TDA7293 Parallel kit from ebay (modular/slave style, no lossy emitter resistors)

The easy little kit

This chip has Fet output built in, so it doesn't need lossy resistors at the output for paralleling.
279672d1335671579-tda7293-parallel-kit-ebay-modular-slave-style-no-lossy-emitter-resistors-tda7293parallelkit.jpg

Making two chips as easy as one.
This is documented in the TDA7293 datasheet as a modular approach.​

Notes-------------------------------------
Ebay link:
(link 1) Two board *stereo* kit TDA7293 Parallel from HappyShop
(link 2) Two board *stereo* kit TDA7293 Parallel from Min9988
(link 3) One board mono TDA7293 Parallel from Happyshop
(link 4) One board mono TDA7293 Parallel from Fly-XY

Power circuit:
Fortunately, the kit came with 220uF power caps for the amp board, which is perfect for clear sound and cool running of TDA7293. This setup with 220uF (or 330uF) power caps assumes that there will be larger power supply capacitance (a real power supply board).

Voltage:
If you push for quality, the Antek AN-3222 transformer is low priced, drops only 2v @13a and has ideal specs for use with TDA7293. If you push for power instead, AN-4228 is about max. However, 25+25vac dual secondaries transformer is typical and that's what I'm using.


Cap values:
I'm changing the 47uF bootstrap cap to 100uF to assist low bass (valid range 68uF to 100uF).

I will omit the 10uF Mute cap (location is right side of the board, near speaker jack) for zero delay.

A highly effective power circuit upgrade is shown at post#30.

Instead of the 22uF FB-shunt cap (which is far too small), I'm using a 680uF 16v cap paralleled with a 0.47uF electrolytic cap for good treble. I'm also using a 1n4007 antiparallel pair as safety clipper to restrict this big cap's discharge to 0.65v. Photo is at post#29

The 105, 1uF box cap is your input cap, but there's other fun options to use, such as 4.7uF (or smaller) Elna Cerafine paralleled with a tiny polyester (to DIY your own low cost blackgate), etc. . . Try some variety and choose which you like.


Resistor values:
The leftmost 22K resistor is Input Load. Valid range is from 15k to 28k. A difference in value can alter the midrange loudness. If you don't need the adjustable feature shown in the schematic with 100kVR||39k, then just use a simple 22k or 25k resistor for input load.

The gain divider is the factory standard 22K/680R and although this will work, I disagree with bad performance that generic values cause. Instead, I would like to use 27K/730R for great quality. If you want quality results, the feedback resistor and the feedback-shunt resistor(s), MUST be placed underneath the board, close to the FB-Shunt cap. The feedback resistor is installed from pin14 to pin2. The feedback shunt resistor(s) are installed from pin2 to FB-shunt cap. It fits easily and shown at post#24.
349465d1368903275-tda7293-parallel-kit-ebay-modular-slave-style-no-lossy-emitter-resistors-tda7293.gif
The above is new text and new schematic. Previously, there had been some problem getting sufficient gain; however, a just-right gain divider setting with resistors direct (not inserted to pcb), and a power circuit update was the combination that got this little amp up to high fidelity.
See assembly photos starting at post#24

It does use a power board:
Due to the power circuit mods for power filtering at the amp board (in the photo attachments at Post#30) we didn't need a CRC type power board, so here's a simpler edition.
429934d1406261198-tda7293-parallel-kit-ebay-modular-slave-style-no-lossy-emitter-resistors-7x2200-simple.jpg
(5x3300u caps per rail and a pair of prefab bridge rectifiers is similar but easier.)

See also Bob's power supply

Yes, new content that uses the schematic (above) starts at post#24--previous discussion might not be applicable to the new schematic, so you will probably want to skip ahead to post 24.
 

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Daniel - a link to the Ebay auction or seller please?
These look great. Very interested.
-Charlie
Sure. There are several vendors. Here is one. Parallel TDA7293 You can find others just by comparing with the photograph in post1.

P.S.
These boards are monophonic--it takes 2 for stereo. These will drive 4 ohm speakers easily.
If bridged (stereo takes 4 kits and 2x op275), they'll drive high power 8 ohm speakers abundantly.
 
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Gain, bridging, preamp and modern sources

Quantity: This amp runs out of capacity for gain prior to reaching max output if driven by a dac, chip player or other modern sources. . . and if you set the amp gain too high, quality is lost. Quality: There could be higher quality by setting lower gain, like 62K/2.7K at the power amp.

