a VFET/SIT thing) was there, the treble extension was even more muted now. I'm listening to different stuff tonight, as I do, so it's not an A/B but even still, the mood is there. Just goes to show it's worth playing with amps while also playing with op-amps.
This is a super cool Christmas present, by the way. Happy holidays everybody.
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No mystic OPAmp,
it is the NISSHINBO / Japan Radio Corporation
JRC 2068 DD (or NJM 2068 DD)
A very nice OPAmp.
Cheers
Dirk 😵
it is the NISSHINBO / Japan Radio Corporation
JRC 2068 DD (or NJM 2068 DD)
A very nice OPAmp.
Cheers
Dirk 😵
I am going into the next round...
Started to stuff a second set of my PEARL 3 -pcbs... This time with the TOSHIBA 2SK209GR as input-JFets.
Matched an octett. Needed only some more than 20. They are pretty close off the role - as Wayne mentioned.
And still playing with the OPAmps. Some of my favourites till now: TI OPA1656, LME49720
The ANALOG DEVICES LT1128 didn't work. Don't ask me why?
Have fun!
Cheers
Dirk 🙂
Started to stuff a second set of my PEARL 3 -pcbs... This time with the TOSHIBA 2SK209GR as input-JFets.
Matched an octett. Needed only some more than 20. They are pretty close off the role - as Wayne mentioned.
And still playing with the OPAmps. Some of my favourites till now: TI OPA1656, LME49720
The ANALOG DEVICES LT1128 didn't work. Don't ask me why?
Have fun!
Cheers
Dirk 🙂
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The Analog Devices LT1128 appears to be a singleton. Its 8 pin package only contains one opamp circuit. However the Pearl 3 PCB laid out by W. Colburn requires dual opamps, having two amplifiers per package.
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You could use one of these if you have a lot of single opamp on hand…
Store Santa works even during Christmas period! 🙂
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PSU Group Buy Update.
64 kits are packed up and ready for shipping.
If you're signed up already or if you're interested in joining the GB See Post #51 for more info. https://www.diyaudio.com/community/...no-crcrc-power-supply-parts-kit.406461/page-3
64 kits are packed up and ready for shipping.
If you're signed up already or if you're interested in joining the GB See Post #51 for more info. https://www.diyaudio.com/community/...no-crcrc-power-supply-parts-kit.406461/page-3
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Yup,
silly mistake... 🙄
But I still have adapters from two-single-OPAmp to dual-OPAmp. Will see if there is enough place around the DIP-8-socket.
Thanks for the hint!
Cheers
Dirk 😆
Been re-reading this thread and see a lot of discussion about setting impedance for MC, and a fairly simple method to zero in on the best setting is to increase the impedance until the highs get a bit tizzy the setting below that will likely yield a nice detailed and open sound.
Hello,
I am not ready for the fancy separate enclosures just yet.
Also I am going to pass the cookie tins for testing.
For the prototype I am using 10 X 10 X 4 inch Hammond NEMA 1 16 Ga steel enclosures bonded together with 12 AWG stranded THHN conductors. Thicker than a cookie tin. The umbilical will be a length of SO or SJ cord. I do not understand using Canare microphone cable with the shield as a current carrying conductor. It seems to me that the braided shield would not do much shielding, same same as the RCA cables connecting the turntable / cartridge signal to the vinyl preamp.
Another thought:
The input stage has a 15 volt positive supply causing the +rail to draw more current than the negative rail. I kind of wonder what adding a parallel resistor to the negative rail load will do? Select the resistor to equal the current draw on both + and - rails.
Thanks DT
https://www.mouser.com/ProductDetail/546-CS10104
I am not ready for the fancy separate enclosures just yet.
Also I am going to pass the cookie tins for testing.
For the prototype I am using 10 X 10 X 4 inch Hammond NEMA 1 16 Ga steel enclosures bonded together with 12 AWG stranded THHN conductors. Thicker than a cookie tin. The umbilical will be a length of SO or SJ cord. I do not understand using Canare microphone cable with the shield as a current carrying conductor. It seems to me that the braided shield would not do much shielding, same same as the RCA cables connecting the turntable / cartridge signal to the vinyl preamp.
Another thought:
The input stage has a 15 volt positive supply causing the +rail to draw more current than the negative rail. I kind of wonder what adding a parallel resistor to the negative rail load will do? Select the resistor to equal the current draw on both + and - rails.
Thanks DT
https://www.mouser.com/ProductDetail/546-CS10104
A very nice addition to a ttbl is some form of end of record lift. I am aware of a few designs and their variations, my favorite being the Audio Technica Safety Raiser, Chinese variations of this can be had for a little over $50, last time that I looked. The downside to this device is that it doesn't fit a lot of tables, my Clearaudio being 1. The Q-Up is what I currently use and it works well enuf, it is very easy to accidentally slide the main unit out of alignment and the lift is not as damped as the AT versions.
I just ordered a bunch with the same thing in mind.
May I ask - what degree of compulsion do you recommend?