DI box - active or passive? where/how much?

[Clarky]

Just bought a VT bass pedal and I prefer the tones out of it to my MXR M80. Only shortcoming is the VT Bass has no DI capability. On an earlier thread it was suggested to me that I could simply link the VT to a DI box. Anyways, Thomann sent me their latest sale brochure today and it shows a very cheap passive DI box (the Millenium DI-E [url="http://www.thomann.de/gb/millenium_die_dibox_passiv.htm"]http://www.thomann.de/gb/millenium_die_dibox_passiv.htm[/url] which is less than a tenner) and they list a number of more expensive active DI boxes (some of which run to over £100. Here is their summary page of DI boxes [url="http://www.thomann.de/gb/cat.html?gf=di_boxes&oa=pra)"]http://www.thomann.de/gb/cat.html?gf=di_boxes&oa=pra)[/url].

So my questions are: is a passive DI box what I need, or an active one (I am an electronics numpty)? Is a cheapie perfectly sufficient? And does anyone have a recommendation of something appropriate and where I could buy it (maybe the Thomann cheapie is the one???)?

Many thanks Clarky

Edited March 20, 2010 by Clarky

[JackLondon]

I think that if you want to maintain that VT tone you'll be better with having a passive DI, can't help you on the price as I don't have to use one!

[BigRedX]

IMO If you don't want to change the sound just capture it you can't beat a good passive transformer based DI box.

[url="http://www.studiospares.com/DI-Boxes/Emo-DIBox-Single/invt/402950"]I use these[/url].

[Clarky]

[quote name='BigRedX' post='780795' date='Mar 20 2010, 02:19 PM']IMO If you don't want to change the sound just capture it you can't beat a good passive transformer based DI box.

[url="http://www.studiospares.com/DI-Boxes/Emo-DIBox-Single/invt/402950"]I use these[/url].[/quote]
Thanks guys. Out of interest, BigRed X, what does the EMO (£84) do that a cheaper passive DI box wouldn't? Is it to do with purity of sound transfer? Exuse my ignorance but I really know NOTHING about these things!!!

Edited March 20, 2010 by Clarky

[BassBod]

A good passive DI will do the trick and retain your sound..but don't get a cheapie! Its all about the quality of te transformer, apparantly. I use a Radial Pro1, you can get them used sometimes. A bit pricey but its the audio equivalent of a spare tyre.

I've seen a modification on Talkbass that adds a DI out to the VT, so that may be worth looking at.

Glad you like it!

[Clarky]

[quote name='BassBod' post='780806' date='Mar 20 2010, 02:30 PM']A good passive DI will do the trick and retain your sound..but don't get a cheapie! Its all about the quality of te transformer, apparantly. I use a Radial Pro1, you can get them used sometimes. A bit pricey but its the audio equivalent of a spare tyre.

I've seen a modification on Talkbass that adds a DI out to the VT, so that may be worth looking at.

Glad you like it![/quote]
Thanks BassBod - is this the Radial you use? [url="http://www.thomann.de/gb/radial_engineering_pro_di.htm"]http://www.thomann.de/gb/radial_engineering_pro_di.htm[/url] About same price as the EMO recommended by BigRed X, so I guess this is the price point for top quality passive DI boxes

Edited March 20, 2010 by Clarky

[BassBod]

Yes - that's the one.

I forgot to say...the VT has a really high output (if you crank it) so I wouldn't use an active DI. When they run out of headroom the distortion is very unpleasant, but when a transformer/passive DI has had enough it will be much more forgiving (you might even like it!).

[BigRedX]

A good passive DI has as few components as possible between to inputs and outputs and high quality transformers to ensure that the DI output is as uncoloured as possible. If the design of the passive box is good there is no headroom for it to run out of. Most active DIs unless they are very expensive will colour the output sound to some extent. Some are even design to do this in an manner that is designed to enhance the sound of the instrument being DI'd. If you want purity of sound then passive is the way to go.

