Gain, Preamp, Efficient Driver

[pra3718]

Excuse me, if it is discussed before.

My current project is tda7265 with Gain=33 (3.3K/100R) Power by 22 (+/-) sounding good but not much louder. Assume, my source is poor or my speaker is not that much efficient, which I can not change because, already I have purchased it. I have only two options.

Option 1 : Increase the gain between 39 to 47 ( Simple for me. )

Option 2 : Adding simple preamp gain between 1 to 2

Which option is good.

Thanks & Best Regards.

[pacificblue]

Does it not go any louder, because the gain is too low? Then both options will work. 25 W into 8 Ohm corresponds to ~14,1 V. With a gain of 33 you need 428 mV for max output power. Modern CD players tend to have more than 2 V which requires no further action. Normal line level should be around 360 mV, so a gain of 39 would be okay. Other devices like MP3 players can have less, e.g. 150 mV. For such a source you would need a preamp with a gain of 3. Check what your source delivers and choose accordingly.

Or does it not go any louder, because you have reached the amplifier's power limit? You will notice, when the amplifier starts to sound distorted. Then neither option will help you.

[pra3718]

Or does it not go any louder, because you have reached the amplifier's power limit? You will notice, when the amplifier starts to sound distorted. Then neither option will help you.

Sound is clear.

[AndrewT]

changing from 3k3 to 4k7 increases the gain by +3dB, from to +30.6dB to +33.6dB.
You will hardly notice any difference.

Measure the maximum output of your source.

A 2times pre-amp is a gain of +6dB
4times is +12dB

[pra3718]

changing from 3k3 to 4k7 increases the gain by +3dB, from to +30.6dB to +33.6dB. You will hardly notice any difference.

Then I need pre-amp.

[AndrewT]

measure the maximum output of your source.

[pra3718]

measure the maximum output of your source.

AndrewT, you are right I should measure the maximum output of my source. If it less than it should be then only I need preamp. But I don't know how to measure it.

My source is DVD Player. It has various features...

Channel : Stereo / 5.1 = If I switch stereo to 5.1 loudness drops.
Speaker : Big / Small = If I switch Big to Small loudness drops.
Subwoofer : On/Off
Prologic II : On/Off/Auto = To change this loudness varies.
It has preset equalizer = If I change NONE to ROCK,LIVE,POP,TECHNO loudness varies.
It has 3D surround effects = To change this loudness varies.

If I keep all features silent and listen only on stereo mode then only it sounds louder.

Now what is your comment.

[AndrewT]

Hi,
connect an interconnect to the main outputs of the player.
Temporarily solder a 10k resistor across the far end of the interconnect.

Play the loudest music source you have and measure the maximum AC voltage across the 10k resistor.
Compare that voltage to the specification given in the users Manual.

I wonder if there is a standard way to generate test tones to put onto the audio tracks of a video DVD to allow checking of maximum output levels?
Any links anyone?

[pacificblue]

Test CDs with defined signal levels, e. g. 0 dB or -10 dB are available. Google turns up several sites where you can download test tones or test signals which can then be copied to a CD/DVD. Software for loudspeaker design and testing often comes with built-in tone generators.

Before you measure the output level with a normal multimeter, check the frequency range in which it works best. If no specs are given, use a tone in the range below 200 Hz. Some meters (at least older ones) don't work well at higher frequencies, because they usually are meant for 50 Hz to 60 Hz only.

[pra3718]

Assume I need Preamp. What is your advice for attached picture.

Is 100R optional ?