need of 10+10W stereo amplifier

[blueroomelectronics]

Whoa, 4" woofer. Why not use a proper 8" to 10" woofer. After all it's all about pushing air around. Can't move alot of air with a drinking straw.

 

[audioguru]

Radioshack sold some speakers in a small sealed cast aluminum enclosure, a 4" woofer and a dome tweeter. They were called Minimus 7 and sounded pretty good, down to about 80Hz. They were rated at 40W but the Korean woofer was stamped "nominal 5W". I added a port to one and with bass boost it was my beach sub-woofer for many years.

 

[audioguru]

Bose sell many expensive (but poor quality) 2.1 sound sytems. The "sub-woofer" is only 4" but has plenty of bass boost to produce loud frequencies down to about 80Hz. They also sell a very expensive radio with transmission lines for enclosures.

 

[♪Musicl☺♥☻r]

Ok . this is my complete schematic for the amp. Let me know any errors out of the drawing.

 

[audioguru]

A quick glance at your huge schematic seems good.
But you saved it as a fuzzy JPG file type instead of as a very clear GIF or PNG file type. I increased the contrast a little to show you.

 

[♪Musicl☺♥☻r]

Thanks audioguru for ur quick galnce into the schematic.
If its free of errors I would concern the impedance for inputs. as I told, can i connect dvd stereo L n R outs directly. or whether it needs any attenuater or impedance matching circuits. or hows the input signal voltage level. plz let me know.

 

[Nigel Goodwin]

The tone control circuit must be fed from a low impedance to work properly, add an opamp buffer to the input, and you could add a little gain there if required as well.

 

[♪Musicl☺♥☻r]

The tone control circuit must be fed from a low impedance to work properly, add an opamp buffer to the input, and you could add a little gain there if required as well.

This is a little 10W amp..so adding one more opamp input I'm scared of overdriving the tda2030 making a distortion. let me say, I won't agree for a distorted output. If it no problem na, plz help me out to add a buffer using a tl074(quad for both buffer n tone ctrl). I dont know anything abt that stuff.
Thanks again.

 

[Nigel Goodwin]

A simple buffer has no gain, your tone control has no gain either (wth the controls flat), so the only gain is your power amp.

I would imagine a little gain from the buffer is probably required - and the volume control will set how loud it is anyway.

 

[ataul]

Ok . this is my complete schematic for the amp. Let me know any errors out of the drawing.

Musicl

Pls change 334Mfd caps to at least 1Mfd at the tone control outputs otherwise it affect the low frequency.

 

[♪Musicl☺♥☻r]

Buffer

Yes, I also thought of the low frequency problm while using 334p in place of a few uFD ther. Here's the buffer cirucuit I done for the impedance problem suggested by NG. i want to know is it correct or not. Whethere input C is required ther or I can directly giv the signal to non-inverting pin. Also I'm not sure abt the gain control I introduced ther using 200K . Plz let me know. I ahav to use two more opamps for buffers so I would prefer a tl074.

 

[ataul]

Why u unnecessary use buffer, i send u a circuit for really u can doing easily.
and no compromise sound quality.yes buffer improve your input impedance but why ? high impedance input can collect other noise too. the tone control circuit is unity gain and TDA2030 have much gain for full drive,the total circuit need around 300mv for full drive.
most cd player have low impedance and more output then 300mv
your circuit is correct for buffer with adding some gain.
Thanks

 

[Nigel Goodwin]

Why u unnecessary use buffer, i send u a circuit for really u can doing easily.
and no compromise sound quality.yes buffer improve your input impedance but why ? high impedance input can collect other noise too.

Because the Baxendall tone control requires a low source impedance, adding a buffer guarantees this - feeding it directly from a CD player 'may' meet the requirements, but it's not guaranteed to.

Noise is no problem, as we're not talking multi-megaohms, only 100K or 47K, something like that.

 

[♪Musicl☺♥☻r]

A simple buffer has no gain, your tone control has no gain either (wth the controls flat), so the only gain is your power amp.

what I'm asking is without any gain how is the low frequencies are boosted to some db(?) right? Is my buffer circuit is ok for the impedance issue.
ataul,
Does ur tone control for eg, bass control affects the mids and highs in either way while moving? I want it to have control only over teh low frequency spectrum n treble ctrl has only over the high.

 

[Nigel Goodwin]

what I'm asking is without any gain how is the low frequencies are boosted to some db(?) right? Is my buffer circuit is ok for the impedance issue.

Apart from the gain control does absolutely nothing, and will give no gain regardless of it's setting.

Adjustment of the tone controls gives frequency dependent gain or attenuation, but with them flat (as I specified) there is no gain.

ataul,
Does ur tone control for eg, bass control affects the mids and highs in either way while moving? I want it to have control only over teh low frequency spectrum n treble ctrl has only over the high.

It's a standard Baxendall circuit, they work EXTREMELY well, and is the same as almost every audio system you ever see.

 

[ataul]

Yes your buffer is ok for impudence issue but have some gain control option too. i dislike with your plan which u adding preset in the feed back path in audio input circuit, for impedance issue just add unity gain buffer in front of tone control circuit. but you must not set extreme high impudence, adding buffer or gain no benefit your sound quality.
You will be get at least+10db gain when you tern your bass control clockwise.
Bass and treble controls are Independence on each other.
Thanks

 

[audioguru]

The 334 capacitor at the output of the tome controls opamp feeds a 50k volume control pot. Its cutoff frequency is 9.6Hz. I think it is fine.

Your buffer had no gain. The gain of an opamp depends on the ratio of two resistors but you had only one resistor. Do it like this:

 

[♪Musicl☺♥☻r]

Thank you. so u mean the 334p should be applied on the tone control input also. Like this. 200K gain control is ok or do I need a 1Meg pot over ther for better control. sorry if again a stupid question.

 

[audioguru]

Thank you. so u mean the 334p should be applied on the tone control input also. Like this.
200K gain control is ok or do I need a 1Meg pot over ther for better control.

No.
The input of the tone controls circuit has a fairly low impedance that needs a higher capacitor value than only 330nF (334) to pass bass frequencies.
The 200k pot in the buffer with the 47k resistor I showed provides an adjustable gain from 1 to 5.3 times.