I dont doubt you.....
As an explanation for playback of CD vs HD downloads played back......I have to take what is given/made and listen to it. What do we actually have out there to purchase and how well does it work is the practical matter of it. Without an atomic clock pressed into service etal. For myself, its best I just be rid of the many points of error or jitter that can creep in during production, mfr and playback of CD's.
THx-RNMarsh
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depends.... hard gold (not pure undoped gold) is ... hard. Trimmers are usually set and forget or not frequentley moved. Some resistive formulations as well as contact material can and do oxidize at the contact and cause problems. Go for the gold multi-contact is the bottom line. I use Spectrol a lot..... they are very stable and reliable pots and trimmers at reasonable costs. Spectrol has been bought by Vishay. Other than ww type, I use a lot of plastic film resistive elements.... even some ceramic multi-turn trimmers of low values.
THx-RNMarsh
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John, if I may, another question. The schematics show a J203 as the current source for both positive and negative references. But the negative one shows a pFET and the positive one an nFET symbol. Now, I might have thought that it was just an incorrect designator, but the unit in front of me has 2N5484 for both current sources. Is it just connected "backward" for the negative CCS, i.e., gate and source shorted and connected to the negative rail and the drain connected to the voltage-setting resistor? This would be different from, but equivalent to, the schematic.
The regs work fine now that I replaced the pass devices with some matched J271, but I was curious about the actual wiring. If you can't remember, that's OK, I can trace it.
The regs work fine now that I replaced the pass devices with some matched J271, but I was curious about the actual wiring. If you can't remember, that's OK, I can trace it.
Dan, my experiences are different from yours. I've never done anything specifically to address jitter, even though high levels of it presented to the circuitry near the DAC could cause audible problems or differences, because of inadequate engineering. To date, I've got SQ that's "good enough" for me by looking in other areas; reduction of possibly jitter related artifacts would just be icing on the cake ...
That bit I had realised, but I clearly asked the question upside down. If gate is forced to zero then you have one degree of freedom fixed so unless the optimal DC operating point is a wide window there's matching/pot twiddling to do. But I shouldn't be lazy and will go off and work it out for myself.
My solution to pots is to get rid of them, entirely. The audible impact has always been too severe every time I've looked in that area, so now I just automatically rip them out of a circuit, without thinking about it.
And, what if you have already gone the extra mile and did all the obvious and easy things and even a few hard ones. And, still the CD vs HD download is clear and detectably different? In marketing to people there are product quality categories labelled.... Good, Better and Best.... at increased price points. Good enough isnt what I am after. I am at the Icing on the Cake place.
THx-RNMarsh
That's why I'm asking, so I can correct them and know what I'm looking for in troubleshooting. It appears that there's also an undocumented styroflex bypass on the current setting resistor. I note that the resistor plugs in, which is a good idea in that it reduces FET matching requirements, you just pop a couple different values in to get the right voltage.
I traced out the CCS part and that was what I had thought, it's the same polarity FET for positive and negative, just rotated between drain and source/gate.
Depends on the sharpness of the null. Often a 10-20 turn is used because of the resolution needed. And, if your standard R value is that number, you are lucky. Or, use a combo of R's to get the value required. Depending on how well you are able to match transistors in other channels the value can be different. I have no problem using quality trimmers so far.
-RNM
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