Wow Evan, that is great news. Valery can say for sure but +-85 sounds a little high for two pair of outputs. Maybe if you stay with 8 ohm load. So glad you finally have it working. A great sounding system. I need to get mine installed in a case so I don't have to drag everything out every time I want to listen to it.
Congrats!!!!
Congrats!!!!
Thanks Terry. Getting work done at a snails pace has its benefits...I get too see others work through things. That's my excuse and I'm sticking to it.
Evan
Evan
Every skydiver knows: careful preparation - less problems in the air 😀
Well... most of them know
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I seem to have bad luck with some projects now matter how well I try to prepare. This one and the No GNFB input seem to be exceptionally buggy for me. The No GNFB input was actually my stupid mistakes causing the problems but this one still is plaguing me with DC offset issues and imbalance on one board. I'm running into DC offset issues with a set of CFA-CFP boards now too so I'm starting to become suspicious of this batch of op amps.
Jeff, do you use LF411 or something else?
Never had issues with it, but faulty batch is possible...
Never had issues with it, but faulty batch is possible...
I noticed both mouser and digikey offer different lf411 parts. I ordered the cheapest and they seem OK.
I'm using LF411. This was just a small batch of 10. I noticed quite a difference in offset voltage when I replaced one but it still wasn't at zero and seemed to drift around. I have more in stock now, hopefully from another manufacturing run. I found it really odd the first pair of CFA-CFP boards were 2-3mV (older stock) and the second pair drifted around -30mV. I haven't run into a bad batch of components like this before but anything is possible.
The strangest thing I've seen so far was that voltage on the input with the first batch on LEDs. It remained there with the LEDs with the dropping resistors as well. It was gone with the last batch of LEDS.
Do you have the full part number of the ones you used? I'd like to compare and see if that has something to do with it.
LF411CN/NOPB Texas Instruments | LF411CN/NOPB-ND | DigiKey
LF411CN/NOPB texas instruments.
I'm sorry I did not order any extra.
LF411CN/NOPB texas instruments.
I'm sorry I did not order any extra.
I just checked mine. The first and second batch were LF411CN. The latest batch are LF411CP so they definitely aren't the same batch. I'll see what happens. Thanks.
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In general LF411 is great for the purpose. FET inputs (high impedance / low input current), very low drift, precise device. But yes - anything is possible 🙄
Do you normally solder them directly in or do you put them in a socket? My iron is temperature controlled but I wonder if I'm burning them.
I used a socket. The only other amp I built with a servo would run without the op amp. I could set the offset and then plug in the op amp and let it keep the offset low as parts drifted.
I used to socket them as well until OS mentioned there may be issues because of the megaohm resistors it was sensing.