New PWM power chips with analog inputs

In the previous article I thinking about the poweramps of my guitar/vocal amplifier. The power supply is ready, I have 1200VA, this is the reason why I want to include more than one guitar amp to this new design. But whats about the top of this amplifier case, where I need poweramps and preamps?

I think for the guitar amp I will use bridged TDA7293 because for 8 or 16 Ohm speakers the bridged amp solution is better. But for keyboard/vocal I wanted to use Class-D TAS chips. These chips have 125W output power for 8 Ohm, but 315W for 4 Ohm. The impedance of additional cabinet for vocal or for guitar can be 4 Ohm (or less) if required. In my previous DIY amplifier I used bridged TDA chips, and I really like it. This is the reason why I want "hybrid" solution. One analog amplifier for guitar with TDA chips, and another one for all others with PWM solution.


This is one example that the 4x200W TDA bridged solution is more than enough for clubs for guitar and vocal (but this is gym):



For the PWM solution I think about TAS5261 chips. This is small power bridge with PWM input, but PWM modulator and A/D converter required. I have no experience with these chips, and these solutions have very small size, I am not sure that I can assemble them.

This chip is 2x210W PWM power-bridge with the smaller package.

This is TAS5261 chip, 1x350W power bridge.

I like these solutions, error and speaker protections included, chips have very good efficiency, no large heatshink required. The efficiency of TDA solution is about 60%, but his PWM chip have more than 90%.

But these TAS chips offered for home theater or home DVD systems, maybe not for instrument amplification. See the datasheet:

• 315W - 4 Ohm
• 220W - 6 Ohm
• 125W - 8 Ohm

This is the reason why I don't want to use this solution for 8 Ohm guitar speakers, but maybe want to use for 4 Ohm vocal or additional cabinets.


The another thing that I don't want to use required additional circuits like A/D converters and PWM modulators. These chips have very small package, and the power is 3.3V only.

The PWM modulator:

The one pin of this chip 0.2mm width, the distance between the middle line of pins are 0.5mm. Very hard to solder and assemble these parts.


But now the TAS PWM power bridges have analog inputs. PWM modulators and A/D converters not required. The package of these new solutions have 44 pin DKD, and the new 64 pin PHD. The 44 pin DKD package is same as like the previous TAS5261 chip. The biggest version of new analog input TAS chips have 600W power output, what is really great on very small size. See the datasheet page 18.

The benefits:

• Very good efficiency (85...93%) no large heatshink (and cooler) required
• Have analog inputs, no PWM modulators and A/D converters needed
• The chip have error protection

But:

• The 600W available on on 2 Ohm cabinet (the output of chips are paralleled)
• 4 Ohm - 300W, what is not bad, but the previous chip have same feature.
• 3 Ohm - 400W (paralleled outputs)
• 6 Ohm - 210W
• 8 Ohm - 160W.

But with these output powers have distortion 10% what is not small enough. If we need better quality, max. 1% distortion, the possible power will much smaller, the chip cannot be paralleled:

• 4 Ohm - 240W. This is same as TDA bridged amplifier but on 8 Ohm impedance.
• 6 Ohm - 160W
• 8 Ohm - 125W

With smaller impedance with paralleled outputs on 1% distortion:

• 3 Ohm - 310W
• 2 Ohm - 480W

I found these solutions if I want to use PWM amplifier. The PWM chip is better than older solutions if I have speaker cabinet with 4 Ohm or less. I am not decided yet what will the poweramp on the top case of my guitar combo: