Thanks for your reply! Im afraid the information you gave me is a bit too condensed for a beginner like me
How do I find out if my phono pre can drive a 10k pot? Trial and error?
Why does the RF interference attenuation of the dr matter in this case?
Maybe this article can help and be useful :
http://leachlegacy.ece.gatech.edu/papers/stepatten/stepatten.pdf
Light Dependent Resistor with jfet buffer for better match with your pre is seductive as well.
Schematic design show by courtesy of Mr Pass.
Good luck
http://leachlegacy.ece.gatech.edu/papers/stepatten/stepatten.pdf
Light Dependent Resistor with jfet buffer for better match with your pre is seductive as well.
Schematic design show by courtesy of Mr Pass.
Good luck
Attachments
RF interference attenuation is simply a capacitor to signal return.
That capacitor loads the source output.
It has the potential to remove some or all of your treble signal.
Doesn't give output impedance which is what you need to know. However looks like it's almost certainly using an op amp buffer on the output which will drive 10k easily. Can you find a schematic?
The 1uF DC blocking capacitor driving a 10k input impedance will roll off the low bass.
I typically aim for CR= 80ms to 100ms at the input of the power amplifier and aim for a full octave below that in the earlier stages.
On this basis, I would use a 10uF MKP or MKT as the output blocking capacitor.
I typically aim for CR= 80ms to 100ms at the input of the power amplifier and aim for a full octave below that in the earlier stages.
On this basis, I would use a 10uF MKP or MKT as the output blocking capacitor.
so scottjoplin says that it will be fine and andrewt says that the current pre amp configuration together with a 10k pot will lead to problems with the bass. did i get that about right?
seems there's never just one correct answer to a question like that
btw: i talked to the guy who designed my phono stage and he said the output impendancenis 10 Ohms. He suggested using a 100k pot or a buffer amp.
i'm a bit confused
seems there's never just one correct answer to a question like that
btw: i talked to the guy who designed my phono stage and he said the output impendancenis 10 Ohms. He suggested using a 100k pot or a buffer amp.
i'm a bit confused
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The lower the output impedance the greater the load it can drive, so that doesn't make sense
1uF driving 10k gives an LF rolloff at 16Hz. You may or may not find that acceptable; this partly a matter of taste, and partly a matter of which speakers you have and where they roll off. If the 1uF is an electrolytic then you really need 10uF instead, so the cap has very little signal voltage across it at the bass end; alternatively, use a 100k pot instead.
10 ohms output impedance can easily drive a 10k pot. 10 ohms plus 1uF can only drive 10k if you are happy to have some bass rolloff.
10 ohms output impedance can easily drive a 10k pot. 10 ohms plus 1uF can only drive 10k if you are happy to have some bass rolloff.
thanks for all your advice.
i talked some more to the designer of the phono stage and figured out that a 20k pot would probably be ideal. i'll keep the phono stage as it is and in combination with a 20k pot the rolloff should be at 6 or 7 hz.
i seem to remember that somewhere on this forum i read about the relationship between S/N ratio and pot values. unfortunately i can't find the post or article anymore. can somebody verify my assumption that a lower pot is desirable because the lower resistance will "kill" (for a lack of a better word) less of the signal and thus less amplification is needed after the pot. With less amplification whatever noise appears in the amp will also be less amplified giving a better S/N ratio. Did I get it right so far?
Would that mean that - all other things equal - a lower resistance pot will play louder (because it "kills" less signal) in any given setting than a higher resistance pot?
i talked some more to the designer of the phono stage and figured out that a 20k pot would probably be ideal. i'll keep the phono stage as it is and in combination with a 20k pot the rolloff should be at 6 or 7 hz.
i seem to remember that somewhere on this forum i read about the relationship between S/N ratio and pot values. unfortunately i can't find the post or article anymore. can somebody verify my assumption that a lower pot is desirable because the lower resistance will "kill" (for a lack of a better word) less of the signal and thus less amplification is needed after the pot. With less amplification whatever noise appears in the amp will also be less amplified giving a better S/N ratio. Did I get it right so far?
Would that mean that - all other things equal - a lower resistance pot will play louder (because it "kills" less signal) in any given setting than a higher resistance pot?
No. All resistors generate thermal noise, no matter how 'good' they are. The thermal noise voltage is proportional to the square root of the resistance, so higher values generate more noise. The signal attenuation, on the other hand, just depends on resistance ratios (given a suitable pot value) not absolute values.
blue velvet 50k pot will do the trick.
I'm looking at the 10k or 20k one, however I have a preamp before the pot
Less amplification after the pot will reduce noise levels
It won't be any louder but noise levels will be less. Lower resistance will also make it flatter response when driving cables or stages with larger miller input capacitance.
I'm looking at the 10k or 20k one, however I have a preamp before the pot
Less amplification after the pot will reduce noise levels
It won't be any louder but noise levels will be less. Lower resistance will also make it flatter response when driving cables or stages with larger miller input capacitance.
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Where to have gain and attenuation is a balancing act. This is worth reading Setting Sound System Level Controls