Wal bass preamp - vintage IC question TAB1043

L

LukeFRC

Well-known member
Hellooooo

random question...

The classic Wal filter based preamp is an odd one, it's been traced a few places and there's a few people who recreate it.

Someone who has been testing out the various modern alternatives finds none of them quite get "the sound" of the original. Where I have been kinda involved in helping trace the original it's interesting that the electrical engineers who know what they are doing all go "oh wow that TAB1043 quad op amp is garbage by modern standards, lets update it" - and then create something that sounds different.
My suspicion is that the IC, biased in a way that saves batteries pulls some of the distortions from the slow op amp into the audio range, but in a pleasing way....

I first started looking to see if I could use lots of LM4250 to recreate the original, partly because it's another really old programmable opamp... partly because I have a few somewhere in my parts box... but then found a few of TAB1042 op amps....

so my question is - is this just a slightly less calibrated version of something similar with different pin-out and one bias pin?

TAB1043 datasheet

TAB1042 datasheet
 
LukeFRC said:
Hellooooo

random question...

The classic Wal filter based preamp is an odd one, it's been traced a few places and there's a few people who recreate it.

Someone who has been testing out the various modern alternatives finds none of them quite get "the sound" of the original. Where I have been kinda involved in helping trace the original it's interesting that the electrical engineers who know what they are doing all go "oh wow that TAB1043 quad op amp is garbage by modern standards, lets update it" - and then create something that sounds different.
Click to expand...
That's exactly what I'd do, to be honest. But I came into the filter camp from Alembic as a reference point, not Wal. ;)

Best of luck with your quest, I'm sure there's a real market for that Wal mojo.
 
There may be some inherent HF loss from the GBW of the TAB chip. Hard to say, not knowing the gain structure and how they used the iset pin. 4250 should be a good replacement as it is low slew as well but may have to work some math if you're splitting current to iset from one pin to two. Or may drop in fine.
 
I think how it is written it works is one pin biases stage 1 and the other biases stages 2-4

While the 1042 has one bias pin.
 
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