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Old 3rd January 2013, 02:43 AM   #111
redjr is offline redjr  United States
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Quote:
Originally Posted by gootee View Post
I...Perfboard? Really? [Full disclosure: I haven't read most of this thread, yet.]....

Tom
Perfboard would not be my first choice either, but IMO it seems like a better alternative to a P2P kludge (no offense Daniel). A chip-amp based design screams PCB. I'm just not sure we wanted to go down that path just yet. Given Klaus' comments, maybe any of the PCB kits available from eBay and then come up with a recommended BOM of better/replacements parts.

Rick
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Old 3rd January 2013, 02:51 AM   #112
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Originally Posted by redjr View Post
I agree. How fortunate to have someone on the forum who's day job is designing these little amps - specifically the TDA729x series.

In the spirit of keeping this little venture simple and inexpensive (at first anyway), why not take the point-2-point that Daniel put forth and instead of a full-blown PCB, mock up the best layout on a perf board? That gives us the best of both worlds to experiment with further layout tweeking (to help eliminate loops) and allow for different component choices.

Klaus - Did I understand you correctly in an earlier post where you recommended the PSU on the same circuit board as the amp. I've often heard that the 'better' option is to remove the PSU from the amp PCB. Am I mistaken?

Bob - I just completed a small amp using the TDA7294. I went with stock amp kits from my favorite China vendor. No exotic parts swapped in. I haven't done a lot of critical listening yet, because the gain on my new Doug Self preamp just blows the volume up on all my amps that don't have volume controls on them! The 7294 also seems to be running a little hot (I guess, @ about 53 degrees C.) I don't know if that's normal or not. I think my heat-sink needs to be beefed up some.

Rick
partner (brother) have the power poara costruirlo PCB that performs well is that amplifier.

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Old 3rd January 2013, 06:02 AM   #113
Jay is offline Jay  Indonesia
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Originally Posted by redjr View Post
The 7294 also seems to be running a little hot (I guess, @ about 53 degrees C.) I don't know if that's normal or not.
That's normal. The heatsink is very thin and of poor aluminum quality. I would go for no more than 20V supply (lower Pmax) with that heatsink.

Quote:
Originally Posted by bcmbob View Post
I just have a temporary heat sink of 1/4" x 3" x 4" flat stock but haven't had any heat related problems even after extended hours of operation.
It depends on speaker load and power supply rail voltage.

If I wont listen in high power (and have efficient speaker) I will prefer lower voltage to allow smaller heatsink and compact amplifier.
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Old 3rd January 2013, 07:22 AM   #114
bcmbob is offline bcmbob  United States
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Originally Posted by SERGIODS View Post
In part this the pcb. to build it.
could you post this information in PDF format.
Hey Sergio, Not quite sure what you are asking for. There is nothing on a new design to publish yet. Or is your question about what I'm using to push the kit I have?
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Old 3rd January 2013, 11:29 AM   #115
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Quote:
Originally Posted by redjr
. . . a better alternative to a P2P kludge (no offense Daniel).
In my opinion, surpassing the performance of a P2P kludge, can be done with a professional layout of a double-sided PCB with very few vias, in order to more thoroughly defeat the mad pinout of these chips. I do not have the skills to create advanced PCB, but I would like to buy some.
Quote:
Originally Posted by redjr View Post
Klaus - Did I understand you correctly in an earlier post where you recommended the PSU on the same circuit board as the amp. I've often heard that the 'better' option is to remove the PSU from the amp PCB. Am I mistaken?
See the sections:
1. Smoothing+Rectifier (the rectifiers and first caps for DC)
Next a cable or resistor or diode or regulator
2. Power supply reservoir "tank" (supports large signal bass)
Next a cable or resistor or diode or regulator
3. Amplifier board power caps (support small signal clarity)

