7293 parrallel or bridge/paralel for best sound?

[sesebe]

Short explanation is needed.

Traces:
blue=G class positiv voltage output=TDA7293 pin13,
green=G class negativ voltage output=TDA7293 pin15,
red=output

In first screenshot can be seen the basic function of G class. Output 10v/div (~25Vpp, 1KHz), power suplly rail 20V/div, yelow trace=input signal.

In second screenshot: maximum out voltage on 8Ω at the cliping limit, 20KHz input frequency, Yelow trace = cliping signal.

In the third screenshot: 20KHz square signal close to the maximim power.

In the fourth screenshot: 50KHz signal close to the maximim power.

In the last screenshot: frecquecy sweep from 10Hz to 100KHz (logaritmic variation) with marquer at 20KHZ (the tranzition from high to low in Yelow trace correspond with 20KHZ in red trace).
The 3dB bandwidth is 150KHz.

Because the transformators are relatively small, the power high voltage (±) rail are stabilized at ±40V using laboratory power supply. Only with transformators, the power supply drop from ~±45V to ~±35V.

Next screenshots show G class distorsions at 20KHz and maximum power on 4Ω load on zoom screen (20X zoom, ~0.24% distorsions) and respectively cliping signals when cliping it is present on 4Ω load.

[geraldfryjr]

Very cool !!!
Please tell us More !!


jer

[sesebe]

High resolution photo of the test board.
The filtering is 4*2200µF/40V low ESR on every power rail.
During the test with sinusoidal signal, the heat spreader become relativly hot (around 60-70°C).
During the listening at high room level, the heat spreader remain at room temperature, I mean that I can't see any temperature change of it.
This is normal because is not any sense to use G class for sinusoidal signal at maximum power.
The class G advantage is maximum when it is used with music signal with a high crest factor.

If there are people interested in this project I can provide more details.
The test board start from first power on, and I do not experienced any problem like other people that worked with this IC.
It remain stable down to 2Ω on resistive load during the testing.

Finally I want to use ± 50V on high rail and ±20V on low rail to obtain around 100W on 8Ω.

[sesebe]

Photo with bandwidth measurement: frequency sweep from 10Hz to 300KHz (logarithmic variation) with marker when the level decrease to 0.7 (23.1V at 150Khz and 32.73V at low frequency) at 150KHZ.

The slew-rate it is around 8.4V/µs, in limits of datasheet.
The stability is ok without zobel on output for frequency from 10 hz to 20Khz, sinus, 90% from max power on 8Ω and 70% from max power for 4Ω.
With zobel all instability was solved. Stable until 2Ω max power (cliping limit) from 10 hz to around 150Khz and square signal of 20Khz.

[sesebe]

Schematics and layout.
If you have useful information about layout and schematics I'm only ears.

[flaotte]

hi, could you post bigger resolution of schematics?

[sesebe]

Hi flaotte,

I can't to post today, maybe tomorow but I think the resolution it is enought because the component values are not updated. The values of components are only to have an idea and are not the test used components.

The values of components that I will finally use will be optimised for the final layout, thaking in consideration that this was a test board.
The final layout it is a big board (~200x300mm) with 2 channells, complex protection circuit, fan controll, power supply's, basic preu and connections for future extension boards. The equalyser (2x5 band's) are allready made and tested on diferent board. The pcb layout are allready made.

Unfortunately now the project it is in standby for a long period because I do not have enough time to finish it.

[flaotte]

Ok, in that case no need for bigger res image. I would like to make this amp for sub-woofer.
G class for LFE movie woofer looks perfect.

are you going to publish final amplifier?

It will be my first amp. I have some experience, but most of it are digital circuits.
Are there any suggestions?
What kind of transformer do I need for two parallel chips? 200VAC for mono?

[sesebe]

Hi,

If will be people interested yes, but I do not know when I will have time to finish.
When I start this project I was interested to finish it to be used at my home for listening. Now I have a verry good comercial amplifier for this task and the finish date was postponed for a undefined time.

Regarding of transformer depends of many things. Type of music that you listen, the average level of power, the impedance of driver....
The ±50t is the maximum for TDA7293 and at this volatge on high rail the output RMS power it is over 120W/8Ω and 200W/4Ω (depends of traf and capacitors). For 4Ω at ±50V two paralel IC are not enought because of current limitations. People from this forum consider that it is neccesar a peak current capability of at least 3 time more than RMS current.
For me a 200W transformer it is enought for mono aplication, for other people you will need over 300W.
In any case the capacitors are verry important now and you will need minimum 10-20mF per rail. The advantage is that you can use a low voltage capacitors (35V) and to connect it in series with midle point at low rails voltage (there are 4 rail power supply).

The diodes between pin7 and pin13, and between pin8 and pin15 are verry inportant to be Schottky (1A it is enought). C1 and C2 filter the voltage for input and VAS sections. I used only 10U low ESR and was suficient.

I look forward to hear how it works yours amplifier!

[sesebe]

Hello,

The Eagle files for this test board.