Groove TubesLLC...the American Tube Company, since 1979.1543 Truman Street, San Fernando, CA91340, 818-361-4500 fax 818-365-9884

www.groovetubes.com

!! PRESS RELEASE !!Soul-0 30R, 6L6GE Class A Series

Groove Tubes is pleased to announce the new Soul-o 30 series of all tube amplifiers whichare hand built in our San Fernando, California factory.

This new S30 series features a new preamp design and a totally new control, which wehave named Pre Bias, that allows the player to adjust the bias voltage on the preamptubes..thereby changing the basic sonic signature of the design from maximum clean toheavy overdrive. Tube amps previously always had this voltage set by the amp designerand is an important feature of the amps’ sonic signature. Our idea was to allow a playerto modify this preamp bias voltage to “customize” the gain and touch factor of his ampfor the various types of guitar pickups on the market today. It can allow a hot guitar to

have more (or less) clean headroom, or a more vin-tage guitar to get heavy shades of tube distortion.The Pre Bias options are Low, Medium and Highand are located directly next to the input.

The S30’s power section design is a cathode biased(or self biasing) Class A design dedi-

cated for use with the 6L6 Pentodefamily of tubes. Class A givesadded warmth and more touchfactor to the amp, and is com-mon to design’s using thesmaller EL84 tubes such as theVox AC30. However, earlyFender and other USA madeamps from the 50’s usually had aDuet of 6L6’s in Class A mode.The legendary Led Zeppelin 1 &2 albums were recorded byJimmy Page with just such adesign, a Supro combo that alsohad a 15” speaker. It was thatinspiring amp tone that also

motivated us to offer this amp in a 1x15” combo design.It is also available in a 12” combo and a Amp Top as well.

The other features: all tube passive EQ section, Pull Boost on the Gain control and longspring Reverb (both these features footswitchable), GT’s transparent FX loop with Mixcontrol, and selectable impedance OT taps for 8 and 16 Ohms. Available from April 2003 inselected GT amp dealerships throughout the world.

A 30 watt Class A Dual 6L6 tube amp with PREBIAS control and tube reverb

Thank you for choosing a GrooveTubes amplifier, and welcome to thegrowing list of artists and friends who shareour lust for true tube tone.

We’ve more than 25 years acquiring theknowledge to design and build your S30amp....so please just take a few minutes toread this guide to it’s operation and learnthe theory behind the unique S30 design.

Construction Details

1 - All components are hand soldered,with over 100 hand soldered connectionson the tubes sockets alone.

2 - All transformers are custom designedand made exclusively for Groove Tubes.

3 - GT S30 amps are all tube, Class Acircuitry designed specifically for use withthe 6L6/KT66 family of power tubes.They come with our own GT6L6GE USAtubes unless otherwise specified.

4 - We use only double sided, doublethick PC boards with double thick traces.We use chassis mount type power tubesockets hand bolted, hand soldered, andthen hand wired to the PCB. PCB andpoint to point construction, best of bothworlds!

5 - Each amp is hand built to order.There are more than 18 hours of skilledhand labor in each S30 amp we build!

6 - There is no particle board in any ofour cabinets, only solid core USAplywood.

Of course all these details cost more, butyou can really hear the difference!

The Preamp StageThe S30 preamp stage design uses fivedual triodes in a Class A design, eachtube performing multiple functions in thecircuitry. The basic preamp controls arePREBIAS, Gain, Pull-Gain +10dB boost,Bass, Middle, Treble, Presence, Reverband Volume.

Our exclusive and innovative PREBIAScontrol is located before the first Gaincontrol, and allows you to literally modifythe bias voltage for both the V1 and V2preamp tube stages. These are the mostinfluential stages to the overall tone andfeel of your amp. In all other amps, thisvoltage is fixed by the designer.

Players have been paying 100’s ofdollars to “mod” their preamp stagevoltages. Now, this “mod” feature is built-in to the S30 preamp. A lower PREBIASvoltage setting will give the preamp stageless output for the same given inputsignal. Hence, more dynamic headroomfor a cleaner tone. The LO PREBIASsetting can also be used to compensatefor hotter guitar pickups, making the ampless “touch sensitive” which is bettersuited for pounding rhythm guitar where“overloading” is not usually desirable.

Likewise, for lower output single coilpickups, switching to a MED or HIPREBIAS position increases gain,expands the frequency bandwidth (morelows and highs) as well as making it moretouch sensitive so as to produce a“hotter” lead tone with noticeably moregain. YOU can shape the pramp frotheguitar pickups and style of playing as theneed arrises.. an instant “hot-rod mod!”

