| 1) What sort of cab should I get for it , the guy who sold it to me
said I should get a cab rated at 200 watts for a 100watt amp , is this
true and if so , why ?
You may want to get matching Marshall Cabs to go with it. I'm
not too familiar with Marshall's offerings in bass cabs. Chances are
they're big and heavy like their 4x12 guitar cabs. Then again, you
might want to get a set of "Thiele" style cabs which would probably
be much smaller (more portable) as well as being more efficient and
tuned better. Thiele was an acoustic engineer that came up with a set
of formulas for designing cabs and porting them for proper tuning. His
ideas have been used by almost every major speaker manufacturer for the
last few decades. This type of cabinet is available in 1x18", 1x15",
4x10", as well as many other configurations. The most popular speakers
used in these cabs is Electro-Voice EVM-series speakers. A single 15"
EVM speaker is rated to handle about 200 watts. The most popular
configuration is to have 1 cab with a single 15" and another cab with
4 10" speakers. This works great if you're biamping, but also works
okay at full-range.
Bass players are usually looking for a nice clean sound out of
their gear (no distortion like guitarists), so you don't want to run
speakers that are rated for less power than the amp is producing. It's
also a nice idea to have some "overhead" so you don't end up slamming
the cone against the speaker frame when playing low frequency notes at
high volume (sharp attach). This is why it's nice to have 200 watts
handling capacity with a 100 watt amp. Also, 100 watt heads are rated
for 100 watts continuous rms power, but can peak out at as much as
double that amount.
The speaker configuration I listed above (1 15" EVM, 4 10" EVM's)
can handle about 400 watts of power. Most bass players are driving
their speakers with at least 200 watts of power (RMS). 100 watts is a
lot of power for guitar (too much in fact) but for bass, it's marginal.
2) The amp has an effects send on the back of it , just one jack plug ,
now I understand what an effects loop is but there's only one input for
this so how do I use it ?
If there is only one 1/4" jack for the effects loop, it must be
a stereo plug, where the tip is send, the ring is return, and the sleeve
is the common ground. Get yourself a y-cord that goes from 1 stereo plug
to 2 separate mono plugs. This type of setup is used on mixing boards
on what's known as channel inserts. It's basically like having an efx
loop on each channel of the mixer. It would be a good idea to get hold
of a manual to make sure this is the right configuration before spending
any money on a y-cord.
3) Theres a setting on the back which controls the impedence 4ohm ,
8ohm , 16 ohm . What should this be set on ( I know it relates to the
speakers but I dont know how to work it out)
This switch should be matched to the speakers you are using. If
you are using 1 speaker rated for 8 ohms, set the switch for 8 ohms.
If you are using 2 8 ohms speakers, chances are you are using them in
parallel, in which case the impedance would only be 4 ohms. There are
many other configurations of speaker cabs and it helps to be able to
figure out speaker impedance to make sure you're set right. If your
amp has 2 speaker outputs (ie: 1 main, and 1 ext. speaker jack) chances
are the 2 jacks are wired in parallel with each other.
Basically there are 2 types of circuits, series and parallel. In
a series circuit, impedances sum, so 2 8 ohm speakers in series will give
16 ohms. In a parallel circuits, impedances do not sum. The formula for
figuring out total impedance for a parallel circuit is as follows:
1
total impedance = --------------------------
1/R1 + 1/R2 + 1/R3 + (etc)
2 8 ohm speakers in parallel is calculated as such:
1 1
--------- = --- = 4 ohms
1/8 + 1/8 1/4
4 8 ohm speakers in parallel is calculated as such:
1 1
-------------------- = --- = 2 ohms
1/8 + 1/8 + 1/8 + 1/8 1/2
Confuzed Yet?? There are also circuits that are a combination of series
and parallel branches. series/parallel indicates that there are multiple
branches of parallel components that are in a series. It looks something
like this:
+ ---------/\/\/----------------/\/\/---------- -
| | | |
|--/\/\/--| |--/\/\/--|
In this case, figure out each parallel branch first then sum the branches
to find total impedance. A parallel/series circuit looks like this:
+ ---------/\/\/-----/\/\/-------------- -
| |
|--/\/\/-----/\/\/---|
In this case, sum the components in each branch (since they are in series)
then use the formula above to figure out the total impedance, since the
2 branches are in parallel with each other.
