Mercedese63,
The AD746 is the dual version, thus it doesn't have the COMP pins.
I have different view on the buffer part. Many good sounding opamps have bad performance (THD) driving low impedance load. But if you like the character of an opamp, then you buffer it with random opamp that will change those character you like, it is possible that you will blame the buffer.
BTW, what are your favorite opamps? Do you like the 744?
The AD746 is the dual version, thus it doesn't have the COMP pins.
I have different view on the buffer part. Many good sounding opamps have bad performance (THD) driving low impedance load. But if you like the character of an opamp, then you buffer it with random opamp that will change those character you like, it is possible that you will blame the buffer.
BTW, what are your favorite opamps? Do you like the 744?
Quite the opposite of my experience with a Lehmann clone headphone amp. With the opamp (TL072) driving its own 3k feedback resistor I got very boring sound. With the feedback resistor moved to the output of the discrete transistors (and hence with the '072 unloaded) some life returned and music was even enjoyable.
Even before then the best parts were Harris, with the first dielectric isolation decent pnp process and the expensive BB & NS hybrids.
I've built a few prototype head amps with op amp buffer schemes.
All very simple. All very very simple.
I've built a current boosted op amp using BD139/140 diode biased, text book circuits. I didn't even use an audio op amp LF351/353....besides noise, I couldn't tell you the AUDIBLE difference between 351 and TL071.
Of course, the output stage was tapped for NFB, included in the feedback loop of the op amp.
All very simple. All very very simple.
I've built a current boosted op amp using BD139/140 diode biased, text book circuits. I didn't even use an audio op amp LF351/353....besides noise, I couldn't tell you the AUDIBLE difference between 351 and TL071.
Of course, the output stage was tapped for NFB, included in the feedback loop of the op amp.
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I designed a very simple op amp head phone buffer in 1980.
It was for monitoring on a mobile disco.
I had the left record deck going through left ear and right record deck going through right ear. It worked a treat even when disco was on full volume.
So the headphones didn't load the op amp too much I put a resistors in series with the outputs.
It was for monitoring on a mobile disco.
I had the left record deck going through left ear and right record deck going through right ear. It worked a treat even when disco was on full volume.
So the headphones didn't load the op amp too much I put a resistors in series with the outputs.
LOL, the LM6171/2 is one of my favourite op amps - if not actually my current favourite. It's very musical, far from boring, and not artificially detailed. What don't you like about it? Most people I have recommended it to have been wowed.
Incidentally, you need something bigger than the standard 100nf by way of bypass caps. It also responds pretty well to decent regulation on the rails - ie. something rather better than an LM317.
The LF353 is not a bad op amp, IMHO, and that of a few others. It was used in the original Meridian 101 preamp and didn't seem to get in the way. There's a longstanding rumour - decades old - that it and the TLO71/2 are one and the the same. I quite like the TLO72 for its get up and go, and it would probably be my choice if I were to design a budget component that needed to be engaging.
Do those simplified published circuits actually reflect the circuit inside? Or are they just functional representations. The impression I got from this rumour was that no one could measure any difference between them and, both being fet amps from the same era, they might actually be the same thing.
I'm glad that others seem to think the LF353 is a reasonable budget audio op amp. The JFET input is what I think I like about it, on a similar way that the OPA541 etc were attractive a few years ago.
LM7171 is one I'd like to try, as is one part I forget the number...but it is something like 1A output Ft of 600kHz.
TLE2301 or NTE1854 !!! that's it, I think....
Heck I have LM759 here, if only I could find a composite Master OP AMP slow enough and quiet enough to build the composite!
I'm actually part way through a Self style Op amplifier for headphones, using multiple paralleled LM833 rather than NE5532, as they are some 20% cheaper, and performance seems, on paper, fairly close.
