Drawmer 1962

Drawmer's 1960 series leaps into the digital age with the launch of the 1962, which combines a specially designed low‑noise preamp, variable tube coloration and audio‑sweetening tools with an optional 24‑bit output stage. Paul White celebrates the year of the tube.

The Drawmer 1960 series of processors started with the still‑popular 1960 dual‑channel compressor, featuring hybrid tube/solid‑state circuitry, on‑board mic preamps, and even an instrument input with EQ. This was later followed by the 1961 2‑channel equaliser, another well‑accepted hybrid design. Now Drawmer have launched the 1962, which, like its predecessors, is resplendent in black with the familiar Drawmer front‑panel styling.

The 1962 is another hybrid valve design, but with a difference — it has the option of a very high‑resolution 24‑bit digital output stage based on Drawmer's proprietary circuitry. Essentially, the new unit is a dual‑channel mic/line preamplifier which features extremely low‑noise operation. The 1962 spent many months in the design stages, and part of the delay in bringing it to market was, apparently, due to Drawmer's desire to bring the preamp noise down to the lowest possible level, to do full justice to the high‑accuracy digital output stage they'd developed.

In addition to functioning as a dual‑channel preamp, the 1962 includes variable high‑ and low‑pass shelving filters, similar in concept to those used on Drawmer's own DS201's side‑chain, plus a 3‑band, fixed‑frequency cut/boost EQ specifically designed for gentle sweetening rather than full‑scale tonal reshaping. Further tonal tailoring is provided by an enhancer stage, which has separate controls for low‑ and high‑frequency enhancement based on a form of dynamic filtering.

The whole point of building valve equipment is to replicate the classic warmth of vintage valve circuitry, which is due mainly to subtle but musically‑pleasing distortions. A variable Tube Drive control on the 1962 enables the user to decide exactly how much tube coloration is appropriate for a given sound source. There are two dual‑stage valves in the audio signal path, and each of the filter, EQ, enhancement and tube drive stages is independently bypassable, so that minimum‑signal‑path recording is possible when required.

Under most circumstances, I'd imagine the two channel outputs would be kept separate, and would either be connected directly to a recording system or patched into a conventional mixer. However, where a situation requires the two channels to be mixed — live recording to a stereo machine, for example — provision is made for mixing them, with control over pan, individual channel level and overall level. Each channel also features a switchable peak limiter, with the limiter circuit located at the end of the signal chain so that any gain changes caused by EQ will be compensated for.

The Tour

The 1962's two audio channels may be operated independently or linked for stereo operation, in which case the control circuitry for both channels' limiting and enhancement circuits responds to the average of the two channel settings. The remaining controls are not linked, so must be matched by hand.

Both mic preamp stages are identical, and are equipped with fairly conventional facilities, including phantom powering and phase inversion — no pad switch is necessary, due to the very high headroom available. A four‑position rotary switch selects the audio input source: Mic; Mic with 48V phantom power; Line; or Aux. A huge 24‑section LED level meter sits above each input stage, and a separate peak LED warns of clipping.

The microphone input stages themselves are extremely low‑noise solid‑state designs, followed by a valve gain stage running at high voltage. The aim here is to enable good‑quality solid‑state mics (or line sources) to take on the character of valve mics. Both the mic and line inputs are on rear‑panel XLR connectors, but there's also a front panel Aux input on a conventional jack for use with instruments. This is compatible with a range of signal sources, from electric guitars and basses to synthesizer modules; if the valve stage is overdriven, significant amounts of harmonic distortion may be created — if desired! The input stage features a Mic/Line Gain knob which provides a maximum of 60dB of gain, while the Aux input has both Gain and Bright switches. The Gain switch provides a 20dB boost to the Aux input; the Bright switch introduces a 2kHz boost of around 10dB, to approximate the voicing of a typical guitar amplifier.

Enabling the 1962's built‑in limiter prevents the signal level from exceeding the 0dB level shown on the gain meter; a red LED illuminates to show when gain reduction is taking place. Insert points on the rear panel allow additional processing, such as compression, to be added to the signal path.

EQ And Filters

The two filters, one high‑pass and one low‑pass, have fixed 12dB/octave slopes and variable frequencies. The high‑pass filter has a range of 15Hz‑200Hz, while the low‑pass filter covers the range between 2.5kHz and 56kHz. A single button, with status LED, switches both the low‑ and high‑pass filters in or out of circuit.

The 1962 has been a long time making the transition from R&D to pro audio store, but I think the wait has been worth it.