Most speaker circuits you come across will be parallel. The reason is
simple. Let's say you had 2 speakers in series. If one of the speakers
gets blown (voice coil becomes an open not a short) your amplifier now
sees an open circuit (no load). There will no longer be any sound output
from the speaker cabinet. Some amplifiers do not like running with no
load. Many tube amps that are transformer coupled can be damaged by
running them (even for a short duration) with no load. The same is true
for any solid state power amp that does not have output protection
circuitry.
If you have a parallel circuit and one speaker is blown (voice coil
is open) the rest of the circuit operates normally. The amp will see
a minimal change in overall impedance, but there is still sound output
and the amp does not get damaged by a no-load condition.
4) On the front there are 3 inputs , 1 , 1+2 , and 2 .What is the
actual difference between these 3 inputs.
It sounds like your amp has 2 channels and you have the option of using
either channel 1, channel 2, or both. It will take some experimentation to
determine what sounds best. The most straight forward approach is to use
one channel at a time. When you use 2 channels at the same time, the
channels can interact and you may end up getting some weird eq effects.
Then again, using both channels may provide some unique tones that you
can't get from one channel.
This may be more info than you were looking for, but it's important
to know how to figure this stuff out. Hope this helps.
Mark (techno-weenie)
|
| I don't want to burst your bubble, but if you're serious about
playing bass and gigging...
A 100watt bass amp is just not enough to do the job, IMHO.
100 watts is more of a "practice" amp than anything useful
for playing out. More common are the 200-250 watt range for small
clubs, GB stuff, etc. If you're going to be playing out on a regular
bass-is (sorry for the sad pun, but I couldn't help myself!!!),
you're going to need a larger amp. I have a little 100watt
Peavey for practice, but I would never use it for a club gig
unless it was an emergency. You will need to drive that Marshall
"very" hard if you want to hear yourself onstage. The harder you
drive your amp, the more distorted your sound will become.
You always want to have enough power available so that you
can get the clean tone and volume you want without driving the amp
too hard (not at all like a guitar amp).
The type of gigs you're doing is very important to you're choice
of amp. If you're playing fairly mellow stuff (folk, acoustic country,
GB-type trio, etc) you can probably get away with a small 200 watt combo
amp (many great little combo's from GK, Trace Elliot, Fender). If you're
playing rock, new country, metal, or anything else fairly loud, you're
going to need at least a 250 watt amp (minimum!!), if you want to be heard
onstage (with a 100watt amp you'll never hear yourself above a 50watt
Marshall guitar amp!!!) I highly recommend Galien-Kreuger 800RB or 400RB.
GK gives you the most bang for the buck, IMO (approx $580 for the 800RB
and $450-ish for the 400RB... thru mail-order). SWR, Carvin Pro500 or
Trace Elliot and Eden are also exceptional amps. Another option is to
buy a seperate power amp and pre-amp (the choice of more and more
bassists these days... considering this myself)
If you're playing a 5-string bass, you really need that extra power
available if you want a nice fat, clean low-B.
Also, a compressor is an absolute MUST for bass. It fattens up your
sound and smooths out the peaks (especially if you're into the
slap'n'tickle stuff).
Do you 'mic' your bass amp or do you use a DI ??(or both.. which I do)
I have a GK 800RB which I bi-amp; 100watts into a 4x10 cab and 300watts
into two 15" Thiele cabs (this is just for my "onstage" sound)
I run into a DI from my compressor as well as mic'ing one of the
10" speakers. This allows the sound-dude to run a clean channel
from the DI and add effects to the hi-end from the mic'd 10" speaker.
You want to avoid adding effects to the low end, it makes your sound
very "muddy". Many newer amps give you both a hi- and a low-end
effects send for just this reason.
I guess the bottom line (another sad pun) is that you always want
to have more power available than you need and that you want to
get the cleanest possible sound from your amp (add effects to taste
afterwards).
Just my 2 cents,
Billy_K
|
| Well, I'll have to put in (yet another) plug for the setup I've been using.
I've got a BBE (Barcus Berry Electronics) model 383 bass preamp, which has
3 band EQ, compressor, bi-amp capability, effects loop, and DI out, and only
cost $199 (mailorder). This feeds a Carvin PB150 amp for the high end
(150w, 1-10" speaker), and a Stewart PA200 power amp (200w mono) into a
Peavey 1-18" cab for the lows. This effectively gives me 350w of power,
which I've never even come close to using. The volume setting usually
stays below "3". For the price I really don't think you can beat the BBE
preamp, even with the Carvin. (My Carvin amp has basically the same preamp
section as the PB-15 straight preamp.)
Good luck, and leave the 50w Bassman amps for the guitarists. :-)
-- Sam
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