TL Audio Hybrid

Capable of handling both mic or instrument signals, TLA's new dual‑channel, combined solid‑state and valve preamp aims to offer super high‑quality performance at an average price. Paul White assesses their double vision.

No matter what recording system you have, a good 'front end' can make the difference between mediocre‑sounding recordings and truly professional results. There are numerous processors on the market designed to fulfil this role, including some excellent solid‑state mic/line preamps at under £500, but decent valve‑based processors tend to be significantly more expensive. TL Audio endeavour to offer the best of both worlds by using tube circuitry where it counts and high‑quality solid‑state circuitry elsewhere in the signal chain. They can thus build high‑performance equipment at an affordable price.

Inside The Box

The dual‑channel TLA PA1 preamp takes exactly the approach described above, being based around hybrid tube/solid‑state circuitry. EF86 pentode valves are used in the mic/instrument preamp stage, where the mic inputs are transformer‑coupled and equipped with switchable 48V phantom power. The output from the preamp is then fed through two further ECC83 triode valve stages to provide a variable gain trim (±12dB) following the input‑gain selector. The last is switchable between 20 and 50dB in 10dB steps. On both channels there are switchable 12dB/octave filters offering HF and LF cut, the LF filter operating at 50, 100 or 150Hz and the HF one at 5, 10 or 15kHz. Channel A is also fitted with a phase‑reverse switch.

The PA1's output stage is solid‑state and provides a balanced XLR line‑driver output plus an unbalanced jack output. The XLR output will deliver up to +18dBu without clipping, so digital gear can be driven easily, and the jack output is ideal for equipment requiring a ‑10dBv unbalanced feed. A large rotary level control is fitted prior to the moving‑coil level meter, and there's a Nominal Gain switch on the rear panel to adjust the level of both outputs. At the lower setting of this switch the jack output operates at ‑10dBu and the XLR+4dBu, while the higher setting raises the level of the jack output to +4dBu and the XLR output to +18dBu.

Mechanically, this is a solidly built processor, with a stylish but purposeful look enhanced by circular, vintage‑style level meters. Its front panel is made from heavy, powder‑coated aluminium with machined recesses for the ventilation grilles and rack bolts. An amber LED shows when the valve stages are being driven fairly hard (giving an indication of the amount of coloration that can be expected) and a red peak LED warns of clipping. The instrument input jacks are located on the front panel and offer a suitably high impedance for use with passive electric guitars and basses. On the rear panel is a small toggle switch to turn on the mains supply, and a standard IEC mains connector, with accompanying selector switch to set the PA1 for 230 or 110V operation.

Studio Test

Conceptually, the TLA PA1 is very simple. Providing you're old enough to remember that moving‑coil meters show average signal levels rather than peaks, it's also very easy to set up. The mic inputs are gratifyingly clean and detailed, with a well‑focused, transparent sound. Indeed, despite the use of valves, the signal‑to‑noise ratio isn't much worse than for a typical solid‑state mixer front end. A frequency response that's flat up to 40kHz (+0, ‑2dB) probably helps to account for the transparency of the sound. Though it has the solidity associated with good tube preamps there's no muddy low end masquerading as extra warmth.

The instrument input works perfectly with electric guitars and basses, but because there's no speaker simulator facility it is suitable only for clean sounds or for sounds that will be processed further. View the instrument input as a variable‑gain tube DI box and you won't go far wrong.

Summing Up

As with other TLA units I've tested, this preamp behaves in a straightforward and predictable manner while delivering a sound quality that belies its affordable price. If you throw enough money at the problem you can get a better‑performing mic amp, but in the context of real‑life recordings with real‑life sound sources, any improvement in noise performance would be largely academic. If you need a good‑quality instrument/mic front end and like the idea of it including properly designed, high‑voltage tube circuitry, the PA1 is a versatile, simple solution that costs less than you might imagine.