From Oakley Sound Sent Thu, Jan 18th 2018, 10:09
From Oakley Sound Sent Thu, Jan 18th 2018, 10:09
> but it's possible to get reasonably-sized polyester caps in this value... This is true. And they're a lot smaller and cheaper than they used to be. > Doesn't the combination of R1 (10k) and R2 (10k after the mod) actually create a -6dB pad as it is? It does indeed. I missed that. That would give the ability of a modded unit to take a larger signal at the input than I first anticipated. And that'll be why Don made his post BBD amplifier four times the gain of the original. However, if we're going to pad that input signal I think an extra 10K resistor prior to the coupling capacitor and connected to 0V would be better than changing the 1M to 10K. Mostly because of the issue with the non zero impedance of the 7.5V reference line. That said even an unmodded unit should be fine with standard consumer line level signals. > What do you think about swapping to audio opamps that swing closer to the rails such as LM4562 or OPA2134? I think the CE300 uses SIL packaged op-amps so without adapter boards it'll be tricky to swap them out. Plus, there's a lot of other single ended electronics in there. I don't think that the limited swing is a problem though. It's more a matter of getting the input levels to suit. Tony www.oakleysound.com