Our equipment

Top of the line

Polyhymnia’s test bench contains a complete set of top-of-the-line test equipment, including the Audio Precision System 2 Dual Domain and the Prism D-Scope. We demand top technical performances from all of our equipment, and often find technical problems that manufacturers have missed. Even so, measurements can’t tell the whole story and listening tests remain vitally important. If it doesn’t sound good, what’s the point?

In the 1990’s, Polyhymnia, then the Philips Classics Recording Centre, embarked on a plan to upgrade the entire analogue signal path, from the microphones through the entire recording and playback chain. This was in contrast to the totally digital recording chain adopted by many other recording studios. Our reasoning was that digital equipment was not yet fully developed, and that good analogue equipment could still out-perform digital equipment (especially AD’s and DA’s) in many areas. In fact, improving the analogue electronics provides clearly audible improvements for every format, from CD to Super Audio CD to DVD-Audio and DVD-Video.

Cables

The first item to be upgraded was our cabling. For this, we contacted the well-known Dutch cable guru, A.J. van den Hul, who designed microphone cables and multi-cables especially for us. Features of these cables include double screening (triple screening for the multi-cables), low capacitance, strength for hanging (a kevlar thread is included!), and almost non-existent microphonics (handling noise). Several kilometers of these cables now form the basis of every recording session, as well as the infrastructure of our studios. Van den Hul also provides much of our digital cabling (low jitter and low signal loss) and all of our loudspeaker cable. For more information, visit www.vandenhul.com.

Microphone Pre-amp

The second item to be re-designed was the microphone pre-amplifiers. This critical part of the recording chain must amplify the miniscule signal from the microphone to a level suitable for AD converters or further processing. In professional applications this is often complicated by interference from electromagnetic fields in the recording space or along the cable runs. Modern technology hasn’t made this easier – everyone in Europe recognizes the typical beep-beep-beep of GSM interference. This is not what you want on your Super Audio CD recording…

Jeroen Olde-Dubbelink spent several years perfecting the design of the Polyhymnia microphone pre-amplifiers. They had to be “interference-proof”, able to drive long cables, and surpass the audio performance of any available design. Jeroen’s design combines extreme immunity to interference, high input impedance (ideal for condenser microphones, the only type we use), wide frequency response (0.1 – 150 kHz), a completely balanced signal path, and low distortion (lower than our state-of-the-art Audio Precision System 2 measurement set). It also includes a unique output stage, which eliminates ground loops, works seamlessly with both balanced and unbalanced inputs, and can deliver high signal levels over extremely long cables. You can even mix with it by putting the channels into series.

Polyhymnia currently has approximately 100 channels of these pre-amps, which are used for all of our recordings.

Mixer

The next item to be modified was our existing PolyGram analogue mixers. These mixers, built in the 1970’s especially for PolyGram’s classical labels, had already been modified several times. The most recent modifications included replacing all of the op-amps with low-offset Burr-Brown models, and removing all of the capacitors in the signal chain, resulting in a fully DC-coupled mixer. Surround monitoring has also recently been integrated into the console. Polyhymnia now has a recording chain, from microphone through mixer, without any electrolytic capacitors or transformers in the chain, and with extremely high bandwidth (more than 150 kHz), extremely low distortion, and low noise.

Microphone Electronics

The final stage of the recording electronics to be tackled was the internal electronics of the microphones. Though Polyhymnia uses only the best microphones from the leading microphone manufacturers (Neumann, Schoeps, Danish Pro Audio, Sennheiser), we were convinced that better results could be achieved with improved electronics. Again Jeroen Olde-Dubbelink spent a great deal of time perfecting his design. The microphone electronics needed to work on standard 48V phantom, be interference-proof, and be easily modified to work with many different microphone models.

Again Jeroen came up with a completely balanced circuit, including even a “dummy capsule” to balance the microphone capsule. Again the design is very high bandwidth, from well beneath 1 Hz to well over 200 khz (both high- and low-frequency cutoff is determined by the capsule itself). The electronics work with extremely high impedance (20 gigaohm) for the capsule load, and an extremely low output impedence of 8 ohms (ideal for driving long cables). The electronics are made with the thick-film ceramic techniques generally used to build satellite electronics. Models have been built for Danish Pro Audio microphones (4006 omni and 4011 cardiod), Neumann 100 series, and Schoeps Colette series.

The audible results achieved have been remarkable; we can finally hear the true sound of the microphone capsules! Particularly impressive are the results achieved with the Neumann microphones; before modification these were good microphones, but not microphones we would have used for the main systems. After modification with our new electronics they have become some of our favorite microphones. We have now modified approximately 125 of our microphones, and use these modified microphones for all of our recordings.

Polyhymnia Surround Controller

With the arrival of high-resolution surround recording, we found ourselves in need of a high-quality surround playback controller, but were unable to find a suitable unit from any manufacturer. So we built our own… Ko Witteveen (a former Philips Classics engineer) and Jean-Marie Geijsen designed the unit, based on existing Olde-Dubbelink designed electronics. The unit is completely balanced; features include an overall level control (via a six-layer Elma switch), source selection, and individual level trim and mute for each channel. The output section is electronically balanced (no transformers), works equally well with balanced or unbalanced inputs, and is immune to ground loops. Bandwidth is from 0.1 Hz to 200 kHz. Distortion is unmeasurable.

Tape recorders redefined

In the last year we have seen an increase in the use of our analogue master recorders. It is well-known that analogue master tapes often contain far more and better signals than those produced by normal tape recorders. This is mainly due to the fact that analogue tape recorders, measured by current standards, have poorly designed playback electronics.

At the end of 2002 we decided to modify our two- and four-track Studer A80 master recorders with new cabling, and replace the playback electronics with our own microphone pre-amplifiers. The results have been astonishing and our mastering studio is now equipped with these modified recorders.