PREBIAS control options: LO offers the most clean headroom, aflatter, more accurate tone and response.Great for calming down those high outputHumbucker type pickups.MED increases the voltage, adding gain,fattening tone, and softening attackdynamics. It provides more compressionas the the player picks harder.HIGH gives the most voltage for the V1and V2 preamp gain stages and reallymakes the overdrive character take off.Thus, more touch, gain and compression.Great for most lead applications or aheavily distorted, yet tight, Metal rhythmtone. Usually this setting will be desiredfor the lower output, single coil pickups. These 3 very different PREBIAS settingsare actually doubled by the possibility to“pull boost” regardless of which PREBIASsetting you are in. This +10dB boost canbe achieved by simply pulling the Gainknob or with the optional footswitch.

NOTE: The V4 and V5 preamp tubes can be alteredbetween using a 12AT7 or 12AX7 tube. Using a 12AT7 in V5 (the power tube drive section)will give a cleaner drive with more dynamics andsparkle. A 12AX7 in V5 adds more drive, a bit fatterand will be louder with more distortion.Much the same attributes and differences can beachieved in V4 by alternating between the 12AX7 and12AT7 dual triode tubes. The S30 leaves the factorywith a 12AX7 in both V4 and V5 for the maximumo v e rdrive and compression. You can safelyexperiment by trying a 12AT7 in either V4 or V5position. Your S30 has a 9 pin straightener attachedto the side of your cab, which can hold an extra tubeand should also be used when changing preamptubes. This keeps your pins straight and clean andyour sockets tight! See tube layout for exact locationof V1 thru V5 preamp tubes.

NOTE: there is also a “secret” gain trim pot locatedunderneath the chassis near the transformer. Thisscrewdriver adjusted internal pot sets the preampgain for the S30 in the non-boost mode (will notchange the Boost position).This can balance the preamp gain to your guitarpickup (more gain for the single coils and less for thehumbuckers). We usually set this control in themiddle from the factory. If you choose to adjust itfurther, please turn of f the amp and also use aninsulated screwdriver for safe operation.

“Passive” Tone ControlsThe S30 tone controls are the Passivetype, similar to those used in the

Blackface era Fender amps. Many amps made today use Activetype tone controls, which have aseparate gain section for each toneband which literally “suck tone”from the preamp. That’s why wedon’t use them. Passive controlsuse a common tube gain stage toboost the entire frequency range,then divide the Bass, Middle, andTreble with passive filters to shapeyour tone. Passive tone controlsare more musical, but are alsointeractive with one another.To get the most out of passive tonec o n t rols, start listening with all

Groove Tubes Soul-o Series Guitar Amplifier Operators Guide

The Soul-o 30TM

TM

S30-15C 15” Combo

S30-15 Top + EX212 Cab

controls at the 12 o’clock position, wherewe “pre t u n e ” your amp here at thefactory. If you want more bass, either: a)Crank up the Bass control; or b) Lower theTreble control then compensate thevolume loss (or gain) by increasing (ordecreasing) Gain and/or Volume controls.Passive controls share a common gainstage, so turning any one of them fully up(or down!) diminishes the effect of theothers. Should you want more “push” or“drive” from the preamp, try setting all 3tone controls at the 3 o’clock position andadjust the EQ from there. This adds moretouch sensitivity to the preamp. Find adrier tone and feel by setting the tonesection to 9 o’clock and adding back toneas needed.NOTE: The S30 preamp design is like the FenderBlackface era amps and more linear than the Marshallor earlier Fender Tweed designs. We follow this withan early USA style two 6L6 Class A output designcommon to all amps from the 50’s. We added anoptional high gain preamp stage typical of the “Metal“amps via the selectable PREBIAS control and Pull-Boost feature. To our knowledge, this is the first timethese designs have been combined in one amp.

The Presence ControlThis control interacts with the S30 poweramp stage, changing the high frequencyresponse. It alters the feedback loop ofthe power tubes. It adds highs to thepower stage, making it noticeably brighter.Use more Presence for an acousticallydead room, and less for live rooms.

The Reverb ControlOur tube driven long spring AccutronicsReverb is deep and harmonically rich andruns in parallel to the signal path so itdoesn’t sap highs as you crank it up.

The Power Amp StageYour Soul-o 30 Class A design is “selfbiasing” and can use any of 8 dif ferentmatched Duets of 6L6, KT66 or 5881Power Pentode (or Tetrode) tube typescurrently available from our GT catalog,and in any of the 1 to 10 power ratings.Changing power tubes (no bias

adjustments needed!) allows you toc u s t o m i z e your amp, dramatically changing thep o w e r, tone and response. Unless ordered otherwise, your S30 ampwill come equipped with our very best6L6, a matched Duet of the GT6L6GEtubes, our USA made Power Tetrode.NOTE: Always turn your amp off, and let the tubes cooldown, before changing tubes.

