Interesting.... I thought each (+) and (-) output neededs it's own attenuator, totaling 4, all ganged together to make true stereo balanced like the diagram below. Maybe I am wrong.
An externally hosted image should be here but it was not working when we last tested it.
Kilowattsky,
you only need two output resistors (1-2k) and a switch to connect these resistors between plus and minus out. Output is taken after the output resistors. Look at the borbely page:
http://www.borbelyaudio.com/upgrades.asp under "potentiometers.
William
you only need two output resistors (1-2k) and a switch to connect these resistors between plus and minus out. Output is taken after the output resistors. Look at the borbely page:
http://www.borbelyaudio.com/upgrades.asp under "potentiometers.
William
Wuffwaff,
After looking at the article it appears that this attenuator arrangement can only be used on the input, the caveat of this configuration is that any switch noise (click etc.) will be amplified and definately heard. That is why I chose to attenuate the output of my preamp instead of the input. Very good article. Thank you for the link to it.
After looking at the article it appears that this attenuator arrangement can only be used on the input, the caveat of this configuration is that any switch noise (click etc.) will be amplified and definately heard. That is why I chose to attenuate the output of my preamp instead of the input. Very good article. Thank you for the link to it.
Hi,
it is sort of logarithmic. I took 2k2 output resistors and calculated the others to give ca. 3dB steps. You will need 22 resistors. The first step is closed (0 ohm) the last open.
The others are:
5600, 2200, 1200, 720, 470, 330, 220, 150, 100, 68, 47, 33, 25, 18, 12,
8,8
6,2
4,4
3,1
2,2
1,5
1,2
some values are not available so you´ll have to take the nearest one. Output impedance will be very low for most of the range. Only the highest leves have a bit more . Here´s the range from -0dB to infinity:
2195, 1579, 1100, 776, 542, 387, 287, 200, 140, 96, 66, 46, 33, 25, 18, 12, 9, 6, 4, 3, 2, 1, 1, 0 (all in ohms)
hope this helps,
William
it is sort of logarithmic. I took 2k2 output resistors and calculated the others to give ca. 3dB steps. You will need 22 resistors. The first step is closed (0 ohm) the last open.
The others are:
5600, 2200, 1200, 720, 470, 330, 220, 150, 100, 68, 47, 33, 25, 18, 12,
8,8
6,2
4,4
3,1
2,2
1,5
1,2
some values are not available so you´ll have to take the nearest one. Output impedance will be very low for most of the range. Only the highest leves have a bit more . Here´s the range from -0dB to infinity:
2195, 1579, 1100, 776, 542, 387, 287, 200, 140, 96, 66, 46, 33, 25, 18, 12, 9, 6, 4, 3, 2, 1, 1, 0 (all in ohms)
hope this helps,
William
Audio signal amplitudes are measured in deciBells (dB). The range of loudness which can be perceived by the human ear varies over 6 orders of magnitude making linear measurements of loudness difficult to deal with. Therefore a logarithmic scale of loudness, the deciBel scale, has been adopted.
This logarithmic measurement of signal intensity describes the amplitude of a signal relative to a standard referrence amplitude. Therefore the dB scale is said to be a relative, not an absolute scale of measurement. The referrence used for 0dB varies according to the circumstances for which the signal is being measured.
To calculate dB for amplitude, the formula the is dB=20 Log(Amp / RefAmp). To calculate dB for power, the formula is dB=10 Log(Power / RefPower).
This logarithmic measurement of signal intensity describes the amplitude of a signal relative to a standard referrence amplitude. Therefore the dB scale is said to be a relative, not an absolute scale of measurement. The referrence used for 0dB varies according to the circumstances for which the signal is being measured.
To calculate dB for amplitude, the formula the is dB=20 Log(Amp / RefAmp). To calculate dB for power, the formula is dB=10 Log(Power / RefPower).
Hi! William I'm trying to finish my Aleph 1.7 and I'm not sure how to hook up the attenuator can you please post the schematic or you can email me at Nbaula@comcast.net. Thank you for yuor'e help?
Hi,
I think Henrik drew the schematic in my X-BOSOZ thread. Here it is:
http://www.diyaudio.com/forums/attachment.php?postid=275942&stamp=1070543170
William
I think Henrik drew the schematic in my X-BOSOZ thread. Here it is:
http://www.diyaudio.com/forums/attachment.php?postid=275942&stamp=1070543170
William
Nbaula,
it should work for every balanced output preamp. You must choose the output resistors (1k-2k) and then calculate the shunt resistor to get the desired attenuation. I´ve got a small excel sheet attached. Here you can calculate the neccesarry resistor values, look at the output impedance and the errors you get when choosing real world resistors.
William
it should work for every balanced output preamp. You must choose the output resistors (1k-2k) and then calculate the shunt resistor to get the desired attenuation. I´ve got a small excel sheet attached. Here you can calculate the neccesarry resistor values, look at the output impedance and the errors you get when choosing real world resistors.
William
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