Low offset op amp for audio

[Newmarket]

Yes Alps had high quality stuff (maybe still do - I no longer work in that field).
Obviously examined at P&G and motivation for P&G 8000 series.
I was doing electronics and embedded there but same space as electromechanical. It's all coming back now - Kilopoise ; Nyebar...

 

[Matt Syson]

I like the P+G 1500 series faders and spent some time getting them past BBC commissioning engineers by shifting the track element by a mm or so. 3000 series pretty good but a fiddle to clean when necessary. 8000 series nice idea BUT just too 'wobbly' (not very robust).
ALPS made some with purple plastic that were pretty good but they were discontinued after a while. The K series were reasonable and relatively cheap and fortunately easy to clean. The carbon track tended to wear fast in the first few months of use but once wiped clean would settle down for a year or more. Going back to pots I know a bit more than I will say here. Do P+G still do the 'lazer trimming' using an AVO 8 multimeter?

 

[Newmarket]

Ah. It was actually the 8000 series that I meant wrt competing with Alps. Corrected now. Was last century when I was there so I'll let myself off

 

[Newmarket]

1500s pre-dated me there but they were very well regarded. And yes 8000 were a bit of a step down from 3000 for a cost benefit. The design engineers were very good and met the remit. But was "clip together plastic" low cost construction couldn't match the rigidity of 3000.
I recall some complaints about the electrical screening but that was caused by customers not understanding the correct way to mount them so that proper contact was made into the carbon loaded nylon body.

 

[gyraf]

Back to OP question: why not just add a simple single-point DC servo?

 

[JohnRoberts]

Back to OP question: why not just add a simple single-point DC servo?

I mentioned a dc servo in post #2 of this thread....

JR

 

[saint gillis]

Thank you for the chat and the interesting information, and thank you for reminding the unusual single-point servo.
But the goal of this thread is to list the op-amps that can nowadays achieve good audio performance (low noise, low distortion) AND low offset

 

[FETlife]

Do we need to consider input bias current aswell?

 

[rogs]

I've found the OPA1641 a very useful audio op-amp. Max DC offset is 3.5mV. See here for overview: https://www.ti.com/product/OPA1641

 

[saint gillis]

Do we need to consider input bias current aswell?

Yes, but let's consider it as a 2nd order criterion

 

[JohnRoberts]

Yes, but let's consider it as a 2nd order criterion

Bias current is a concern with high impedance resistor values.

We have three options; 1) bipolar inputs with relatively high bias current, 2) fet input with naturally low bias current, and 3) trick bipolar with circuitry to perform a first order compensation for bias current.

I prefer door #2 for hi Z circuitry, door #1 for conventional low to moderate impedance circuits.

JR

 

[Mr. Moscode]

LF 411 :
VIO Input offset voltage VIC = 0, RS = 10 kΩ avg: 0.8 Max: 2 mV
Offset is trim-able.