Swart AST Head II Manual

AST HEAD Mk II & Cabinet Tech Info

Specifications

• All Tube circuit ~18-20w twin 6V6 High Class A Biased AB

• Can be powered by 6V6 or 6L6 Family (no KT-66)

• Tube stage Master Volume that is bypassable for Purists

• Cathode "AUTO" Biased (no need to bias)

• JJ 12AX7(3) - JJ 12DW7 - JJ or TAD 6V6 - JJ or TAD GZ34

• Tube Rectification ~ GZ-34 or NOS 5Y3 (See below)

• Sub NOS 5Y3 for earlier breakup/increased compression

• 100% Tube Reverb & Tremolo ~ Quality Spring Tank

• Hi/Lo Inputs for better PU Output matching

• Hand wired point to point ~ Made in USA

• Standby Switch ~ Amp warmed up|extends tube life

• Carbon Comp Resistors for BEST TONE

• Mallory, Sprague and JJ Caps, selected for Application

• Finest silver tinned cloth & Teflon covered wire

• Twin Outputs to run two Cabinets

• 4 / 8 / 16 Ohm selectable ~ Rear Panel Switch

• IEC 1A Slow-Blow 20mm | 500ma Long Fuse

• Dedicated 2 button foot switch included

• Extra Large Rubber Feet for Vibration/Protection

• As all Swarts, optional Export Transformer/Plug ~ $30

• Solid, finger-jointed Cabinet ~ Lacquered Tweed

• 1x12 cab standard with Mojo BV-25 ~ Options available

• Head Dimensions: 17 7/8W x 9D x 10H ~ 19lbs

• 1x12 Cab Dimensions: 24W x 11D x 16 7/8H ~ 26lbs

NOTES

TREMOLO in MV Mode
When in MV mode and you have the Master Volume at 3 or below, the TREMOLO, which is bias regulated, will be weaker. It's best to have the master volume at 4 or above for proper tremolo reproduction.
External Speakers
With the AST Head mk II, you can run one or two speaker CABS. Please make sure to set the impedance correctly to handle the load. For instance, if running one cab, always place in OUTPUT 1 and set the impedance to the cab's rated impedance. If running TWO cabinets from outputs 1 & 2, make sure you set the impedance to the combined "parallel" load of both cabs. For instance, if CAB 1 is 8ohms and CAB 2 is 8 ohms, you would set the load to 4ohms. If cab 1 is 16ohms and CAB 2 is 16ohms, set to 8ohms. You can mismatch impedance somewhat, but try to get closest to load. Of note, you can get a nice result running a 16ohm load from an 8ohm out setting for a bit more compression/sweetness when pushed.
NO power at all? CHECK IEC socket FUSE
see below

- Click above for full size-

The heart of the matter - AST Head II Chassis with all tube circuitry - Click above for FULL view. See additional 4th 12AX7 dedicated to the Master Volume Circuit, totally bypassable for the purist. This unique Master Volume was developed to quell the potential leeching of TONE by the typical MV implementation. Swart would not marry a MV with the AST until a solution was found. We feel this is perhaps the best MV implementation out there.

~ Click above and below for full high resolution views ~

External Speakers
With the AST Head mk II, you can run one or two speaker CABS. Please make sure to set the impedance correctly to handle the load. For instance, if running one cab, always place in OUTPUT 1 and set the impedance to the cab's rated impedance. If running TWO cabinets from outputs 1 & 2, make sure you set the impedance to the combined "parallel" load of both cabs. For instance, if CAB 1 is 8ohms and CAB 2 is 8 ohms, you would set the load to 4ohms. If cab 1 is 16ohms and CAB 2 is 16ohms, set to 8ohms. You can mismatch impedance somewhat, but try to get closest to load. Of note, you can get a nice result running a 16ohm load from an 8ohm out setting for a bit more compression/sweetness when pushed.

**NOTE: There is an extra Fuse located above the IEC socket. If your mains fuse is intact and amp won't power up, check this fuse by prying cover with flathead. You'll see the fuse plus one spare. Only use Slo-blow of equal value.

AST Head (2 Fuses).............IEC 1A Slow-Blow 20mm | 500ma Long Fuse

Tube chart and info is on BACK of rear head panel.

Click above for AST Head II ~ Tubes can be changed from the front
Sub 6V6~6L6 with NO BIAS HEADACHE.

Click above for insane SUPER close-up at 1900px ~ HIGH BANDWIDTH

**Click above to view AST Head II & Cab from back

**NOTE: There is an extra Fuse located above the IEC socket.
If your mains fuse is intact and amp won't power up, check this
fuse by prying cover with flathead. You'll see the fuse plus
one spare. Only use Slo-blow of equal value.

Tube Chart and Serial # Located on back of Head inside Panel (4 screw Removal)