Rothwell Audio Signature One Moving Coil Phono Preamplifier

Of course, noise performance alone isn't the only consideration when seeking the ultimate sound quality. To achieve the wide bandwidth and low distortion required for superb sound the transformers employed have to be very high quality. For this reason the transformers used in the Signature One are supplied by Lundahl of Sweden. The core material used is a cobalt based uncut amorphous strip which gives a high inductance factor (to extend the low frequency bandwidth) without the need for an excessive number of turns of wire, which in turn keeps the winding resistance low (to minimise Johnson noise) and inter-winding capacitance low (to extend the high frequency bandwidth and to minimise ringing). The unusual coil geometry also has the benefit of rejecting interference from external stray magnetic fields to minimise hum pickup.

However, the real benefit of using transformers is the sublime sound quality. This is due to the very different way in which transformers behave compared to transistors. Whereas the distortion spectrum of a transistor circuit tends to produce increasing distortion as frequency rises, transformers produce less distortion with rising frequency and produce lower levels of intermodulation distortion. This gives transformers a smooth and transparent sound without any of the unpleasant harshness which can afflict transistor circuits.

The Signature One's transformers can be configured for step-up ratios of 1:10 and 1:20, so that the vast majority of modern moving coil cartridges can be accomodated.

Following on from the Signature One's transformer-coupled inputs comes the discrete transistor section of the circuit. Using discrete transistors allows elegently simple Class A circuitry to be used. This is used in preference to the Class B or Class A/B push-pull circuitry employed within op-amps because Class A circuits are completely free from crossover distortion, and given that the total amount of distortion a circuit exhibits is less important than the type of distortion it exhibits, and crossover distortion is the worst sounding distortion mechanism possible, discrete Class A offers sound quality which simply sounds right. Whereas op-amps use negative feedback to reduce crossover distortion, Class A circuits avoid it altogether and so sound natural and fatigue-free.

Following the first active gain stage is the passive RIAA equalisation using multiple audiophile polypropylene capacitors. Then comes the second active gain stage and a Sziklai-configured output buffer for low distortion and low output impedance capable of driving any interconnect cable.

The signature One's power supply is an onboard linear regulated DC supply using a toroidal mains transformer for low magnetic field radiation, oversized reservoir capacitors with two stages of filtering and a low noise discrete transistor regulator. Since the DC supply is the raw material from which the amplifier creates the output signal this attention to detail pays dividends in a high signal-to-noise ratio and by revealing low level detail.

There is also an earth link/lift switch so that hum-free performance can be achieved regardless of the turntable's earth wiring scheme.

The Signature One is designed and built in the UK. Each unit is carefully assembled in-house with rigorous and continuous quality control and thoroughly tested before approval for sale. Each unit is built with the kind of pride and care that is only possible with small scale manufacture by people with a passion for quality audio and music reproduction.

Technical Specifications:

• Gain: 62dB/68dB
• Input Impedance: 
• Low Gain: 470 ohms
• High Gain: 117 ohms
• Output Impedance: 75R
• Sensitivity for 500mV o/p: 
• Low Gain: 0.4mV @ 1kHz
• High Gain: 0.2mV @ 1kHz
• Headroom: >20dB
• Signal/Noise: >87dB
• Power Supply: internal, linear regulated 24 volts DC
• Mains Voltage: 120VAC/235VAC
• Power Consumption: 2W
• Dimensions: 430 x 250 x 74 mm
• Weight: 4kg

We endeavour to despatch same day for orders placed up to 1pm on available stock items (items with stock message "Usually dispatched within 24 hours"). Please remember to check with us first for a physical stock check if next day delivery is important to you. Any items with stock message "Usually dispatched within 72 hours" are items that we do not hold in stock but order in from the importer or manufacturer as soon as a customer order is received. Occasionally these may be delayed beyond 72 hours due to importer/manufacturer stock levels but we will inform you as soon as we can if this is the case.

UK Orders

We despatch the bulk of our UK mainland items on a 24 hour service – Free of Charge. Non Mainland locations - Isle of Man, Isle of Wight, the Scilly Isles, the Scottish highlands and Islands, the Channel Islands and Northern Ireland may take a day or so longer and are not Free of Charge. Smaller items are delivered using Royal Mail 24 or special delivery. Larger items are delivered using a courier service such as DPD or UPS.

International Orders

Due to the nature of our products and brand restrictions we are only able to send certain items internationally. Smaller items are delivered using Royal Mail Small Packets Airmail with International Tracked and/or Signed depending on value of item and availability of the service. Larger International shipments are sent by insured and tracked services using UPS. If there are any delays due to specific customs regulations, etc, you will be contacted by Hifisound or by the courier with a request for any further information required. Customs duties can apply for shipments to any countries outside of the UK depending on where the product you have bought is made. Customers are responsible for all taxes and duties incurred when the items enter their country.

Collect in Store or Home Install

At the request of the manufacturer some items cannot be supplied by mail order but you can click and buy them and then elect to collect them from our store or arrange a home install (if applicable). Applicable items clearly state that they are Collect in store or home install. Once ordered you will receive a message prompting you to contact us by phone or email to arrange for us to deliver and install or to reserve and collect from our store at your convenience, you will also be advised of the delivery time / stock availability as not all Home install / collect in store items are held in stock.