TDA7293 TDA7294 TDA7293V TDA7294V without Zobel Network by driven Band Pass Subwoofer - Page 2 - diyAudio
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Old 15th September 2012, 09:51 AM   #11
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Quote:
Originally Posted by danielwritesbac View Post
And with a 4 ohm speaker? WOW!! Max spec for TDA7293 is 100w, and with 4 ohm speaker the rail max is +/-32.7vdc, or approximately a 22+22 transformer. Also, max spec is not for long term use (except with the most careful design possible, including overcurrent management). For lasting, it should be run less than max.

However, your subwoofer amp designer chose to use more than max. OOPS! Cause of breakage is confirmed as overcurrent failure (short lifespan, wearing out).
The most easy solution therefore seems to be the use of only one half winding of the power supply transformer to create a supply voltage of approximately +/- 18V. That means 6db less undistorted maximum sound pressure level (because only a quarter of the output power is at disposal).
But then the reliability would be sufficient even at 4 ohms load impedance.
A solution for the mass/GND creating I have for such cases (the winding midpoint now isn't longer available by the transformer).
Quote:
Originally Posted by donpetru View Post
Please, post electronic diagram. It may not be necessary to attach zobel network/boucherot network, but to tell you exactly I need to see electronic diagram.
The developer
http://www.thommessen.com/english/th..._frameset2.htm
don't published information like service manual and schematic diagram.
But the topology of the power amp section is very close to that one from the data sheet of the TDA7293V.

BTW - by my own powered subwoofer projects I use always an additional zobel network suitable to the to the particular bass driver(s) mostly 10-30uF and 8R2

Last edited by tiefbassuebertr; 15th September 2012 at 10:00 AM.
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Old 15th September 2012, 07:00 PM   #12
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Quote:
Originally Posted by tiefbassuebertr View Post
The most easy solution therefore seems to be the use of only one half winding of the power supply transformer to create a supply voltage of approximately +/- 18V.
Either cut the power or. . . why not double the chip? TDA7293 Parallel kit from ebay (modular/slave style, no lossy emitter resistors) That is really easy and supports full power.

P.S.
Generally, supporting 4 ohm speakers with a chip amp needs "Parallel Chip Amp"
Simply double the chip for double-current capacity.
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Last edited by danielwritesbac; 15th September 2012 at 07:03 PM.
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Old 16th September 2012, 09:50 AM   #13
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Quote:
Originally Posted by danielwritesbac View Post
Either cut the power or. . . why not double the chip? TDA7293 Parallel kit from ebay (modular/slave style, no lossy emitter resistors) That is really easy and supports full power.

P.S.
Generally, supporting 4 ohm speakers with a chip amp needs "Parallel Chip Amp"
Simply double the chip for double-current capacity.
Because this would be too many effort and trouble at the modul similar like Thommessen Proteus SW 1.0:
Proteus SW 1.0

Last edited by tiefbassuebertr; 16th September 2012 at 09:52 AM.
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Old 16th September 2012, 09:59 AM   #14
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Quote:
Originally Posted by tiefbassuebertr View Post
Because this would be too many effort and trouble at the modul similar like Thommessen Proteus SW 1.0:
That's strange. I thought it was minimal cost and 20 minutes soldering.
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Old 3rd October 2012, 05:20 PM   #15
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Quote:
Originally Posted by danielwritesbac View Post
That's strange. I thought it was minimal cost and 20 minutes soldering.
the risk of unwanted effects is too high for me, because the lenght of the connection wires from the second device for parallel mode are too long.
But what about the solution from follow URL:
TDA7294 + Power Transistors AMP (TDA7293 to come also)
- go to schema from post #16

Last edited by tiefbassuebertr; 3rd October 2012 at 05:23 PM.
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Old 3rd October 2012, 05:35 PM   #16
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Quote:
Originally Posted by tiefbassuebertr View Post
the risk of unwanted effects is too high for me, because the lenght of the connection wires from the second device for parallel mode are too long.
But what about the solution from follow URL:
TDA7294 + Power Transistors AMP (TDA7293 to come also)
- go to schema from post #16
Yes, that will handle more current.
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