hello
I read elements that I don't understand, it concerns the adaptation of input and output impedances. Either between pream/amplifiers or between amplifier stages and with loudspeaker impedances.
Can you give me some documents or threads that I can read to understand the impact of these factors on sound, bandwidth etc...
Or give me the technical explanations to give me an informed opinion.
Yours sincerely
If you have them in French it would be perfect, otherwise I'll translate them.
I read elements that I don't understand, it concerns the adaptation of input and output impedances. Either between pream/amplifiers or between amplifier stages and with loudspeaker impedances.
Can you give me some documents or threads that I can read to understand the impact of these factors on sound, bandwidth etc...
Or give me the technical explanations to give me an informed opinion.
Yours sincerely
If you have them in French it would be perfect, otherwise I'll translate them.
When you are dealing with RF transmission or using transformers to convert
power efficiently it is convenient to think in terms of impedance matching
but around here we usually want low source impedance and higher load
impedance.
We like our line level circuits with maybe 100 kohm inputs and 100 ohm outputs.
We like amplifiers with fractional output impedance driving 8 ohm loads.
and so on.
power efficiently it is convenient to think in terms of impedance matching
but around here we usually want low source impedance and higher load
impedance.
We like our line level circuits with maybe 100 kohm inputs and 100 ohm outputs.
We like amplifiers with fractional output impedance driving 8 ohm loads.
and so on.
Just to expand on Nelson's answer:
Matching maximizes power transfer.
Low Output z, High input Z maximizes voltage transfer.
Usually for audio, we want a flat voltage output.
The Firstwatt F1 is a counter example.
Matching maximizes power transfer.
Low Output z, High input Z maximizes voltage transfer.
Usually for audio, we want a flat voltage output.
The Firstwatt F1 is a counter example.
What is the effect on sound as load impedance increases? Is it the same as increasing source impedance?
I ask this because I'm building a Balanced Zen line stage, There is a 10K pot on the input which is supposed to change impedance along with a 5K pot on the output side.
If the input is "volume" control, what effect to adjusting "volume" have on the impedance? What effect to the sound quality as volume is adjusted?
Is the output 5k pot a fine adjust to change sound quality because of different amplifier inputs?
I understand what impedance is, I just have trouble with what it does, or doesn't do.
If the input is "volume" control, what effect to adjusting "volume" have on the impedance? What effect to the sound quality as volume is adjusted?
Is the output 5k pot a fine adjust to change sound quality because of different amplifier inputs?
I understand what impedance is, I just have trouble with what it does, or doesn't do.
Looking at the Balanced Zen Line Stage, The P1 and P2 are simply 10K volume pots.
The 100K in parallel is simply to have a path to ground in case a wiper opens.
The input impedance varies less than 10% depending on the wiper position.
The most obvious use of the output attenuators is to allow less attenuation on the input.
This may alter the distortion spectra of the FET. It would be interesting to try it.
HTH
The 100K in parallel is simply to have a path to ground in case a wiper opens.
The input impedance varies less than 10% depending on the wiper position.
The most obvious use of the output attenuators is to allow less attenuation on the input.
This may alter the distortion spectra of the FET. It would be interesting to try it.
HTH
I found this, it should explain what I'm looking for. Sorry it's not in French.
Understanding Impedance |
Understanding Impedance |
Audio wavelengths on copper wire are at least 15Km long (20KHz) , so the transmission line problems that happen when a cable is not impedance matched only apply to telephone lines and not to your (relatively short) stereo cables. Within a building dimensions, all connections are as good as a direct connection at audio frequencies. Have a read about standing waves and tuned stubs if you are interested in radio frequency cables.
But your speaker is a mechanical device with all kinds of messy resonances and resonance modes. At low frequencies, your woofer has a "parallel" resonance that is best controlled by driving it with a low or even slightly negative impedance (very tricky). But at higher frequencies, you can get "series resonances and they are best controlled with high impedance termination, which limits the current into series resonance impedance dips. So the best plan is to build out your woofer with a choke only and pad the mid and tweeter with build-out resistors since they probably need attenuation anyway.
also see:Speaker impedance curve explained with examples | Audio Judgement
But your speaker is a mechanical device with all kinds of messy resonances and resonance modes. At low frequencies, your woofer has a "parallel" resonance that is best controlled by driving it with a low or even slightly negative impedance (very tricky). But at higher frequencies, you can get "series resonances and they are best controlled with high impedance termination, which limits the current into series resonance impedance dips. So the best plan is to build out your woofer with a choke only and pad the mid and tweeter with build-out resistors since they probably need attenuation anyway.
also see:Speaker impedance curve explained with examples | Audio Judgement
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