Looking for an alternative to TAB1043 IC

[belwar]

Here is the datasheet

http://62.231.140.52/tnThumbnails/Da...DSA-112013.jpg

Can anyone suggest a drop in replacement for this? Im looking for something very low noise.. Any ideas? I can buy some old ones off E-bay, but i'd like to find a new one

bel

[Enzo]

Don't know, what is it used in and what does it do there?

[belwar]

Is an opamap in a bass pre-amp

[52 Bill]

Is an opamap in a bass pre-amp

I could barely make out on the datasheet that it is a "quad programmable" opamp.

I doubt that it is pin for pin swappable with any other part. What brand bass is it used in?

[Albert Kreuzer]

What brand bass is it used in?

Wal.
Obsolete since the early eighties.
Not pin compatible to any other quad opamp I know of.
You could use a TL064/074, but it would involve some serious surgery.

Cheers,
Albert

[Steve Conner]

Is that "programmable" as in, it has a bias pin that you can load with a resistor to set the internal bias currents? These used to be popular in battery-powered equipment (like active basses?) because you could set them to a low current for longer battery life.

Nowadays, you'd use a low-current op-amp like the TLC27L4. Or a regular low-noise one like the MC3307x if you're more worried about performance than battery life. The programmable op-amps would have had lousy performance (GBW, distortion, output drive capability) when running at low current. If you're looking for an upgrade, try keeping the same chip and turning the current up!

Or is it programmable as in an OTA? These are used to make voltage-controlled filters, and I heard the Wal basses had filters. The LM13700 is about the only OTA that anyone still makes.

[Albert Kreuzer]

Is that "programmable" as in, it has a bias pin that you can load with a resistor to set the internal bias currents? These used to be popular in battery-powered equipment (like active basses?) because you could set them to a low current for longer battery life.

Yes.

Here is a better data sheet:

[Steve Conner]

Thanks Albert. This does indeed look like a disaster area of an op-amp, especially in the low-power mode. Whenever you see "performance similar to the 741" in a datasheet, you know it's time to run screaming. Almost any modern op-amp would be an upgrade.

Unless the circuit is designed around the crappiness. For instance, I notice the GBW is 50kHz in low-power mode! If it were a car, that would be 0 to 60 in 2 weeks. It might be that if you swap in an amp with more GBW, it would become unstable. Or maybe the poor GBW causes distortion that fattens the tone of the bass.

I'd still recommend investigating the bias set resistors on pins 8 and 16, with a view to finding out what current the amp is running at, and beefing it up if it's in low-power mode. This will make it run more like a modern op-amp would, and you can see how that affects your tone.

[J M Fahey]

Hi Bewar. Did you trace that bass preamp?
*Maybe* you can reproduce it around a modern quad op amp.
Even a slow and not that silent TL064 will be better than the original.
You might reuse up to 90% of the original board topology, only rerouting some tracks to different pins, in any case less work than starting from zero.
If you dare ....
EDIT: I've been looking at the pinouts. The conversion is not *that* difficult.
You won't use the programming pins, that means two less to worry about.
The +/- power pins are roughly in the same place, good.
Also the inverting inputs.
The outputs and the non-inverting inputs are swapped, in all 4 op amps.
Not that difficult, if you can accept a slightly larger board, and don't run for the "pretty board of the year" contest.
In the worst case, a couple "ugly/unsophisticated" extra wire links would solve the problem.

[David Schwab]

Hi Bewar. Did you trace that bass preamp?

Old thread... but I'm tracing one right now.

Of course I ended up here by looking for the TAB1043.

I wonder what they use in the new Wal basses?

[J M Fahey]

Please post what you trace. It will be very interesting and useful.
Classic active basses are basic passive ones with usually a buffer and relatively simple tone control added, but Wal must have done something else, considering they had 4 op amps to play with,

[David Schwab]

The recent Wal basses have a buffer for the pickups, and then use a low pass filter for each pickup. When you pull up on the frequency knob, you increase the Q. There is also a "pick attack" treble boost EQ function, and they have a balanced XLR output using a transformer.

The earlier Wal basses had a similar preamp, but with a passive tone control, and a midrange boost along with the pick attack.

[Q7J113]

I know it has been awhile, but did anyone get anywhere drawing up the preamp?