I guess I'm less impressed than Demian is -- I'm trying to figure out how you got 50dB of attenuation at 2kHz with a peak that broad, unless there's some limiting function at work in the sim. I also don't want my oscillator loaded with 600 ohms, but then that's a personal choice. In any case, if that attenuation can be real, then you've got a winner.
This is a quick sim of a filter synth I tried. Its a 3 pole Butterworth. It uses 1 Henry inductors. I first tried an elliptic but that needed 500H inductors. The passband is 100 Hz. The 1 Henry inductors are available from Triad. They almost certainly will have much higher distortion than any other element in this design. I don't think there is a practical 1 H air core. It may be the size of a Tesla coil.
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It's not practical because the inductors are huge. The nonlinearity of iron core inductors really mucks up the AC response.
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cute. The dips are set at the second and third harmonic. Those inductors are still huge, and they would need iron cores to be something you can put into a box. I can't even find a place to buy them, since the biggest I can get from Parts Express are about 10mH. I don't know if the iron cores were included in the simulation.
@dimitri -- not sure why we suddenly started talking about notch filters -- but the active Twin-T (RC only, positive feedback) is just better all the way around. But to clean up residual oscillator distortion, a low-pass or bandpass is needed. A simple LC peaking filter, one part each, has sufficient Q and selectivity to do the job. With a pretty good oscillator to start with -- an HP 239 or 339, or a KH 4402 -- an extra 10-20dB of suppression will take you mostly into noise.....
Neat Dimitri, I never saw that when I did my stuff. A 4" by 4" coil with 1300 turns of #16 wire is about 100mH and 4 or 5 Ohms (or am I way off). In the second one the coil does not see fundamental? and maybe could be cored??
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Thanks. Yeah, the LME49720 is a good opamp.
I just hate waiting around for parts to show up in the mail. That's one of the downsides of this hobby: virtually everything has to be mail ordered.
Low distortion oscillator
Hello,
Have you looked at the oscillator circuit in the Amber 3501?
Manual is available from Index of /manuals
I also have a printed copy of the manual, as well.
I have one of these and I measure its internal oscillator at ~0.0008% and it has not been adjusted since is it was done at the factory back in the 80's.
Only problems, that I have had is a couple of tantalum caps blow, easy to find them, just by looking around and smelling
Last week one went inside the shielded DC/DC converter pcb.
The majority of the parts are NE5534 parts!! & old Motorola transistors, 2N4401/3
Regards
Rick
Hello,
Have you looked at the oscillator circuit in the Amber 3501?
Manual is available from Index of /manuals
I also have a printed copy of the manual, as well.
I have one of these and I measure its internal oscillator at ~0.0008% and it has not been adjusted since is it was done at the factory back in the 80's.
Only problems, that I have had is a couple of tantalum caps blow, easy to find them, just by looking around and smelling
Last week one went inside the shielded DC/DC converter pcb.The majority of the parts are NE5534 parts!! & old Motorola transistors, 2N4401/3
Regards
Rick
Searched eBay, did not find an Amber 3501, what am I doing wrong?
Yes the Amber designer/s knew their analog circuit design very well. I wish I was as smart
I like the pre-amp design and the output amplifier.
Oscillator circuit , obviously works well!!Yet another one to figure out.
I start looking at the parts, the only two that I saw that are out of date. CA3280 OTA went obsolete in 2005. The MPQ6542 is obsolete as well.
I think that the pre-amp can be adapted for a good phono pre-amp
The output amplifier would make a good headphone amp.
I plan on using PSPICE to sim these circuits just to learn from them. Maybe make them on day!!
I have used HP 333,339,8903, I still like the Amber!!
Rick
Yes the Amber designer/s knew their analog circuit design very well. I wish I was as smart
I like the pre-amp design and the output amplifier.
Oscillator circuit , obviously works well!!Yet another one to figure out.
I start looking at the parts, the only two that I saw that are out of date. CA3280 OTA went obsolete in 2005. The MPQ6542 is obsolete as well.
I think that the pre-amp can be adapted for a good phono pre-amp
The output amplifier would make a good headphone amp.
I plan on using PSPICE to sim these circuits just to learn from them. Maybe make them on day!!
I have used HP 333,339,8903, I still like the Amber!!
Rick