The fine‑tune EQ comprises three fixed‑frequency cut/boost controls designated Low, Mid and High. Low provides up to 10dB of cut or boost, with a gentle 6dB/octave slope, while Mid is a 6dB/octave band‑pass control designed to emphasise presence. High is also a 6dB/octave shelving filter, providing up to 10dB of cut or boost. Though this appears to be a very simple equaliser, it has a very sweet sound and isn't designed to provide the same functionality as, say, a parametric EQ. As the name implies, it's there for fine‑tuning the sound. A single button bypasses this whole EQ section, as well as the rear‑panel insert point.

Enhancement of one kind or another has become part of the recording landscape of the past decade, and the circuit used here is designed to emphasise transients using Drawmer's own Dynamic Spectral Enhancement system, or DSE. LEDs above the two Enhance controls give some idea of how much processing is going on, and a Bypass button allows Low and High enhancement to be switched in or out.

Each channel includes a tube gain stage designed specifically to introduce a controlled amount of tube coloration. The harder the tube is driven, the greater the degree of harmonic enhancement added, and ostensibly, the more warmth and detail the sound takes on. Again, this stage may be bypassed when not required.

Output Stage

Each channel's output level (outputs are available on rear‑panel XLRs) is controlled by the Channel Output Level control. An 8‑section LED meter above the control monitors the signal level. As supplied from the factory, the signals subsequently fed to the Mix output stage are independent of the channel Level controls, but if you prefer to take the Mix input post‑fader, you can reconfigure PCB jumpers inside the unit to achieve this.

The Stereo Mix section allows the two channels to be mixed and the overall mix level to be adjusted. Separate pan controls are provided for the two channels, but there's no way to balance the two levels from here. Instead, you either have to reconfigure the Channel Output Level controls or tweak the Input Gains. Up to three external stereo line‑level signals may be mixed in with the channel signals via the rear‑panel Stereo Mix jacks. Eight‑section stereo LED level meters monitor the output levels.

Output Level is a continually‑variable stereo control that sets the level of the Mix outputs. The gain range is from ‑15dB up to +20dB, though adjustment of this control does not affect the signal level fed to the digital section. The signal levels of the two channels are visible on the two vertical 8‑segment meters in the Stereo Mix section.

Digital Section

The digital section at the extreme right‑hand side of the front panel only becomes active when the optional D62/T module is fitted. If no module is fitted, the LEDs don't light and the controls have no effect. Available as a rear‑panel slot‑in module, the D62/T employs a high‑resolution analogue‑to‑digital converter proprietary to Drawmer, and also offers a number of different output formats, which include various dither types as well as a useful high‑resolution mode for recording two channels of 24‑bit audio to three tracks of a 16‑bit recorder. When the 1962 is in high‑resolution mode, two tracks record the most significant 16 bits as normal, and seven of the eight least significant bits from each channel are combined to form a third 16‑bit signal recorded to the third track. Because this is a proprietary system, the 1962 also includes replay modes so that recordings made in this format can be decoded. Of course, a perfect 24‑bit system would have a dynamic range of 144dB, something that can't be achieved using existing technology. Drawmer's system manages an impressive dynamic range (analogue in to digital out), of around 123dB — as good as the industry's best‑performing converter systems, and better than a theoretically perfect 20‑bit converter. In the digital domain, the dynamic range is 136dB — just 8dB short of theoretical perfection.

Front‑panel controls access all the main functions of the D62/T and the switches on the D62/T's rear panel (Input Select and Output Select) should normally only need setting during installation or when changing I/O formats. Sample rate is selected by a single front‑panel button that continually steps through the 48kHz, 44.1kHz and External Clock options. Internal clock is also available at the rear panel Word Sync Out BNC socket. Ext Clk enables the 1962 to lock to an external clock source via the BNC or the TDIF1 socket.

The front‑panel Word Length button selects between 24‑, 20‑, 18‑ and 16‑bit output resolution, and the Source button enables the digital output to be sourced from either the channel outputs or the stereo mixed output. Finally, there's a 16‑position rotary switch offering alternative types of dither and noise‑shaping to suit different types of programme material, as well as the high‑resolution record and playback options. Positions 1 to 10 provide a number of dithering options (see 'All of a Dither' box), while position 12 turns dither off.

Dither is an established system that involves adding a low level of mathematically‑generated noise to a digital signal that is being reduced in bit length — from 20‑bit to 16‑bit, say — in order to reduce the effect of quantisation distortion at very low signal levels. Properly implemented, dither allows decaying signals to fade more smoothly into the noise floor; without dither, very low‑level signals are represented by so few bits that they are severely distorted.

A more recent development, again used by many different manufacturers, is noise‑shaping. This involves spectrally redistributing the added dither noise so that most noise occurs in the parts of the audio spectrum where the human ear is least sensitive. Because of the differing spectral content of different styles of music, different dither noise‑shaping profiles have been developed, so that the user can pick the most appropriate one for the material being processed.

