OK, thanks. I did not know that. This makes it even harder to use this SMD opamp because it's so small that it's hard to get all the SMD resistors and other components really close to the pins if there are power supply bypass caps in the way. I don't think the LME49990 is good for DIY design, even if I design my own boards. I'm going to try though. This is getting off topic though.
Lets not generalize if a part is good for DIY or not, a lot depends on the design of the PCB, regardless what the application is. Yes you can argue that some DIY's are not well versed in layout or SMT soldering, but that can also apply to many seasoned EE's in a professional capacity. It really depends on your experience, regardless of your credentials.
Rick
Rick
Rick,
By any chance can you suggest some appropriate mfgr's part numbers, and a suggested PWB layout sketch for power supply decoupling in an application like this? I vaguely recall some other forums where somebody tried to use the LME4990 and had stability problems. They concluded it was interaction between the opamp's inherently high gain-bandwidth product, and the PWB layout. Would be helpful to see a layout geometry that's known to work.
Dale
I now finally figured how this works with only little attenuation of the spectral lines, although on the AP2322 (Sys2) this time -- won't matter much. Damn Win7 won't run the old APWin for some reason, so I post this next time I'm on XP again. I also measured the close-in behaviour of Viktors' oscilllator, no problem there that I could identify, will post that, too.
Hi Dale,
Look at Owen's thread,
http://www.diyaudio.com/forums/headphone-systems/179298-wire-ultra-high-performance-headphone-amplifier-pcbs.html
For parts, there are litterly 100's of possibilities, go to Mouser and search/filter for
capacitor-smt-mlc-50V-1u-X7r
capacitor-smt-mlc-50V-100n-X7R
capacitor-smt-mlc-50V-10n-NPO(COG)
Owen's threads have part #'s (BOM's)
A number of IC mfg have app notes on hi-speed layout design techinques. I know TI /Intel have many. I will attach some that I have sitting on my jump drive.
You can also look at my thread for my layout of the LME49830 as well,
http://www.diyaudio.com/forums/solid-state/220962-lme49830-latfet-yet-another-design-review.html
and Owen's LME49830 LatFET design,
http://www.diyaudio.com/forums/solid-state/196932-wire-amp-class-ab-power-amplifier-based-lme49830-lateral-mosfets.html
Look at Owen's thread,
http://www.diyaudio.com/forums/headphone-systems/179298-wire-ultra-high-performance-headphone-amplifier-pcbs.html
For parts, there are litterly 100's of possibilities, go to Mouser and search/filter for
capacitor-smt-mlc-50V-1u-X7r
capacitor-smt-mlc-50V-100n-X7R
capacitor-smt-mlc-50V-10n-NPO(COG)
Owen's threads have part #'s (BOM's)
A number of IC mfg have app notes on hi-speed layout design techinques. I know TI /Intel have many. I will attach some that I have sitting on my jump drive.
You can also look at my thread for my layout of the LME49830 as well,
http://www.diyaudio.com/forums/solid-state/220962-lme49830-latfet-yet-another-design-review.html
and Owen's LME49830 LatFET design,
http://www.diyaudio.com/forums/solid-state/196932-wire-amp-class-ab-power-amplifier-based-lme49830-lateral-mosfets.html
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Good de-coupling
I have attached pic of the LME49830 layout, showing the PS decoupling, hope this helps.
Ground planes are so important, in some of the hi-speed design layouts we did in the past, we used NELCO material and stacked up the PCB, having very small distances between planes, so that they acted as distributed capacitance layers, sandwich power planes between ground planes. One design we used 16 layers with a number of embedded power/ground planes. This was done in 0.062" total thickness for a PCI FF PCB. I'd have to look at the stackup again to find the material specified, but you should get the idea.
Rick
I have attached pic of the LME49830 layout, showing the PS decoupling, hope this helps.
Ground planes are so important, in some of the hi-speed design layouts we did in the past, we used NELCO material and stacked up the PCB, having very small distances between planes, so that they acted as distributed capacitance layers, sandwich power planes between ground planes. One design we used 16 layers with a number of embedded power/ground planes. This was done in 0.062" total thickness for a PCI FF PCB. I'd have to look at the stackup again to find the material specified, but you should get the idea.
Rick
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Related to this topic (no worth starting another thread): I've had the chance to scan the manual of the calibration fixture (067-0938-00) which was used to verify distortion performance of the Tektronix SG505. The PDF is made available here:
067-0938-00 - TekWiki
Good inspiration for those interested in building a passive notch filter!
Samuel
067-0938-00 - TekWiki
Good inspiration for those interested in building a passive notch filter!
Samuel
You would think they could compress this file a little more. Seems pretty much
what Bruce Hofer told me, the passive notch is the only way to go.
EDIT - none around today but one sold for ~$300 a few years ago.
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That puts distortion back in, if it's not a pain for Tek and AP it's OK by me.
Reminds me -- maybe not this manual but many --
Many test equipment manuals can be downloaded at: www.BAMA.edebris.com/manuals
They are all free.
I'm in the process of trouble-shooting an HP339A (spare parts buy) and found a dozen coax lines plugged into various gold plated pcb and they used funky made RCA jacks and plugs which are tin or something - not gold plated... even on the output of the very sensitive oscillator. Geeze. And thru crummy corroded switch contacts and fuses/fuse holder and Molex-like contections (also tin) the pristine signal has to go thru. Geeez. After I find the problem (so far one relay contact not making contact) I'll have to replace or clean such contact points. Great electronics design circuitry but all the mechanicals are inferiour.
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Richard-
Why would you think HP would be "audiophile" about such things? They reserved the gold to gold stuff for the RF instrumentation.
My Boonton uses SMC connectors for the audio links except for the balanced input, which is a gold Molex. but Boonton is an RF instrument company, not an audio company.
Why would you think HP would be "audiophile" about such things? They reserved the gold to gold stuff for the RF instrumentation.
My Boonton uses SMC connectors for the audio links except for the balanced input, which is a gold Molex. but Boonton is an RF instrument company, not an audio company.
never entered their mind -
What makes you think/assume, that is what I think? I'm not even an audiophile myself.... any more than you are. I'm sure that audiophile never entered their minds. But reliability should have... always did before. So, why did they Gold Plate the PCB traces on the oscillator board. RF? (dont need an answere). It was just a mess up..... even the front panel knobs are mostly cracked/broken on most units as they used polystyrene for dials etc etc etc. You can make excuses for them.. but, I ain't giving them a break on this model....
What makes you think/assume, that is what I think? I'm not even an audiophile myself.... any more than you are. I'm sure that audiophile never entered their minds. But reliability should have... always did before. So, why did they Gold Plate the PCB traces on the oscillator board. RF? (dont need an answere). It was just a mess up..... even the front panel knobs are mostly cracked/broken on most units as they used polystyrene for dials etc etc etc. You can make excuses for them.. but, I ain't giving them a break on this model....