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Author Topic: Using a choke for a TDA7293 amp  (Read 567 times)

Aleksandar

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Using a choke for a TDA7293 amp
« on: May 06, 2018, 06:35:38 PM »

I am thinking about using a choke for the power supply of a TDA7293 amp as a means to filter out all that DC ripple. The amp would be running at +- 32-36 Volts. What would be the specs of the chokes that I need?

Also, can I use chokes for the preamp section, which is built around two TL072 chips, or the ones used in the power amp supply would suffice?
« Last Edit: May 06, 2018, 06:37:37 PM by Aleksandar »
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Jazz P Bass

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Re: Using a choke for a TDA7293 amp
« Reply #1 on: May 07, 2018, 01:09:51 AM »

"I am thinking about using a choke for the power supply of a TDA7293 amp as a means to filter out all that DC ripple"

What ripple?
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J M Fahey

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Re: Using a choke for a TDA7293 amp
« Reply #2 on: June 03, 2018, 04:30:06 PM »

And in any case nowadays chokes are not used any kore becausetb they are the very expensive solution.
If you are annoyed by ripple just increase capacitance.
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GB

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Re: Using a choke for a TDA7293 amp
« Reply #3 on: August 12, 2018, 05:28:34 AM »

Yeah... agree with JM. Not worth it.
The TDA will inherently reject power supply ripple in any event.
The TL072 should be de-coupled from the PS with a couple of (say) 100 ohm resistors in series and 100uF caps behind them on each of the + and - supply rails... as OP Amps normally are.
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Loudthud

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Re: Using a choke for a TDA7293 amp
« Reply #4 on: August 13, 2018, 01:19:16 AM »

Using chokes is no guarantee that your amp will be hum free. A bad grounding scheme can introduce hum that you can hear when there is no signal. In general you need to know how much current will pass through each choke. Once you get  up to the several Amp territory, you are looking at a 5 pound (2 kilogram) chunk of iron and for a dual rail amp, you will need two. That is the case when you pass all the current for the power supply through the chokes.

Link to data sheet: https://www.mouser.com/datasheet/2/389/tda7293-957143.pdf

The TDA7293 is a 15 pin chipamp so it may be possible to only pass the current for the driver stage through the chokes. (This allows the use of much smaller chokes.) This is uncharted territory, you'll need to experiment and you may blow up some chips before you get it right. A simple RC decoupling network might work just as well.

When a solid state power amp clips to the rails, any ripple on the rail is transferred to the speaker. Tube amps do the same thing. It's hard to hear this hum because the amp is as loud as it will go at that point. If you want to eliminate this hum, you need to lower the Voltage to the driver stage so the it "runs out of gas" before the output transistors clip to the rails. This lowers the power output by perhaps 10%.

Another way to eliminate this "slamming the rails" hum is to not let the power amp clip to the rails. You can do this with a Master Volume control, but this only works if the power amp is acting as a Voltage amplifier with no mixed mode feedback. Mixed mode feedback means current flowing in the speaker determines if the power amp needs to "Go to the rail" to make current in the speaker follow the input. (Flame On Non-believers)

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Enzo

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Re: Using a choke for a TDA7293 amp
« Reply #5 on: August 13, 2018, 02:10:41 AM »

All WHAT DC ripple?

A zillion hifi stereos and other solid state amps and none have chokes.  Ever see a choke in a PA power amp?

Just my opinion, but it sounds like a solution looking for a problem.
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