That's pretty hard-core. I believe Frank McIntosh used to also test his gear by directly comparing live instruments to recordings played through his amps.
What, I have to figure it out myself??
Seriously though, I see there is LT Spice for Mac, so I could give it a try. Its rather amazing that SPICE is still the go to simulation software. Hasn't it been around since the 70's?! Nice to see that LT is keeping it available.
Sorry, yes I did truncate the schematic. I cut both right before the opamp out feeds into a pair of transistors/jfets. The Mac schematics are HUGE! Included is a more complete story.
Thank you very much! I will definitely check the opamp handbook before trying my hand at anything.
Seriously though, I see there is LT Spice for Mac, so I could give it a try. Its rather amazing that SPICE is still the go to simulation software. Hasn't it been around since the 70's?! Nice to see that LT is keeping it available.
Sorry, yes I did truncate the schematic. I cut both right before the opamp out feeds into a pair of transistors/jfets. The Mac schematics are HUGE! Included is a more complete story.
Thank you very much! I will definitely check the opamp handbook before trying my hand at anything.
Attachments
a ne5534 driving 51.1 ohms at high frequency? Doug Self used 220 ohms in the 2012 pre-amp.
if you want to drive that 51.1 ohms load it should be buffered it like they do in the LT1115 design with the LT1010 buffer example.
try to simulate these circuits first to verify if they are worthy. anyone sim that LT1115/LT1010 circuit yet? not even 15 minutes worth of effort.
I doubt the Bews implementation drives 51.1 ohm, or maybe that is how they arrive at fuzzy distortion. iirc my ne5533 design used the example out of the signetics datasheet or there app manual. I used big yellow philips polystyrene caps.
if you want to drive that 51.1 ohms load it should be buffered it like they do in the LT1115 design with the LT1010 buffer example.
try to simulate these circuits first to verify if they are worthy. anyone sim that LT1115/LT1010 circuit yet? not even 15 minutes worth of effort.
I doubt the Bews implementation drives 51.1 ohm, or maybe that is how they arrive at fuzzy distortion. iirc my ne5533 design used the example out of the signetics datasheet or there app manual. I used big yellow philips polystyrene caps.
rsavas makes good points, one reason why i said "not state of the art".
you can ease this problem to some degree by adding a series resistor and adjusting the passive LPF at the back end.
another thing to watch out for in these designs is the opamp running out of open loop gain so your riaa accuracy drops at the high end (along with increased distortion). again, some of this can be compensated for to some degree, but you're starting to leave the realm of "simple".
maybe peruse this link from andy_c: Andy's Active RIAA Phono Equalization Design Page
for opamp preamp designs, you can never (ok, ok, never say "never"
) go wrong by adding a buffer.
best regards,
mlloyd1
you can ease this problem to some degree by adding a series resistor and adjusting the passive LPF at the back end.
another thing to watch out for in these designs is the opamp running out of open loop gain so your riaa accuracy drops at the high end (along with increased distortion). again, some of this can be compensated for to some degree, but you're starting to leave the realm of "simple".
maybe peruse this link from andy_c: Andy's Active RIAA Phono Equalization Design Page
for opamp preamp designs, you can never (ok, ok, never say "never"
) go wrong by adding a buffer.best regards,
mlloyd1
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Speaking of buffers, anyone check out the P8 volume control buffer that Apex (Mile) posted in his threads some time ago? I keep track of these things you know
i sim'd it up and it is measuring absolutely no thd. not a blip in the fft plot. Anyone care to try it for yourself & explain why it is so good? It measures less than the simulator measures its own source, how can that be?
See attached. You will need to sort out the models, but I am using Bob Cordell's models for most of them. I'll gather up the models and post them too, just need to re-name them and put in the install dir lib cmp folder.
The pitchfork buffer is a great example to use for the low Z MM phono eq, looks to be almost the same as P8
I guess you can call this my spice pre-amp sand box. the plr mc pre is also a nice ckt as well. anyone have a favourite to add to my collection?