The EMO units are virtually bomb-proof. I have 2 single-channel ones that I bought second-hand about 15 years ago and judging from the state of them they'd been gigged hard before I got them - most of the lettering had almost worn off - I've gigged them pretty hard myself since then and they're still going strong. From an interfacing PoV they look slightly more versatile than the Radial one, with inputs for Instrument, Line and Speaker level (although I wouldn't connect the speaker input to anything more powerful than a 100W amp) and loop throughs for the instrument and speaker inputs.

[Clarky]

[quote name='BigRedX' post='780864' date='Mar 20 2010, 03:41 PM']From an interfacing PoV they look slightly more versatile than the Radial one, with inputs for Instrument, Line and Speaker level (although I wouldn't connect the speaker input to anything more powerful than a 100W amp) and loop throughs for the instrument and speaker inputs.[/quote]
Again please excuse my ignorance but would I need this versatility if all I am doing is using this to convert my VT Bass pedal to a DI signal? Cheers BigRed X

[BigRedX]

Mo probably not. If the output needs to go somewhere else other than the DI you need a pass through socket that outputs the signal at the same level as the input. An earth lift switch is a must-have though to stop the DI connection creating a humming earth loop.

[Clarky]

[quote name='BigRedX' post='780871' date='Mar 20 2010, 03:49 PM']Mo probably not. If the output needs to go somewhere else other than the DI you need a pass through socket that outputs the signal at the same level as the input. An earth lift switch is a must-have though to stop the DI connection creating a humming earth loop.[/quote]
That s very clear, thanks again

[Silent Fly]

[quote name='JackLondon' post='780785' date='Mar 20 2010, 02:06 PM']I think that if you want to maintain that VT tone you'll be better with having a passive DI(...)[/quote]
[quote name='BigRedX' post='780795' date='Mar 20 2010, 02:19 PM']IMO If you don't want to change the sound just capture it you can't beat a good passive transformer based DI box.(...)[/quote]
[quote name='BassBod' post='780806' date='Mar 20 2010, 02:30 PM']A good passive DI will do the trick and retain your sound..(...)[/quote]
[quote name='BigRedX' post='780864' date='Mar 20 2010, 03:41 PM']A good passive DI has as few components as possible between to inputs and outputs and high quality transformers to ensure that the DI output is as uncoloured as possible.(...)[/quote]

I disagree but I may be totally wrong of course.

Can someone of you guys tell me the reasons behind what you say? (Technical reasons, experience, A/B blind tests...)

[quote name='BassBod' post='780823' date='Mar 20 2010, 02:55 PM'](...)
I forgot to say...the VT has a really high output (if you crank it) so I wouldn't use an active DI.(...)[/quote]

Again, I think the opposite is true but I may be wrong. Could you explain why an active DI wouldn’t be suitable for strong signals?

Edited March 20, 2010 by Silent Fly

[Adrenochrome]

FWIW I'll be using a cheap Behringer active DI tonight. I think it sounds fine and is reliable.

[JackLondon]

My experience of using passive DI comes from the studio when I was recording last year, the bloke had an active box with which we recorded one track and when I listened back it wasn't a good sound, we plugged a passive box and it made it sound more natural to me, with active box there's was that little amount of boost which was even visible on the recording software, it couldn't have been playing dynamics as it was using an 8 second loop that was recorded on my effect! I'm sure Max that with proper design a quality components you use your boxes are clean, many manufacturers however tend to cut corners here and there which means that what it says on the tin isn't what it actually does!

Cheers
Jack

[Phaedrus]

Could be some useful info here:

[url="http://www.radialeng.com/re-jdi-faq.htm"]http://www.radialeng.com/re-jdi-faq.htm[/url]

or here:

[url="http://www.radialeng.com/re-j48-faq.htm"]http://www.radialeng.com/re-j48-faq.htm[/url]

or in any of the Radial J- or Pro-series DI Product FAQs:

[url="http://www.radialeng.com/re-products.htm"]http://www.radialeng.com/re-products.htm[/url]


I'll be getting one of these once the gig money from the new band starts rolling in :

[url="http://www.radialeng.com/re-pro48.htm"]http://www.radialeng.com/re-pro48.htm[/url]

Compact, active, phantom-powerable, claimed to have plenty of headroom for active basses (both my bain basses are active), Radial quality & reputation, decent pricepoint.


