Other than cost and not needing a power source, is there any advantage to a passive direct box over an active one? Is there a situation where a passive DI would be better?
Active vs Passive Direct Boxes
- Thread starter Chuck Simon
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Re: Active vs Passive Direct Boxes
In general you should focus on the impedance of the active vs passive models you are considering as it relates to the load the pickup will see (both normal and padded down for the active) and also the transformer. There is no good generalization between all active and all passive. A great passive DI will have the benefit of a quality transformer that a cheap active DI will not.
*EDIT* To be more clear, the best active DI's get closer to the best passive DI's for noise handling (From what I know) but the best passive DI's still win for absolute level handling.
In general you should focus on the impedance of the active vs passive models you are considering as it relates to the load the pickup will see (both normal and padded down for the active) and also the transformer. There is no good generalization between all active and all passive. A great passive DI will have the benefit of a quality transformer that a cheap active DI will not.
*EDIT* To be more clear, the best active DI's get closer to the best passive DI's for noise handling (From what I know) but the best passive DI's still win for absolute level handling.
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Re: Active vs Passive Direct Boxes
Passive DIs behave a lot better in overload (read: sound better). Remember that an active DI is really just a boutique pre-amp with fixed gain, attached to a line driver. Good active DIs can take the load off a piece of gear not accustomed to driving long cable runs, but regardless you're inserting another preamp and gain stage in the signal chain.
I would not look at "cost" as an advantage of passive DIs. You can build a cheap active that works pretty well, just like a cheap mixing desk. Passives are little more than a transformer, maybe with some circuitry for high pass and padding. Better transformer = higher price = better performance. There's a reason why the JDI costs $200. Passives may offer better durability and noise rejection as well, but you'd expect that out of a high performance DI.
Passive DIs behave a lot better in overload (read: sound better). Remember that an active DI is really just a boutique pre-amp with fixed gain, attached to a line driver. Good active DIs can take the load off a piece of gear not accustomed to driving long cable runs, but regardless you're inserting another preamp and gain stage in the signal chain.
I would not look at "cost" as an advantage of passive DIs. You can build a cheap active that works pretty well, just like a cheap mixing desk. Passives are little more than a transformer, maybe with some circuitry for high pass and padding. Better transformer = higher price = better performance. There's a reason why the JDI costs $200. Passives may offer better durability and noise rejection as well, but you'd expect that out of a high performance DI.
Re: Active vs Passive Direct Boxes
About the only area where a passive DI might be better is in a high RF environment, due to superior RF rejection of transformers.
JR
About the only area where a passive DI might be better is in a high RF environment, due to superior RF rejection of transformers.
JR
Re: Active vs Passive Direct Boxes
That is basically what I have always felt. If the instrument needs an additional preamp then I go active. if the instrument has its own preamp built in then I prefer to stay passive.
My active DI are a Radial PZ Pre or Fishman Aura which have additional tone shaping. Most of the time I am using passive i am using Radial Pro DI's
That is basically what I have always felt. If the instrument needs an additional preamp then I go active. if the instrument has its own preamp built in then I prefer to stay passive.
My active DI are a Radial PZ Pre or Fishman Aura which have additional tone shaping. Most of the time I am using passive i am using Radial Pro DI's
Re: Active vs Passive Direct Boxes
Thanks for the replies so far.
I have a few Countryman Type 85's and am totally pleased with their performance. I'm just wondering if a high quality passive offers any advantage over a high quality active, and if it would be worth while to pick up at least one.
Thanks for the replies so far.
I have a few Countryman Type 85's and am totally pleased with their performance. I'm just wondering if a high quality passive offers any advantage over a high quality active, and if it would be worth while to pick up at least one.
Re: Active vs Passive Direct Boxes
I have an active DI with an adjustable gain, which I refer to as my one and only 'cheap' DI.
an ebay find; new old-stock from a liquidated music store, paid $10 for it!
R~
I have an active DI with an adjustable gain, which I refer to as my one and only 'cheap' DI.
an ebay find; new old-stock from a liquidated music store, paid $10 for it!
