[linux-audio-user] Bass V-amp vs V-amp

[Cesare Marilungo]

Jean-Baptiste Mestelan wrote:

> Thanks Paul and Cesare.
>
> I use the jack input on my mixing console.
> The soundcard is a Delta 44, which has no preamps, and will accept a
> line-level signal.
>
> Sorry, but I've never really understood too well impedance issues :-/
>
> I just found this on the web, which suggests that an active bass
> (which I got) already has low-Z output, and therefore requires no DI ?
> http://www.whirlwindusa.com/ftp/tech/tech03.pdf
>
> A high impedance line that is interacting with outside electrical
> interference will act more like an "antenna" than a low impedance
> line. This problem can get worse as the cable gets longer. This effect
> is usually insignificant for a guitar or high-Z microphone plugged
> into an amp with a 15' cord but it can have a big effect if that same
> signal is sent 100' down a snake. These are reasons why a high
> impedance signal is almost always converted to low impedance with the
> use of a Direct Box (DI) before being sent long distances.
>
> Another reason for the use of a DI is that it takes a two conductor
> unbalanced line and converts it to a three conductor balanced line.
> This is a separate issue, not to be confused with impedance. It is a
> common misconception that all lines that use regular tip/sleeve ¼"
> guitar cord type connectors are high impedance. Not so. The output
> from a guitar that has a battery operated active preamplifier or
> pickup system will be low impedance in nature. So will the output of
> an electronic keyboard, guitar preamplifier or guitar effects
> processor. The signals are unbalanced but LOW impedance in nature.
>
> On 8/10/06, Paul Coccoli <pcoccoli at gmail.com> wrote:
>
>> On 8/10/06, Jean-Baptiste Mestelan <mestelan at gmail.com> wrote:
>> > I wondered if I such a  DI box would make sense in my recording 
>> setup :
>> > bass ---> mixing console ---> soundcard
>> >
>> > How useful would it be to insert a DI  ?
>> > bass ---> DI --> mixing console ---> soundcard
>> >
>> > A guitarist friend of mine has tried to convince me so, but I did not
>> > exactly grasp the whole argument ... I would have thought that the
>> > console already serves as a preamp, but I may miss some point ?
>> >
>> > Thanks for advice.
>> >
>>
>> It should sound better using a DI since it will match the impedance.
>> What type of input are you using on the mixing console?
>>
>> Borrow your friend's DI to hear the difference for yourself.
>>
You can always disable every other effect from the V-amp and just use it 
as a DI box. It serves this purpose for a guitar so it should go well 
with a bass too.

If you're going to buy a direct input box consider some better preamp 
that can add some warmth to the sound. I just got a ART Studio V3 Tube 
amp (it also has a small valve). You should find it around $75.

Anyway, while searching something else I've found this [wikipedia]:

[...] Another important sonic innovation was McCartney's discovery of 
the direct injection <http://en.wikipedia.org/wiki/Direct_injection> 
(DI) technique, in which he could record his bass by plugging it 
directly into an amplifying circuit in the recording console. This 
provided a vastly improved level of presence, power and fidelity over 
the old method, which was to record the bass through an amplifier with a 
microphone. [...]

http://en.wikipedia.org/wiki/Sgt._Pepper_Lonely%27s_Hearts_Club_Band


Cheers,

c.

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