The CATO design features a differential tube input stage with
adjustable gain that is DC-coupled to a class-A single-ended MOSFET output
stage. LINK TO
SCHEMATIC This output stage has a very low output impedance
providing high current drive capabilities. MOSFET devices possess electrical
characteristics that are similar to vacuum tubes and thus enhance the sonics of
the driver stage.
The input stage is a differential amplifier with a constant
current diode supplying the cathode current. The two anodes, which produce two
out of phase signals, are converted to a single-ended signal, using a current
mirror circuit. An 2SJ79 P-channel MOSFET, is used in a common-source mode as a
class-A single-ended SE output stage and its drain resistance has been replaced
with a second constant-current source to increase its gain and linearity.
This current source is derived from a 2SK216 N-channel MOSFET. We have
included a dc nulling servo circuit therefore eliminating the need for a huge
DC voltage blocking cap on the output.
A gain select switch allows you to easily choose the perfect
gain setting and is supplied with 3 gain settings of 3dB, 6dB and 10dB. Of
course these settings can be easily modified by changing a few resistors.
CATO linestage uses a +/- 24Vdc anode supply and 6.3Vac for the
heaters. The 24Vdc supply is provided by onboard voltage regulators and the
tube's filaments are powered-on all of the time with just the dc voltage
switched at turn on. Power is provided by two low noise encapsulated toroid
transformers.
One of the more interesting features of our CATO design is its
use of the ECC86/6GM8 low voltage tube. The 6GM8 falls into the car radio
tube category from the 1950's and 60's with specifications rated for linear
operation provided with anode voltages supplied by a car battery, i.e. 12
volts. The 6GM8 can be operated at higher voltages and in fact sounds better
at these elevated potentials and thus we operate CATO from a + 24V supply.
The 6GM8 is an exceptional tube featuring very low noise and low microphonics,
but don't let the 6GM8 tubes scare you, the CATO also operates extremely well
with the ECC88/6DJ8, 6922 and its other variants. You will be amazed at just
how good these tubes sound run at low voltages. The 6922 actually measures
lower distortion in this circuit.
CATO2 VACUUM TUBE LINESTAGE
Our new CATO2 Linestage has been designed with affordability
in mind yet we have spared no expense when it comes to quality. Its DC-coupled
all class-A operation makes for a very sweet sounding pre-amplifier and its
single-ended low impedance output stage provides more bass slam and dynamics
than you will find in any other vacuum tube linestage!
As is typical with all of our products, CATO is
built with nothing but top quality components including an ALPS volume
control, precision 1% metal film (non-inductive) resistors, film and
foil polypropylene signal caps, ceramic tube sockets and Teflon coated
OFC hookup wire, - all housed in a nicely built hardwood chassis.
The CATO kit includes everything required
to build a complete and functioning line level preamplifier. A detailed
step-by-step assembly manual is included and all parts are individually
packaged and labeled reducing the chance for error.Don't want to assemble a kit? No problem,
let us build it for you! Just add the Assembly Fee option to your
shopping cart and we will do all of the work. Plus, factory assembled
units a warranted for a period of three years. Choose from 1 to 5 inputs. If choosing the
one input version then no selector switch and knob are included.
Options with 2-5 inputs include the additional rca input connectors,
extra Teflon hookup wire and a super high quality Grayhill selector
switch and knob.Class-A DC-coupled tube amplification with
single-ended (SE) mosfet output stage. See left sidebar for circuit
details.
Features Include:Class-A DC-coupled tube amplification with
single-ended (SE) mosfet output stage. See left sidebar for circuit
details. Servo circuit nulls all DC offset voltage
eliminating the need for large output capacitors. 3 selectable gain settings allows you to
adjust CATO's output level for your system's sensitivity.Stylish re-designed hardwood chassis with
brass cone footings and non- resonant lexan covers.Available with 1 to 5 inputs. Why pay for
five sources if you don't need them! What's Included:The CATO kit provides everything needed to
build a complete line level preamplifier including the hardwood chassis
with hardware, connectors and hookup wire, two CATO amplifier modules,
one power supply module plus a shielded power cord. Tubes are not
included so please order a set from the right sidebar.
The hardwood chassis is supplied
fully assembled but unfinished so pick your favorite oil, lacquer or poly
finish to bring out the beauty of the wood. The CATO shown in our photos is
contructed of Tigris hardwood panels with Cocobolo corners. Most of our kits
will be supplied with Ebony corners as it is much easier to apply a finish.
CATO's chassis dimensions are 2.0"(55mm) height x 13.5"(343mm) width x
10.0"(254mm) depth.
PRICING AND
OPTIONS
Cato Kit with One Input $685.00
Cato Kit with Two Inputs $755.00
Cato Kit with Three Inputs $770.00
Cato Kit with Four Inputs $785.00
Cato Kit with Five Inputs $799.00
For a Factory Assembled Model add $180.00
THE SALE PRICE ASSEMBLY FEE FOR A FACTORY ASSEMBLED UNIT IS
$144.00. Click the ADD TO CART Button to add this Option:
Factory Assembled Models are warranted for 3
years.
DON'T FORGET - TUBES ARE
NOT INCLUDED. ORDER HERE ==>
TUBE SELECTION:
The CATO Linestage design is based around the ECC86/ 6GM8 and
6DJ8/ 6922 variants. Recently the tube sellers on EBAY have pushed the NOS 6GM8
tubes to exorbitant prices so we have redirected our focus on the readily
available 6922. We have some NOS 6GM8 stock remaining - see below. Please note: Tubes ARE NOT Included with your linestage
purchase so please choose from our selection below.
TUBE PURCHASES ARE NOT DISCOUNTED
DURING OUR SALE EVENTS
