audio attenuator headphone to line
in [Repair]
|
Prev: 1394 Connectors
Next: Backiline 600
From: tg on 10 Jul 2010 12:06 I want to make a simple audio attenuator by soldering a couple of resistors into a cable, similar to here: http://www.epanorama.net/circuits/speaker_to_line.html this page talks about attenuating speaker level down to line level with 10k and 1k but I want to attenuate headphone level down to line level. I haven't done this before and want to get it right so can anyone advise on the correct resistor values to use?
From: Fred McKenzie on 10 Jul 2010 13:49 In article <4c389aba$0$27995$db0fefd9(a)news.zen.co.uk>, "tg" <nospam(a)nospameverever.net> wrote: > I want to make a simple audio attenuator by soldering a couple of resistors > into a cable, similar to here: > http://www.epanorama.net/circuits/speaker_to_line.html > this page talks about attenuating speaker level down to line level with 10k > and 1k but I want to attenuate headphone level down to line level. I haven't > done this before and want to get it right so can anyone advise on the > correct resistor values to use? My recollection is that "line level" is related to the level that would drive a telephone earpiece, and be generated by a telephone's carbon microphone. In other words, line level is not greatly different from headphone level. Just as anyone would adjust a volume control to set their personal listening level, you would need to adjust the amplifier output for the desired line level. The only network needed might be for impedance matching to the line. If your headset amplifier has a very low output impedance, a series resistor equal to the line impedance may be all that is needed. What kind of "line" are you working with? Some are balanced, but the circuit you refer to is for an un-balanced line. For a balanced line you may need an audio transformer. Fred
From: tg on 10 Jul 2010 19:57 > What kind of "line" are you working with? Some are balanced, but the > circuit you refer to is for an un-balanced line. For a balanced line > you may need an audio transformer. the line input is a 1/4" TRS socket on an m-audio microtrack II. http://www.m-audio.com/images/global/manuals/MT11_flyerUK_LR.pdf Strangely enough I haven't been able to find any proper specs on the microtrack but I know it commonly takes microphones and such. Headphone output is too 'heavy' for a decent recording into this input so I need to attenuate it. I can't use any boxes or such because the headphone device and the microtrack will be used on the move, often in the open, on foot, running on batteries. Thus I have to integrate any attenuation into the cable. Thanks for any further advice.
From: Arfa Daily on 10 Jul 2010 21:10 "tg" <nospam(a)nospameverever.net> wrote in message news:4c390954$0$12156$fa0fcedb(a)news.zen.co.uk... >> What kind of "line" are you working with? Some are balanced, but the >> circuit you refer to is for an un-balanced line. For a balanced line >> you may need an audio transformer. > > the line input is a 1/4" TRS socket on an m-audio microtrack II. > http://www.m-audio.com/images/global/manuals/MT11_flyerUK_LR.pdf > Strangely enough I haven't been able to find any proper specs on the > microtrack but I know it commonly takes microphones and such. Headphone > output is too 'heavy' for a decent recording into this input so I need to > attenuate it. > I can't use any boxes or such because the headphone device and the > microtrack will be used on the move, often in the open, on foot, running > on > batteries. Thus I have to integrate any attenuation into the cable. Thanks > for any further advice. The resistor values you suggested give an attenuation of 10 : 1 which is probably rather too much. OTOH, I'm surprised that you find a headphone output too 'heavy' to feed a standard line level input. The output from the headphone socket of an iPod, for instance, feeds a standard line level input on an amplifier, without issue. I do it every day with a variety of different amplifiers, as I use my iPod as a source of test music for amplifiers after repair. Even if the output from the headphone socket does seem a little OTT to drive the recorder's line input, you can reduce it by turning down the volume control on the source device. If, however, you still want to externally attenuate the headphone signal, prior to driving it into the recorder, then a ratio of 2 : 1 might be more appropriate, so just use a couple of equal value resistors . You're never going to match the impedances properly, as the output of the source device's headphone socket, is likely to be somewhere between a few ohms, and 32 ohms. The line input on the recorder will likely be around 47k ohms. Just use two 1k resistors. If that doesn't give enough attenuation, double up on the 'top' resistor to say 2k2. Only thing that might make all of that wrong, is if the input that you are trying to use on the recorder, is not a 'line level' input. I say that because you talk about the device "commonly taking microphones". A microphone input is probably anything up to 100 times more sensitive than a line level input. If this is the case, then you might need an attenuator of 50 : 1 or more. In which case, try 47k for the top resistor, and 1k for the bottom one. Arfa
From: David Nebenzahl on 10 Jul 2010 22:24
On 7/10/2010 9:06 AM tg spake thus: > I want to make a simple audio attenuator by soldering a couple of resistors > into a cable, similar to here: > http://www.epanorama.net/circuits/speaker_to_line.html > this page talks about attenuating speaker level down to line level with 10k > and 1k but I want to attenuate headphone level down to line level. I haven't > done this before and want to get it right so can anyone advise on the > correct resistor values to use? According to that propaganda sheet, the Micro Track II will accept input from "studio monitors (and/or headphones)". So can't you just plug it directly into the headphone output? (Not sure what they mean by "and/or" here. I've always held that this usage ("and/or") is needlessly confusing and should never be used, as "or" as it's commonly understood is not an exclusive or, so it means one, the other, or both.) -- The fashion in killing has an insouciant, flirty style this spring, with the flaunting of well-defined muscle, wrapped in flags. - Comment from an article on Antiwar.com (http://antiwar.com) |