your LED, your gadget, your eyes
go high as you want
ZM's Thumb of Rule is for still normal LEDs, even if "hieff"
what you have is hysterical LED, step to blue dwarf
go high as you want
ZM's Thumb of Rule is for still normal LEDs, even if "hieff"
what you have is hysterical LED, step to blue dwarf
well, it's just a matter for how long one's trash is accumulating
I started hamstering all things electronic nearly 40yrs ago ....... just laziness is preventing me to toss 75% of that
not that it is exactly trash, but realized I will need 3 more lives to use them actually
bummer is that majority of that I can't find anyone to donate to (Greenhorns, yeah)
example - who needs 1L5 or 1R5 tubes?
I started hamstering all things electronic nearly 40yrs ago ....... just laziness is preventing me to toss 75% of that
not that it is exactly trash, but realized I will need 3 more lives to use them actually
bummer is that majority of that I can't find anyone to donate to (Greenhorns, yeah)
example - who needs 1L5 or 1R5 tubes?
High offset with BJT op amps???
Hey all, just finished up my build of a WHAMMY a couple nights ago, and after a couple false starts (a backwards e-cap and a bad solder joint on a power resistor), it's running great and sounds awesome. Here's the issue: I have a Burr Brown OPA2604 in it now, and I measured a DC offset at the headphone jack of less than +/- 1mV on both channels. I also have an NE5532 and an LME49720 to swap in, but when I measured the DC offset for either, I get a near perfect reading on the left channel (less than 0.5mV), but I saw a reading of around -105mV on the right channel! Oddly enough, the offset was about the same using either op amp, and it was perfectly fine when I switched back to the OPA2604. I expected to see a slightly higher offset on both channels with the BJT-input devices, but nothing like this.
I verified that both the positive and negative supply voltages were correct at the op amp pins, and made sure all the pins were seated properly in the socket, so I'm at a loss as to what the issue could be. One twist I should mention is, I modified the resistor values around the op amp to minimize the offset in case of a BJT-input device and to set the gain to exactly 4x. I'm confident that I didn't screw it up, though, because if I did, there'd still be a noticeable DC error with the OPA2604. It also wouldn't be likely to appear only on one channel without other effects (e.g. obvious gain difference between channels).
Anyone have any ideas what could be going wrong??
I'll detail the build later (casework, inputs and outputs, modifications like the resistor value changes, etc.) but I'd really like to get this DC offset thing resolved first...
Hey all, just finished up my build of a WHAMMY a couple nights ago, and after a couple false starts (a backwards e-cap and a bad solder joint on a power resistor), it's running great and sounds awesome. Here's the issue: I have a Burr Brown OPA2604 in it now, and I measured a DC offset at the headphone jack of less than +/- 1mV on both channels. I also have an NE5532 and an LME49720 to swap in, but when I measured the DC offset for either, I get a near perfect reading on the left channel (less than 0.5mV), but I saw a reading of around -105mV on the right channel! Oddly enough, the offset was about the same using either op amp, and it was perfectly fine when I switched back to the OPA2604. I expected to see a slightly higher offset on both channels with the BJT-input devices, but nothing like this.
I verified that both the positive and negative supply voltages were correct at the op amp pins, and made sure all the pins were seated properly in the socket, so I'm at a loss as to what the issue could be. One twist I should mention is, I modified the resistor values around the op amp to minimize the offset in case of a BJT-input device and to set the gain to exactly 4x. I'm confident that I didn't screw it up, though, because if I did, there'd still be a noticeable DC error with the OPA2604. It also wouldn't be likely to appear only on one channel without other effects (e.g. obvious gain difference between channels).
Anyone have any ideas what could be going wrong??
I'll detail the build later (casework, inputs and outputs, modifications like the resistor value changes, etc.) but I'd really like to get this DC offset thing resolved first...
An easy thing to check first is: did you accidentally solder in one or more wrong resistor values? Check the resistance of EVERY resistor that connects to opamp pins 2, 3, 5, and 6. If it's not EXACTLY what Wayne put on the schematic (post #2 of this thread): INVESTIGATE. Make sure you've got 1.0K and not 0.1K or 100K, and so forth.