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Old 25th June 2007, 08:22 AM   #101
Pocoyo is offline Pocoyo  Indonesia
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Default DRV 134

Hii Alex

Why not make drv 134 pcb too for all of us
Lets make a group buys again

make the first order from now - end of june
your pcb looks cool

Give us the tools and we finish the Job
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Old 25th June 2007, 10:49 AM   #102
alexw88 is offline alexw88  Hong Kong
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No, I have not done the layout for the DRV134 board

I just bought it from diyzone.net
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Old 25th June 2007, 12:39 PM   #103
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Default drv 134

hii alex

can you help me to buy drv 134 board alex
because i dont understand the letter

or you will make this board yourself ?
so we can buy again from you
we believe 100% your design

waiting for answer
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Old 25th June 2007, 01:34 PM   #104
alexcd is offline alexcd  United States
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I can't find any DRV134 chips out there. I am stuck without them!
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Old 25th June 2007, 04:01 PM   #105
alexw88 is offline alexw88  Hong Kong
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I think the DRV134 is a bit old so not many stores are selling them.

Try RS online : http://www.rs-components.com/full.html

I found they have DRV134 at the HK site and their "Global Export" site under North America.

If you can't find DRV134, consider the newer (and improved) line drivers : THS4131, OPA1632, AD8138.

Or, build the balanced line driver with 2 opamps. ( http://sound.westhost.com/project51.htm )

Another option would be using transformers.
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Old 25th June 2007, 05:42 PM   #106
alexcd is offline alexcd  United States
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Thanks. I'll build my own boards for these. Anyone else interested in using the OPA1632?
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Old 25th June 2007, 05:55 PM   #107
alexw88 is offline alexw88  Hong Kong
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If you are interested in OPA1632, please also have a look at the datasheet of ths4131, it has more information on how to use the chip.

e.g. Figure 38 of ths4131 datasheet is an example of a non-balanced input to balanced output circuit.
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Old 3rd July 2007, 11:34 AM   #108
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Default ths4131 driver

alex, i have read the stats on the ths4131 and cmrr is approaching that of a good transformer. do you believe that rod elliots twin op amp design is much better than the standard drv setup using the 4131 chip. using the twin setup and driving each leg separate would make sense. thanks
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Old 3rd July 2007, 02:52 PM   #109
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alex, why did you choose the .2 ohm output resistor instead of .1 ohm. is the extra resistance necessary which it also robs voltage from speakers. i have just placed an order to farnell and was wondering about this. also, before i start soldering parts are there any last minute changes you would have made which i could incorporate in my build. thanks
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Old 3rd July 2007, 03:30 PM   #110
alexw88 is offline alexw88  Hong Kong
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I just learn from another forum

(http://av-forums.net/plus/viewthread...ra=page%3D1###)

that differential opamps like opa1632 or ths4131 themselves have low input impedence and needed to be driven by a low output impedence source. Otherwise you will get current noise. So you need to use a standard opamp to buffer the input first if your preamp is passive.

I used 0.2 ohm because I want to reduce current flow between chips. Note that Jeff Rowland used 0.5 ohm and 0.2 ohm in their amps.

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