Maybe that chip needs it. I haven't used it. If this improves it, the chip was either intended for another use and low quiescent current draw was an important spec. or you could make a better choice in chips.
If you read the datasheet, just for 3 seconds, you would know that this was, and still is, a quite decent, low noise, low distortion audio opamp.
Not intended for other uses particularly.
Among today's opamps maybe a few will rival the LT1115, but not many IMHO.
Not intended for other uses particularly.
Among today's opamps maybe a few will rival the LT1115, but not many IMHO.
Well, I haven't used it because there are others I use.
I'll say one thing. If it needs an external circuit to improve performance, it wasn't well conceived. THat's what leads me to believe its intended use may be in a different direction.
Think about this. The 4136 was intended as an audio amplifier, complete with non-standard pinout. Does that mean it was good choice back then? No! It had very low current consumption and I think that was one of the primary design concerns. I'll look, and may find the LT1115 is intended for portable applications (meaning low current draw is a prime concern).
... Hmm, lowest distortion. That means the current sink doesn't help it.
I'll say one thing. If it needs an external circuit to improve performance, it wasn't well conceived. THat's what leads me to believe its intended use may be in a different direction.
Think about this. The 4136 was intended as an audio amplifier, complete with non-standard pinout. Does that mean it was good choice back then? No! It had very low current consumption and I think that was one of the primary design concerns. I'll look, and may find the LT1115 is intended for portable applications (meaning low current draw is a prime concern).
... Hmm, lowest distortion. That means the current sink doesn't help it.
I really like Linear Technology's products. Not really audio related, but when I've used LTs product in switching power supplies, it worked. ... and worked how it was in the datasheet.
I have just went through the datasheet of the LT1115 and what is in the appnotes? An MC preamp (and an MC input + riaa with series correction network, not in feedback loop - what I'm not interested in now, but I remember that when I've used opamps, I've preferred series riaa network over feedback loop clearly. ).
Back on page 11, why it needs a servo? Would this block subsonics also?
Interesting.
Anyway, now I wait for the PCBs and will try a few opamps, including AD797 (is that considered a proper opamp?) in the circuit I've shared. Maybe I get a pair of LT1115, but not with the servo first.
Thanks!
JG
I have just went through the datasheet of the LT1115 and what is in the appnotes? An MC preamp (and an MC input + riaa with series correction network, not in feedback loop - what I'm not interested in now, but I remember that when I've used opamps, I've preferred series riaa network over feedback loop clearly. ).
Back on page 11, why it needs a servo? Would this block subsonics also?
Interesting.
Anyway, now I wait for the PCBs and will try a few opamps, including AD797 (is that considered a proper opamp?) in the circuit I've shared. Maybe I get a pair of LT1115, but not with the servo first.
Thanks!
JG
LT probably have (had) the nicest datasheets out there, stylistically at least, and lots of interesting ICs.
I am using ortofon step up transformers, but one day i with try this simple circuit.
Attachments
Adding to the great suggestions here, I might point you to research Wyn Palmer’s LOMC phono stage.
The LOMC input uses a choice of AD797 or LT1115, among others, and can be configured for MM as well. The MC gain is 63dB, with an additional +10dB boost available, and 28dB of headroom across the spectrum to 50kHz. The sequence of versions for this phono stage saw improvements in layout and added feature sets. It is quite resistant to hum pickup and has straight forward build documentation. He has offered the design up since 2020 for no charge.
Wyn has at least 40-years with Analog Devices and is a Fellow-elect within AD. His initials are found on the dies of some op amps.
Best wishes.
It was testing day today.
I've finished 2 versions:
Pickup is Hana SL, RIAA&preamp is 6072 based circuit.
The good news is, both works fine. The Hiraga needs DC adjustment, the opamp based doesn't require any adjustment. After a setup and a quick test with oscilloscope and signal generator, then listening.
No noise issues, no 50/100Hz hum.
Before the AD797 I've tested with a few opamps I have at home, some are not cheap, but the AD797 clearly wins. Easy. Not bad. Quite similar freq response like the transformer, maybe a bit more base and the space, details, body of instruments are there. On the other hand, one side of an LP is enough. It makes me tired.
Than, I've tried the Hiraga (With unknown transistors at the moment! I've purchased 50psc of "2SC1775A", maybe it is, but who knows. I've selected 4 based on beta.) For hear it first, I did not like. The reason is, less treble, less details. Unconnected after 5 min.
... but, I've did tested each a few times and I've realized the Hiraga also has all the details, also volume setting was wrong (it has smaller amplification). If I listen for a few minutes, I clearly prefer the AD797. If I listen at least a side or a full album, I prefer the Hiraga.
I've kept rotating the AD797, Hiraga, Denon transformer for sometime just a track, sometime for an album.
The AD797 is not bad, quite close to the transformer, but the transformer is better. Same details level, but doesn't make me tired. I've expected this to be honest, but, it came really close. Maybe pairing it with a bit less detailing amplifier it would better.
The Hiraga, I think it has potential. Will try with other transistor, just for fun, and now I'm thinking to find some good SOT23 transistor and build it surface mount, put it into a tube/case like the Sony (or Ortofon T5) transformer with a power connection on the side.
Can you recommend surface mount transistors for the job?
Thanks,
JG
I've finished 2 versions:
- the Hiraga through hole
- the AD797 through hole
Pickup is Hana SL, RIAA&preamp is 6072 based circuit.
The good news is, both works fine. The Hiraga needs DC adjustment, the opamp based doesn't require any adjustment. After a setup and a quick test with oscilloscope and signal generator, then listening.
No noise issues, no 50/100Hz hum.
Before the AD797 I've tested with a few opamps I have at home, some are not cheap, but the AD797 clearly wins. Easy. Not bad. Quite similar freq response like the transformer, maybe a bit more base and the space, details, body of instruments are there. On the other hand, one side of an LP is enough. It makes me tired.
Than, I've tried the Hiraga (With unknown transistors at the moment! I've purchased 50psc of "2SC1775A", maybe it is, but who knows. I've selected 4 based on beta.) For hear it first, I did not like. The reason is, less treble, less details. Unconnected after 5 min.
... but, I've did tested each a few times and I've realized the Hiraga also has all the details, also volume setting was wrong (it has smaller amplification). If I listen for a few minutes, I clearly prefer the AD797. If I listen at least a side or a full album, I prefer the Hiraga.
I've kept rotating the AD797, Hiraga, Denon transformer for sometime just a track, sometime for an album.
The AD797 is not bad, quite close to the transformer, but the transformer is better. Same details level, but doesn't make me tired. I've expected this to be honest, but, it came really close. Maybe pairing it with a bit less detailing amplifier it would better.
The Hiraga, I think it has potential. Will try with other transistor, just for fun, and now I'm thinking to find some good SOT23 transistor and build it surface mount, put it into a tube/case like the Sony (or Ortofon T5) transformer with a power connection on the side.
Can you recommend surface mount transistors for the job?
Thanks,
JG