i'm returning to this topic after doing some reading of "The Art of Electronics" (Horowitz / Hill, 3rd Ed.). Earlier in this thread it was mentioned that a lower resistance pot puts more "load on the source". I never quite understood what exactly that was supposed to mean. Now I stumbled upon this sentence in the book mentioned above:
Signal sources (e.g., oscillators, amplifiers, and sensing de- vices) all have an equivalent internal resistance. Attaching a load whose resistance is less than or even comparable to the internal resistance will reduce the output considerably. This undesirable reduction of the open-circuit voltage (or signal) by the load is called “circuit loading.” Therefore you should strive to make Rload ≫Rinternal , be- cause a high-resistance load has little attenuating effect on the source
Is that explaining what "load on the source means"? It seems to make sense to me 🙂
Signal sources (e.g., oscillators, amplifiers, and sensing de- vices) all have an equivalent internal resistance. Attaching a load whose resistance is less than or even comparable to the internal resistance will reduce the output considerably. This undesirable reduction of the open-circuit voltage (or signal) by the load is called “circuit loading.” Therefore you should strive to make Rload ≫Rinternal , be- cause a high-resistance load has little attenuating effect on the source
Is that explaining what "load on the source means"? It seems to make sense to me 🙂
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Just do away with the potentiometer and its problem and use Discrete well matched high quality resistors for the voltage divider, digitally controlled. Like This:
Home > Forums > Source & Line > Analog Line Level 
Preamp Control -Volume,input,mute, remote
Enjoy 🙂
Home > Forums > Source & Line > Analog Line Level Preamp Control -Volume,input,mute, remote Enjoy 🙂
Indeed, but that does not have to confine the pot, to its traditional fairly mundane use.
Is the ethos of the forum is to discover new things ? or to continually repeat the past.
In this case just celebrating variations of patent 1357773 Rheostat ,or drawings made by Sir Charles Wheatstone in 1843
Choosing a pot should as I see it equally have the ability, to encompass designs which enable the pot away from just processing audio signals - whilst acknowledging a pot is being chosen for duty somewhere in that circuit as part of a passive preamplifier.
Your design has several issues. Put an op amp (5532 or 5534) after DAC and after the pot (voltage follower). You need two/channel. BTW you need a log law pot.
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additio: All mechanical pots have a left/right deviation of 3..20! dB at the end positions.
If you can't live with it, you have to change to other technologies: stepped attenuator, relay att, digital volume pot, etc.
If you can't live with it, you have to change to other technologies: stepped attenuator, relay att, digital volume pot, etc.
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A good friend of mine (making audio devices for 40 years) once told me, that it is not the job of good audio devices to roll-off the signal and limit the bandwidth. If a signal is bothersome or dangerous, it has to be eliminated at the front of the source.
He has instructed you wrongly, YouTube
The World Beyond 20kHz Article By Earthworks Audio Founder David E. Blackmer
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The man must be a bat or Count Dracula. I always find it funny when older people talk about 96 kHz or even 192 kHz sampling and even hear up to 10-12 kHz!
That is just disrespectful. David is not so small minded to be just thinking of himself.
You should have noticed he garners opinion from many groups to inform of what is
perceived, and expresses findings in terms of the plural ( we) rather than the singular.
If you listen to what he says, where wide bandwidth is catered for, it seemingly improves
lower audible frequencies. He also talks in terms of perception rather than directly hearing
frequencies beyond what is our upper threshold.
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It does in this thread, which is clearly about choosing a suitable pot for a conventional passive preamp which uses the pot as a signal voltage diviver. Choosing a pot for some other circuit use belongs in another thread.Chris Daly said:
It is the amplifier which drives the speakers, so the amplifier is exactly the right place to put in any protection the speakers need, such as bandwidth limitation. The source is the wrong place to do this.diyralf said:
That is then given equal prominence as a sticky type thread ? There are many exciting ways of using potentiometers in passive preamps which require discussion. ..
You could start a thread about the exciting issue of choosing a control pot for an LDR volume control, then ask the Mods to make it a sticky. I am going to guess that they might decline, on the grounds that part of the justification for LDR volume controls is that the pot is not really in the signal path so doesn't really matter too much.
On the other hand, people are always popping up asking about how to choose a passive volume pot value to use between X source impedance and Y load impedance so it makes sense to put the answer in a sticky.
On the other hand, people are always popping up asking about how to choose a passive volume pot value to use between X source impedance and Y load impedance so it makes sense to put the answer in a sticky.
This thread is a sticky. It is a thread which remains at the top of the forum area, not being displaced by more recent non-sticky threads.
Not sure if this is the correct location for this question but here it goes.
I’m building a dual mono passive preamp using Dact SMD pots. The chassis for each is
a repurposed Leads and Northrop Aryton Shunt Galvonometer. There are heavy duty binding post terminals with large brass posts. For aesthetics and simplicity’s sake I would like to keep these. What sonic degradation might I experience forgoing the RCA jacks here? I have
Read that RCAs are a flawed design sighting skin effect and phase issues. I don’t have an issue with them though I’ve always thought that a solder joint is the weakest link in the signal path.
I’m building a dual mono passive preamp using Dact SMD pots. The chassis for each is
a repurposed Leads and Northrop Aryton Shunt Galvonometer. There are heavy duty binding post terminals with large brass posts. For aesthetics and simplicity’s sake I would like to keep these. What sonic degradation might I experience forgoing the RCA jacks here? I have
Read that RCAs are a flawed design sighting skin effect and phase issues. I don’t have an issue with them though I’ve always thought that a solder joint is the weakest link in the signal path.
Attachments
No. You can safely ignore anyone who told you that. RCAs are flawed, but nothing to do with skin effect or phase. RCA is often flimsy, can have poor contact resistance, and makes the signal contact before ground. However, it is successfully used in most domestic audio systems.Rockaway said:
The weakest link in a signal path is the transducers: microphones, speakers.
Using binding posts for inputs may mean a bit more hum because you unavoidably introduce some loop area.
I know that capacitance is a factor with passive pre’s.
The shielding on an RCA jacket must contribute to this. If I keep
Exposed area of the cable short on the top where it attaches to the binding posts seems like little RF could “get in”.
The brass posts inside are within the thick walled aluminum chassis and theoretically
Immune to RF magnetic fields ground loops etc.
The shielding on an RCA jacket must contribute to this. If I keep
Exposed area of the cable short on the top where it attaches to the binding posts seems like little RF could “get in”.
The brass posts inside are within the thick walled aluminum chassis and theoretically
Immune to RF magnetic fields ground loops etc.