The conflict between quality versus quantity is resolved with a preamp, such as the very adjustable class A Moosefet IRF510 or the NE5534 class A preamp at Decibel Dungeon.

Modern sources:
The concept is that a bigger higher voltage transformer in your power amp didn't make your computer bigger, didn't make your computer more powerful.
For more information, download and use free RightMark Audio Analyzer.
With a high power amp: The source works harder (noise) -or- The amp is about maxed for gain (noise) -or- You use a nice preamp.
A preamp allows you to run a gain stage on nice clean regulated/capmulti power, thus that portion of your gain is clean.

Bridging:
A bridge adapter, such as homemade version with op275, provides an additional, yet upside down, copy of the source signal. Even if built for unity, 1x, this device is effectively unity doubled (two copies), or 2x. It uses regulated/capmulti power and approximately the same parts as any good preamp. At end result, the output gets twice as big without increasing the demand from the source device.

See Rod Elliot bridge adapter circuit and you can read the good explanations there. And, see the very similar schematic attached below:
 

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Power circuit looks like:
Transformer >
Rectifier >
Smoothing caps (big ordinary standard power caps)
cable >
Tank caps (speaker return, star ground, big low esr caps)
very short cable >
Amplifier bypass caps (low esr 220uF caps upon the amp board/chips)

The one spot to use the standard power cap (like Mallory or Nippon Chemicon) is where you want to destroy signal and this need is present at the rectifier (power noise signal must be flattened) where you want smoothing, 0hz, no signal, DC. I use six 2,200uF per each rail. The group makes a low inductance assembly. So, the tone is good, but that thing still works to smooth DC.

However, all of the other caps are signal caps and can be low-esr type. The low esr types are great for bypass ("pass the buck") and decoupling since they transit the signal intact. That would be terrible at a rectifier but fantastic everywhere else. ;)

That was an overly complex way to say that you can have some large capacitance ("tank caps") near the amp board (to help the speaker) without having to put the rectifier section ("smoothing caps") near the amp board.

The result looks like a CRC with cable instead of "R" for low loss results and yet still work.
 
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Mr.daniel,
Did you find the sound quality of TDA7293 kit parallel build more lavishing or is it that the LM1875 parallel build outperforms this on 8ohms load? Which one you like the most among both?
Thanks.
Those are both competent amplifiers, therefore nearly identical sound and high resolution for both. Comparisons between the two, look like any attempt to compare small amp versus big amp. I've tried to answer the question of which I like best, but cannot do so. You'd have to choose depending on how much output power you'd need.
 
So I take it you like this Ebay amp then? I have a 20db gain preamp that I really enjoy. Would that be sufficient to drive this amp to full capacity?
I like this amp board for the easy way to drive difficult speakers at high power. I like the convenience that any fine tuning is done to only the "master" chip--not having to do everything twice. I like the layout of the board that is pretty despite 30 pins. And, I like that parallel chip amplifiers can sound effortless when used at less than max. It takes 2 amp boards for stereo.

It is most likely that any little preamp will do fine.
.
 
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Darp,
you have the transformer, measure it.
Connect mains and with secondaries open circuit measure the input voltage and the output voltage.
Now scale the output voltage up to the value it would be if the mains input voltage is at maximum supply tolerance.

I'll guess that the open circuit output voltage will be around 35Vac when mains is at maximum.
 
Tractor versus sports car

Like a high torque tractor that doesn't falter under heavy load, this amp is a heavy current pusher especially for 4 ohm speakers where low loss is more important than a bit more output device noise, so there's not much advantage to use it with 8 ohm speakers.
Your transformer is over the practical maximum for use in a normal unregulated power supply with this chip. Datasheet maximums are for broadest figures maximizing the number of customers, so the maximums are for selling, not for using. Regulated power is possible; however, the labor and materials costs should probably be used for a different amplifier.