R~
Re: Active vs Passive Direct Boxes
Some one used the magic word, pre-amp (although not exactly). The big thing to consider is what is in front of the DI. For instance if you are using a bass guitar that has an active pick-up than a passive Di will do just fine. Putting an active DI after an active pick-up may introduce some overloading problems. Unless you are the musician providing your own DI based on these principles than you should have both in your tool box. Also someone mentioned the Countryman Type85 active box- it's great. The only issue is unless you bought it new than the polarity could be either Pin 2 or Pin 3 hot. I bought one new and it's Pin3 hot (they make them this way) and I own 2 used (One Pin 3 and the other was modded for Pin 2). Does this matter? yes and no. if I tried to put them on a stereo key line it will work until that key player goes to a Wurly patch which is Dual Mono. At that point cancellation city.
Here's a great article that explains some of the mystery behind the active/passive debate...
http://www.prosoundweb.com/article/print/passive_or_active_which_to_choose
Some one used the magic word, pre-amp (although not exactly). The big thing to consider is what is in front of the DI. For instance if you are using a bass guitar that has an active pick-up than a passive Di will do just fine. Putting an active DI after an active pick-up may introduce some overloading problems. Unless you are the musician providing your own DI based on these principles than you should have both in your tool box. Also someone mentioned the Countryman Type85 active box- it's great. The only issue is unless you bought it new than the polarity could be either Pin 2 or Pin 3 hot. I bought one new and it's Pin3 hot (they make them this way) and I own 2 used (One Pin 3 and the other was modded for Pin 2). Does this matter? yes and no. if I tried to put them on a stereo key line it will work until that key player goes to a Wurly patch which is Dual Mono. At that point cancellation city.
Here's a great article that explains some of the mystery behind the active/passive debate...
http://www.prosoundweb.com/article/print/passive_or_active_which_to_choose
Re: Active vs Passive Direct Boxes
I have been using the Countryman Type85 DI's for about 15 years with many different active pick-up basses, acoustic guitars and keys, and have never had an overload problem. If that is the only issue, then I guess I have answered my own question regarding the need to add a good passive DI to my arsenal.
Kip, I never thought about the pin 3 vs pin 2 issue, so thanks for the tip!
I have been using the Countryman Type85 DI's for about 15 years with many different active pick-up basses, acoustic guitars and keys, and have never had an overload problem. If that is the only issue, then I guess I have answered my own question regarding the need to add a good passive DI to my arsenal.
Kip, I never thought about the pin 3 vs pin 2 issue, so thanks for the tip!
Re: Active vs Passive Direct Boxes
I spend a lot of time that seemed to work in three's of the years with guitars. So my work box (all gear is new with him and then goes into rental stock for my small company) has three Type 85's, Three Klark DI's- but I ended up using a pair of Stereo Whirlwind Di's and I'm fine with that set-up.
Most DI boxes have a pad built into their circuitry. An interesting note about the Klark DI (the ones with the Blue rubber) is that while they have a -30dB pad button on the outside they do not have a pad in their circuitry so it runs way hotter than what we are used to seeing as input stage. For instance, an acoustic guitar with a passive system might arbitrary need 30dB of gain on the pre-amp to bring it to a nice unity level. The same guitar on the Klark needs only 10dB of pre-amp gain. Another way to look at it is that the gain knob may be turned to 12:00 on the countryman to reach line level and it's already line level with the Klark. But the klark does have the beautiful xlr input for quick line checking.
Someone already mentioned Radial- the D2 is a great addition for a passive DI and it's stereo. All mic boxes need a good pair of stereo di's for those key's.
I spend a lot of time that seemed to work in three's of the years with guitars. So my work box (all gear is new with him and then goes into rental stock for my small company) has three Type 85's, Three Klark DI's- but I ended up using a pair of Stereo Whirlwind Di's and I'm fine with that set-up.
Most DI boxes have a pad built into their circuitry. An interesting note about the Klark DI (the ones with the Blue rubber) is that while they have a -30dB pad button on the outside they do not have a pad in their circuitry so it runs way hotter than what we are used to seeing as input stage. For instance, an acoustic guitar with a passive system might arbitrary need 30dB of gain on the pre-amp to bring it to a nice unity level. The same guitar on the Klark needs only 10dB of pre-amp gain. Another way to look at it is that the gain knob may be turned to 12:00 on the countryman to reach line level and it's already line level with the Klark. But the klark does have the beautiful xlr input for quick line checking.