Mark

[dannybuoy]

I use a Radial JDI with my VT, probably the best passive DI out there but the cheaper ProDI should suffice. Radial designed their own transformer for this model rather than using the more expensive Jensen one used in the JDI.

A drawback with passive DI boxes is that they don't have a very high input impedance so aren't the best solution for plugging in a passive bass directly as you'll lose a little bit of treble.

I think the drawbacks of active DIs (mainly only the cheaper ones?) is that the electronics could colour the signal or distort on high input signals like the bypass of a Boss pedal can. I've used a soundman's cheap active DI live where a sharp 'tic' could be heard every time I hit a loud note, so I pulled out my JDI and job done!

[Clarky]

[quote name='dannybuoy' post='780980' date='Mar 20 2010, 05:56 PM']I use a Radial JDI with my VT, probably the best passive DI out there but the cheaper ProDI should suffice. Radial designed their own transformer for this model rather than using the more expensive Jensen one used in the JDI.

A drawback with passive DI boxes is that they don't have a very high input impedance so aren't the best solution for plugging in a passive bass directly as you'll lose a little bit of treble.

I think the drawbacks of active DIs (mainly only the cheaper ones?) is that the electronics could colour the signal or distort on high input signals like the bypass of a Boss pedal can. I've used a soundman's cheap active DI live where a sharp 'tic' could be heard every time I hit a loud note, so I pulled out my JDI and job done![/quote]
Thanks Danny and other contributors. Based on an unscientific survey (2 votes for Radial, 1 for EMO) I have ordered a Radial (the more basic ProDI). Will be moving on my MXR M80 as a result, which should cover the cost of this :-)

Edited March 20, 2010 by Clarky

[BassBod]

My comments are based on my experiences - I often use active DI's (a Raven Labs, active with a transformer??). I have had problems with active DI's clipping and producing very harsh distortion on gigs, but only either with high output active basses or when driving from a line output on a preamp. The VT has enough output to drive a power amp, so I'd expect that to overload most active DI's if you weren't careful.

[escholl]

[quote name='Silent Fly' post='780947' date='Mar 20 2010, 05:26 PM']Can someone of you guys tell me the reasons behind what you say? (Technical reasons, experience, A/B blind tests...)[/quote]
Because passives use those transparent, uncoloring components, transformers. Clearly. As opposed to the flat response, low noise, low distortion, stable input impedance presented by an active input stage, which couldn't possibly sound transparent.

It sounds to me like a lot of people (no offense intended guys) who just haven't set their gain stages correctly, and thus are overloading the input. Or are just using cheap actives. Or both.


[quote name='dannybuoy' post='780980' date='Mar 20 2010, 05:56 PM']A drawback with passive DI boxes is that they don't have a very high input impedance so aren't the best solution for plugging in a passive bass directly as you'll lose a little bit of treble.[/quote]
More than that -- running a passive bass direct into a transformer will present it with a load that has resistance, capacitance, and inductance. Also known as a filter. And not just for highs, depending on how it reacts with the inductance, capacitance, and resistance of the bass pickups and cable, it will reshape the frequency response all over.

[Silent Fly]

[quote name='escholl' post='782582' date='Mar 22 2010, 05:15 PM'](...)
It sounds to me like a lot of people (no offense intended guys) who just haven't set their gain stages correctly, and thus are overloading the input. Or are just using cheap actives. Or both.(...)[/quote]
This was my first reaction as well. I may be missing something though.

[quote name='escholl' post='782582' date='Mar 22 2010, 05:15 PM'](...)More than that -- running a passive bass direct into a transformer will present it with a load that has resistance, capacitance, and inductance. Also known as a filter. And not just for highs, depending on how it reacts with the inductance, capacitance, and resistance of the bass pickups and cable, it will reshape the frequency response all over.[/quote]
I agree.

Having said that, the [i]frequency response reshape[/i] may be pleasant to hear.

[BassBod]

One point I should have been clearer on - the active boxes that have "spiked out" on me have been cheaper (but generally excellent) DI's running from line outputs (sometimes active basses as well) and on phantom power. I suspect its the cheaper designs running on phantom that causes the problem. I use active DIs for upright bass with absolutely no issues....but for amped up rocknroll I opt for a transformer...or a Sansamp!

