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Class D Switching Power Amplifiers and Power D/A conversion

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Old 11th August 2007, 03:51 AM   #11
Pano is offline Pano  United States
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Well it's funny about Charlize losing her cap. I've been working on the same thing, but with transformers. Brian and I have discussed this a bit off list.

You have to be very, very careful when you leave out the caps. Using the Bias Cap as the ground reference is clever, but it needs attention. If you have a DC offset circuit like the Trends, it screws up things. (Charlize does not have one).

Anywho, it can be done and is a clever idea - you just have to be careful about it. The circuit I'm working on will not have the grounding and power supply problems of the prevoius capless circuits. Wish me luck!
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Old 11th August 2007, 01:39 PM   #12
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I was thinking about trying transformers, but with the cost of a decent transformer at around $70 each; I lost interest pretty fast.
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Old 11th August 2007, 03:50 PM   #13
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It should also be mentioned that anyone who has the original Charlize does not need to buy v2 to be able to DC couple.

I'm not trying to take sales away from Yeo, but I don't see the need for a new board just to switch the connection of one wire.

BE SAFE

If you want to try this you need to check for any voltage potential between the source ground and the BIASCAP pin BEFORE you connect the source. If there is any voltage between these two points you have done something wrong. I would first check to see if the source groung and power supply ground are truely isolated.

Brian,

Is it possible to use OPA1632 to DC couple the input for a single ended application? I have been trying some simulations and I can only get it to work properly with a balanced input.

Click the image to open in full size.
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Old 11th August 2007, 04:53 PM   #14
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Ok, I think it will work this way. A benefit of doing it this way would be the ability to add a switch to change between which output to use.... a phase switch. Or, it could be used with a chip like the TA2020 to be able to bridge and DC couple.

Please tell me if I'm completely off course with this.

Click the image to open in full size.
Click the image to open in full size.
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Old 11th August 2007, 11:03 PM   #15
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It's true you can run the little darling san input cap, costs nothing and as many people have said the best sounding cap is no cap.
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Old 12th August 2007, 12:03 AM   #16
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ahem, ahem.

this little tweak of removing the input cap is just one of the many we have incorporated into the new charlize.

sorry, we are not keaned to disclossing more. we are sick of all those copy-and-paster guys out there.



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Old 12th August 2007, 12:19 AM   #17
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Use a THS4131 fully differential chip, for your buffer/pre and set the 2.5 v bias with its Vocm pin....
http://focus.ti.com/docs/prod/folder...t/ths4131.html
with a dpst swith/relay you've got a phase invert control, or with a non balanced bridge Tripath chip, you can use 2 and you're set for balanced bridged operation

Heck, without much effort you could repurpose the board from TwistedPear
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Old 12th August 2007, 01:13 AM   #18
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Quote:
Originally posted by pmkap
Use a THS4131 fully differential chip, for your buffer/pre and set the 2.5 v bias with its Vocm pin....
http://focus.ti.com/docs/prod/folder...t/ths4131.html
with a dpst swith/relay you've got a phase invert control, or with a non balanced bridge Tripath chip, you can use 2 and you're set for balanced bridged operation
Hellooooooo helloooooo hellooooo helloooo...........

Sorry, I thought I heard an echo.

THS4131 and OPA1632 are basically the same chip.

I'm in the process of making the layout for the above circuit. Then I will have a DC coupled T-amp with zero DC offset and a phase switch.

Here is a pic of a DC offset adjust board I just made for an AMP32.

Click the image to open in full size.
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Old 12th August 2007, 03:24 AM   #19
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theAnonymous1,

Yes, you're correct. I didn't look at the post with the OPA134 carefully enough to see it connected to a label 'OPA1632 Vocm'. I hadn't realized that the OPA1632 had that feature.
Sorry.....
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Old 12th August 2007, 05:19 AM   #20
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Quote:
Originally posted by theAnonymous1
Is it possible to use OPA1632 to DC couple the input for a single ended application?
It is possible but the OPA1632 is not an instrumentation amp (inamp for short). The method I described is best done using an inamp. Something like TI's INA128 http://focus.ti.com/docs/prod/folders/print/ina128.html would probably work well.
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