Hi
I am working on my old Studiomaster 16-16-2 mixer. So far I´ve done some recap work on the PSU and one channel to see how it effects the noise level of this mixer (It got a bit better).
Anyhow I also wanted to try out some OPamp replacing and replaced
TL07x (TL071 & TL074) with TLE2071 & TLE2074 since they are supposed to be direct replacement parts for the old TL07-series, however now that I put the mixer together again there is a very high noise level, when I switch back to the old TL07x´s it disapears. Do I need to add some other value caps to bypass the new OPamps ?
I also tried to replace the NE5532 with OPA2134 but that results in even higher levels of noise. I´ve googled some on replacing the NE5532 and got a few sugestions on what to replace with one of them being the OPA2134 and also OPA2604.
Do you guys have any other suggestions on what to choose or tips on solving the above problems.
Best wishes,
synthguru
I am working on my old Studiomaster 16-16-2 mixer. So far I´ve done some recap work on the PSU and one channel to see how it effects the noise level of this mixer (It got a bit better).
Anyhow I also wanted to try out some OPamp replacing and replaced
TL07x (TL071 & TL074) with TLE2071 & TLE2074 since they are supposed to be direct replacement parts for the old TL07-series, however now that I put the mixer together again there is a very high noise level, when I switch back to the old TL07x´s it disapears. Do I need to add some other value caps to bypass the new OPamps ?
I also tried to replace the NE5532 with OPA2134 but that results in even higher levels of noise. I´ve googled some on replacing the NE5532 and got a few sugestions on what to replace with one of them being the OPA2134 and also OPA2604.
Do you guys have any other suggestions on what to choose or tips on solving the above problems.
Best wishes,
synthguru
TI data sheet:
The TLE207x series of JFET-input operational amplifiers more than double the bandwidth and triple the slew
rate of the TL07x and TL08x families of BiFET operational amplifiers. Texas Instruments Excalibur process
yields a typical noise floor of 11.6 nV/√Hz, 17-nV/√Hz ensured maximum, offering immediate improvement in
noise-sensitive circuits designed using the TL07x. The TLE207x also has wider supply voltage rails, increasing
the dynamic signal range for BiFET circuits to ±19 V. On-chip zener trimming of offset voltage yields precision
grades for greater accuracy in dc-coupled applications. The TLE207x are pin-compatible with lower
performance BiFET operational amplifiers for ease in improving performance in existing designs.
I think you may have converted your amplifiers to oscillators and the noise is actually the oscillation. You'll need a scope to sort this one out.
Speed purely for speed's sake is not always helpful. High gain high speed amps are usually more successful in lower impedance environments.
G²
The TLE207x series of JFET-input operational amplifiers more than double the bandwidth and triple the slew
rate of the TL07x and TL08x families of BiFET operational amplifiers. Texas Instruments Excalibur process
yields a typical noise floor of 11.6 nV/√Hz, 17-nV/√Hz ensured maximum, offering immediate improvement in
noise-sensitive circuits designed using the TL07x. The TLE207x also has wider supply voltage rails, increasing
the dynamic signal range for BiFET circuits to ±19 V. On-chip zener trimming of offset voltage yields precision
grades for greater accuracy in dc-coupled applications. The TLE207x are pin-compatible with lower
performance BiFET operational amplifiers for ease in improving performance in existing designs.
I think you may have converted your amplifiers to oscillators and the noise is actually the oscillation. You'll need a scope to sort this one out.
Speed purely for speed's sake is not always helpful. High gain high speed amps are usually more successful in lower impedance environments.
G²
To be more specific than stratus46, in replacing 4558's with 33078's I had to put .1 uf on the bottom of the socket between the power supplies, and put 22 pf (maybe, they were R.S. grab bag parts) across the feedback resistors, to kill the 1 mhz oscillation that resulted. I put .1 about 2 " away between one of the rails and signal ground. I had a scope. Didn't require much thought, look at the slew rates on the datasheets. I drilled holes in the PCB with a #40 drill chucked in a hand crank stanley drill, to cut the violence and chance of damage. I just bent the cap legs over and soldered onto the trace. Put a big light under your PCB before drilling to make sure it is not multilayer and you don't hit another trace. Good luck.
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