LFD - The Technical stuff
An overview:
LFD Audio believe that audio amplifiers can be most easily optimized if the basic amplifier topology is kept as simple as possible. Feedback is generally kept to a minimum, provided the distortion is sensibly low. They don’t accept that very low distortion produces subjective improvements.
Actually it’s preferable to have slightly higher total harmonic distortion that possesses higher levels of lower level harmonics, compared to a lower figure made up from higher harmonics. Also it’s important to have well-designed signal routing and earthing combined with the best selection of high quality passive components.
This philosophy normally produces amplifiers that may at first appear unusual. Typically the printed circuit boards (PCBs) will be topologically laid out according to the circuit and will always utilize star earthing. Signal routing within the amplifier topology is kept to an absolute minimum when transferred onto the PCB and is typically 5 times shorter in length than an average amplifier.
LFD don’t advocate the use of signal routing on a PCB, since subjective evaluation has established that high quality audio cables exhibit less degradation compared to printed circuit board tracks.
Consequently, it may be found that there is more wiring within an LFD amplifier compared to its immediate competition. Each separate cable assembly is subjectively evaluated to establish the best possible choice. Often single strand cables and multi strand cables will be mixed within a given product.
Passive components
The selection of passive components is a very important factor in the design of an amplifier. Subjective evaluation is essential in this selection, together with reliability. It has been found that the most optimum component for a particular circuit location may differ from every other similar part. As an example, it’s not normally possible to use the same resistor type for every resistor within an amplifier, each position must have a type that produces the best subjective results.
This process also applies to the choice of capacitor used within the circuit and any capacitor used as a power supply decoupling component. The iterative procedure is very time consuming and means that product development is slow and methodical. There is no easy solution to this problem, but perseverance does bring its rewards of better sound quality.
The power supply
Power supply design plays an important part within any amplifier, so great care is required in this area. Generally they believe local decoupling is beneficial within an amplifier, combined with a main supply that exhibits low impedance even up to high frequencies.
The power supply return paths within an amplifier must be clean and well executed, otherwise there may be undesirable coupling within the circuit. The mains transformer design also has an influence on sound quality, and we have found that transformers with lower copper losses and better regulation often confer improvements.
Many factors affect the subjective performance of an amplifier, so each one must be carefully addressed to produce an excellent sounding product. They believe that their philosophy does bring rewards in the areas of better transparency, resolution and dimensionality. Remember that fashions come and go, but true quality always lasts.
Stereonow stock the LFD Integrated Zero
The LFD Integrated Zero and its limited Edition version, are simple to use 50W and 60W per channel MOSFET amplifiers, offering 5 inputs and a separate tape facility.
In standard form the amplifiers omit the phono stage (record player equaliser), however this particular facility can be supplied at extra cost.
To raise the performance of the Integrated amplifier above normal expectations, custom wiring based upon PC-OCC and LC-OFC technologies are used, together with the utilisation of high quality passive components. DC coupling is also employed in both models to alleviate the degradations caused by capacitors placed in the signal path.
Further enhancements have been achieved by adopting an entire Aluminium chassis and lid; thus reducing magnetically coupled distortions. Star earthing, separate power supplies for the input and output stages, together with high current delivery, allow these amplifiers to drive even difficult loudspeakers with ease.
The Limited Edition (LE) model of the Integrated Zero, improves upon its smaller brother in the areas of power supply design and the choice of superior passive components. The Limited Edition now becomes a viable alternative to similarly priced separates, particularly when its performance and visually attractive single chassis configuration are considered.
Specifications for the integrated
| Power Output 8ohms | 50W, 60W (LE) |
| Input Impedance | 8k2 minimum |
| Gain | 33dB (Line) |
| Input Sensitivity | 0.4V, for full output |
| Bandwidth | 1Hz-50kHz |
| Gross Weight | 6.5kg, 8kg(LE) |
| Size | 432mm x 332mm x 63mm |
Specifications for the optional Phonostage
| Input Impedance | 47k |
| Gain at 1kHz | 53dB(MC) 38dB(MM) |
| Bandwidth | 7Hz-60kHz |
Stereonow stock the LFD Linestages LS1, LS2 and LSB
All linestages in this series are dedicated line level amplifiers offering comprehensive input switching and tape recording.
A very low output impedance endows each amplifier with the ability to drive relatively long or highly capacitive cables with ease and removes the bandwidth limitations in some passive preamplifiers.
Another advantage of the zero feedback circuit topology adopted for the LS1, LS2 and LSB, is the significant reduction of transient distortions and dynamic overload. Although the linestages share similar topologies, the ascending cost of each product allows improvements in the power supply and the utilisation of superior passive components. The LSB is a special version of the LS2, with one balanced and 4 unbalanced inputs, and an unbalanced/balanced output.
Special Features
- Dual mono construction
- Zero overall feedback
- Star earthing
- Custom LC-OFC and PC-OCC wiring
- Regulated and RC smoothed power supply
Stereonow stock the LFD Powerstages PA1, PA2 and PA3 monos
The PA1, PA2 and PA2M are MOSFET power amplifiers designed to drive the majority of loudspeakers presently available.
All combine a high input sensitivity to allow the use of passive preamplifiers if required. Although they share similar circuit topologies, the more expensive models have superior power supplies and use custom made passive components and wiring.
The PA2M is a mono version of the PA2 and utilises separate power supplies for each channel and a larger output stage for even better sound quality. This amplifier is available in either a single chassis to match the LS2 or in two separate enclosures. A balanced input version of the PA2 and PA2M can be supplied to match the LSB or any other balanced linestage.
Special Features
- DC coupling from input to output
- Custom PC-OCC and LC-OFC wiring
- Star earthing
- Split input and output power supplies
- MOSFET output stage
Powerstage Specification
| Power into 8R | 60W (PA1) 75W (PA2) 90W (PA2M) |
| Input Sensitivity | 0.5v for full output |
| Gain | 33dB |
| Input Impedance | 48k |
| Bandwidth | 1Hz-50kHz |
| Gross Weight | 8kg (PA1) 9kg (PA2) 14kg (PA2M) |
| Size (PA1,PA2) | 482mm x 335mm x 70mm |
| Size (PA2M) | 300mm x 387mm x 70mm |
Stereonow stock the LFD Phonostages, MC1 and MC2
Phonostage MC1 and MC2 have been designed as dedicated RIAA equalisation stages for Moving Coil cartridges only.
A separate power supply enclosure is employed to reduce hum pick up from mains transformers and provides a greater degree of flexibility in positioning.
A low output impedance allows even long interconnect cables to be used. Both phonostages use similar topologies, but the MC2 utilises custom made passives and a floating input bias scheme similar to the State-of-the-art Battery Disc preamplifier.
Special Features
- Separate PCB for each channel
- Zero overall feedback
- Star Earthing
- Dedicated PC-OCC wiring
- Independent L/R power supplies
Phonostage Specification
| Gain at 1kHz | 68dB(MC1) 69dB(MC2) |
| Output Impedance | 12R |
| Input Load 1 | 50R(MC1) 120R(MC2) |
| Bandwidth | 7Hz-70kHz |
| Size | 300mm x 360mm x 70mm |
| PSU size | 220mm x 300mm x 68mm |