I poked around a bit here, but did not find what I needed. Essentially, I want to make my own version of this:
Harrison Labs 12 dB RCA Line Level Audio Attenuator Pair
Not so much the dual RCA jack part, but the attenuation circuitry. I have a couple of components which put out way too high of an audio signal, and cracking the volume control on the preamp just a hair from silence just blasts out of the speakers. This -12dB attenuator would do what I needed. Yet, I want to wire up my own.
I am thinking this attenuator would use either a series resistor, or a voltage divider (L-pad) to do this. Since the input impedance I'm looking at seems rather average (~25k ohms), I am thinking I could plug this into one of the online L-pad calculators and find some ballpark values for the resistors.
Such as this one: troester.org | L-Pad Calculator
The calculator shows both solutions (series resistor, or L-pad)--any advantage to either one? Something tells me the L-pad may be the better of the two.
I'm not sure what the Parts Express solution has inside of it, but I imagine it is rather simple. (And I am thinking their -12dB is only a ballpark figure, given the variety of input impedances on many components.)
Any help appreciated. Thanks for reading!
Harrison Labs 12 dB RCA Line Level Audio Attenuator Pair
Not so much the dual RCA jack part, but the attenuation circuitry. I have a couple of components which put out way too high of an audio signal, and cracking the volume control on the preamp just a hair from silence just blasts out of the speakers. This -12dB attenuator would do what I needed. Yet, I want to wire up my own.
I am thinking this attenuator would use either a series resistor, or a voltage divider (L-pad) to do this. Since the input impedance I'm looking at seems rather average (~25k ohms), I am thinking I could plug this into one of the online L-pad calculators and find some ballpark values for the resistors.
Such as this one: troester.org | L-Pad Calculator
The calculator shows both solutions (series resistor, or L-pad)--any advantage to either one? Something tells me the L-pad may be the better of the two.
I'm not sure what the Parts Express solution has inside of it, but I imagine it is rather simple. (And I am thinking their -12dB is only a ballpark figure, given the variety of input impedances on many components.)
Any help appreciated. Thanks for reading!
L-pad its the way to go, just a series resistor is going to have considerably variable attenuation according to the input impedance of the downstream kit. Assuming your input impedance is never going to be below 25kohms then a shunt arm of 2700ohms looks about right. Then the series R will be 8200ohms.
if just "cracking the volume control on the preamp just a hair from silence just blasts out of the speakers" then you have far more than +12dB of too much signal.
Probably more like +30dB to +60dB too much.
Try a 10:1 ratio of attenuating resistors for ~-21dB.
i.e. use 10k in series and 1k0 to ground. The signal across the 1k0 becomes your new output signal to feed the cable and the next component in the string.
If that is still too loud, then try tacking on an EXTRA resistor in parallel to the 1k0.
a second 1k0 increases the attenuation to ~-26dB, or adding a 470r comes out at -30dB
Probably more like +30dB to +60dB too much.
Try a 10:1 ratio of attenuating resistors for ~-21dB.
i.e. use 10k in series and 1k0 to ground. The signal across the 1k0 becomes your new output signal to feed the cable and the next component in the string.
If that is still too loud, then try tacking on an EXTRA resistor in parallel to the 1k0.
a second 1k0 increases the attenuation to ~-26dB, or adding a 470r comes out at -30dB
@AndrewT: agreed, a couple of sources are very loud, and I will look at other ratios. That is one reason I want to do my own, so I can tweak. Video game consoles are notorious for high output, in fact, so I know I will need the stronger attenuation there.
This is part of a large basement system where I have all of my older "stuff" connected--older video formats like LD and VHS, game consoles, a couple of CD players, all the recordable gear (reels, cassette, 8-track, DAT, MD, etc.). I already have a custom switch box feeding the old preamp, so I'm possibly hard-wiring some attenuation into a couple of its inputs.
This is part of a large basement system where I have all of my older "stuff" connected--older video formats like LD and VHS, game consoles, a couple of CD players, all the recordable gear (reels, cassette, 8-track, DAT, MD, etc.). I already have a custom switch box feeding the old preamp, so I'm possibly hard-wiring some attenuation into a couple of its inputs.
CD is typically 2Vac to 2.3Vac from a full size separate.
small portables may be less, or even a lot less to save on battery drain.
Older analogue equipment tends to be less than CD, but are specified a different way so difficult to know their maximum output, but typically 200mVac to 1Vac.
Professional gear tend to have higher outputs, 2Vac to 4Vac may be typical.
I don't know anything about games consoles, but surprised they have "line-level" outputs that are notoriously high, meaning higher than CD & Pro.
small portables may be less, or even a lot less to save on battery drain.
Older analogue equipment tends to be less than CD, but are specified a different way so difficult to know their maximum output, but typically 200mVac to 1Vac.
Professional gear tend to have higher outputs, 2Vac to 4Vac may be typical.
I don't know anything about games consoles, but surprised they have "line-level" outputs that are notoriously high, meaning higher than CD & Pro.
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