Someone already mentioned Radial- the D2 is a great addition for a passive DI and it's stereo. All mic boxes need a good pair of stereo di's for those key's.
Re: Active vs Passive Direct Boxes
The pad in typical active DI (AFAIK) is generally in the output stage to drop the instrument level down to mic preamp level, or low enough to not overload a typical mic input. A pad on the input would conflict with the design goals of high input impedance and low noise.
Transformer DI have a turns ratio but this isn't literally a pad... no power is scrubbed off, but level and impedances are transformed based on the ratio.
I have seen specialty DI for speaker level signals but these were specialty items and not general purpose DI. The one I recall had unique frequency response shaping appropriate for mimicking instrument speaker's acoustic signature, not GP DI use.
So to answer the OP's question, an active DI could be overloaded by speaker level output, but for that matter a transformer DI designed to accept instrument level signals could also be saturated by speaker levels.
It is difficult for me to think of the entire DI category as something that could ever be covered by one design. Two, maybe even three sub categories.
JR
The pad in typical active DI (AFAIK) is generally in the output stage to drop the instrument level down to mic preamp level, or low enough to not overload a typical mic input. A pad on the input would conflict with the design goals of high input impedance and low noise.
Transformer DI have a turns ratio but this isn't literally a pad... no power is scrubbed off, but level and impedances are transformed based on the ratio.
I have seen specialty DI for speaker level signals but these were specialty items and not general purpose DI. The one I recall had unique frequency response shaping appropriate for mimicking instrument speaker's acoustic signature, not GP DI use.
So to answer the OP's question, an active DI could be overloaded by speaker level output, but for that matter a transformer DI designed to accept instrument level signals could also be saturated by speaker levels.
It is difficult for me to think of the entire DI category as something that could ever be covered by one design. Two, maybe even three sub categories.
JR
Re: Active vs Passive Direct Boxes
~~:smile: All professional active DI boxes that have pads have them on their input to keep a high level input from overloading the active circuitry. EG:
Not sure what gave you that idea.
~~:smile: All professional active DI boxes that have pads have them on their input to keep a high level input from overloading the active circuitry. EG:Re: Active vs Passive Direct Boxes
I'm no electrical engineer either an couldn't begin to speculate the order of components and their functions. I called Klark to find out why they put a -30dB pad swich on the box because I was having issue with the signal being too hot without the pad and way too low with the pad. I wished they had made it a -10 or -20dB pad because I felt -30dB was too drastic.
I was told by Klark that most DI boxes have at least attenuation pad. One built in to their circuitry to drop voltage for the pre-amp. Then if you chose you can buy a DI with an additional external pad to give you a little attenuation. The reason for the -30dB pad was that KT didn't put the internal pad in their circuitry (or if they did it's not as drastic as other direct boxes) to try to preserve the original source signal and to extend the dynamic range. That source signal could be an instrument or an xlr (if the mic or line needed a little transformer help)
I wish I knew more about the circuitry but the drawing of the Klark DN100 merely shows a transformer and a pad in front of the transformer triggered by an external bu
tton.
I'm no electrical engineer either an couldn't begin to speculate the order of components and their functions. I called Klark to find out why they put a -30dB pad swich on the box because I was having issue with the signal being too hot without the pad and way too low with the pad. I wished they had made it a -10 or -20dB pad because I felt -30dB was too drastic.
I was told by Klark that most DI boxes have at least attenuation pad. One built in to their circuitry to drop voltage for the pre-amp. Then if you chose you can buy a DI with an additional external pad to give you a little attenuation. The reason for the -30dB pad was that KT didn't put the internal pad in their circuitry (or if they did it's not as drastic as other direct boxes) to try to preserve the original source signal and to extend the dynamic range. That source signal could be an instrument or an xlr (if the mic or line needed a little transformer help)
I wish I knew more about the circuitry but the drawing of the Klark DN100 merely shows a transformer and a pad in front of the transformer triggered by an external bu
tton.
Re: Active vs Passive Direct Boxes
I have designed a few different DIs (two active while only one was a serious commercial product), though not lately.
