OH! I was thinking output impedance of a guitar ~220K; however, there's also output impedance of pedals/effects, which have op-amps and near 0R, except for whatever they happen to use for output series resistance.
Assuming that the guitar amp has a tube/mosfet/jfet buffer at input, it may handle what the heck ever, right? In that case the lower values, like JMFahey's post, may be more important per noise reduction?
Assuming that the guitar amp has a tube/mosfet/jfet buffer at input, it may handle what the heck ever, right? In that case the lower values, like JMFahey's post, may be more important per noise reduction?
Considering noise I assume the noise of notebook output will be pre-dominant. So there is not much you can gain with a lower impedance divider.
Generally the lowest impedance divider is the best, giving best suppression of eventual disturbance by badly screened cables, sound degration caused by cable capacitance of longer cables etc.
Generally the lowest impedance divider is the best, giving best suppression of eventual disturbance by badly screened cables, sound degration caused by cable capacitance of longer cables etc.
Some can pass RMAA quality control (but this particular laptop has not been proofed). For a typical computer, the major noise output is on groundside, which is possible to filter. Generally, computers like to drive 12k and smaller figures. Generally they're capable of 0.9v max, beyond which they clip/distort themselves (so that max settings are counterproductive).
That is just another way to say that it is an almost overwhelmingly unsuitable headphone source, unless its particulars are addressed, and even then, it needs some help. For hi-fi output that's a fair challenge!
However, today's usage is that the laptop is serving as a virtual instrument tone generator for a midi keyboard, per piano practice needs, using GarageBand software; there are a plentiful amount of guitar amplifiers present and the MacBook Air's internal speakers (squeakers?) are insufficient to reproduce piano.
hmm, I do not grip what you are talking about.
I talked about residual audio noise of poor headphone drivers inside the laptop.
'
I think what you're looking for is Figure 1. The "Summed Output" plugging into the bass amp.
Why Not Wye?
The laptop's headphone output is very low impedance (we hope), and the bass amp's input impedance is very high (I expect), so I'd think the resistor values shown would be fine.
Of course the resistor values could be multiplied by two, or by whatever. Or use Figure 2. The whole thing's a voltage divider in disguise.
.
I think what you're looking for is Figure 1. The "Summed Output" plugging into the bass amp.
Why Not Wye?
The laptop's headphone output is very low impedance (we hope), and the bass amp's input impedance is very high (I expect), so I'd think the resistor values shown would be fine.
Of course the resistor values could be multiplied by two, or by whatever. Or use Figure 2. The whole thing's a voltage divider in disguise.
.
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Some laptops may use an unfiltered Class D headphone amplifier. This means feeding lots of HF hash into your guitar amp. Some amps will ignore it, especially if they start with a low pass filter. Some will be troubled by it. Using large resistor values with a longish cable will reduce the HF.
Agree.
In general I consider headphone outputs noisy/dirty , doubly so because they expect a headphone directly connected so between their inductance, high frequency rolloff and user ears rolloff
, designers can save a few cents by being unsophisticated (read it as crude ) and yet get away with it.
Of course, some do care, I consider that a bonus
Cheap MP3 players are usually very dirty, just scope them. Ugh!
EDIT: you might add a small ceramic capacitor after the mixing resistors, maybe even inside the plug, to rolloff supersonic garbage.
As an example, 2 x 1K resistors would yield a combined impedance of 500 ohms.
That with a 22nF cap would be 3 dB down at 16KHz,way above anything expected at a Bass Amp input.
Or use a 10nF one if you intend to play Music at a PA amplifier.
In general I consider headphone outputs noisy/dirty , doubly so because they expect a headphone directly connected so between their inductance, high frequency rolloff and user ears rolloff
, designers can save a few cents by being unsophisticated (read it as crude ) and yet get away with it.Of course, some do care, I consider that a bonus
Cheap MP3 players are usually very dirty, just scope them. Ugh!
EDIT: you might add a small ceramic capacitor after the mixing resistors, maybe even inside the plug, to rolloff supersonic garbage.
As an example, 2 x 1K resistors would yield a combined impedance of 500 ohms.
That with a 22nF cap would be 3 dB down at 16KHz,way above anything expected at a Bass Amp input.
Or use a 10nF one if you intend to play Music at a PA amplifier.
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