Best op amp

[Shakey 1047]

Can anyone suggest the best low noise, low current op amp to use in a guitar booster circuit using a 9v battery. the one in it at the moment is a TL071. Cheers.

[Mark Hammer]

You will be hard-pressed to find anything that produces better guitar tone than that. Noise levels can be improved with some other chip-choices, but will depend on the surrounding components. So if you just want a chip you can insert into a socket without changing anything else, you're okay with a 71.

You CAN, of course, power a TL071 with considerably more than 9VDC for even greater headroom, although you'll need to be certain that any caps in the circuit are rated at a high-enough voltage to accommodate supply-voltage changes.

So, for instance, if you were to power with 18V, you'd probably want to be sure that any electrolytic caps were rate for at least 25V.

[pdf64]

OP27; they're lower noise, and, to my ears, sound nicer (though the electrical engineer in me hates to concede that one opamp type can sound any different to another).

[Jazz P Bass]

As of late, the main spec for onboard boost type circuits is how little current that they draw.

I just finished up a Fender Strat with a boost circuit.

It came with the LF442.

[Leo_Gnardo]

As of late, the main spec for onboard boost type circuits is how little current that they draw.

There's a lot to be said for that - who wants to be swapping batteries all the time, or have one fail mid concert or mid session.

Consider also the single-FET Alembic Stratoblaster. Not huge gain, granted, but keeps the tone clear as you drive long cable or lower-impedance effects. Clarity through simple circuitry, I like that a lot. And a 9V battery lasts for months.



Google an "improved" version, it has a loading resistor, you can choose a value to "brown" your tone to taste, or even put in a pot or switch to select pickup loading on the fly.

[Mark Hammer]

The location of the booster was never specified. If outside the instrument, current draw is moot. But if in the instrument, then I concur with others that current draw matters, and there are other things to choose from.

But current draw aside, the conventional use of boosters is to push other parts of the chain harder for solos and such. If it was a mic preamp for sampling I'd offer other chips up for consideration, that are cleaner and have more usable bandwidth. But most players are going to use a booster to make some other part of their rig generate more overdrive, such that the audio quality of the chip becomes moot. And as for bandwidth, there are precious few chips that can't deliver useful gain in the 7khz bandwidth that guitar generally demands.

Noise specs IS a genuine consideration, but actual noise levels will depend on what is around the chip, just as much, if not more than, the chip itself. Read the article on chip choices here: http://hammer.ampage.org/files/Device1-8.PDF The data is old, and the choices more limited, but the principles remain true: some things that have bad noise specs in one context, can have better ones in another.

[Shakey 1047]

Thank you all for your replies, that gives me plenty to think about.