Setting gain... figuring out the numbers?
Re: Setting gain... figuring out the numbers?
4.95V Watch the decimal...TroyO wrote:The DAC lists "Output swing" as "0.010 to VDD – 0.040" so running at 5V for VDD means a total swing of 4.5v?
"voltage out, peak to peak"TroyO wrote:The BTL Amp datasheet states "Plugging 2 × VO(PP) into the power equation, where voltage is squared, yields 4× the output power from the same supply rail and load impedance." But I can't find anything saying exactly what VO(PP) actually IS.
Or you could attenuate the inputTroyO wrote:If the voltage swing of the amp maxes out at 10V PP, and I have 4.5V PP coming in I want a gain of 2.22 V/V for "Max output" right? (And then a voltage divider using a POT to attenuate it from there.)
It's a free countryTroyO wrote:Last question... would it be better to "overdrive" the gain just a tad.... say 2.5 V/V so that while all the way up would be somewhat distorted you could "trim" the volume pot back down to be sure you were getting the max available, or should I just follow the numbers?
Re: Setting gain... figuring out the numbers?
4.95V Watch the decimal...
"voltage out, peak to peak"
Or you could attenuate the input
It's a free country
Re: Setting gain... figuring out the numbers?
Re: Setting gain... figuring out the numbers?
Zener wrote:The gain of an amp depends on its load
TroyO wrote:Maybe I need to phrase it better... I can't find in the datasheet a "Swing value" or what the max peak to peak output voltage of the device is. Hmmm, with a 4 Ohm load, and a 2 Watt rated output I'd think 8V was the max output voltage swing... but I can't seem to find in the datasheet where I can validate my assumption. I was hoping someone could point me to where in the datasheet it's listed, and/or confirm that it really just doesn't tell you that info.
Opps... actually that's what I meant to do, I will also be adding in the low pass filter as used in the WaveShield schematic.
True enough.... there's a lot of "Rule of thumb" things with electronics, I was just wondering if the common practice is to leave some trim room on audio circuits or go exactly by the numbers?
Re: Setting gain... figuring out the numbers?
Re: Setting gain... figuring out the numbers?
Re: Setting gain... figuring out the numbers?
Re: Setting gain... figuring out the numbers?
Re: Setting gain... figuring out the numbers?
Re: Setting gain... figuring out the numbers?
Re: Setting gain... figuring out the numbers?
Re: Setting gain... figuring out the numbers?
Re: Setting gain... figuring out the numbers?
TroyO wrote:OK, I am following a lot better... the step by step helps.
1.75V RMS from 4.95V(PP) DAC Output
2.83Vrms Out for 4 Ohms @ 2W (1.62 V/V Gain) (Interesting... it's mighty close to what I came up with before by doing it the "wrong way")
3.16Vrms Out for 8 Ohms @ 1.25W (1.81 V/V Gain)
Ohh, another question.... the datasheet lists the resistor equation for gain calculation as:
AV = –125 k / RI
I have been ignoring the negative resistor value.... since I can't seem to locate a -72.5k resistor. (Wouln't that be a battery, I guess? ;-) Am I missing something there?
Re: Setting gain... figuring out the numbers?