Finally made a LM1875 amp

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AndrewT

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Joined 2004
gychang said:
if metal is used would conduct, original question is applying heat sink without conducting electricity but with conduction of heat...
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Is this a question or a statement?

Post1 (the original) said:
After having a stack of boards sitting around for a year, my friend Allan convinced me to help him make an amp with them. We put a stereo amp together with them last night. I am quite pleased at how the boards work together.

Now it is time to put together a nice compact chassis for it. We used a small Avel Lindberg 2x18vac transformer.

Here is a pic:
 
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HAL2010

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Joined 2007
Has anyone built a version of the ChipAmp with LM1875 using differential inputs and a gain of 10? If you remove C2, one hole becomes the - input and just put the other resistor where C1 would go for balanced inputs.

Looking at 1K ohm and 10K ohm for the resistor values. The LM1875 is compensated for a gain of 10 or higher, so that should be fine.

Starting out with a +/-20VDC supply as I have one already for trials. Should get about 15watts from that from the datasheet. Should be fine for a high sensitivity full range driver.

Any thoughts greatly appreciated.
 
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HAL2010

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Joined 2007
danielwritesbac said:
LM1875 can use a gain of 10 at the minimum documented operating voltage; however, for higher voltage the gain comp is likewise higher. If you wanted extremely low gain, see LM675 in inverting mode, which, in some conditions, can achieve as low as 1:1.
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I am using the LM1875 as a balanced input amp, not single ended input. The gain of 10 should be fine. It might need the Zobel network on the output for stability with the speaker.

It is really more of a question if anyone has used it in balanced (differential) input mode.
 
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HAL2010

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Joined 2007
Have the LM1875T ChipAmp boards and moded the circuit for balanced inputs. Working well so far with DC coupled inputs and outputs. Using a gain of 11 to keep it stable and the stock Zobel network.

Have built four channels for the OB triamped planar magnetic mids and tweeters with servo subs.

Also built on LM3875TF ChipAmp with balanced inputs to try as well.
 

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