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Old 5th December 2009, 05:05 PM   #1
chingyg is offline chingyg  South Africa
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Default TDA2030 tone control

Hey guys:

I am a newbie to audio so here is my stupid question

I am building a stereo power amplifier with TDA2030, in bridged mode, powered by a modified +-14V computer SMPS (i have completely modified the output line of the -12V line to allow it to sink a large amount of current)

the power amplifier's schematics is:
Click the image to open in full size.

however I would like to add a tone control to the amplifier too, and this is the circuit diagramtone control.jpg

Would it work if I connect my source (cellphone's output, abt 1V peak to peak, I think) to the tone control circuit and then to the input of the TDA2030 amplifier? would the signal be strong enough to drive the chip at full power or do I need a pre amplifier in front or after the tone control to compensate for the tone control's lost (-20dB is what the simulator tells me)

thank you
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Old 5th December 2009, 05:26 PM   #2
Minion is offline Minion  Canada
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Well a Passive tone controll is going to drop quite a bit of voltage so there will be losses , I would suggest maybe a Make up gain stage either before or after the tone curcuit (I would put a buffer at the front and a make up gain stage at the end) ......

Tone circuits like the one you posted pretty much sound best with the Pot at 10 or without frequncy attenuation so to get a more robust versitile tone controll I would suggest an active 3 band tone controll , there are even some very simple to use eq/Tone controll IC"s , I recently did a 5 band Graphic with a BA3812 that actually sounds pretty good .....

Good luck
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Old 5th December 2009, 05:46 PM   #3
sangram is offline sangram  India
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Change those 22K resistors to 47K, the additional 6dB gain should compensate for most of the loss.

The 2030 does not like being bridged, I can tell you that. It survives but the sound quality goes to pot. The current capability of the chip is very low, and it doesn't like sinking current at all. I'd be surprised if you got more than 30 clean watts out of it.

For cellphone output, it should do however, and the 47K/680 ohm combination should have sufficient gain from the signal for max output, tone control notwithstanding.
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Old 5th December 2009, 05:56 PM   #4
chingyg is offline chingyg  South Africa
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What about the LM1875, is it a better choice? and can I substitute it straight into the circuit designed for the bridged TDA2030?
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Old 5th December 2009, 06:04 PM   #5
sangram is offline sangram  India
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How much output power do you need?
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Old 5th December 2009, 06:06 PM   #6
chingyg is offline chingyg  South Africa
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As much as I can from the available supply voltage, +-14V
In to a 8 ohm load

Last edited by chingyg; 5th December 2009 at 06:14 PM.
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Old 5th December 2009, 07:04 PM   #7
sangram is offline sangram  India
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The LM1875 will fit that circuit just fine (I think it is even pin-compatible), though I don't about it bridged. For such a low voltage bridged is your only option for real power, though bridging puts a lot of stress on the output stage - I don't know about these little 3A chips cutting it.

I had bridged a set of 2030s for a stereo amp and it worked. The sound quality was not great and the chips ran terribly hot - I ran off a +/- 19V supply. If you're not super-critical about the sound quality you could go ahead and try.

The problem with your requirement and these chips is that you will get a maximum of 10V swing per output half, or 20V total. 20V into 8 ohm load is ~2.5A, with the 3-4A current limit of these chips you're running too close to the output maximum. Some back-of-envelope calculations show the output at about 50 watts, or 25 watts per chip. The chip's output rating is 22 watts. To make this work you will need 4 chips, or a different chip.
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Old 5th December 2009, 07:09 PM   #8
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Quote:
Originally Posted by chingyg View Post
As much as I can from the available supply voltage, +-14V
In to a 8 ohm load
Well.if I were you, I would not use any tone controls.The fewer components in the signal...the better!.
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Old 6th December 2009, 07:24 AM   #9
chingyg is offline chingyg  South Africa
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Quote:
Originally Posted by sangram View Post
The LM1875 will fit that circuit just fine (I think it is even pin-compatible), though I don't about it bridged. For such a low voltage bridged is your only option for real power, though bridging puts a lot of stress on the output stage - I don't know about these little 3A chips cutting it.

I had bridged a set of 2030s for a stereo amp and it worked. The sound quality was not great and the chips ran terribly hot - I ran off a +/- 19V supply. If you're not super-critical about the sound quality you could go ahead and try.

The problem with your requirement and these chips is that you will get a maximum of 10V swing per output half, or 20V total. 20V into 8 ohm load is ~2.5A, with the 3-4A current limit of these chips you're running too close to the output maximum. Some back-of-envelope calculations show the output at about 50 watts, or 25 watts per chip. The chip's output rating is 22 watts. To make this work you will need 4 chips, or a different chip.
I dont have to run the chip to full power, 40W is more than enough for my need. I will start building it next week, with LM1875 that is.
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Old 6th December 2009, 12:54 PM   #10
chingyg is offline chingyg  South Africa
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here is the circuit I worked out
beat box.jpg
its one channel, the tone control is connected straight to the LM1875 chips, which is powered by +-14V supply.
on the simulator it shows the amplifier can reach full power (+-24V at 500mV input level, with the volume control on full)
I was planning to start building it tomorrow, however my power supply just blew up in my face, so I would be going on computer PSU hunt again next week.
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