Sep 12th, 2015
Modified ART TPS II
It appears that ART actually did take my advice and used some of my design concepts in the TPS II Preamp. The ART TPS II is a well built and flexible stereo mic or instrument preamp with one control to vary the tube gain, harmonics, and equalization characteristics. The original TPS II system is a bit too heavy handed on many settings and too obvious when processing the preamp signal. I correct this to an even higher quality sounding device with a more usable euphonic nuanced character. For $220 PLUS RETURN SHIPPING COST, my modification makes this unit even more tempered across the fifteen presets and creates a nicer, fine, adjustable “tube” sound. This machine is beautifully built and nicer looking than even some of the really fancy stuff on the market.
Most designs create an obvious tube character by high gaining or overdriving a tube to cause a little harsh or soft fuzz quality. The modification I do creates a consistent, nice second harmonic distortion without overdriving the tube, in that the tube will create the preferred harmonic enhancement at low sonic levels, more natural and subtle sonic details in the instrument's sound. The timbre of acoustic guitars or even complete mixes passed through the unit will be thickened or brightened depending upon which of the fifteen settings is selected at the front control. In fact, the tube gain is lessened, thereby improving the noise floor and dynamic headroom. In some settings, an Output Protection Limiter (OPL) engages for a true, soft “tube limiting” of the sound. This is a less obvious effect but perfect for acoustic preamping and reduces the chances of harsh clipping effects.
In the original TPS II design, some settings are intensely loud while others are obviously too low. My modification causes the settings to be more gradual in coloration (from super clean to dry to warm to slightly gruff) and the output control and metering to more honestly reflect the actual signal level through the tube. Now the user can overdrive the system for guitar preamping effects if desired (but not to be used as outright tube fuzz box). I also add another control, neatly installed on the right side of the unit, to gain up the tube harmonics at any chosen preset to further stress the tube’s sonic character. Another trick allowed by my redesign is to patch out of the first channel back into channel two, stacking different tube characters for a really obvious effect. The added on control now actually can force the tube to create more or less adjustable enhancement of in phase or out of phase second harmonics. Harmonies of in phase enhancement are perceived as “warmer,” veiled, velvety and out of phase harmonic are perceived as drier, slightly present or slightly aggressive to make bass tones more thick or dry.
OPL setting: has a tube limiter effect which can be obvious if driving the tube hard watch the tube meter level. This circuit has also been modified to create a nicer tube limiting or dynamics, similar to vintage tube compressor of the 1960, 1970. This compression effect works when signal levels cause the tube level meter move into the red, odb level, mode effect with complex music, less so with solo instruments.
Use of tube voicing encoder: This is the crucial control for general tone quality, to make bright, warm sound effects (the manufacturers' description is basically correct). However when pointer is set for lower settings (9 o'clock to 3). The added on harmonics enhance control at far right now acts as an in phase or out of phase, forcing the tube to produce nice 2nd harmonic, maybe 2% or so at each end of the setting, with the control centered, very limited enhancement.
When the encoder is used in upper settings (with higher gain design) then the enhance control acts as less to max effect. Possibly creating really obvious tube character at the far CCW position, again very music dependent.This modification is the result of previous experimentation with the MPA preamp and opinions from the other studios, musicians and years of use by myself. I spent months plugging in various mics and recording acoustic guitars, hand drums, and vocals.I changed various parts in the circuit, running a spectrum analyzer each time to qualify the appealing kind of distortion desired. In this way I have voiced the tube harmonic character, equalization, and compression to truly be more likable in real world recording use. Popular demand also wants a unit where players can swap tubes for a supposed more favored sound, and indeed on this design changing the tubes can be effective.
ART has created a solid design to get this machine to be 75% great, but I wanted even more. More for me, more for you. I know of no other company that has done such a remarkably clever product as this. I can only thank them for an excellent foundation to build upon. And their willingness to talk with me and take my suggestion to build such a device, they do listen to their customers!Now more TPS info. The tube gain control I add on the right of the machine can either enhance or lessen the tube character. It should be set to avoid red light clipping. The OPL setting has a tube limiter effect which can be obvious if driving the tube hard, so watch the tube meter level. You can now also plug an XLR +14dB professional line level signal into the mic input jack on the back panel and adjust the impedance control to match levels. Use the mic input on the front panel for microphone use.