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Hi DIY Audio Group and Johnego,
I have been doing this "audio stuff" a very long time and worked closely with great analog circuit engineers like Bob Pease at National Semi. I will tell you the LME49713 is the best sounding opamp we ever created on the very special LME high voltage process that is gone now. We did extensive listening sessions comparing VFB and CFB opamps and for most applications we preferred the LME CFB's (LME49713HA) with the exception sometimes being for +/- DAC outputs where the identical +/- inputs on the VFB opamps present identical loads to the DAC's. The +/- inputs on a CFB opamp are different input circuits.
Anyway we designed the LME49713HA CFB opamps to exceed the AD811 specs and made some significant changes to optimize it for audio (rather than video) but the bandwidth is still very high (which is a good thing for a lot of reasons) and thus requires careful PC layout to prevent oscillations. The AD811 was based on the AD9610 metal can mil spec opamps and one of the best measuring and sounding opamps ever...also super expensive and impossible to find. I still have a few for personal projects.
We attempted to do our critical listening tests (after all the measurement tests) single and double blind but there is always room for error/disagreement in all listening results.
Just wanted everyone on this forum to think/try VFB and CFB (voltage feed back vs current feedback) opamps in their new designs. I mentioned the older AD811 ADI CFB parts because the last I heard the LME high voltage process was shut down by TI.
Best “Retired” Audio Regards Everyone,
audioman54
I have been doing this "audio stuff" a very long time and worked closely with great analog circuit engineers like Bob Pease at National Semi. I will tell you the LME49713 is the best sounding opamp we ever created on the very special LME high voltage process that is gone now. We did extensive listening sessions comparing VFB and CFB opamps and for most applications we preferred the LME CFB's (LME49713HA) with the exception sometimes being for +/- DAC outputs where the identical +/- inputs on the VFB opamps present identical loads to the DAC's. The +/- inputs on a CFB opamp are different input circuits.
Anyway we designed the LME49713HA CFB opamps to exceed the AD811 specs and made some significant changes to optimize it for audio (rather than video) but the bandwidth is still very high (which is a good thing for a lot of reasons) and thus requires careful PC layout to prevent oscillations. The AD811 was based on the AD9610 metal can mil spec opamps and one of the best measuring and sounding opamps ever...also super expensive and impossible to find. I still have a few for personal projects.
We attempted to do our critical listening tests (after all the measurement tests) single and double blind but there is always room for error/disagreement in all listening results.
Just wanted everyone on this forum to think/try VFB and CFB (voltage feed back vs current feedback) opamps in their new designs. I mentioned the older AD811 ADI CFB parts because the last I heard the LME high voltage process was shut down by TI.
Best “Retired” Audio Regards Everyone,
audioman54
The LF351 was used in the Audiovalve RKV hybrid headphones amp. A very decent sounding amp (I had it in kit form).
The lme49713 was a perfect output stage for headphones. Too bad it got discontinued.
The lme49713 was a perfect output stage for headphones. Too bad it got discontinued.
Yes, I'm very aware that the AD746 is the dual version of the AD744 w/o the compensation pins.
I have probably at least of 100 pcs. of each so I've been well aware of the differences between the 2 op-amps for years now.
Most op-amps weren't designed to drive low impedance loads in the first place and I don't use them in applications where they're expected to do so.
I ONLY use op-amps for low-gain preamp applications so their output current is usually more than adequate for those applications.
If a certain noninverting op-amp circuit sounds one way without a buffer and then sounds obviously worse with the addition of some type of buffer after it, then yes it's only common sense that one "blames" the buffer for the reduced sound quality.
There's no buffer that's absolutely 100% transparent that I've come across.
Should you come across one, by all means let me know.
For driving headphones there are numerous discrete designs that will leave many op-amps(even with a buffer) designs in the dust when it comes to output current and sound quality.
As for op-amps that I like, yes I like the AD744/746 as well as the ole' AD711/712 from Scott.
The AD4627-1, AD4610-2 and AD8597/8599 are also some of my favorites.
In addition, in the right applications I have found that many of the JRC bipolar chips, that many people on here try to degrade and dismiss, can sound very good and most can be purchased for less than $1USD each.
As for the LM4562/LME49720/LME49860...they just don't "do it" for me in all the circuits I've tried them in over the years but there are many loyal followers here for those chips.