N-Period=1
Fourier components of V(vin)
DC component:-1.84786e-012
Harmonic Frequency Fourier Normalized Phase Normalized
Number [Hz] Component Component [degree] Phase [deg]
1 1.000e+04 1.000e-01 1.000e+00 -0.00° 0.00°
2 2.000e+04 7.022e-11 7.022e-10 -3.07° -3.07°
3 3.000e+04 1.052e-10 1.052e-09 -2.10° -2.10°
4 4.000e+04 1.403e-10 1.403e-09 -1.62° -1.62°
5 5.000e+04 1.753e-10 1.753e-09 -1.35° -1.35°
6 6.000e+04 2.104e-10 2.104e-09 -1.17° -1.17°
7 7.000e+04 2.454e-10 2.454e-09 -1.06° -1.06°
8 8.000e+04 2.804e-10 2.804e-09 -0.98° -0.98°
9 9.000e+04 3.154e-10 3.154e-09 -0.92° -0.92°
Total Harmonic Distortion: 0.000001%(0.000000%)
N-Period=1
Fourier components of V(p8_out)
DC component:-4.08424e-006
Harmonic Frequency Fourier Normalized Phase Normalized
Number [Hz] Component Component [degree] Phase [deg]
1 1.000e+04 9.996e-02 1.000e+00 -0.37° 0.00°
2 2.000e+04 8.601e-11 8.604e-10 -30.20° -29.83°
3 3.000e+04 1.906e-11 1.907e-10 -60.00° -59.63°
4 4.000e+04 7.063e-11 7.066e-10 -14.47° -14.10°
5 5.000e+04 1.190e-10 1.190e-09 -8.01° -7.64°
6 6.000e+04 1.633e-10 1.634e-09 -5.56° -5.19°
7 7.000e+04 2.048e-10 2.049e-09 -4.03° -3.66°
8 8.000e+04 2.449e-10 2.450e-09 -3.00° -2.63°
9 9.000e+04 2.836e-10 2.837e-09 -2.30° -1.93°
Total Harmonic Distortion: 0.000000%(0.000000%)
i sim'd it up and it is measuring absolutely no thd. not a blip in the fft plot. Anyone care to try it for yourself & explain why it is so good? It measures less than the simulator measures its own source, how can that be?
See attached. You will need to sort out the models, but I am using Bob Cordell's models for most of them. I'll gather up the models and post them too, just need to re-name them and put in the install dir lib cmp folder.
The pitchfork buffer is a great example to use for the low Z MM phono eq, looks to be almost the same as P8
I guess you can call this my spice pre-amp sand box. the plr mc pre is also a nice ckt as well. anyone have a favourite to add to my collection?
N-Period=1
Fourier components of V(vin)
DC component:-1.84786e-012
Harmonic Frequency Fourier Normalized Phase Normalized
Number [Hz] Component Component [degree] Phase [deg]
1 1.000e+04 1.000e-01 1.000e+00 -0.00° 0.00°
2 2.000e+04 7.022e-11 7.022e-10 -3.07° -3.07°
3 3.000e+04 1.052e-10 1.052e-09 -2.10° -2.10°
4 4.000e+04 1.403e-10 1.403e-09 -1.62° -1.62°
5 5.000e+04 1.753e-10 1.753e-09 -1.35° -1.35°
6 6.000e+04 2.104e-10 2.104e-09 -1.17° -1.17°
7 7.000e+04 2.454e-10 2.454e-09 -1.06° -1.06°
8 8.000e+04 2.804e-10 2.804e-09 -0.98° -0.98°
9 9.000e+04 3.154e-10 3.154e-09 -0.92° -0.92°
Total Harmonic Distortion: 0.000001%(0.000000%)
N-Period=1
Fourier components of V(p8_out)
DC component:-4.08424e-006
Harmonic Frequency Fourier Normalized Phase Normalized
Number [Hz] Component Component [degree] Phase [deg]
1 1.000e+04 9.996e-02 1.000e+00 -0.37° 0.00°
2 2.000e+04 8.601e-11 8.604e-10 -30.20° -29.83°
3 3.000e+04 1.906e-11 1.907e-10 -60.00° -59.63°
4 4.000e+04 7.063e-11 7.066e-10 -14.47° -14.10°
5 5.000e+04 1.190e-10 1.190e-09 -8.01° -7.64°
6 6.000e+04 1.633e-10 1.634e-09 -5.56° -5.19°
7 7.000e+04 2.048e-10 2.049e-09 -4.03° -3.66°
8 8.000e+04 2.449e-10 2.450e-09 -3.00° -2.63°
9 9.000e+04 2.836e-10 2.837e-09 -2.30° -1.93°
Total Harmonic Distortion: 0.000000%(0.000000%)
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It would definitely be interesting to see how Bews implements the single op amp. Hopefully someone familiar with the design will offer some insight. That said, I am extremely impressed with both the level of support and expertise of this forum. Lots of great information!! Thanks for point out the issues with the Mac design. Seems like it will need some work before implementing into something that is worth spending a lot of time on.maybe peruse this link from andy_c: Andy's Active RIAA Phono Equalization Design Page
for opamp preamp designs, you can never (ok, ok, never say "never"
best regards,
mlloyd1
Thank you very much!! Your expertise is greatly appreciated and I will def look over that page.
