I am attempting to diagnose an intermittent issue with the Essence STX PCIe x1 audio card in my Asus CM1630-06. Every now and then, the card will present massively excessive gain and a 3 kHz "howl" symptomatic of loss of negative feedback in the I-V; I have isolated the problem to the analog section of the STX. (The problem presents itself, when it occurs, at whatever analog output is active: Headphone, 2 Speakers, or Front Panel. However, it is undetectable at a second computer equipped with a Creative Laboratories SB0350 PCI audio card, which takes the STX' digital output through a front-mounted I/O Drive).
Is there any consistent issue with the stock JRC2114D operational amplifiers, in terms of internal hardware failure that would result in intermittent loss of negative feedback; or is the current-output section of the Asus AV-100 audio chip itself a suspect in this problem? And need I look into the JEDEC 8-pin DIP sockets for the I-V? I would appreciate some info about a most probable diagnosis prior to upgrading the analog section with new National Semiconductor op amp chips (probably a pair of LM6172IN's for the I-V and one LME49860NA for the buffer).