Direct Boxes for Bass?

  • Thread starter Thread starter jokerone
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rob aylestone said:
I beg to differ. The first DI boxes were designed for exactly this purpose. To break the feed from guitar to amp to allow another piece of kit to 'sniff' a bit of it to use for recording or more often PA. It was only later that a few designs appeared that did not have the link sockets. It also explains the need for the ground lift switches, which otherwise serve no purpose, as there is no duplicate ground path to break.
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Oooer! Fight! Fight! Heh!
Interesting one this, I shall try to get a definitive answer.

There are many myths surrounding DI boxes.... The practice of using two passives "back to back" to feed an amp on the studio floor from a guitar in the control room led to the myth that a guitar amp needed to "see" a very high impedance source for re-amping.
Bllx of course.

Dave.
 
I'm going to start using my new Radial PZ Pre for feeding my bass DI signal into my US800. :) Couldn't hurt (although I've been happy enough with the signal quality). The PZ also works like a DI box, so I'll now be able to split my electric guitar into the amp feed and DI to the US800 for recording both amped and unamped signal at same time - always had to decide whether to record dry (and PodFarm) or amped guitar before.
 
ecc83 said:
+1 Ash'. The point about an "always active" pedal is especially moot. This trick can be used for all manner of instruments to give a low 'ish Z feed in fact feed the pedal into a cheap passive DI and you largely get over the level problem and get a balanced out.
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I'm not completely sure what you're trying to say there, but the voltage step down is a characteristic of the transformer in the DI (It's what they do!) and mostly independent of both source and load. I know this from both theory and practice. You're much better off psuedo-balancing out of the pedal if you've got a long enough run that it will make a difference and/or need to break a ground loop.

The 50ft cable. This is not doing the "damage" that might be thought when feeding the very low (compared to 1meg gitamps) input Z of a desk. Yes, a low Z robs HF from an INDUCTIVE source like a pickup but it compensated to some extent for cable capacitance*. But yes! You probably formed a quite complex LCR network there that serendipitously resulted in a good sound.
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The roll off from cable crapacitance is not really affected by load-Z, no. It's the high impedance of the source that makes it an issue. It's probably true, I suppose, that even with 50' runs the cutoff frequency is too high to be significant since the Low Z input and pickup inductance are already rolling off well below that, but...

When you say "serenipitous", it sounds like I didn't know exactly what I was doing and wasn't expecting exactly the result I got. ;)
 
Farview said:
Yes, it can split the signal, but its main purpose is to turn the instruments signal into the type of signal a mic preamp expects to see.
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No. Its main purpose is to present a higher impedance load to the pickups than the mic pre alone, with the added benefits of reducing the effective source impedance so you don't lose quite so much treble on the longer run from DI to wherever and balancing the signal to help pick up less noise along that same run. The preamp will take what it gets and amplify it without any real expectations. Wish I could find a chick like that!
 
Are we all really going to argue about which little part of what a DI box does is the one true reason for using it?
 
"Serendipitous".

Well maybe you had tried it before and knew it would do what you wanted. I just did not think you had sat down and worked through all the component values and cable capacitances to arrive at a frequency response! If so? Have a ceegar!

And I am sorry but the load is important ref the HF loss since it is the bottom half of an attenuator and the lower it gets, for a given source Z the less effect the capacitance will have.

Re the buffer feeding the passive DI? The transformers are usually only about 10:1 so the guitar pups "see" about 150k for a standard mic input. This load robs a bit of level but the pedal does not. The pedal however is not balanced so stuff it into a passive DI....

Not a lot in it I grant you but sometimes, every little helps.

And yes Jay. I'm done. Great respect all round.


Dave.
 
It depends on what you want out of a DI. There are DIs that just put your bass down on hard drive as is, and there are DIs that allow you to shape the tone on the unit. I personally use a BBE Bmax bass preamp. It's technically a DI, but with some standard hardware tone shaping options like an eq section with parametric mids, a shitty compressor, and a sonic maximizer (both the sonic max and the comp can be bypassed thank God).