Hi rsavas: I assume you're referring to R213 in the C34V Mac schematic? Is the NE5532 much different than the NE5534? I ask because the Phillips application data sheet for the NE5532/3/4 series shows the NE5532 with 49.9 ohms with lower capacitance to ground.
Attachments
5532 is internally compensated, 5534 requires and external compensation network. 5534 can have the off set voltage nulled out, which is important for dc instruments but not for audio.
All these low drive op amps need a following op amp or jfet like Mc to drive a cable to the power amp. They use up the drive current running the complicated feedbackk network. My Herald disco mixer runs the RIAA op amp into a network of 10 kohm mixer resistors which mix in CD player, Radio, and the other RIAA input, boost 10x with another 33078 op amp. then out the RCA cable to the power amp. RCA cable has xx pf per foot capacitance, which it takes current to drive. For longer cables from a pro mixer to a stage, Peavey uses 4580 op amps on output for more drive current.
I'd bbring up the LM4562 op amp with hot drive at this point, but they just quit selling them. NJM4562 is not equivalent. There is an RIAA circuit on the LM4562 datasheet. I wonder if the hot drive circuit would work with LM675 which is in production but costs about $6.
All these low drive op amps need a following op amp or jfet like Mc to drive a cable to the power amp. They use up the drive current running the complicated feedbackk network. My Herald disco mixer runs the RIAA op amp into a network of 10 kohm mixer resistors which mix in CD player, Radio, and the other RIAA input, boost 10x with another 33078 op amp. then out the RCA cable to the power amp. RCA cable has xx pf per foot capacitance, which it takes current to drive. For longer cables from a pro mixer to a stage, Peavey uses 4580 op amps on output for more drive current.
I'd bbring up the LM4562 op amp with hot drive at this point, but they just quit selling them. NJM4562 is not equivalent. There is an RIAA circuit on the LM4562 datasheet. I wonder if the hot drive circuit would work with LM675 which is in production but costs about $6.
No sweat... The NE5532 is able to deliver 38mA of current, according to it's datasheet. With a 50 Ohms load, that means it's able to put out a 1.9Vpeak (about 1,3Vrms).
I don't think most RIAA applications will need that level of output.
yup that is the ckt, same as I have in the application manual too. now that I think about it some more i think this the way I made it back in college. It worked fine, as far as i could tell. is it right, at that time I did not question it as I trusted their better judgement on how to apply their device vs a green tech. to me now it does not look like it is the best way to do it, but I could be wrong. Using Doug Self's example, he did not do it as Signetics had done.
they say in the app note that they used a ne5532 because it has many advantages,
it is lower cost and the not so obvious advantage is related to the thermal tracking and consistency of parameters of both amplifiers integrated on the same monolithic chip. to bad no more ne5533a as it was the best solution then lower noise than a 5532 and it was a dual 5534.
since 5532 is internally compensated for unity gain, at least 34dB of feedback exists for a 10MHz gbp. lab measurements showed less than 0.01%thd into 600 ohm, less than 0.005% into 10K, separation better than 70dB at 100,1k,10K. unweighted noise greater than 70dB, A weighted better than 80dB.
Using this reasoning,
these days I would choose a polymer ecap for the 47uF feedback cap. if you use a 5534 you could eliminate the feedback ecap and use the offset null pot, but that adds cost and you have to do the adjustments.
that app manual is available on line
https://ia801904.us.archive.org/19/...415016/1979_Signetics_Analog_Applications.pdf
see page 209
they say in the app note that they used a ne5532 because it has many advantages,
it is lower cost and the not so obvious advantage is related to the thermal tracking and consistency of parameters of both amplifiers integrated on the same monolithic chip. to bad no more ne5533a as it was the best solution then lower noise than a 5532 and it was a dual 5534.
since 5532 is internally compensated for unity gain, at least 34dB of feedback exists for a 10MHz gbp. lab measurements showed less than 0.01%thd into 600 ohm, less than 0.005% into 10K, separation better than 70dB at 100,1k,10K. unweighted noise greater than 70dB, A weighted better than 80dB.
