Strangelove424
500+ Head-Fier
- Joined
- Apr 4, 2012
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I recently put the stock op amps back into the IV position and put a 49860 (the descendant of the stock 4562) in the buffer. I have come to the conclusion that it sounds best this way. The 49860s in IV position creates an extremely bright sound, far brighter than neutral I think. The STX, with 49860 op amps, has always been the odd man out in all my gear - the bright source. I have a Denon AVR that has an accurate DAC and headphone out, and after putting the stock op amps back in the STX both sources now sound very similar. If the measurements that were included for each of our cards were done with JRC2114s, and the circuit itself designed for those op amps, then by changing the op amps I think those measurements are no longer valid. Once the op amps are switched, there is no telling how our card is behaving without testing. I don't have proper testing equipment, but I would be willing to bet the 49860s create a higher distortion level in the higher frequencies than the stock op amps, despite the fact that the TI opamps themselves have better specs. Implementation in the circuit is everything, and despite having lower THD+N, perhaps the TIs have different voltage characteristics that don't mesh with the STX's design.
These impressions were gathered on both a DT880/600 and HD600, so I don't think one op amp favors a warm headphone or the other a cold one. With the TI op amps in the IV spots, the Beyers displayed an almost bullet-like quality to the high frequencies and the HD600's treble sounded grainy. After playing with EQ, I found the bullet-like highs on the DT880s and graininess on the HD600 was a symptom of increased activity in the 4khz-8khz region, which the TI49860s seem to emphasize. The stock op amps gave both headphones a more balanced response, and made them sound more similiar to my other sources. I truly believe the JRCs are closer to neutral as implemented within this specific circuit design.
I had ordered 49990s and adapters, and was planning to try that next. But after reading about heat and stability issues, I am coming round to the idea of leaving the card alone. Just my two cents.
These impressions were gathered on both a DT880/600 and HD600, so I don't think one op amp favors a warm headphone or the other a cold one. With the TI op amps in the IV spots, the Beyers displayed an almost bullet-like quality to the high frequencies and the HD600's treble sounded grainy. After playing with EQ, I found the bullet-like highs on the DT880s and graininess on the HD600 was a symptom of increased activity in the 4khz-8khz region, which the TI49860s seem to emphasize. The stock op amps gave both headphones a more balanced response, and made them sound more similiar to my other sources. I truly believe the JRCs are closer to neutral as implemented within this specific circuit design.
I had ordered 49990s and adapters, and was planning to try that next. But after reading about heat and stability issues, I am coming round to the idea of leaving the card alone. Just my two cents.
