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Cascade Bypassing

post #1 of 4
9/9/10 at 11:49pm
Thread Starter 

I am modifying a clone of the Lehmann BCL and am thinking of upgrading the decoupling capacitors going to the OPA which I have rolled from a OPA2134 to LT1364.

 

The original capacitors are Elna RE3 470uF 35V bypassed with a ERO MKC1860 0.022uF 400V. The headamp sounds great all-round except for the mutant trebles that seem somewhat too incoherent with the rest of the sound. I figured this has got to do with the supplies to the OPA and read up on stumbled upon the idea of cascade bypassing.

 

The question is, I only have enough space on the board for 2 capacitors for each rail. I read on diyaudio that "bypassing a capacitor locally/directly on its terminals is not good and should be avoided". Is this true? If so, how should I go about it and should I even be considering cascade bypassing in the first place and why?

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post #2 of 4
9/10/10 at 10:51am
Thread Starter 

After reading up some more, stumbling on some simulations and Rob Elliot's article, I decided that proper cascade bypassing is out of my league. Will try replacing the Elna RE3 with Silmic II equivalent and Orange Drop 0.022uF 600V (that I have laying around) for the ERO and hope the sound smooths out a bit.

 

Appreciate any help I can get. I don't think the LT1364 is supposed to sound this wrong here...


Edited by aspenx - 9/10/10 at 10:52am
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post #3 of 4
9/12/10 at 5:16am

the 1364 is a very fast and wideband opamp, its very possible that what you are hearing is actually the opamp oscillating. if so, you may be able to tame this by installing a filter at the input or in the feedback loop to limit the bandwidth.

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post #4 of 4
9/12/10 at 8:50am
Thread Starter 

EDIT: Problem solved simply by raising the gain.


Edited by aspenx - 9/20/10 at 10:16am
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