[Silent Fly]

This is how I see it.

A DI should not add anything to the sound. In other words, it should not “have a sound”. If it does, it becomes a signal processor with XLR output. When the DI contribution to the signal is distortion is obviously a bad thing.

Apart from the usual characteristics that apply to every product (e.g. cost/performance, customer service, reliability…) the most important thing about a DI is its transparency. How this is achieved is not that important. There are excellent DIs that are transformer based, other that are equally good that are transformerless.

There are several web sites that explain the pros and cons of active and passive DIs but all of them agree on one thing – the choice of active/passive should be based on the application and requirements.

So… does the strength of the signal matter? Does it enter in the “application and requirement” equation? It does but indirectly.

DIs perform two separate functions: convert the impedance and convert the connection from unbalanced to balanced.

/// impedance conversion
Converting the impedance is the most important function of a DI. Guitar and basses are designed to be connected to high impedance devices. If they need to be connected to a recording desk with low impedance input, they need an interface.

If another device (e.g. a pedal) is placed between instrument and recording interface, the impedance conversion may not be necessary because [i]the majority of pedals convert the impedance[/i]. The instrument sees the high impedance of the pedal, the pedal see the low impedance of the recording interface.

/// unbalanced to balanced conversion
The vast majority of the recording interfaces and mixers have XLR-balanced input. Because DIs main purpose is to be connected to mixers it makes sense to have a XLR-balanced output.

Balanced connections are designed to minimize electromagnet noise but in a studio environment where electromagnetic fields are minimal this is rarely an issue. Moreover, cables are usually short this also reduces the likelihood of picking up electromagnetic noise.


If the signal strength becomes an issue, because for instance some device clips, it is very unlikely that the signal is coming from a guitar or a bass. Almost certainly the signal comes from an active device. Active devices can be connected directly to a mixer or recording interface without a DI.

[i]If a DI clips with a guitar or bass, it means only one thing: the DI cannot perform its basic function. [/i]

/// DI clipping: active vs passive
Active DI clip for one reason: the peak of the signal amplitude is too close to the [i]internal[/i] power supply level. To increase the headroom, the DI needs a higher voltage power supply. (Just to be clear it doesn’t mean that you can take a DI design to operate a 9V and connected it to an 18V power supply to increase the headroom – the DI needs to be designed to operate at higher voltage).

Passive DIs don’t have power supply so in theory cannot clip …and they don’t. In practice something more complex happens.

Passive DIs are based on transformers. A coil converts the input signal in a magnetic field. The magnetic field, through a metallic core, is send to another coil. This second coil converts back the magnetic field in an electrical signal.

Everything works nicely (more about it later) if the signal is below a certain level. Above a threshold, the magnetic core looses its linearity and start distorting the sound. The deviation from linearity takes place gradually and for weak signals the distortion is more a colouration but if the signal is too strong the colouration becomes audible.

With an active DI, to remove the clipping is necessary increase the power supply. For a passive DI the non-linearity can only be removed using special (and often expensive) materials that have limited non-linearity.

/// Why I prefer active DIs
I have nothing against passive DIs. They work nicely and they have the great advantage of operating without power supply.

When I described the way the transformer inside the passive DIs works I assumed an almost theoretical environment. Apart from the non linearity of the transformer coil, there is also to consider the fact that transformer coils interact with the pickups creating a filter that inevitably change the frequency response (non necessarily in a bad way).

If properly designed and built, active DIs can address all the issues of passive DIs with the advantage of being more compact, easier to repair and more suitable for tweaking if required.

/// Sansamp VT Bass and DIs (active or passive?)
Providing a DI is necessary, this is a case where [i]a good quality[/i] passive DIs can perform as well as an active DIs.

The reason is not the fact that passive DIs do not clip. The main reason is that the impedance conversion has already being performed by the pedal. The DI input is connected to an active device and the only thing it does is convert the unbalanced line to balanced.

[Phaedrus]

Thanks for that SF - lots of clear detail in there.


Mark

[EmpInfNed]

 

[Baloney Balderdash]

This might help some (more specifically the video of the specific post in the thread linked to):

 

Edited April 7, 2023 by Baloney Balderdash