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Chip Amps Amplifiers based on integrated circuits

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Old 22nd May 2014, 12:06 PM   #2741
bcmbob is offline bcmbob  United States
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Very creative! I have a lot of LM3886 related stuff in the drawer and your build encourages a new adventure into P2P.

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Old 28th May 2014, 01:33 AM   #2742
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Default tda7265

simple small tda7265 25w *2 on one chip(with this small trafo maybe 10-15wpc)
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File Type: jpg 2014-05-24 20.12.23.jpg (223.8 KB, 860 views)
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Old 30th May 2014, 07:46 PM   #2743
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Default 7293 plywood chipamp getting friends

psu almost done and a high bitrate flac player using raspberry in progress.
BurrBrown dac module still missing

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Old 2nd June 2014, 11:01 AM   #2744
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[QUOTE=onuhannes;3945608]psu almost done and a high bitrate flac player using raspberry in progress.
BurrBrown dac module still missing

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Old 14th June 2014, 07:32 PM   #2745
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for onuhannes: where have you bought your 2 cabinets ? they seem to be made of wood ?

Thanks for your reply...
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Old 15th June 2014, 03:08 PM   #2746
Mihkus is offline Mihkus  Estonia
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Those bigger ones seem to have 4GD35 as woofers... But I have no idea what those tweeters are...
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Old 26th July 2014, 08:01 PM   #2747
Elvee is offline Elvee  Belgium
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Default Chip-Lab

Here is my latest baby: it is a lab amplifier, which means an equipment that will only occasionally reproduce audio, but will mainly serve as power driver for various experiments, 4-quadrants supplies, measurements, emulation of power systems, 400Hz or 60Hz generation, etc, etc.

Once you have tasted the convenience of such an amp, you inevitably become addicted: I have already built a huge number of them but I never have enough.

All the previous versions (except for a notable one) used discrete circuitry, at least for the power section.

This one is based on LM12's: they are stable, have good performance and include thermal protections impossible to achieve with discrete devices.
Here, the two power channels have an additional protection in the shape of a fast fuse (included in the FB loop). This affords one more protection layer, because such amps are sometimes included in complex setups, with supplies that can widely exceed that of the Opamp itself and require external protection.
The power channels are configurable as +10 and -10 gain blocks.

4 additional lower power channels are also included:
-two are high-accuracy, based on OPA27's, with one configurable for +1, +10 and +100 gains and the other as +10 or -10
-two are general-purpose, based on the NE5532: one as +1 and +10, the other as +10 or +100.

All the gain-setting resistors are either 0.1%, or have been hand-picked to 0.1% to ensure a good enough accuracy, essential for any lab gear.

The active circuits are complemented with variable attenuators based on high quality potentiometers.

All the coaxial outputs are protected by 50 ohm resistors, and the inputs have series 1K to 5K resistors..

The PSU uses a 200VA/2x22V toroidal and 2 32,000µF capacitors, plus two 20V regulators for the low-power channels: no rocket science, just plain and dependable electronics.

The whole thing is built as a class II device: no earth connection. In addition, the chassis is floating wrt. to the signal ground: this is essential for a test instrument, it gives a maximum of flexibility.

Since the mechanical design is centered on the principal elements, capacitors, heatsinks, transformer, etc, I had the opportunity to size it optimally: large enough to work comfortably, but as small as practical to fit into my already overcrowded lab.

Why use SMB connectors for most interconnects?
They have many advantages from my point of view: they are of the quick connect/disconnect variety, they mate reliably and give excellent contact, they have a controlled impedance, they use very little real-estate (the front panel has 16 of them, and it's far from cramped), and I can have them by the buckets (and the patch-cords too). All this means they are ideal for me.

I have made a tentative here: the heatsinks have a very good anodization, and I used it as an insulator for the LM12's. Risky? Maybe, but I made scratching and 500VDC tests, and they were all conclusive.
If it fails, it will result in a blown fuse, and I can always revert to the good (or not so good) insulation methods.
We will see....
Attached Images
File Type: jpg lab1.jpg (266.0 KB, 70 views)
File Type: jpg lab2.jpg (241.0 KB, 69 views)
File Type: jpg lab3.jpg (574.2 KB, 71 views)
File Type: jpg lab4.jpg (405.9 KB, 72 views)
File Type: jpg lab5.jpg (574.7 KB, 65 views)
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Last edited by Elvee; 26th July 2014 at 08:06 PM.
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Old Yesterday, 12:03 AM   #2748
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Elvee, very nice work.
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