Had anybody ever built audio preamp using instrumentation op-amps (like AD620) and what are the experiences? How does it sound?
instrumentation opamps are good for IV, so I would think with a bit of bandwidth limiting they could make a nice preamp too.
Why should anybody built audio preamp using instrumentation op-amps if there are dedicated audio op-amps available?
Hi,
to my taste there are only two positions in audio circuits where OPs can shine. That are DC-Servos and high-gain stages like Phono-circuits.
If You want to build a symmetrical-input Phono-stage Instrumentation amps may be the parts to look for. The already named INA103 and its younger little brother INA163 are excellent for usage as input devices for phono stages for low-out MCs to high-out MMs (though I would recommend other OP-amps for the latter simply because most MMs are no symmetrical sources).
The optimum noise source resistance of the INAs is around 200Ohms (High-out MCs) and the noise figures are low enough to accommodate even lowest-output MCs (<1nV/sqrHz and low 1/f-breakpoint).
The optimum gain range is around 100, i.e +40dB, which also fits this application very well. Their Ref-input pins may be driven by a DC-servo to keep output offsets small (a common problem in high gain stages). Their gain can easily be tailored to the demand by varying just one resistor.
All this allows for the design of extremely flexible and first quality phono-stages that can accommodate nearly each and every pick-up on the market.
jauu
Calvin
to my taste there are only two positions in audio circuits where OPs can shine. That are DC-Servos and high-gain stages like Phono-circuits.
If You want to build a symmetrical-input Phono-stage Instrumentation amps may be the parts to look for. The already named INA103 and its younger little brother INA163 are excellent for usage as input devices for phono stages for low-out MCs to high-out MMs (though I would recommend other OP-amps for the latter simply because most MMs are no symmetrical sources).
The optimum noise source resistance of the INAs is around 200Ohms (High-out MCs) and the noise figures are low enough to accommodate even lowest-output MCs (<1nV/sqrHz and low 1/f-breakpoint).
The optimum gain range is around 100, i.e +40dB, which also fits this application very well. Their Ref-input pins may be driven by a DC-servo to keep output offsets small (a common problem in high gain stages). Their gain can easily be tailored to the demand by varying just one resistor.
All this allows for the design of extremely flexible and first quality phono-stages that can accommodate nearly each and every pick-up on the market.
jauu
Calvin
some of the best performing audio opamps were not designed for audio, but low noise instrumentation, they are in fact in most cases 'too good' so need to be hobbled to remain stable
Hi,
could anybody explain what an Audio-OP-amp is??
What qualifies an OP-amp as ´Audio´ type?
Does it feature some additional mysterious pin named audio?
Has it been bespoken by a priest of the Audio High-Church?
Does it deliver sonic voltages ore even ultrasonic currents?
*sigh* If only I knew 😕
jauu
Calvin
could anybody explain what an Audio-OP-amp is??
What qualifies an OP-amp as ´Audio´ type?
Does it feature some additional mysterious pin named audio?
Has it been bespoken by a priest of the Audio High-Church?
Does it deliver sonic voltages ore even ultrasonic currents?
*sigh* If only I knew 😕
jauu
Calvin
In most cases "Audio"-grade shows what the device couldn't be used for other precision and serious applications.
For example THS6012 has "audio" version TPA6120 with more voltage drift and slightly worse other parameters.
yeah I dunno either, its a term that does seem to be catching with the producers of them though. I suppose its something that is stable within the frequencies of interest for audio? I actually didnt mean to use the term above, was meant to say 'snip....some of the best opamps were not designed for audio....'
or re-worded to say:
Some of the best Audio Opamps were not designed for audio, nor specified for audio duty.
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