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Chip Amps Amplifiers based on integrated circuits

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Old 12th April 2003, 09:31 PM   #1
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Default Gainclone monoblocks

Since there were voices that TDA7294 might sound the best of all amp chips, I decided to built monoblocks based on that IC. I used some small heatsinks and aluminum bars and angles, also found some old transformers which fitted pretty nicely in here.
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Old 12th April 2003, 09:34 PM   #2
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Here's the look from the inside. Everything is layed out logically. It starts with AC input module, then the transformer, behind transformer are bridges, filter caps and the circuit.
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Old 12th April 2003, 09:36 PM   #3
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I used MSR860 diodes this time and I don't think that you really need a PCB for that.
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Old 12th April 2003, 09:39 PM   #4
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Here's the pic of p2p wiring. It is as short as it gets and I used 4 x 1000/50 BG per channel. The front end PS pins are bypassed with 4.7 N BG. I used 33u for bootstrap cap (Nichicon Gold) and Riken 10K and 220K resistors. Mute and standby pins are connected with 22k and 10K resistors to pos rail. No blocking cap and no pots. I believe the signal path is less than 30mm indeed. It's the length of input resistor, the chip itself and the output pin is soldered directly to the output post.
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Old 12th April 2003, 09:41 PM   #5
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I used 1/4 plates for the bottom covers and spikes as feet.
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Old 12th April 2003, 09:46 PM   #6
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Here's the amps in action. My comments? It seems like the amp is very stable (no oscillations and hum whatsoever). After initial hooking up, I thought that they sound very good, but after listening some more to different material, I think they sound weired. I suspect that it may be caused by that orange wiring or maybe MSR diodes, but something isn't completely right. They are very detailed and bass is great, but midrange isn't satisfactory yet. I will let them warm up and play some more. I'm not using any pot and the amps are connected directly to the DAC's output. I also used 2 BG caps in parallel per rail, maybe it's too much capacitance?
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Old 12th April 2003, 10:02 PM   #7
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Nice work! (as usual)

Those extrusions look just like the ones I'm currently using. Are they the same size as this extrusion:

<center>
<img src="http://www.accelindustrial.com/model79.gif">
</center>

se
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Old 12th April 2003, 10:18 PM   #8
joensd is offline joensd  Germany
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Not just another nice construction!
More pictures for my inspiring amp-pictures-folder.
I have to admit I never liked to work with metal but these little amps make me rethink and probably get into it.

Thanks again for more inspirations!

BTW: You obviously meant the TDA7294!?
I think the TDA7394 was a stereo chip.


Jens - is gonna hunt for some thick alumium bars soon
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Old 12th April 2003, 10:37 PM   #9
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Yes, I meant 7294 and I already fixed my mistake.

Those are the same extrusions and I'm using 4.5" lengths. I put a 1" square bar between the fins. It improves the looks as well as acts as connecting element between 3/8" side panels and the heatsink. The angles are 1 1/2 extrusions from Home Depot. I only have to anodize the side panels, and I'll do it whenever opportunity arises. The other black thing on top is a plastic mesh I attached with double sided tape, couldn't be easier.

I also have to admit that I really like to work on those small amps. It's much easier than building big aluminum enclosures, with enough detail, it doesn't have to look plain (that was my intention this time) and the results are comparable. It's almost like working on a Swiss watch
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Old 12th April 2003, 11:40 PM   #10
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Peter,

what are you doing with filter at AC input? and
what about your cheapo AC cord and worst both not the same.
Hope they are not brand new!
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