penance
Arrogant Cock
Apparently TacT will be releasing thier own phono stage, maybe it may help....
3DSonics said:2) Use the EQ with uncommon sense (read my little essay, I'll post it here later)
Croc said:1. i understood that 8024 in analog mode (ADC+DAC) did alter sound quality - your review provides one more evidence for that.
Croc said:isn't deq2496 is better in this regard? i don't know - other dacs, higher sampling rate, etc................
Croc said:2. is there expirience of moding deq2496?
Croc said:3. why don't you use it anymore?
Croc said:4. isn't this thing PC controlled?
Croc said:if NO - what are all those computer screen screenshots at behringer's site?
Croc said:5. i didn't undestand whether deq2496 also provides "Auto-Q" function?
Croc said:6. as i intend to buy it online from US with no local waranty - it's important to know are there known reliability issues with behringers?
Croc said:sorry, screenshots that i saw are from 8024:
what are they?
from MIDI interface?
Croc said:regarding sound degradation - i guess it's about balance of sound altering against improvement of RC.
Croc said:what people say - how is it compared in this regard (sound degradation) with tact and deqx?
Croc said:what do you mean by "levels"?
3DSonics said:Hi,
Excactly that. Levels, as in Signal levels.
The DEQ2496 offers a selection of 3.1V or 9.8V for digital full scale on the input/input. The DEQ2496 offer a 113db dynamic range compared to these voltages.
Now if you feed the DEQ a level of 0.31V and have set it to use +22dbu full scale level your dynamic range is down to 83db, well below CD standard. The result will be audible distortion and general poor sound.
Now change your gainstrutcure so that your Amplifiers overload with exactly 3.1V RMS on their inputs, select the +12db full scale level and crack up your preamp and you have a dynamic range of 113db velow clipping, well past CD standard, so in fact you can attenuate the system overall by around 20db without loosing resolution from CD Sources.
As you can see, "getting the levels right" is absolutely crucial and the difference between great results and poor ones.
Ciao T
Croc said:have to ssay that i lost you.
till today never got to understand all this dbfs/dbu stuff![]()
3DSonics said:Hi,
Okay. In principle db is just a measure which is logarythmic and indicates a relative value compared to a given reference.
Now:
1db = 1.12
2db = 1.25
3db = 1.41
6db = 2
10db = 3.16
12db = 4
18db = 8
20db = 10
For digital audio the standard reference is "digital full scale" usually abbreviated to fs (full scale). This means once you get there you have turned every bit on and there is nowhere to go after this. So increasing the input level will not turn on any more bits because they are already all on. In analog terms we call that clipping.
So, 0dbfs is the point where the ADC/Bitstream clips. In digital all measures are commonly referenced to that 0dbfs even though commonly peaks should remain a db or two below that imaginary line.
So a dynamic range of 113db means the loest signal to still change the output is -113dbfs, which BTW is equivalent to 19 Bits. So even though the ADC and DAC are claimed to be "24 Bit" they and the analogue circuitry produce so much noise that only 19 Bits of this resolution is genuinely available, but that is still 3Bit or 18db more than with CD.
Now for dbu, dbu is a pro audio measure which is defined as 0.775V and comes from the old dbm where the reference was 1mW (the m) into 600 Ohm. Thus 0dbu = 0dbm if the load is 600 ohm and in voltage terms it is 0.775V.
Knowing that the Behringer DEQ2496 inputs are rated as requiring 22dbu Input level for 0dbfs or clipping of the bitstream we can look at our table above and find that 22db is 1.25*10.
Now we know that 0dbu is 0.775V so +22dbu is 0.775 * 1.25 * 10 or 9.68V. So we need to apply 9.68V to the input to use the full dynamic range of the ADC and that which is available from the DEQ2496. Equally, if the DAC in the DEQ2496 outputs 0dbfs (or clipping) we know the Output Voltage is 9.68V.
Lets drop the EQ between Amplifier and Preamplifier in a normal HiFi System like yours.
Your Amplifier is a Citation II, which if stock has a gain of around 27db for an output power of 60 Watt on the 8 Ohm Tap. I'll spare you the math to work out the input sensitivity and tell you that it comes to around 1V for full power. BTW, on the SF Cremona's you have this would in an "average room" translate into around around 100db for the pair of speakers at a listening position 3m from each speaker.
Now if our Amplifier will overload with 1V input but the Digital equaliser will output 10V when it overloads we have a clear level mismatch, which for the volume totally tuned up to the point where the speakers overload amounts to 20db. These 20db result in only 93db dynamic range for the system.
Okay, lets do something else.
We switch the DEQ2496 to +12dbu full scale. Now we know that the full scale output will be around 3V. This is still 10db higher in level than what we need to overdrivedrive the Amplifier, so if we then add around 6db attenuation (say a 3k3 series resistor and a 3k3 shunt resistor) on the amplifier input will will have matched the levels pretty well as now the level on the DEQ's output will be 2V to overload the Amplifier. In other words, instead of throwing away 20db dynamic range in the EQ we now only loose 4db, which is a sensible safety margin.
The 16db we have gained BTW are pretty much 3 Bit worth of resulution or in other woirds the difference between DVD-A and CD!!!!
Any clearer?
Ciao T