https://www.audiosciencereview.com/...ng-on-an-eigentakt-amplifier.7671/post-191851
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https://www.miveraaudio.com/forum/main/comment/5d09e8d47668730061a7b5b2
The
Purifi input board buffer uses TI
OPA1612 opamps. If you have a look at the datasheet, based on the information they provide, the objective performance is outstanding:
http://www.ti.com/lit/ds/symlink/opa1612.pdf
TI made a newer version of this opamp, with higher current output called the
OPA1622:
https://www.audioxpress.com/news/Te...eneration-OPA1612-Audio-Operational-Amplifier
And after that they released an enhanced version with built in thin film resistors, and EMI suppression provisions, that is actually capable of delivering better real world performance in a final implementation. The data sheet specs are not as good, but due to the internal laser trimmed resistors, and EMI provisions, real world performance should be better:
http://www.ti.com/lit/ds/symlink/ina1620.pdf ]
So opa1612
Features
- High-Fidelity Sound Quality
- Ultralow Noise: 2.8 nV/√Hz at 1 kHz
- Ultralow Total Harmonic Distortion + Noise:
–119 dB THD+N (142 mW/Ch into 32 Ω/Ch)
- Wide Gain Bandwidth Product:
32 MHz (G = +1000)
- High Slew Rate: 10 V/µs
- High Capacitive-Load Drive Capability: > 600 pF
- High Open-Loop Gain: 136 dB (600-Ω Load)
Lm4562
KEY SPECIFICATIONS
• Power Supply Voltage Range: ±2.5V to ± 17V
• THD+N(AV=1, VOUT = 3VRMS, fIN = 1kHz)–RL=2kΩ:0.00003% (typ)–RL=600Ω: 0.00003% (typ) -
130dB
• Input Noise Density: 2.7nV/√Hz (typ)
• SlewRate: ±20V/μs (typ) DESCRIPTION p) • Input Offset Voltage: 0.1mV (typ) • DCGainLinearity Error: 0.000009%
However what you have to understand is that the OP amp isn't the only factor. Board design and layout can make a significant difference.
Looking at these buffers op amp specs in isolation is all well and good but you need to see measurements of final Implementations, preferably not just the buffer board but the entire finished amp output.
Otherwise it's just all marketing guff and subjective (usually uncontrolled and faulty) opinion.
This is precisely the trap that the "op amp rollers" fall into. They look at specs, replace their ne5532 with a wizz bang op amp and expect overall circuit performance to improve and therefore sound quality. They then use uncontrolled methods to assess sound quality and will incorrectly conclude their new op amp is smoother, has lifted veils and made blacks blacker. Amir's measurements of doing this demonstrate nothing useful changing.
It is quite possible that different buffers can sound different, that's not the argument I am making, which I think some have misinterpreted. However you have to ask yourself if they do sound significantly different under controlled conditions, then why? If it is the case then differences will be measurable.
Ask yourself which one is transparent? It's actually OK to colour the sound if that's what you want, but if you want tone controls, why not use tone controls?