What remotely audible characteristics of this remarkable device are you having problems with?
And how did analog designers manage to produce such landmark designs as the Tektronix 7000-series mainframe oscilloscopes and plugins in the late 1960s before circuit simulation was remotely a twinkle in the eye?
Or the NASA Apollo missions?
Now sure I use Spice simulation too - but I accept it to be what it is: a cop-out in lieu of the level of circuit understanding of earlier generations
And how did analog designers manage to produce such landmark designs as the Tektronix 7000-series mainframe oscilloscopes and plugins in the late 1960s before circuit simulation was remotely a twinkle in the eye?
Or the NASA Apollo missions?
Now sure I use Spice simulation too - but I accept it to be what it is: a cop-out in lieu of the level of circuit understanding of earlier generations
The 1656 could very well be used in instrumentation/measurement tools where every last drop of its performance would be salient. I realize this is DiyAudio, but a decent number of folks do float in and out of precision analog design here, and no one has mentioned anything about audibility in a while (beyond the noise metric, which is fair for high gain apps)
Great! Trust Turing to have been ahead of the curve by decades. Shame he was hounded into suicide for the then illegal crime in the UK of being gay and being in a relationship.
Did you measure this yourself? Impressive not to get any 50 Hz into the measurements.
^ Jan, we have all kinds of users on this forum that wouldn't have the context to know you (and HPW) wouldn't come from that direction. And I'd argue we're probably the minority when talking about opamp selection for non-audio-playback reasons. So let's not be too grouchy.
No grouchiness intended! But I stand with my point, if you think that an OPA1656 somehow changes your music, it's, well, what's there to discuss?
Jan
there are situations where this would matter.
you could have an extremely high gain circuit.
Well I have 1,000 of them and I can report quite accurately that even in a quiet room they do not make any sound!!!
Not sure if we have the same understanding of "noise figure" but nevertheless, OPA1656 is less noisy than the OPA827, 2.9nV/rtHz vs. 4nV/rtHz both flat. Where OPA827 shines is DC precision (150uV offset vs. 500uV for the OPA1656) but that's largely irrelevant for audio applications.
True, but you could argue that if you painted yourself in such a situation you probably should have made a different design decision ;-)
Jan
Well I have 1,000 of them and I can report quite accurately that even in a quiet room they do not make any sound!!!
Ed, you're sooo funny ;-)
Jan
High Frequency THD Rise and output current
Hi,
just wondering, if someone has more insight in OPA1656s THD behaviour at higher audio frequencies.
Datasheet:
Fig 7 shows THD+N vs frequency at Vout=3V(rms).
With G+1 and 2000R load, I(rms)=1,5mA, THD+N shows ca 0,00003% @10kHz (nice!)
With G+1 and 600R load, I(rms)= 5,0mA, THD+N shows ca 0,000055% @10kHz
When operating OPA1656 at higher signal voltages with a 2000R load,
output voltage then e.g. 6Vrms , I(rms) consequently 3mA:
Does the THD+N curve stay nearly flat over frequency or should I expect rising THD+N from 3kHz onwards?
What would be a reasonable maximum output current I(rms), that still provides a flat THD+N vs Freq curve?
Hi,
just wondering, if someone has more insight in OPA1656s THD behaviour at higher audio frequencies.
Datasheet:
Fig 7 shows THD+N vs frequency at Vout=3V(rms).
With G+1 and 2000R load, I(rms)=1,5mA, THD+N shows ca 0,00003% @10kHz (nice!)
With G+1 and 600R load, I(rms)= 5,0mA, THD+N shows ca 0,000055% @10kHz
When operating OPA1656 at higher signal voltages with a 2000R load,
output voltage then e.g. 6Vrms , I(rms) consequently 3mA:
Does the THD+N curve stay nearly flat over frequency or should I expect rising THD+N from 3kHz onwards?
What would be a reasonable maximum output current I(rms), that still provides a flat THD+N vs Freq curve?
Yes, but I couldn t find this specific information in the datasheet:
Fig. 7) & 9) are for 3Vrms,
Fig. 8) is valid only for 1kHz, but not for 5....20kHz
The 2k-load plot in Fig.7 stays nicely flat towards higher frequencies with Vout=3V(rms).
I wonder how the 2k-load curve would look like for higher Vout, 6V(rms), 9V(rms)? Is there an output voltage where the curve will start to bend upwards at higher frequencies?
Fig. 7) & 9) are for 3Vrms,
Fig. 8) is valid only for 1kHz, but not for 5....20kHz
The 2k-load plot in Fig.7 stays nicely flat towards higher frequencies with Vout=3V(rms).
I wonder how the 2k-load curve would look like for higher Vout, 6V(rms), 9V(rms)? Is there an output voltage where the curve will start to bend upwards at higher frequencies?