Alternative:
With those 30+30 vac transformers, I suggest to use the discrete Honey Badger project instead. Yes, it is a big project, but it handles your transformers, and the board from the diyaudio.com store turns complexity into something as easy as soldering practice. OStripper's test transformer has very similar voltage to yours, so you'd be easily in the voltage "sweet spot" for high quality results.
Here's the boards:
The diyAB "Honey Badger" Class AB Power Amp - 150W/Channel (2 Channels) - PCBs
Here's a build tutorial:
http://www.diyaudio.com/media/build-guides/diyaudio-diyab-build-guide-v1.0.pdf
Here's a schematic example for easily matching Mouser parts:
http://www.diyaudio.com/forums/atta...746574-diyab-amp-honey-badger-honeybadger.gif
Here's a link to Honey Badger build thread:
http://www.diyaudio.com/forums/solid-state/211905-diyab-amp-honey-badger-build-thread.html
 
Many Options

I checked the listings on EBAY....

There's a myriad of offerings with prices all over the place. If anyone ever wanted an inexpensive, quicky kit or completed AMP, this would be one place to start - especially if one prefers mosfets instead of bipolars for their output.

One or two sellers even offer a preamp - I'm not ready to say how good it my or not may be.

By starting this thread, you may have bitten off a pretty good chunk for us to chew.:)

May you never have a cold solder joint.
 
For kits, I'd distrust anything that has the power supply on same board as the amp. The "included" power supplies are normally minimum "get by" designs that fit into the smallest space possible, which makes the board cost lowest possible, also at the cost of least possible audio quality. oops.

SO, I like the very tiny double-sided amp boards + DIY power supply board.
Those are clean.
From obviously the same designer as this compact parallel board, you can also find even smaller solo chip boards, and those can work well with 8 ohm speakers. I've seen both TDA7293 and TDA7294 kits available with a pair of the tiny double-sided boards.
The design is so elegant!
In my opinion, only the smallest of double-sided boards have thoroughly tamed the TDA7293, TDA7294, crazy pinout. So, it is the smallest boards that can give the clean performance, like a point to point, except easier to build.

The kits do all seem to come with bankrupt component values, either like the datasheet, or insignificantly better (and there's not much way to do worse), which is all a hot-running mid-fi of some sort. Sometimes the included caps are all very small for the only reason that tiny caps are less likely to be mashed in the mail. :) So, some of the designs have components selected for non-audio reasons.
However, some of the boards are good and you can plug in whatever components you'd like to use. I'm just glad that they finally invented nice little double-sided boards to support these chips! :D

P.S.
Compare: The kit boards that were available back in 2008 were approximately postcard size, per each chip, and were single sided with such a huge mess that it hindered audio quality. So, let's continue to avoid the big sloppy single side boards. :)
 
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Lots of Choices

In looking at the various offerings, It's easy to eliminate those you (Daniel) suggest rejecting. Actually, I'd reject any that come already soldered.

I have a dislike for power supplies and audio circuitry on the same chassis/board. There are some offered with separate power supplies and you must assemble and solder them yourself.

This seems like these are ready made for the DIY as you can easily change the value of those components you deem necessary. The big advantage is you now have a PCB that is ready to go. And, at some of the prices asked, it's not too unreasonable to buy more than one.

May you never suffer a cold solder joint
 
The suggested supply is 24 V.
That comment sort of makes sense in the case of a 24+24VAC transformer driving a split rail power board to about 35+35VDC.
See the TDA7293 Datasheet: http://www.st.com/st-web-ui/static/active/en/resource/technical/document/datasheet/CD00001887.pdf
Can I use up to 40 V?
DC????
With 8 ohm speakers:
You can use a 28+28VAC transformer with a good split rail power board for DC power at almost 40+40VDC as suggested by the TDA7293 datasheet.

With 4 ohm speakers:
For 4 ohm speakers, I'd suggest a 25+25VAC transformer so that the split rail power board outputs about 36+36VDC.

With either 4 ohm or 8 ohm speakers:
A 25+25VAC transformer And a split rail power board, is pretty much standard for this amplifier.
Can I use up to 40 V?
AC????
Definitely not a 40+40VAC transformer. The amp would explode.
 
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lol...I laughed and you guys probably laughed too... sorry for my "murky" question, the suggested supply was +,- 24 V DC. So thank you for clearing it up, I'm glad I can use 25V AC that will give me 35 DC out. Also this particular board has "only" 100uF/100V caps, not 220uF or 330uF as Daniel suggested, so I will change that too. BTW can I use 63V cap instead 100V caps, as supply is only 35V DC? And if I bridge two amps, should that rating be lifted to 100V then? Thanks again...