The ability to record and restore 24‑bit stereo data (actually, it's 23‑bit, as the remaining bit is used for another purpose) to three tracks of a 16‑bit multitrack recorder is a very valuable one. Replay from the multitrack machine is handled by switch positions A, B, C and D. When this feature is used with a Tascam DA88 or DA38, conventional 16‑bit recordings are routed to all track pairs simultaneously; high‑resolution audio recording (in either 24‑, 20‑ or 18‑bit format) is sent to track groups 1,2&3 and 5,6&7 of the tape machine. In high‑resolution mode (selected by choosing a bit‑resolution of 18, 20 or 24), a conventional 16‑bit signal is sent to tracks 1/5 and 3/7, with a composite track comprising the least significant bits routed to tracks 2/6.

To replay a high‑resolution recording, it is necessary to select the appropriate 'decode' switch position to pick up either tracks 1,2&3 or 5,6&7, then play the digital signals back through the 1962 via the TDIF interface. In replay mode, if a high‑resolution recording is detected, positions A or B select tracks 1,2&3, while C and D select 5,6&7. The actual bit resolution is detected automatically. Because it is not possible to select a dither option at the same time as selecting a TDIF mode, the dither setting relating to switch setting 1 is always used.

In Use

Using the 1962 is perfectly straightforward, and for minimum‑signal‑path recording, it is necessary only to bypass the filter, EQ, enhance and tube drive sections. However, I found the filter section extremely useful, especially for shaving away unwanted bottom end in both vocal and instrumental material. The high filter provides a simple means of removing irrelevant top end from guitar parts and similar restricted‑bandwidth parts.

Though the EQ section is only included for fine‑tuning and is ostensibly just a 3‑band, 'fixed everything' design, it actually sounds very nice indeed. Most signals being recorded through a preamp of this quality shouldn't really need much in the way of EQ anyway, so the scope provided by the EQ section is probably a lot more than would ever be needed in practice.

I was a little doubtful at first about whether it was a wise move to include an enhancer in a high‑quality mic preamp, but this particular design can be considered almost as an extension of the EQ — except that it can do things the EQ can't. The High enhance control, in particular, adds a very nice sense of openness and transparency to the top end, almost in the same way as an 'air' EQ, but because of its dynamic nature, it tends to accentuate detail without bringing up noise. At the low end, the enhancement adds warmth and thickness to a sound, and though this is, again, quite subtle, it's effective enough to make me wonder whether there was any need for the tube drive stage at all!

Switching in the tube drive at high drive settings produces a very controlled, but nevertheless quite audible, degree of enhancement. Apparently, at the maximum setting up to 50% distortion is available, but, because this is mainly second harmonic, what the tube does add is sweetly authentic — not faked, hyped‑up or overdone. Having said that, it's unlikely you'll need to set it flat out very often.

Summary

I've used Drawmer's 1960 compressor and 1961 equaliser for some time now, and they still manage to impress me with their ability to sound musical in just about any situation. The 1962 slots into the series nicely, combining a seriously clean mic amp and line DI front end with some genuinely useful audio‑sweetening tools. Having a digital output option is something of a first for Drawmer, but they've obviously put a lot of thought into it, including their own system for producing a 24‑bit output resolution. Listening to signals recorded at a deliberately low level, the effect of using dither is quite dramatic. Instead of fading into noise and grunge, the dynamic range is significantly extended, and if you select the non‑noise shaped dither option, it's immediately obvious that the signal is much noisier than when shaping is used. Telling the difference between the various dither options is not so easy and requires a good choice of D/A output converter and suitable, low‑level test material.

Having a TDIF interface is good news for the many professional post‑pro houses using Tascam machines, but less so for the thousands of ADAT owners around the world, so I can only hope that an ADAT interface option surfaces sooner rather than later. The system of using extra tape tracks to record additional bits, to provide a means of recording up to 24‑bit audio on 16‑bit machines, isn't new, but you normally have to buy a separate box to do the job. Here the system is built in, so Tascam DA88/38 owners have a bonus already.

Even without the digital I/O option, the 1962 is an extremely flexible mic amp/DI preamp that can be used in squeaky clean solid‑state mode or with the benefit of fully variable tube coloration. The EQ section, while not as flexible as a fully parametric design, is perfectly suited to gentle sweetening, and the enhancer is smooth enough to be treated as an extension to the EQ rather than as an obvious effect. With the digital module installed, the 1962 is ideally suited to stereo high‑resolution recording, either to a DA88 or to one of the new high‑resolution DAT machines. The 1962 has been a long time making the transition from R&D to pro audio store, but I think the wait has been worth it.