I repeat IMO there could be 2 or 3 categories for what we now call DIs, based on their different applications.
The traditional design brief and primary rationale for an "active" DI, is high input impedance and low noise to buffer a passive guitar pickup, or passive keyboard pickup (like Rhodes, anybody remember them?). One metric that is valued for such DI applications is high input impedance to not load down the relatively high source impedance pickups (some active DI claim tens of MegOhm). Active DI can draw power from 48V phantom so intelligent use of that available voltage can provide more than enough signal headroom to accommodate passive pickups. FWIW If the passive pad is completely switched out of the input when not used, it is possible for an active DI to deliver adequately high input impedance when desired "and" have an input pad if needed.
If the guitar or keyboard has active electronics it will have a relatively low source impedance so can tolerate a low impedance pad, but likewise it can also drive a passive transformer DI directly. Passing signals through an extra active stage, when not needed is generally undesirable. (Note: for recording I lean toward using active instead of transformer stages for slightly better signal integrity. For live use transformers are desirable for ease of managing ground potentials and generally less parts to fail than with active circuitry.)
Using DIs to interface with speaker level signals, or hot line level outputs from active electronics is perhaps popular today, but an evolution away from the original intent of DIs. It sure seems to me that any sources that are too hot for a 48V supplied active DI, may not really need a DI.
But the customer is always right, and manufacturers will make and sell them pretty much anything they ask for. Modern DIs have evolved into a hybrid cross between preamp, ground isolation, un-bal to balanced, swiss army knife, doing whatever it takes.
JR
Not sure what gave you that idea.
View attachment 867
I have designed a few different DIs (two active while only one was a serious commercial product), though not lately.
I repeat IMO there could be 2 or 3 categories for what we now call DIs, based on their different applications.
The traditional design brief and primary rationale for an "active" DI, is high input impedance and low noise to buffer a passive guitar pickup, or passive keyboard pickup (like Rhodes, anybody remember them?). One metric that is valued for such DI applications is high input impedance to not load down the relatively high source impedance pickups (some active DI claim tens of MegOhm). Active DI can draw power from 48V phantom so intelligent use of that available voltage can provide more than enough signal headroom to accommodate passive pickups. FWIW If the passive pad is completely switched out of the input when not used, it is possible for an active DI to deliver adequately high input impedance when desired "and" have an input pad if needed.
If the guitar or keyboard has active electronics it will have a relatively low source impedance so can tolerate a low impedance pad, but likewise it can also drive a passive transformer DI directly. Passing signals through an extra active stage, when not needed is generally undesirable. (Note: for recording I lean toward using active instead of transformer stages for slightly better signal integrity. For live use transformers are desirable for ease of managing ground potentials and generally less parts to fail than with active circuitry.)
Using DIs to interface with speaker level signals, or hot line level outputs from active electronics is perhaps popular today, but an evolution away from the original intent of DIs. It sure seems to me that any sources that are too hot for a 48V supplied active DI, may not really need a DI.
But the customer is always right, and manufacturers will make and sell them pretty much anything they ask for. Modern DIs have evolved into a hybrid cross between preamp, ground isolation, un-bal to balanced, swiss army knife, doing whatever it takes.
JR
Re: Active vs Passive Direct Boxes
It makes a big difference, especially on an acoustic instrument. If the signal that hits the player's ears from the monitor is in polarity with the signal that hits his ears from his instrument, the monitor will reinforce it. If the polarity is reversed, it will cancel. Of course neither the reinforcement nor the cancelation will be absolute owing to the frequency and phase inaccuracies of the mic/pickup and the monitor. Once the reversed signal becomes loud enough, it "takes over" and gets the job done - but the monitor level will be a lot hotter than otherwise necessary.
It makes a big difference, especially on an acoustic instrument. If the signal that hits the player's ears from the monitor is in polarity with the signal that hits his ears from his instrument, the monitor will reinforce it. If the polarity is reversed, it will cancel. Of course neither the reinforcement nor the cancelation will be absolute owing to the frequency and phase inaccuracies of the mic/pickup and the monitor. Once the reversed signal becomes loud enough, it "takes over" and gets the job done - but the monitor level will be a lot hotter than otherwise necessary.