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Analog Line Level Preamplifiers , Passive Pre-amps, Crossovers, etc.

Simple asym  to symmetic buffer
Simple asym  to symmetic buffer
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Old 15th August 2019, 02:51 PM   #11
Turbowatch2 is offline Turbowatch2  Germany
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Join Date: Aug 2013
Location: Northern germany
Yes, you are right, the layout and picture are quite confusing, and do not make sense on first sight. I did not have the time to do a schematic, but will do. The C should buffer the +- voltage supply, the whole buffer is DC coupled.
The NE5532 (a real one!) has to drive 8k inputs, the gain is OK. It has to drive an ICEpower 250A amp that needs such a buffer.
It has to be changed to unity gain, it is x10 right now. At 1.60€ it is impossible to get a cheaper solution and the size makes it perfect to be soldered directly at the RCA input.
As I have to get 8 symmetric input buffer price is a factor. There are other, larger solutions out there, but none of them is a real good design.
With this tiny board only two resistors have to be changed and one input connected to another.

Im just asking here, as I have never seen such a simple solution for converting an asymmetric signal to symmetric. Sure I will do some serious testing before using it in the final installation and use a real NE5532. Seems to be a really good OP-amp. I wander what the Chinese put into their fake chips. They sound cruel, this is no voodo, but easy to hear. Even the old TL072 did a better job.

Last edited by Turbowatch2; 15th August 2019 at 03:05 PM.
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Old 20th August 2019, 11:35 PM   #12
sgrossklass is offline sgrossklass  Germany
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Join Date: Nov 2004
Location: Germany
Originally Posted by Turbowatch2 View Post
I wander what the Chinese put into their fake chips. They sound cruel, this is no voodo, but easy to hear. Even the old TL072 did a better job.
If it even is an opamp (rather than, say, a comparator), I'd be guessing LM358 - they are ubiquitous general purpose dual opamps, super cheap when bought in bulk and will sustain +/-15 V. (The trusty NJM4558 can be similarly inexpensive but isn't as common. You bet counterfeiters would be looking for liquidations of old stock for maximum profit margin.) Their crossover distortion tends to be plainly obvious on a scope, it's that bad. Add a resistor from output to V-, about 10k, maybe 4k7 or 3k3 - if it sounds OK then, that's a dead giveaway.
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