Thursday, July 26, 2012

Prototype PCB with soldering mask

I made this movie how I made very good quality prototype PCB with soldering mask.

Tuesday, July 24, 2012

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

  • 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:

About the top of my new guitar amplifier design

This project stopped for years, but the wood case of my new guitar amplifier is ready. The rason of long time delay while I did nothing is that I used my old amplifiers. One is my previous DIY guitar amp have been disasembled, and I have a Carlsbro GLX100 amplifier with Eminence ReadCoat speaker, whats are very good solutions. This is the reason why I don't hurry with my new idea, but now I take apart my old DIY amplifier and the power supply have been moved to the new wood-case.

My old rack mounted amplifier was stereo for guitar, because I  using multieffect. I have Boss GT8, where not only the effects have stereo outputs, this is dual guitar effect, where I can use different amplifiers for left and right channels. This is the reason, why I have combo design but with two speakers for stereo solution:

After the wood case, I have metal cases for electronic circuits:

This is the back of the wood case: without the middle slat because I need space to fix the speakers.

 The power supply built to the bottom of wood-case. I know that all other industrial solution have same case with other circuits on the top, but now I have more space on the top for amplifiers and equalizers. I think the larger distance between transformer and circuits have benefits:

The design of wood case was realy good, I made model of paper, and got to the professional carpenter, who manufactured and assembled:

The bottom of this amplifier is done, this is the power supply. From the power supply the required voltages wired to the top of amplifier case:
Here I have +/- 40V for poweramps, +/-18V for preamps, +24V for LED-s relays, and coolers.

But the most important question is what I have on the top

Because the power supply built to the bottom, I have more space on the top. The power of toroid transformer is 1200VA. I want to place guitar preamplifiers and amplifier (stereo for multieffect), and one more stereo poweramp for additional cabinets for vocal or keyboards. I need parametric equalizer, if I have enough space on the top-case, separated for left and right channels. I need audio mixer with mic preamps for vocal or another audio sources with headphone and line outputs.

But the most important question is, what will be the power amplifier on the top case. On this time, I want to build some digital class-D poweramp maybe for vocal only not for guitar. I have PWM power bridges, what is 1x315W, and I have 2x210W TAS chips:
1x350W with TAS5261 is would be enough for guitar, but this power available for 4 Ohm only. The guitar speakers are 8 or 16 Ohms. On 8 Ohm this chip have 125W output power. Now I think, for guitar (where the speaker is 8 Ohm) I will use bridged TDA7293 chips, where I got 200-220W for 8 Ohm speakers. This chip is very popular on guitar amplifier market, Marshall, Carlsbro using this solution. And for example the Crate Powerblock is PWM poweramp.

Because the vocal or additional guitar speakers have less than 8 Ohm impedance, the PWM chip is good solution. The benefit of PWM chip is the very high efficiency. But the disadvantage is the very small size of chip, TAS5261 have digital PWM inputs only, so I need PWM modulator like TAS5028 for example. TAS5028 is more small than TAS5261, so more harder to build the PCB. Finally the PWM modulators have digital inputs, so I need A/D converter for analog input devices.
I'm not sure that I can build complex design with these very small chips. The another detriment is that the PWM modulator and the A/D converter need 3.3V only, what is used for DVD players orfor computer soundcards. I don't think that the vocal or guitar amplifier design is same as like the home theater systems. The power stage of this idea need only non-symmetrical power voltage, +50V. I have +/-40V for TDA bridged solution, what is much better. I can bridged the TDA chips, but I can't bridge TAS power chips, because this is already internally bridged. At he moment I think the bridged TDA circuits are better and easier to build for guitar and vocal.

I take apart my old amplifier, old circuits for sale

I "disassembled" my good old power amplifier. This version was very good but the part of this device needed to my new idea. I used this old version for 10 years, without problem. This amplifier contains two stereo devices, one for guitar, and one for microphones/keyboards. I built this double-stereo amp to 2 rack mounted cases: one for power supply, and one for the amplifiers.

The old power supply:
It was the old power supply on the rack case #1. The toroid transformer is  1200VA, the Greatz on the heatshink is 10A, softstart, stabilized power supply for preamplifiers and EQ, simple power supply for amplifiers. By the speakon connectors the output voltage can be changed from +/-10v to +/- 70V for poweramps only. One speakon is the output for poweramps, and one 5 pin connector is for preamplifiers and mixers. The toroid transformer have 4x10W and 4X15V output AC voltages for poweramps, and 2x15V for preamps, and 1x18V for LED, relays, and coolers.

This power supply is good solution for my new guitar amp project, but without speakons, because the different output voltages are not required for the new design. Now I have only one speakon for poweramps, and one 5 pin connector for all others:
This is the box of new power supply, assembled from the parts of old one. This case placed to the bottom of new combo. The required power voltages will be wired to the top of amplifier. The content of upper case not ready, and I want to design something new.

The old amplifier:

The poweramp, 6 input mixer,10 channel equalizer built to another rack mounted case. This is old photo with one poweramp on heatshink, but this part of amplifier has been duplicated. One of then used for guitar, the another one is for keyboard and vocal. This is all-in-one sulution, but for small or larger clubs was good solution:

There are the list of very good circuits what I don't  need for new amplifier design, so there are for sale:

4x200W poweramps with TDA7293 assembled to heatshink with cooler:
The poweramps are two stereo circuits with bridged TDA7293/7294 circuits. Very reliable circuits. All stereo boards have speaker protection with UPC1237 chip.

The equalizer:
10 bands stereo RANE copy equalizer. This is active filter circuit design, the "Q" of EQ is permanent for all bands, what is very interesting solution. See more... With small PCB relays the have true bypass, and the circuit can be switch between +/-6 and +/-12 dB modes.
6 input audio mixer:
Very simple audio mixer with 6 stereo inputs. All inputs have gain and volume pots. Two of them have jFET preamplifiers for guitars with 4x gain, 4 of them have op-amp preamplifiers for all others with 100x gain.

Here are the gallery of my "disasembled" but error-free circuits and prototypes. Write me if you need something:

Monday, July 9, 2012

The power supply moved to new amp

The power supply of my stereo guitar amp is moved to the new place and ready. The old circuits can be fixed to the new "box", what is smaller but higher. The toroid transformer is 1200VA, with 4x15V, 4x10V AC for high power circuits, 2x15V AC for small power circuits, 1x18V AC for relay and LED. The DC and 24V AC voltages wired to the top of combo with 5 point cable, the +/-41V DC power for amplifier wired with speakon connector to the top of amplifier case: