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Old 3rd August 2007, 02:05 PM   #1
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Default Adding gain to this buffer....

I found this simple buffer schematic here on the forum and would like to know the proper way to add a small amount of gain.....

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Can the standard method of gain for a non-inverting configuration work, or are there other things that need to be considered?

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Old 3rd August 2007, 02:15 PM   #2
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Thats the way to do it.

If it's only a small amount of gain, nothing else has to be concidered.
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Old 3rd August 2007, 02:24 PM   #3
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Thank you Jan.

Yes, only a gain of around 2 or 3.

I am planning to add this buffer to an amp that has a passive volume control. The amp is Tripath TA2022 based and I would like to lower it's gain and add some to the buffer instead.

Is there a huge difference between running an OPA2134 at +/-12v instead of +/-15v? I have a boat load of positive and negative 12v regulators, but no 15v.
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Old 3rd August 2007, 02:43 PM   #4
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As you are using it to drive Line Level signals well below 5 Volts, there will be no difference using 12V or 15V. Various temperature of the OPAmp has much more influence.
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Old 3rd August 2007, 04:34 PM   #5
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I forgot I made some mono "cmoy" boards with adjustable gain way back when and never used them for anything. If I remove the coupling caps, 100k resistors, and splice in the 47R resistors I'm all done.

(SMD on the bottom)
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Old 3rd August 2007, 04:37 PM   #6
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Quote:
Originally posted by theAnonymous1
I am planning to add this buffer to an amp that has a passive volume control. The amp is Tripath TA2022 based and I would like to lower it's gain and add some to the buffer instead.
What are you looking to gain by doing that? Er, no pun intended.

se
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Old 3rd August 2007, 04:40 PM   #7
AndrewT is offline AndrewT  Scotland
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Hi,
+-12Vdc will give a maximum output into a high impedance load of about 8Vac.
+-15Vdc gives about 10Vac.
The difference is a loss of headroom of less than 2db.
Go for it, but use a unity gain buffer.
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Old 3rd August 2007, 04:47 PM   #8
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Quote:
Originally posted by Steve Eddy


What are you looking to gain by doing that? Er, no pun intended.

se
The Tripath amp is kind of noisy with the recommended gain. I've tried lowering the gain and it also lowered the noise, but then it doesn't play as loud (duh).

Adding gain to the buffer isn't a good solution for this?
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Old 3rd August 2007, 04:55 PM   #9
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Be careful because the opamps at the input stage of the Tripath amp are powered by a single 5V rail. We have no idea what the specs of the opamps internal to the chip are, so it would probably be a good idea to make sure the maximum possible input voltage is below 5V peak to peak (biased around 2.5V of course).
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Old 3rd August 2007, 04:56 PM   #10
AndrewT is offline AndrewT  Scotland
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Quote:
Originally posted by theAnonymous1


The Tripath amp is kind of noisy with the recommended gain. I've tried lowering the gain and it also lowered the noise, but then it doesn't play as loud (duh).

Adding gain to the buffer isn't a good solution for this?
explained like this, then it begins to make sense.
It's worth trying sending a higher level signal to the amp. But now you need more headroom. +-18V supplies for 12Vac gets back 3.5db of headroom ref 6db of gain. You still lose out but much better than +-12V supplies.
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