Other options are the MXR+80, Sansamp bass driver DI, Behringer BDI21, Darkglass B7k, AMT BC-1 etc... I have only used the sansamp and thought it worked fine. Demos of the other preamps sound pretty good as well though, even the behringer.

Then you have your straight no frills DI box like the countryman type 85, Radial pro DI etc...

What you plug into those is what comes out at the other end.


My personal vote is for tone shaping, but some like to do it in the box after the fact and that's fine as well.
 
Ok, so if I have an amp (lets say an ampeg PF-500) with an XLR line out from the amp head.

(1) Running the XLR line out to the mixer will give me all the tone from the amp head (treble/mid/bass) without being amplified? (True/False)

(2) a DI like the sansamp bass driver's treble/mid/bass are redundant for a situation like described in question 1? (True/False)

(3) If I own an amp head with with an XLR line out, a DI is still useful to split the signal into the mixer (True /False)

thanks for nursing my stupidity... :)
 
Guitargodgt said:
It depends on what you want out of a DI. There are DIs that just put your bass down on hard drive as is, and there are DIs that allow you to shape the tone on the unit. I personally use a BBE Bmax bass preamp. It's technically a DI, but with some standard hardware tone shaping options like an eq section with parametric mids, a shitty compressor, and a sonic maximizer (both the sonic max and the comp can be bypassed thank God).

Other options are the MXR+80, Sansamp bass driver DI, Behringer BDI21, Darkglass B7k, AMT BC-1 etc... I have only used the sansamp and thought it worked fine. Demos of the other preamps sound pretty good as well though, even the behringer.

Then you have your straight no frills DI box like the countryman type 85, Radial pro DI etc...

What you plug into those is what comes out at the other end.


My personal vote is for tone shaping, but some like to do it in the box after the fact and that's fine as well.
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I think you may have answered the questions I just posted. thanks!
 
jokerone said:
Ok, so if I have an amp (lets say an ampeg PF-500) with an XLR line out from the amp head.

(1) Running the XLR line out to the mixer will give me all the tone from the amp head (treble/mid/bass) without being amplified? (True/False)

(2) a DI like the sansamp bass driver's treble/mid/bass are redundant for a situation like described in question 1? (True/False)

(3) If I own an amp head with with an XLR line out, a DI is still useful to split the signal into the mixer (True /False)

thanks for nursing my stupidity... :)
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1. I have only ever done that with a SVT3 pro. The line out gave the preamp of that head direct so eq and all that was there. The problem with not being amplified is a lot of these heads need a load on them or you fry em. I always er on the safe side and keep a load on any head I am doing this with (plugged into a speaker cabinet).

2. Kind of. It's pretty much the same thing but obviously different preamps will sound different.

3. Yes I think so. Sometimes the blend sounds good as well. I do it on guitar as well so I have something to use for editing later if I need it (a DI signal is spikey in appearance and you can see the transients better for reference if you need them).
 
Guitargodgt said:
1. I have only ever done that with a SVT3 pro. The line out gave the preamp of that head direct so eq and all that was there. The problem with not being amplified is a lot of these heads need a load on them or you fry em. I always er on the safe side and keep a load on any head I am doing this with (plugged into a speaker cabinet).

2. Kind of. It's pretty much the same thing but obviously different preamps will sound different.

3. Yes I think so. Sometimes the blend sounds good as well. I do it on guitar as well so I have something to use for editing later if I need it (a DI signal is spikey in appearance and you can see the transients better for reference if you need them).
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thanks.
So I can't run the head free of the amp via the pre-amp XLR line out without damaging it? that sucks.. :(
 
ecc83 said:
"Serendipitous".

Well maybe you had tried it before and knew it would do what you wanted. I just did not think you had sat down and worked through all the component values and cable capacitances to arrive at a frequency response! If so? Have a ceegar!
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Well, you know, I didn't figure out the exact rolloff point, but I wasn't really shooting for one. Kinda just eyeballed it and said "That oughta work!" ;)

And I am sorry but the load is important ref the HF loss since it is the bottom half of an attenuator and the lower it gets, for a given source Z the less effect the capacitance will have.
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Yeah, I dig that.

