Point 2 Point (no PCB) for TDA7293, TDA7294, TDA7295, TDA7296. - Page 12 - diyAudio
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Old 29th April 2013, 06:02 PM   #111
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Quote:
Originally Posted by martin martinez View Post
They usually sound nicer and louder, and more abuse withstanding. so its gonna be parallel 7293, p2p, and still deciding the feedback string
TDA7293 Parallel kit from ebay (modular/slave style, no lossy emitter resistors) <--click there
I've described it (with the new values) in that parallel amp thread at Post#1, but did not have time to make a new schematic. If you can go by the description to get the part values, the operating voltage is same as yours and should make same results, a storm of hi-fi.
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Last edited by danielwritesbac; 29th April 2013 at 06:18 PM.
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Old 29th April 2013, 11:09 PM   #112
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a nice sounding storm-
i wait for.
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Old 29th April 2013, 11:36 PM   #113
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iīll be trying some of those boards, thereīs a good chance to get many "small"
but good sounding amps; for use in my stage aplications. And stil can parallel bridge i need more powerfull, like for bass and drum fill subs.Wonder how theyīll do with some
shakers (vibration xducers)
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Old 2nd May 2013, 06:11 AM   #114
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Recipe for TDA7294 "mids&treble" amplifier:
120k feedback resistor, but 2k7 resistor series to 500R trimmer for feedback-shunt resistor. Cap sizes at small signal, is 220u+1u electrolytics for nfb-shunt cap, and the input cap is not larger than 0.47uF (preferably smaller). Speaker negative has a series capacitor not larger than 330uF (preferably smaller). And, due to reduced bass current, the amplifier can be run easily from regulators for high quality sound. This Mids&Treble amplifier does quite well at amplifying the little higher pitched audio signals to huge proportions for much amazement. Each chip can drive an array of midranges and tweeters. You'd need very powerful bass amplifiers just to keep up with it--about 500W to 1 kilowatt Class D to a woofer with a passive crossover may be enough, but that depends on speaker efficiencies.
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Last edited by danielwritesbac; 2nd May 2013 at 06:15 AM.
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Old 5th May 2013, 08:11 PM   #115
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ok! thatīs interesting; maybe with active xover filter.
And bridged tdaīs + bipolar for subs?.
So the hi gain together with input cap value and nfb string
plus the cap in series at the output will make it more dynamic
for hi freq and most lof is filtered?.
Does it need compensation if i use RC filter: c in series with +,
R series w -, at the tweeter?
i use something like 4x series-parallel 2,2uf and 1x 15-20W, 15-52 ohm.

Last edited by martin martinez; 5th May 2013 at 08:17 PM. Reason: question marks
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Old 16th May 2013, 12:37 AM   #116
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Default my p2ps!

this how its going.
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Old 16th May 2013, 04:44 AM   #117
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Quote:
Originally Posted by martin martinez View Post
Does it need compensation if. . .
It doesn't need external compensation added when:
1). There's good amplifier power layout (not all boards meet that criteria)
2). When run at a gain of in the neighborhood of approximately 38X*
*Both voltage and layout can change that gain factor.

P.S.
It is possible to use compensation as an effect with the mids&treble application, if one wants to make Piezo tweeter arrays sound a bit more like electrostatic/ribbon tweeter sound. Apparently, overdo is much too easily done, so the output would need to be measured.
P.P.S.
So far, compensation experiments have failed to allow a lower gain setting; however, I believe that a LOT LESS power supply voltage will allow a lower gain setting and produce a practical output quality despite lower gain and a lot less power. However, success on that would depend on speaker efficiency. Also applicable to small devices, such as table radios that don't need 70 watts.
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Last edited by danielwritesbac; 16th May 2013 at 05:04 AM.
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Old 16th May 2013, 06:06 PM   #118
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Thanks!
then maybe is enough with
what is already in the circuit.
need to check for temperature.

well this pair is 2x 75k-2,7k-220uf
noninverting so 29x gain, right?
and the rest goes by your schematic.
Itīs gonna be bridged with the
25-0-25 xfrmer and 4x4700uf.
(local 2x220uf on each chip).
as soon as i get back will
finish and test it.
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Old 16th May 2013, 08:38 PM   #119
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Martin, that's my older schematic and designed for under-volting. I did not realize at the time that it was the low voltage that made for good tone despite low gain. If you have some trouble with the tone, replace the 75k with 100k and it should be really very merry (at exactly 38X).

You might try one of them that way and compare to see if there's a useful difference.
For bass amp, see my newer schematic.

Also, first power up needs some precautions:
Light Bulb Tester saves the day! <--link
Check for DC offset before connecting speaker.

P.S.
A bipolar capacitor or back to back polar cap in series with the speaker negative cable, is generally a good to protect test bench speakers, and valuable speakers as well. If used as a permanent install with valuable speakers, right-size the capacitance to promote best bass extension by aiming the roll-off to coincide with, or somewhat lower than, speaker roll-off ("hook the corner frequency"); and, also bypass the output cap assembly with a Nichicon ES 4.7uF or 10uF little green bipolar electrolytic for pure treble.
The approach is very popular to decrease distortion from tweeters, midranges and subwoofers; however, it shouldn't be surprising that it also works for normal woofers. The performance boost is very slight with woofers; however, it is a combination of a little bit more bass at the speaker and a little bit more headroom at the amplifier, depending on signal, of course, since the idea of using the protector for a performance boost involves the efficiency of giving the speaker a bit less of what it can't do. Smaller woofers with more roll-off respond to that a bit more noticeably than larger woofers with less roll-off.
Somewhere in-between the amplifier designer versus speaker designer, this well working protection/efficiency has gone missing. But it remains true that speakers don't require DC and amplifiers don't really require excess loading all the way down to 1hz. So, there is probably some gains to be had by defining the audio band more precisely and corresponding to equipment operating tolerances.
I tried this protector on my test speaker and was pleasantly surprised at the output, so I tried it on all of my speakers, and it worked every time. The main difference is that with the protector in place, cranking up the bass on the EQ results in more real bass instead of more booming. That's fairly appreciable. See also Bob Cordell's website on the topic. If you combine my caps idea with Bob Cordell's active EQ, you'll get a huge amount of real quality bass.
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Last edited by danielwritesbac; 16th May 2013 at 09:02 PM.
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Old 17th May 2013, 03:53 AM   #120
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Is more gain needed if it has line-mic pres,
and graphic eq(+-12vps) integrated at the
chasis itīs going to be fitted?
As always, thank you very much for your
time and attention.
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