Advanced power circuit:
When there is a regulator or diode followed by small capacitance for providing preamp/predrive with only fast transient support for small signal. . . it is then possible to have significantly large capacitance located on the amplifier board for supporting the output devices large signal, without degrading the small signal.
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Old 3rd January 2013, 05:34 PM   #116
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Originally Posted by KSTR View Post
Further, I'm not a fan of fully independent mono-blocks (even when in the same chassis), so a complete stereo PCB with most of the supply components on board seems more adequate for most builders I would think. For DIY we also have the option to make use of unorthodox layout/component placement as we do not need to care about feasibility for mass production (which means sticking to all SMT parts located on the same side).
Non-independent mono-blocks? Okay. Will this do? With only one transformer, it doesn't cost much.
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File Type: gif TankAndSmoothingNosag-DM.gif (53.0 KB, 435 views)
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Last edited by danielwritesbac; 3rd January 2013 at 05:51 PM.
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Old 3rd January 2013, 07:01 PM   #117
KSTR is offline KSTR  Germany
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^ Yes, something similar to this. The xformer, rectifiers and main big reservoir can be shared while the sections after series resistors or other series elements (and in GND nets also) would be seperated between PCBs, being located on-board. Then a local GND bus connecting PCBs would establish a quiet and common GND. All this applies in case of mono PCBs (or multichannel >2CH), with stereo PCBs things would be rather simple; PSU (P2P or PCB), 3 wires, Amp-PCB.
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Old 3rd January 2013, 09:05 PM   #118
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Default doubt

Quote:
Originally Posted by bcmbob View Post
Hey Sergio, Not quite sure what you are asking for. There is nothing on a new design to publish yet. Or is your question about what I'm using to push the kit I have?
I need:
PCB (copper side), can not find it.
Componentized (PCB components). If this
Diagram. If this

an example of PCB:
Click the image to open in full size.
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Old 4th January 2013, 02:40 AM   #119
gootee is offline gootee  United States
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Originally Posted by redjr View Post
Perfboard would not be my first choice either, but IMO it seems like a better alternative to a P2P kludge (no offense Daniel). A chip-amp based design screams PCB. I'm just not sure we wanted to go down that path just yet. Given Klaus' comments, maybe any of the PCB kits available from eBay and then come up with a recommended BOM of better/replacements parts.

Rick
Sorry. Now I am re-thinking it...

I guess there are a few general options, with trade-offs, to be considered.

Not needing an etched PCB would probably mean that a lot more people would build one. It would at least mean that it could be more-readily built, and someone who wanted to build one could start almost immediately.

If the sound quality could also be superb, and the result was mechanically good and easy to construct, then not using a PCB pattern would definitely be an option worth considering.

For the reservoir caps, I would like to have consideration given to something similar to Terry Given's cap bank board. It uses a non-etched two-sided PCB. All you need is a drill. Use a slightly larger drill to remove copper from edges of holes for connections to bottom side. Cut cap leads, bend parallel to copper, and solder. Unless two PCBs were used, it would have to have all ground plane on one side and the power plane side would be split into two planes, for the power rails. The chipamp could be located over the line between the power planes. Check out the link and see what impedance Terry measured with his network analyzer!

If a small piece of perfboard or PCB were used for only the chipamp circuit, that board could be mounted on short standoffs, OVER one end of the cap-array PCB. Then, the chipamp's power leads could go down through the small board and connect directly to the power planes. Any ground connections could also go straight down to connect to the ground plane. See attached sketch.

That configuration would also provide more freedom for the layout of the small board.

A set of links to the posts about the wonderful cap-array board is at the bottom of the post at:

(NOTE that Terry meant to say RADIAL, not axial, in the post at the first link!)

LM3886 component selection

Cheers,

Tom
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Last edited by gootee; 4th January 2013 at 02:55 AM.
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Old 4th January 2013, 06:32 AM   #120
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Tom, that looks really nice for powering amplifiers with regulated front end, like this from Ilimzn:
Click the image to open in full size.
This is great!
The regulators have served as the necessary series element so that we can put big caps to help the output devices do good bass, without making the predrive section unintelligible. I like this schematic for demonstrating have your cake and eat it too. It is compatible with Tom's power board description at post 119.
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Last edited by danielwritesbac; 4th January 2013 at 06:47 AM.
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