The Trinity Amps The Overdrive Special Design (OSD) was designed using similar principles as Howard Dumble in his ODS amplifiers but with less frills and lower power. His amps were used by used by Stevie Ray Vaughn, Eric Johnson, Carlos Santana, John Mayer, Robben Ford, Larry Carlton etc..
The OSD effectively has two foot-switched channels – Clean and Overdrive. The “spanky” clean preamp has a percussive nature is extremely inspirational. This preamp stays nice and clean and allows you to crank the power amp to achieve a highly percussive tone that taps into the compression and sustain of the power amp tubes.
The magic of the OSD comes from the Overdrive channel sound. The Overdrive channel provides a very smooth, sweet sustaining distorted tone. Activating the Overdrive circuit adds two additional gain stages and the result is an Overdrive that ranges from clean and harmonically rich to smooth and thick with ample saturation.
The amp uses using 6V6 output tubes in fixed bias mode. Since most on-stage set-ups are miked, 22 watts is both sufficient and surprisingly loud even for medium gigs, especially in this design. This lower wattage helps keep volume levels manageable and makes it very useful in a studio.
The preamp uses 3-12AX7 tubes for the Clean channel, Overdrive channel and the Phase Inverter. On the back of the amp there is a control to configure Overdrive Trim. The Overdrive channel and Pre-Amp Boost (PAB) are activated with a footswitch connected to the back of the amp. There is also a passive effects loop.
The amp has one input going straight to the first tube stage.
The first tube triode is followed by a passive tone stack with controls for Treble, Middle, Bass and Volume. There are two mini toggle switches on the front panel for Mid Boost and Rock/Jazz and the Volume control can be pulled out for a brighter sound.
Volume / Pull Bright – Volume adjusts the signal strength coming out of the tone stack, and going into the second tube stage. Think of this as a gain control primarily for your clean channel, but it will impact the Overdrive mode as well. The Bright switch is a push-pull located on the Volume control.
Mid – toggle switch increases the value of the treble capacitor in the tone stack to boost the midrange frequencies.
Rock/Jazz – toggle switches between a Fender-esque voicing (Rock) and a more hi-fi-type of voicing (Jazz) with less bass and gain. Rock has a fatter midrange and a deeper, spongier bottom end. Jazz tightens up the bottom end and adjusts the contour of the midrange, giving the amplifier more of a hi-fi response.
The Treble, Mid, Bass tone stack is followed by another triode stage. The resulting signal is either fed straight into the power amplifier (Clean channel) or into the Overdrive channel circuitry.
The output section uses a standard long tail pair phase inverter utilizing negative feedback. The phase inverter section of the amp also features a Presence control. This will add sparkle and clarity to your tone. Prior to the phase inverter there is a Master Volume control which is very effective at setting the overall volume of the amp.
The ODS is somewhat unique in that it uses a lot of filtering in the power supply. The large filter capacitors help keep the tone tight and focused because you don’t want loose sounding bass especially in Overdrive mode!
For the Overdrive channel to attain its very smooth, sweet sustaining distorted tone, it is carefully tuned in terms of gain and frequency response.
The Overdrive channel and Pre-Amp Boost (PAB) are activated with a two-button footswitch. Both the channel switching and PAB switching is done by two relays inside the amp.
The PAB accentuates midrange frequencies and attenuates low frequencies, making it great for cutting through during a solo. Engaged, you will also notice an increase in gain and distortion characteristics. This is useful for pushing the power section, lead boost and getting a bit of extra dirt from the amp.
The Overdrive channel is two cascaded triodes being fed from the clean channel signal. Gain is attenuated before and after each of the two triode stages in the Overdrive channel. This limiting of gain keeps the amp smooth and prevents over the top harsh distortion tones. The Overdrive channel features two front panel controls – Ratio and Level.
Ratio serves a sort of volume control for the overdrive channel.
Level adjusts the amount of gain, and in turn distortion in the overdrive mode.
On the back of the amp there is a Trim control that controls the amount of signal sent into the first stage of the Overdrive circuit. Lower settings is more touch-sensitive, lower gain sounds. Higher settings are more compressed, higher gain, and harmonically complex.
The OSD layout is well thought out. Due to its compact size, a heavy-duty printed circuit board is used which holds only the resistors, capacitors and relays. This hybrid design provides a compact and noise free design with excellent reliability. Parts selection, lead dress, voltages, tube selection and speaker selection are critical in getting a reliable and good sounding amp.
- Channels: 1
- Controls Main: Volume/Bright; Treble; Middle; Bass; Master; Presence
- Controls OD: Trim; Level; Ratio
- Power output: 22 Watts
- Preamp Tubes: 3 -12AX7
- Power Tubes: 2 – 6V6
- Rectifier: Solid State Diode
- Bias: Fixed
- Choke: no
- Speaker: per customer choice
- Outputs: 2
- Speaker Output: 4, 8, 16 switched
- Voltage Support: 115 V 60Hz – 240 V 50Hz
- Weight: Head: 20 lbs., 112 Combo 50 lbs.
- Switches: Rock / Jazz; Mid Boost
- Other: Footswitch for PAB (pre-amp boost) /OD; Effect In / Out
- Dimensions: Head: 15-1/2″ W X 7-1/2” H X 9-1/2 ” D
- Circuitry based on Dumble ODS #124 Skyliner
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All prices are listed in US dollars. Orders ship from Brighton, Ontario, Canada, applicable taxes not included. Specifications and prices subject to change without notice.
Trinity Amps Inc.
+1-613-438-5854 Canada EST
14656 County Rd. 21