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Old 27th April 2005, 03:56 AM   #1
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Location: Simcoe Ont
Default Volume control +4db

I want to run my +4db alalog outputs directly to active studio monitors. My only means of contoling volume, are the input sensitivity or by software. My other option is to use a mixer or monitor matrix, most of them seem to colour or mask the signal to some degree. Can I not use a stereo potentiometer or a pair of potentiometers? If so, What value and how should they be wired?
Thanks in advance
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Old 27th April 2005, 04:08 PM   #2
AndrewT is offline AndrewT  Scotland
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Hi,
+4db referenced to what?
What is your output impedance?
How long and what capacitance are your interconnects?
Yes you can use a pot or two but give us some clues to get started.
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Old 29th April 2005, 05:39 AM   #3
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I do not know my output impedence. The manual does not specify. I believe it is +4db balanced. It would definately be studio standard. My monitors are also +4db, the input impedence of those is specified as 10k ohms.
Another option for monitoring is an old allen and heath mixer I have. The sound is very transparent but it would need to be modified. It does not have a monitoring section so I would have to make one. The eq pots are not detented (no center) so I would like to bypass them. They are 100k pots. I thought about eliminating the pots and substuting resistors but could only find 47k resistors locally.
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Old 29th April 2005, 07:23 AM   #4
AndrewT is offline AndrewT  Scotland
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Hi,
10k recommended input impedance moves us forward a little.
You can use a dual 10 log pot as a stereo volume control.
These are not very accurate at low volumes (high attenuation) and you could look up log law faking & use 100k lin with 10k faking resistor for improved accuracy (balance).
But you still need to find out more info & tell us cable capacitance and lengths. +4dbwhat, you need a reference. Decibel (& bel) are a ratio not an absolute. See if it's dbm, dbu, dbV or some other, these are all referenced to standard audio/radio voltages. Not dbA which is a (filtered) sound level.
Good luck in your searches.
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Old 29th April 2005, 04:02 PM   #5
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Default Output att.

tech rep says it is +4dbV
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Old 30th April 2005, 11:57 AM   #6
AndrewT is offline AndrewT  Scotland
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Hi,
0dbV is 1Vrms and +4bdV is 1.58Vrms or 2.24Vpk
Your average music level is likely to be 3 to 20db below these maximum levels, depending on the type of music you listen to.
So your average level at maximum volume (deafening) is going to be 1.12V(+1dbV) down to 158mV(-16dbV) and obviously at times of quieter listening likely to be 20 to 40db below these averages i.e. 112mV(-19dbV) down to 1.6mV(-56dbV)
any of these outputs will be OK with a 10K or 100K (faked) pot and similarly with most poweramps. However some hi gain poweramps will have a sensitivity below 1Vrms and you will have to keep your volume control down to suit these. If you find that you are operating at the bottom of the pot rotation then try an inline resistor before the pot to expand the usable range. For a 10K pot try a variety between 22k and 100K. Noise may start to become a problem at the higher end of this range in whch case change all components down by a factor of ten (but this only applies if you need to expand the range a lot) i.e. 100K dropper +10kpot becomes 10K dropper + 1k pot with a total input resistance of 11K.
You still have not told us about proposed cables. This will affect high frequency response unless addressed.
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