~Toft ATB 24 upgrade CAL gives new life to a classic work horse.
In a world comprised of home budget studios and digital project workspaces, there’s rarely room to necessitate the voluminous, large format mixing desks of yesteryear. That said, more and more options for approaching an analog workflow hit the market every month to accommodate those users who just can't quite seem to shake their grip on analog summing and signal processing and give into the hype behind their digital counterparts - and for good reason! While experts may say that the gap is quickly narrowing, DAW's and plug-ins still can't quite grasp the warmth, clarity, summing, comfort, style, or preordained coolness of a classic analog desk. The good people at Toft Audio Group get that!
Toft's (ala Malcolm Toft of Trident Recording Studios) introduction of the Toft ATB series consoles, affectionately named and modeled after the Trident 80B (ATB is a homonym for Eighty-B), have taken some of the original flare of its namesake (primarily the widely popular 4-band EQ circuit) and combined it with a fairly neutral mic pre, abbreviated signal routing solutions, and even the option for digital I/O (optional card slot) that typically characterize smaller digital board options. Add in the classic aesthetics of wood fixtures via the stained wood end-caps and arm-rest, as well as some VU meters in the master section, and you've got a retro vibe created in your studio space that sets the pace for rendering some vintage-inspired jams. And while the ATB series boasts all these things, it does so with a smaller footprint and a price more accessible to the average "Joe".
We here at Creation Audio Labs got a chance recently to dissect the Toft ATB, in all its elegant simplicity, and improve upon it with a slew of our trademark updates.
We give special thanks to the owner - Franklin, TN’s own songwriter/producer Derek George, who asked us to help refurbish and update his desk. Derek has produced five #1 hits with artists such as Randy Houser, Joe Nichols, and Chase Bryant.
One of the biggest, immediate issues our resident tone-wizard and vice-president of research & development, Alex "Skip" Welti, found, was that the voltage rails feeding power to the channel strips were directly connected to the circuit without rail resistors. This leaves a virtually wide-open gate between your board and potentially fatal power-anomalies which could short out the power supply or leave your channel strips burnt to crisp; not to mention your session postponed indefinitely. Rail resistors are low ohm, flameproof resistors meant to burnout like a fuse in case a capacitor or IC chip short circuits. Then instead of blowing the main fuse in the power supply which takes down the entire console, you get a brief puff of smoke and only the offending module(s) goes off. Additionally, the rail resistors in conjunction with filter capacitors have the added benefit of reducing crosstalk between channels through the power supply. Making this simple addition was a relative cinch. Just a matter of severing a few power traces and bridging the gap between the voltage rails and each channel strip PCB with some delicately placed, heat-shrink insulated resistors. Then applying some higher value filter capacitors nearby to decouple the channel from the power supply more effectively which reduced crosstalk between inputs through the power rails.
In addition to the fuse resistor upgrade, we were able to overhaul the input channel strips, subgroups, and master section with lower noise, lower distortion, higher slew-rate op-amps. The PCB's for the Toft we worked on came pre-loaded with IC sockets for easy, solder-free replacement of chips. The use of rail-to-rail opamps gives an extra few volts of headroom, but we also modded the power-supply to boost the +/- 16V output up to +/- 18V, for even more headroom. There is no adjustment for this, so we had to recalculate a pair of resistors in the power supply. Altogether, the headroom was increased by about 6.5V peak-to-peak after accounting for the additional fuse resistors.
For the mic pre, we found the Toft ATB was using the Burr Brown INA217. This is a really good IC and widely used, but at first glance doesn’t leave much room to be modified. A possible chip “update” would be the THAT Corporation THAT1510 chip. Also, we noticed the Toft was using 12V Zener Diodes to ground on the mic input for protection… Zener Diodes are a source of noise and easily burn out when faced with a big surge spike. We replaced the Zeners and cut a few traces to add silicon diodes connected to the power rails for protection. These are lower impedance, so offer better protection with less self-noise. As well, this method of protection increases the input headroom from 12V to the 18V rails. In addition, we added generous power decoupling caps around the mic pre with the goal of lowering the noise floor as much as possible. We also replaced the stock, generic capacitors through-out the signal path with the same ultra-low ESR (equivalent series resistance) electrolytic capacitors that we employ in our Soundcraft Ghost mod, but with a few alterations to the values. In several places we were able to eliminate coupling capacitors because the new op-amps have very low DC offsets.
Overall the mod gave the Toft ATB tighter phase response, punchier bass, better definition and clarity. It all also reduced crosstalk between channels, added depth to the stereo field for wider panning effects, as well as lowered the noise floor and increased the headroom.
Be sure to call us at 615.884.7520 or email us at info@CreationAudioLabs.com if you're interested in upgrades to your Toft or similar board today!
Guitarist/performer, songwriter, live sound engineer, audio post production specialist, repair technician, husband, father - these are just a few of the hats resident tech Michael Frazier wears. Michael graduated with a BA in Audio Production in 2009 from the Art Institute of Tennessee - Nashville, and has been working with Creation Audio Labs in their console maintenance/modification department since then, apart from his work at Gibson guitars from 2012-2015