What this preamp is? I say that its a 5 yrs slow investigation of how far simple classic concepts can take us for replaying vinyl. No super clever circuitry aids (the designer ain't particularly bright in handling complex electronics anyway, not an engineer), SE open loop, few junctions, an alike philosophy PSU to package it. There are loose ends of course in this minimal control approach that may allow some parts coloration come through. How do you solve this? With money, can be an automatic answer. And if you want it be best? With more money! Well, not always... With experience in building and tuning and decent parts you can make it sing great. Just takes some hands on and after a couple you get the knack.
He has integrated MingDa. As for RIAA caps, they have remained equal. The only thing that has changed is the output cap. I dont doubt you tha spending more money is not necessarily the best route. I personally do not buy into that thinking. I was just saying that the circuit is very much worth tailoring and I wish i had more experience with individual caps as I think you could pretty well define your sound with this thing. If RIAA cap is about value more than anything, I will take that approach and use good quality Siemens Ks in exact values. Reasonable price and very well regarded polystyrenes, mostly due to tight winding and superior quality control. Or so i have heard. I will focus my playing with the output cap.
As you know, I very much like your philosophy. Not trying to improve anything. Just tweaking to my ears, as these designs seem well suited for.
As you know, I very much like your philosophy. Not trying to improve anything. Just tweaking to my ears, as these designs seem well suited for.
Your conclusion makes scientific sense.
But even though I am not a believer in much of the nonsense reported in sound quality comparisons, I must forewarn about reading too much into a purely "capacitance value" effect.
In a RIAA stage the capacitors are imposing a very significant impedance to passing the Audio Signal. This is quite different from coupling capacitors where the audio portion of the AC signal is insignificant.
Where a capacitor has significant impedance at the wanted audio signal frequencies then dielectric does have a significant effect on the way the signal is transferred across the capacitor.
Dielectric will have an audible effect even when cap values are very accurately matched. It may take extreme differences in dielectric parameters to show the audible effect for some of the caps in the RIAA, but do not discount the notion that some caps may show an effect for what might appear to be quite small differences in cap parameters.
But this can ONLY be validated if the differences in cap values are very rigorously eliminated for the whole range of operating temperatures inside the working RIAA stage.
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You.
@Andrew,
Caps have a sound. I dare not even speculate as to why this is, but they do. Both of the coupling caps do pass the signal, so i assume that they will ultimately put their "performance imprint" on the sound. Significant is a tough question. It is significant enough that the value is important for the passage of the signal across the full audio band. Dont know if that is correct thinking.
@Andrew,
Caps have a sound. I dare not even speculate as to why this is, but they do. Both of the coupling caps do pass the signal, so i assume that they will ultimately put their "performance imprint" on the sound. Significant is a tough question. It is significant enough that the value is important for the passage of the signal across the full audio band. Dont know if that is correct thinking.
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significant or not?
If you have a 1uF coupling capacitor with a perfect dielectric and zero parasitics (impossible but a vacuum dielectric may get closer than plastic films)
feeding a 100k input stage with audio frequencies over the full range of 20Hz to 20kHz, then the impedance seen by a 20Hz signal is 100k + [1/2/Pi/F/C] = 100k + 7958ohms.
The 7958ohms is just under 8% of the total impedance seen by the signal. That could possibly be defined as insignificant.
If the input Zin of the stage were instead 10k, then the total impedance seen by the signal is now 10k + 7958ohms.
I and most others would define that as a significant impedance due to the same 1uF capacitor.
If you inserted a pair of 22uF back to back bipolars with an effective capacitance of 11uF along with the 10k Zin, you would now have 10k + 723ohms. I think that would just about become insignificant.
One of Whitlock's papers suggests a single 220uF bipolar for a coupling cap. I think he has the same ideas in mind.
When the signal across the capacitor is insignificant, the capacitor can only contribute insignificant added distortions to the signal. In this insignificant situation the type of capacitor also becomes insignificant.
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Totally agree, but I was warning against the urge to replace caps with "better" ones without taking care to use the EXACT same values, because that can lead the experimenter to believe some cap types might sound "better" than others.
Value is critical is this case.... off course, if you are sure about the correct values then you can choose "better" caps.... allready mensioned my choice of polystyrenes on tin foil
Now I am using NOS military teflons (inexpensive from russia) and found they are quite good once we use the correct values.
Now regarding interstage coupling caps, the value is not so critical and these have an imediate effect on sound.
Changing from foil polyprops to something more elaborate as foil on teflon gives tremendous imediate benefits.
Interesting theory but I found that normally small value film capssomehow sound faster and cleaner than big value EL.
Even when comparing between films only, smaller values sound faster than higher values.
Consider what capacitor parameter could be causing the "change" in sound quality.
Could it be esr, or esl, or da, or some other.
Simply guessing at what to try next will not get to eliminating the distortion that is being heard. Especially if the distortion cannot be eliminated entirely and can only be attenuated until it is sufficiently below the noise floor that it becomes impossible for any human to detect.
Could it be esr, or esl, or da, or some other.
Simply guessing at what to try next will not get to eliminating the distortion that is being heard. Especially if the distortion cannot be eliminated entirely and can only be attenuated until it is sufficiently below the noise floor that it becomes impossible for any human to detect.