Speaker Impedance Selectorand Speaker Output JacksThe S30 custom wound outputtransformer has 3 secondary windings forselection between 4, 8, and 16 ohmsspeaker loads. Always try to exactlymatch the speaker load with theimpedance selector for maximum power.Use the #1 speaker jack for just onespeaker (or as a combo amp). The #2 jackis for adding a second speaker.NOTE: The #1 jack has shorting circuitry which turnsthe amp off if there is no speaker connected.

GT’s Parallel FX Loop w/ MixThis is the most tonally transparent FXloop possible. When properly set, our loopallows you to use any digital or analog FXunit mixed in parallel with your originalpreamp signal with no sacrifice of tone!Most oops are the Series type, so the FXunit is placed is between the preamp andpower stage...so the sweet, fat, tubepreamp signal is changed into a thin,wimpy transistor signal. We call this “thetone sucking transistor FX l o o psyndrome”, and the GT’s parallel loopwith Mix control is the cure!

To Operate:Set the FX unit 100% Wet and 0% Dry.Now, you can use the Mix control on theS30 rear panel to adjust the desired levelof the FX box. Usually, best resultshappen with a Dry:Wet ratio of 98%:2%. Another cool trick is to insert an ordinaryfoot controlled volume pedal in the signalpath returning from the FX to the “INPUT”of your S30 FX loop. This allows you togradually increase or decrease the FX l e v e lwithout changing the amps volume!

Soul-o Speaker CabinetsGT cabinets are “tuned” for guitar playing.They are fundamentally diff e rent than mostother guitar cabinets on the market today.We use 3/4” solid core plywood for thetop, bottom, back and sides but alightweight 5/8” plywood speaker baff l eb o a rd. We slant the baffle board upwardsfor better projection, and “tune” it’sresonance to optimize the tone for guitar.This design produces tighter bass notesavoiding the common “Big E String Mush”syndrome. GT guitar cabs come with our exclusive“Classic Clone”, USA made speakers.These are made to our specifications,inspired by our favorite 60’s era speakers.

www.groovetubes.com

Groove Tubes LLC - Custom Shop Products1543 Truman Street, San Fernando, California 91340 USA, Tel 818-361-4500 Fax 818-365- 9884 www.groovetubes.com

©2003 Groove Tubes LLC. All rights reserved. Groove Tubes, the “GT-in-a-circle” logomark, Groove Tubes Custom Shop, Groove Tubes Custom Shop Products, Soul-0 and S30 are trademarks andservice marks created and owned by Groove Tubes LLC. All other marks are the property of their respective owners. All specifications subject to change without notice.

Technical Specs:Input: 1/4 “ phone jackInput Level: -10 dB nominallyFX Input level: +4dB dB nominally

Preamp Tube SectionV1 - 12AX7V2 - 12AX7V3 - 12AU7V4 - 12AX7 or 12AT7V5 - 12AX7 or 12AT7V6 & V7 - 6L6/KT66

Power Section:30 watts RMS Class A type @ 4, 8. 16 OhmsOptional 6L6 Family types:GT5881, GT6L6R, GT6L6R2, GT6L6C, GT6L6CB,GT6L6GE, GT6L6S, GTKT66HP and GTKT66C

AC requirement: 117 VAC Standard100 VAC (special order), 230 VAC (special order)

H.T Fuse: 1 Amp Slo-Blo

AC Fuse: 100-120VAC@3A Slo-Blo 230 VAC = 1.5A Slo-Blo

Weight: S30-12C Combo 42 lbs.S30-15C Combo 44 lbs.S30 Top 32 lbs.

Options: Footswitch (Boost & Reverb) with 25’ cordSlip Cover with pocket for footswitch and cables

Soul-o 30 Amplifier Operators Guide

SIGNALPATH

6L6 6L6

V5 V4

V2 V1V3

FRONT PANEL INPUT

OUTPUTXFMR

POWERXFMR

SECRET GAINTRIM POT

for non boostmode only

TUBE LAYOUTV1 - 12AX7V2 - 12AX7V3 - 12AU7

V4 - 12AX7 or 12AT7V5 - 12AX7 or 12AT7V6 & V7 - 6L6/KT66

Speaker Cabinet Options

S30-12C - 1 x 12” speakerS30-15C - 1 x 15” speakerEX112 - 1 x 12” speakerEX212 - 2 x 12” speakersEX410 - 4 x 10” speakersEX115 - 1 x 15” speaker

Rear Panel Features