I won't be replying to anymore posts about op-amps in this thread since my opinions/views are just one of hundreds on this forum.
Good luck with your project & happy listening!
While I was working my way through trying different integrated op amps, I wound up liking the ad744, jrc2114, sometimes jrc5532 more often than any others. Also the Muse parts have a very nice detailed sound that wasn’t heard in any of the others, although at a higher price.
I kind of saw that my bank account was draining fast, ordering small quantities of parts, paying for shipping, while trading one sonic benefit for another between the myriad of parts. It was also starting to look like my childhood collection of Hotwheels, and nearly as fun. I decided to finally just go ahead and try some popular discrete parts and end the hemorrhaging. That was 4 years ago.
There should be an op amp section in public libraries!
Also, the ad744 was nicer with a bit of bias also.
I kind of saw that my bank account was draining fast, ordering small quantities of parts, paying for shipping, while trading one sonic benefit for another between the myriad of parts. It was also starting to look like my childhood collection of Hotwheels, and nearly as fun. I decided to finally just go ahead and try some popular discrete parts and end the hemorrhaging. That was 4 years ago.
There should be an op amp section in public libraries!
Also, the ad744 was nicer with a bit of bias also.
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Hi everyone,
Long time lurker here, this thread is amazing, 234 pages spanning nearly 10 year, I dont have time to read it all, but have stumbled through a few pages of it.
Quick question, I have a NAD 1130 preamp , it's simple enough inside, but it still sounds great even though its over 30 years old, I'm going to recap it soon ( they must be degrading by now) and I see that it has 1 opamp, yes only 1, a NJM2043D a 8 pin 2 channel opamp, It's a 30 year old opamp, there must be even nicer sounding opamps out there by now I could put in there instead, any recommendations??
The opamp is fed by a RC filter network, the feedback loop contains the bass/treble RC filters and the output goes to a fet circuit which allows for the switching of the output between high and low.
It's an impressive sounding little preamp given its age, for those interested the phono stage is a discreet bipolar differential amplifier design with mc/mm selection and input capacitance selection, it feeds into the input selector which feeds into the opamp and filters, this goes to the low voltage outputs, there is a second discreet differential amplifier for the high voltage output (which I dont use).
The dc on the board is +23.5, and -21.5 volts.
Any easy to get opamp recommendations would be appreciated .
Thanks in advance
Long time lurker here, this thread is amazing, 234 pages spanning nearly 10 year, I dont have time to read it all, but have stumbled through a few pages of it.
Quick question, I have a NAD 1130 preamp , it's simple enough inside, but it still sounds great even though its over 30 years old, I'm going to recap it soon ( they must be degrading by now) and I see that it has 1 opamp, yes only 1, a NJM2043D a 8 pin 2 channel opamp, It's a 30 year old opamp, there must be even nicer sounding opamps out there by now I could put in there instead, any recommendations??
The opamp is fed by a RC filter network, the feedback loop contains the bass/treble RC filters and the output goes to a fet circuit which allows for the switching of the output between high and low.
It's an impressive sounding little preamp given its age, for those interested the phono stage is a discreet bipolar differential amplifier design with mc/mm selection and input capacitance selection, it feeds into the input selector which feeds into the opamp and filters, this goes to the low voltage outputs, there is a second discreet differential amplifier for the high voltage output (which I dont use).
The dc on the board is +23.5, and -21.5 volts.
Any easy to get opamp recommendations would be appreciated .
Thanks in advance
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Is the opamp running directly off the voltages you mention, or is there further regulation on the board? Measure the voltage on pins 4 and 8 of the opamp to be sure.
If it is running on such a high voltage then your choice is limited.
If the voltage is -/+18 or lower then you have much choice and I would probably suggest the LM4562.
Another option (if feasible) would be to reduce the rails to -/+18.
If it is running on such a high voltage then your choice is limited.
If the voltage is -/+18 or lower then you have much choice and I would probably suggest the LM4562.
Another option (if feasible) would be to reduce the rails to -/+18.