Using this reasoning,
the ckt is fine and my concerns are alleviated.
these days I would choose a polymer ecap for the 47uF feedback cap. if you use a 5534 you could eliminate the feedback ecap and use the offset null pot, but that adds cost and you have to do the adjustments.
that app manual is available on line
https://ia801904.us.archive.org/19/...415016/1979_Signetics_Analog_Applications.pdf
see page 209
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Thought I'd through a more modern Burr-Brown option into the ring. The OPA1642 makes an excellent single stage MM phono pre-amp. For MM cartridges there are two major noise considerations that most people ignore and simply look at broadband noise spectral density. First, input current noise of the op amp is really important because MM cartridges are highly inductive. For example, the Shure M97xe has an inductance of 650mH. At high frequencies, the input current noise multiplied by the cartridge impedance may be much larger than the input voltage noise. Second, low frequency noise (both voltage and current) is critical because the RIAA gain curve is highest at low frequencies. For these reasons, the best choices for MM phono preamps are op amps with front ends that use, JFETs, super-beta BJTs, or BJTs without input bias current cancellation. The OPA1642 is a JFET part (consider it an updated OPA2134).
Attachments
opa1641 is an excellent choice, I would certainly use it over a ne5532a in this app unless you have a ton of them to use up. wonder if one could actually hear a difference? i guess i will have to make one up and find out for myself, stick my head beside the speaker.
i suspect that Doug Self only used ne5534a in elektor pre-amp 2012 MM design because it is avail in dip-8. he did say to me, putting a j310 in front of a ne5534a will improve the noise by a few dB. I thought that there are better choices than a j310, so more improvement could be made if using a lower noise device like a bf862. wonder if it would make any noticeable difference, well until you drop the needle and groove noise pre-dominates.
I do wonder why they can make discrete jfets, ie bf862 with lower voltage noise than they can with the jfets in a opamp such as opa164x series? probably some semicon physics reason that I will never understand.
So who is putting one of these together? should fit nicely in a 100x100mm pcb, all for 10 @ $13 from pcbway The day has come where we can get a pcb's for the same or less than the parts costs for proto's.
i suspect that Doug Self only used ne5534a in elektor pre-amp 2012 MM design because it is avail in dip-8. he did say to me, putting a j310 in front of a ne5534a will improve the noise by a few dB. I thought that there are better choices than a j310, so more improvement could be made if using a lower noise device like a bf862. wonder if it would make any noticeable difference, well until you drop the needle and groove noise pre-dominates.
I do wonder why they can make discrete jfets, ie bf862 with lower voltage noise than they can with the jfets in a opamp such as opa164x series? probably some semicon physics reason that I will never understand.
So who is putting one of these together? should fit nicely in a 100x100mm pcb, all for 10 @ $13 from pcbway
The day has come where we can get a pcb's for the same or less than the parts costs for proto's.
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I have used the BF862 in a phono before and it works beautifully in a composite circuit with an op amp. The only issue with the BF862 is that the gate leakage gets surprisingly high at even moderate VDS values, but this is more of an issue on higher impedance transducers like piezo pickups.
Fundamentally there's nothing limiting JFET input op amps from achieving these noise voltages. In fact, even CMOS is entering the realm of voltage noise spectral densities previously reserved for BJTs (OPA1652). However, the challenges arise from the fact that the rest of the op amp is inside the feedback loop with the front end. When we make low-noise JFETs they're BIG, meaning lots of input capacitance, which can create a 2nd pole in the loop gain curve of the amplifier and cause stability headaches. You also have to dump a lot of current into them, which means more die area has to be taken up by compensation capacitors inside the op amp. So the die for such a device is going to be expensive, and when some systems engineer (me) takes this concept to a customer, they're probably going to ask why they just can't put a BF862 in front of a regular op amp?
All that being said, keep an eye on the new op amp offerings over the next few years. There's a lot of really great JFET, CMOS, and super beta BJT op amps being introduced by several companies.
Fundamentally there's nothing limiting JFET input op amps from achieving these noise voltages. In fact, even CMOS is entering the realm of voltage noise spectral densities previously reserved for BJTs (OPA1652). However, the challenges arise from the fact that the rest of the op amp is inside the feedback loop with the front end. When we make low-noise JFETs they're BIG, meaning lots of input capacitance, which can create a 2nd pole in the loop gain curve of the amplifier and cause stability headaches. You also have to dump a lot of current into them, which means more die area has to be taken up by compensation capacitors inside the op amp. So the die for such a device is going to be expensive, and when some systems engineer (me) takes this concept to a customer, they're probably going to ask why they just can't put a BF862 in front of a regular op amp?
All that being said, keep an eye on the new op amp offerings over the next few years. There's a lot of really great JFET, CMOS, and super beta BJT op amps being introduced by several companies.
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