Scratch djs generally use only two tracks so mixers are built around that. You won't find many scratch spec mixers with three channels (but they do have multiple inputs) and the top of the range gear is generally two channel. The reason for that is that a third channel isn't really necessary and complicates the electronics - in a scratch mixer each channel gets a load of configurations which then combine with the crossfader setup.
An adjustable crossfader changes how quickly the sound fades in and out - the fader curve. This curve can be a V or rounder or square - its a bit difficult to explain without listen to it in action but it affects your sound sharply. You want it to be as adjustable as possible. You also need a seriously good replacable (or indestructible) crossfader as they take a helluva lot of abuse.
You can get a Pioneer DJM 707 for funny money if you look around and its spec is excellent!
# 2 Channels
# 4 Line Inputs
# 2 Turntable Inputs
# 2 Switchable Phono/Line Inputs
# 2 Fader Start Inputs
# 3 Band EQ per channel(-26dB to +6dB)
# EQ On/Off switch
# 1 Mic Input (Neutric / 1/4" combo)
# 2 Band Mic EQ
# Transform switches
# Reverse switches
# Non-Contact Crossfader (eq. to Rane TTM 56)
# Adjustable Channel Fader curve
# Independantly Adjustable Cross Fader Curve
# Adjustable Cross Fader Lag
# Adjustable Cross Fader Tension
# Headphone Monitor auditioning
# Session inputs / outputs with level control
# Reinforced headphone jacks
# Stereo Send / Return
# RCA & XLR Outputs
I see
Djstore.co.uk is selling it for 300 quid but I can get it at 150 (NEW!) here in Poland so there must be a good deal available in the UK.
From what I've heard of it - it really is an
incredible scratch mixer. Seems Pioneer wants to promote its 909 which is basically the same but has an effects board and a display - at 700 quid so they're selling the stock of 707s off cheaply.