Re the buffer feeding the passive DI? The transformers are usually only about 10:1 so the guitar pups "see" about 150k for a standard mic input. This load robs a bit of level but the pedal does not. The pedal however is not balanced so stuff it into a passive DI....
Click to expand...
When I was running from my pedals into a passive DI into a mic pre I ended up adding a pretty silly amount of gain at the other end of the cable, and adding a lot more noise than necessary. In the studio nowadays I just run unbalanced from a pedal to a line input. Live I'm running a pseudo-balanced line from the pedal to a mic pre set at unity. Both give much better noise performance than I was getting before.


To the OP - it completely depends what you want to do with the direct signal, but if you're happy with using the EQ on the amp head AND it has a Master Volume AND that MV doesn't affect the level of the Line Out, then you don't really need anything else. Unless there's a ground loop. Is there a ground lift switch for that Line Out.
 
jokerone said:
thanks.
So I can't run the head free of the amp via the pre-amp XLR line out without damaging it? that sucks.. :(
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Try running it and seeing if the master volume has any effect on the signal you get from the DI output. Sometimes the power amp section doesn't matter and you can keep the head volume pretty much off while you use the preamp section.
 
ashcat_lt said:
To the OP - it completely depends what you want to do with the direct signal, but if you're happy with using the EQ on the amp head AND it has a Master Volume AND that MV doesn't affect the level of the Line Out, then you don't really need anything else. Unless there's a ground loop. Is there a ground lift switch for that Line Out.
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Running two likes (one amp EQ and one direct has its advantages for recording it sounds like) But I have an Active Jazz bass with eq knobs, and the amp has eq knobs, so it doesn't sound like I need to spend the extra $$$ for a sansamp with more eq knobs. Just a simple DI sounds like it will work. thanks.
 
Guitargodgt said:
Try running it and seeing if the master volume has any effect on the signal you get from the DI output. Sometimes the power amp section doesn't matter and you can keep the head volume pretty much off while you use the preamp section.
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From what I read in the manual the volume doesn't effect the XLR line out. (could be I mis-read it).
http://www.ampeg.com/pdf/PF_heads_OM.PDF

I didn't see anything about DO NOT play without LOAD in the manual. Just the normal legal CYA (do not play underwater, in a electrical thunderstorm under a tree, etc.. ) :)

Actually, their manual is great compared to Sear's Radial Arm Saw manual. (i.e, Do not saw off your own hand.. ) :rolleyes:
 
Honestly, with an active bass, all you really need is a Y cable. (Insert caveat about possible ground loop)
 
jokerone said:
Ok, so if I have an amp (lets say an ampeg PF-500) with an XLR line out from the amp head.

(1) Running the XLR line out to the mixer will give me all the tone from the amp head (treble/mid/bass) without being amplified? (True/False)
Click to expand...
Yes, minus the sound of your speaker cabinet, obviously. Some heads have a switch on the line out that switches between 'pre' and 'post'. If switched to 'pre', you will just get the signal from the bass guitar. If it is set to 'post', you will get all the EQ and such from the amp.

jokerone said:
(2) a DI like the sansamp bass driver's treble/mid/bass are redundant for a situation like described in question 1? (True/False)
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The Sansamp, specifically, is actually an amp simulator. So it would be redundant, since you have an amp. Other things that Guitargodgt calls DI's have compressors and EQ's that may, or may not, be better suited than the amp line out for the sound you are trying to record/send to the PA.

jokerone said:
(3) If I own an amp head with with an XLR line out, a DI is still useful to split the signal into the mixer (True /False)
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It depends. Normally the XLR line out would be what you send to the mixer. If you want to send another signal to the mixer, for example: one without the amp sound on it, you could use a DI for that.
 
jokerone said:
thanks.
So I can't run the head free of the amp via the pre-amp XLR line out without damaging it? that sucks.. :(
Click to expand...
Sometimes you can, sometimes you can't. It depends on the amp you are using. Read the manual to find out. You can (almost) always have it plugged into the cabinet and turn the master volume all the way down. On most bass amps I've tried, that doesn't turn down the direct out.
 
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