DI - passive or active?

[Sugarman]

What is the best DI box for vintage bass, electrc guitar, Rhodes? - (all passive pick-ups)

And what about old analog synths? active or passive DI box?

[Blast9]

Good question... I was wondering what the differences were myself, and found a useful wikipedia reference:

http://en.wikipedia.org/wiki/DI_unit

Worth everyone having a read

[beats workin']

it's my understanding that passives are good for sinths and rhodes while actives are better for guitar and bass. please correct me here if I'm wrong. i generally use the DI on my pres or a countryman for guitars and basses and use a passive on my rhodes if I'm not amping it up. when running DI I usually use one of my altec 1567s pres to add some nice grit.
david

[seriousfun]

Originally Posted by beats workin'

...passives are good for sinths and rhodes while actives are better for guitar and bass...

Everything else equal, this can be true.

A passive magnetic or piezo pickup equipped instrument will interact with a passive DI, changing as the instrument's volume and tone controls are changed. An active DI will present a stable load to a passive instrument.

An active instrument - keyboard, active-pickup bass, etc. - won't have this problem, and a passive DI can be cheaper and will have fewer components in the signal path, potentially having less distortion and noise.

[Sugarman]

I want to record everything through my pair of V76 preamps.
And I just read on the above mentioned article http://en.wikipedia.org/wiki/DI_unit that you should not amplify twice. I guess in my situation this would mean that my p-bass (with passive pickups) should go through a passive DI box and then go into a V76 preamp for the amplification, right...(?)

Great article - thank you!

[joelpatterson]

In the manual for my dual Radial (passive) DI was a whole dialectic discussion about the evolution of DI's in general and the distinction between actives and passives. I thought it was extremely strange for a manual to go into detail like this, because usually manuals are written VERY defensively, like nothing they say can be in the slightest doubt. "Your ON switch is the way to turn on your device. If you want the device to go "on", rock the "ON" switch gently until it locks in the "ON" position. Your device is now on. Please refer to the manual before proceeding further."

And the gist, as I got it, was that the output in the olden days of your average guitar or bass was so low that passives might not really cut it, so actives were brought into play, but they had disadvantages insofar as "purity of the signal" was concerned, but fear not, today's instrument pickups are far robustier and this particular Radial Dual DI was so overwhelmingly built it is the finest device on the market bar none, thanks for showing the keen foresight to purchase a product that should provide you with a long lifetime of service under normal conditions, except as noted.

[Snatchman]

I use a Radial " Duplex" ( passive) DI. It sounds really good! But...I've found that when using it, getting good results depends on what signal quality ( instrument, synth, etc.) you have before the DI and the quality of the pre-amp behind the DI...!..YMMV

[Sugarman]

Originally Posted by joelpatterson

but fear not, today's instrument pickups are far robustier and this particular Radial Dual DI was so overwhelmingly built it is the finest device on the market bar none, thanks for showing the keen foresight to purchase a product that should provide you with a long lifetime of service under normal conditions, except as noted.

Today's instrument pickups? But the ones I use 90% of the time are at least 30 years old... Fender p-bass, Rickenbacker bass, old stratocaster, Rhodes, Gibson EB-2 bass etc...
So this mean I should use an active DI in your oppinion (because of the weak pickups)?

[seriousfun]

Originally Posted by Sugarman

... you should not amplify twice. I guess in my situation this would mean that my p-bass (with passive pickups) should go through a passive DI box and then go into a V76 preamp for the amplification..

No.

A DI does not amplify (some preamps have direct instrument inputs so you can plug these directly into a line input, but then you don't need an separate DI or Preamps...). Its transformer is to bring the high-level/high-impedance output of a passive instrument down to the low-level/low-impedance signal the mic pre wants. Some transformers used in passive DIs have fewer or more windings, changing the output a little, but that's what Preamp gain controls are for.

As with everything to do with sound, you should always listen and choose the best sounding option - of course the best sound is sometimes obtained by putting a passive instrument through a passive DI - but typically an active DI is the best solution for a passive instrument (and vice versa).

[Sugarman]

Originally Posted by seriousfun

No.

A DI does not amplify (some preamps have direct instrument inputs so you can plug these directly into a line input, but then you don't need an separate DI or Preamps...). Its transformer is to bring the high-level/high-impedance output of a passive instrument down to the low-level/low-impedance signal the mic pre wants. Some transformers used in passive DIs have fewer or more windings, changing the output a little, but that's what Preamp gain controls are for.

As with everything to do with sound, you should always listen and choose the best sounding option - of course the best sound is sometimes obtained by putting a passive instrument through a passive DI - but typically an active DI is the best solution for a passive instrument (and vice versa).

Interesting, I thought it worked the opposite way
I thought the DI was supposed to raise the level of the instrument in order to feed the micpre more.. That the output of the passive instrument is too weak...

Is it possible to go directly from bass to micpre with a single jack-xlr cable...?

[seriousfun]

BTW the Wikipedia article linked-to above is wrong in a few ways.

A DI certainly does perform impedance matching, and an active DI does not by its nature have a preamp (at least not one that brings the signal up to line level) - an active DI's amplifier circuitry is there to present a stable, appropriate impedance to the following Preamp.

[seriousfun]

Originally Posted by Sugarman

Interesting, I thought it worked the opposite way
I thought the DI was supposed to raise the level of the instrument in order to feed the micpre more.. That the output of the passive instrument is too weak...

Is it possible to go directly from bass to micpre with a single jack-xlr cable...?

A magnetic-pickup, for example, has more output than a condenser microphone. A mic pre is designed to take the tiny signal from a microphone and provide lots of gain to feed a line input (EQ, Compressor, A/D or tape recorder, for example).

If you connect directly to a mic Preamp (without a direct instrument input), the instrument will be at the wrong level and the wrong impedance - hence, the need for at least a transformer so the low-impedance input of the Preamp doesn't load the instrument pickup, causing poor, non-linear sound.

[Sugarman]

Originally Posted by seriousfun

A magnetic-pickup, for example, has more output than a condenser microphone. A mic pre is designed to take the tiny signal from a microphone and provide lots of gain to feed a line input (EQ, Compressor, A/D or tape recorder, for example).

If you connect directly to a mic Preamp (without a direct instrument input), the instrument will be at the wrong level and the wrong impedance - hence, the need for at least a transformer so the low-impedance input of the Preamp doesn't load the instrument pickup, causing poor, non-linear sound.

I see... Thank you - nice info!

[Blast9]

Hmm... Someone in the know really should log in to wikipedia and edit the errors. That's whats so cool about that site!

Whaddayathink seriousfun?