Point 2 Point (no PCB) for TDA7293, TDA7294, TDA7295, TDA7296. - Page 4 - diyAudio
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Old 1st February 2013, 02:17 AM   #31
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So sorry,, i have childish ?s,,,by the way what types of capacitor you use for input cap,,i,e .68uf ? tantalum ,polyester, propylene ? or just electrolyte ?
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Old 1st February 2013, 06:21 PM   #32
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Quote:
Originally Posted by simply14prem View Post
thank you so much for your quick reply.
Should we not put a 100nf in the psu board ?
It is true that we should not. Please avoid extra bypass for now.

Later, and only based on merit, you can try any of the following:
Electrolytic of 2.2u or smaller.
Polyester of 33n or smaller.
Polypro/ceramic of 4n7 or smaller.

You can see if any of those help audio, later, after the amp is up and running. Omit for now.
Quote:
Originally Posted by simply14prem View Post
Can I use 2.2K instead of 2.7k,
Yes, for 1w drainer resistors.

However, for 1/4w drainer resistors, you can use 4 of 10k in parallel to make a 1w 2.5k resistor.

Drainer resistor value adjusts time to drain. Adapt to suit.

Quote:
Originally Posted by simply14prem View Post
is the color of LED specific ?thank you.
These indicators are very important for safety and also error detection.
The LED Forward Voltage Drop figure is important and we want 2v or less (preferably less than 2v) so:

Clear body led (with the top filed flat for wide angle viewable) Red, Yellow or Amber. And, Red is best, 1.6v, yellow okay, 1.7v, and amber works, 1.9v.

Colored body led of green orange or red, is internally a yellow led and colored body led are useful because so easily wide angle viewable.

LED Resistor Calculator
Please don't run more than 8ma on a 20ma led.
Observe resistor wattage tolerances too.

I'd like both rails identical for voltage, so if you want different colors, used the colored body LED (they're yellow led inside).
Quote:
Originally Posted by simply14prem View Post
what types of capacitor you use for input cap,,i,e .68uf? tantalum, polyester, propylene? or just electrolyte?
You can make a good head start easily with a 1u electrolytic. Otherwise, I'd use polyester.
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Old 2nd February 2013, 11:20 AM   #33
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Quote:
Originally Posted by danielwritesbac View Post
LED

These indicators are very important for safety and also error detection
one silly Question,how does led help in safety,,error detection ?
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Old 2nd February 2013, 02:48 PM   #34
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Mainly, the feature is to keep fingers away from lethal charge.
Compare:
♦ Without LED's, handling a power supply to use a multimeter for finding out how much charge is a lethally faulty idea because lethal charge may be present at time of handling, and that's horrible.
♦ However, waiting for the LED lights to turn off indicates that the remaining charge is probably not lethal.

See the difference?
Those LED's might save your life.

With the LED's, some error detection is also done at power up/down time.
If one LED goes either on or off before the other, that indicates an amplifier problem or hookup problem. The very first time I added LED's to a power board, it indicated that one of the screw connections was slightly loose. This condition was detected easily and immediately.

Because of the features of safety enhancement and fault detection, I have added LED's to ALL of my power supplies.
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Last edited by danielwritesbac; 2nd February 2013 at 02:51 PM.
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Old 2nd February 2013, 06:30 PM   #35
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Thank you so much Daniel.Actually I have started constructing the psu like you have,I have only 12x2200uf,50V.The shop has got 4700uf,50v,3300uf,50v good quality caps.Can I use 3300 or 4700 ,50 v with 12x2200uf caps ?Anyway the design,the stuff is so awesone,,heavy in a sense,,I just kept starring at it.
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Old 3rd February 2013, 12:43 AM   #36
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I called it a BEAST ,I have never design a psu like that.,,,There is a slight problem,There is a very small voltage imbalance in two of the secondary(dual secondary),Any method to level them,,or should I rewind the transformer?
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Old 3rd February 2013, 04:11 PM   #37
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So is the bridge diode 1004 you are using good? Is it fast ?I have 1010, I think I will get a couple of those 1004s.Do you know any fast acting bridge diodes ?
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Old 3rd February 2013, 08:54 PM   #38
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Quote:
Originally Posted by simply14prem View Post
Thank you so much, Daniel. Actually I have started constructing the psu like you have. I have only 12x2200uf, 50V. The shop has got 4700uf, 50v; 3300uf, 50v good quality caps. Can I use 3300 or 4700, 50v with 12x2200uf caps? Anyway the design,the stuff is so awesome, heavy in a sense; I just kept starring at it.
It would be wrong to throw a 3300u or 4700u in amongst that group of 2200u; however, you can put the 3300u OR 4700u before the resistor--The odd value caps can go directly at the bridge rectifier.
Example (one rail described below--other rail is copy of same):
Rectifier, 3300u, Resistor||Diode, 2200u, 2200u, 2200u, 2200u, 2200u, 2200u, cable, amplifier

Notice that it is the Series Element (Resistor or Cable or Transistor or Inductor or Regulator or Diode or PCB Trace are series elements) that allows us to connect a different size capacitor. The series element (such as a Resistor) creates a "Ballast" that helps Prevent problems in the power circuit.

Rules of thumb:
Don't put more than 7 caps directly in parallel
Don't directly parallel different size capacitors

Here's a larger size power supply built to this spec.
Click the image to open in full size.
I made it for the TDA7293-Parallel amp, and that power supply is just barely big enough to attempt powering one Honey Badger Monobloc. If there's anything beastly about this little power supply, that is aggressive charge speed for high resolution bass support.
Quote:
Originally Posted by simply14prem
I called it a BEAST, I have never design a psu like that. There is a slight problem--There is a very small voltage imbalance in two of the secondary (dual secondary), Any method to level them, or should I rewind the transformer?
Does this occur when loaded or only when unloaded?
Are the bridge rectifiers exactly the same model for both secondaries?
You can try snubbing the transformer secondaries (2u polyester + 50R variable resistor makes adjustable RC's) to remove noise. Try it first on your "too high" side.
Can you post a photograph?
Quote:
Originally Posted by simply14prem
Do you know any fast acting bridge diodes?
Fairchild Stealth are suitable, well behaved in linear supplies and extremely fast, but 8 of them are more difficult to install than a pair of KBPC1004's.
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Old 4th February 2013, 01:27 AM   #39
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Xformer have been rewinded as it is EI, so I love winding it in bifiller.It's cool now except the spark when power goes off.
Now I will play with the amp.
1.I will try 680+120=800,for the FB shunt R.
2.Put a buffer from NE5534, with or without the Class A biased transistor.
I think my amp is still muddy.I need to tweak it.
Also Daniel, I can't find any 2u to use from rail to rail, so sad.
Plz check these buffers ,,actually i like the one posted.Plz recommend me a good buffer.
Building a buffered Gainclone chip amp.
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Last edited by simply14prem; 4th February 2013 at 01:51 AM.
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Old 4th February 2013, 12:32 PM   #40
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Sparks? That's construction error. The connections are a bit flimsy and voids are causing sparks, so you need MUCH THICKER traces (probably needs reinforced with wire and solid soldering).

Also, the pi filter resistors need to be paralleled with minimum pin length and not look like a fishing net.

I think I see a ground loop that might cause dulling, so that needs fixed. Hey, I've made a drawing for you.

The green traces have the conductor Thickest to Farthest caps.
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