DNM Products - Capacitors (overview)

DNM Capacitors (overview)

On this Page : Slit-Foil Caps T-Network Caps

For full technical specifications for the T-Network
Capacitor, see our TNC Full Details page.

It is a well-known fact in the audio industry that capacitors make a big difference to the sound quality of an amplifier, but few people have spent much time researching the reasons why.

In essence, a capacitor is two large plates of conductive material, separated by an insulator. As the charge in one plate rises, it transfers across the electrolyte to the other plate and an ac current flows.

Electrolytic capacitors are electro-chemical devices and their internal chemistry prevents the use of low resistance material like copper.

So aluminium conductors with a higher resistance must be used and this makes the capacitor's internal design quite critical for audio applications. Also, capacitors are like batteries in that they have a limited operating life depending on the quality of their materials and their running temperature - a higher temperature gives a shorter life.

Makers of quality audio amplifiers should never cut costs on the capacitors as it drastically shortens the useful life of the amplifier.

Slit-foil Capacitors
A major improvement in audio capacitor performance came in 1984 with a DNM invention, the slit foil capacitor.

Slit-foil capacitor: construction diagram
Cut-away view of Slit-foil capacitor

Conventional capacitors, being made of large, coiled, thin strips of aluminium, are prone to induce eddy currents across their conducting surface. These currents prevent the capacitor from doing its job optimally, thus degrading subjective sound quality. By introducing a series of tiny slits in the foil conductors these eddy currents are dramatically reduced, so improving the subjective and measured performance.

The slit foil capacitor is made exclusively by BHC Components and it is now used in quality hi-fi products the world over.

T-Network - the world's Best Audio Electrolytic Capacitor

T-Network Capacitors, photo

The T-Network capacitor originally evolved because DNM Design required reservoirs that behaved only as capacitors, without unwanted effects such as stray resistance, inductance and eddy current generation caused by the presence of two vast conducting surfaces in the circuit.

In 1994 DNM Design, in association with BHC Components, developed the T-Network capacitor to minimise these unwanted effects. Instead of the single positive and negative terminals found on two terminal capacitors, the T-Network has 2 inputs and 2 outputs.

These extra terminals are connected in a T pattern at the centre and ends of each capacitor plate, guiding the plate current along a controlled path. The T-Network design reduces the effect of unwanted resistance and inductance and the technology is combined with slit foil plates to eliminate eddy currents.

These capacitors are an order of magnitude better than normal 2 terminal ones and they transform the performance of linear and switching audio amplifiers.

Improved Capacitor Performance

Graph showing T-Network capacitors improved filtering

Graph showing T-Network capacitors improved filtering

In tests under load, the TNC capacitor's ability to attenuate is 11dB better than a two terminal capacitor and this extra performance is maintained up to extremely high frequencies

Subjectively, the performance of the T-Network is absolutely unparalleled - it transforms the sound of even the best amplifiers.

Objectively, T-Network capacitors improve the measured high-frequency filtering by reducing the source impedance of the power supply. The high frequency advantage offered by the T-Network has additional benefits for manufacturers trying to comply with EMC regulations.

Equivalent Circuits
Conventional Capacitor, equivalent circuit diagram

Conventional Capacitor, equivalent circuit diagram

Conventional reservoir capacitors share the input and output current pathways generating voltage spikes from the charging current as it mixes with outgoing load current in the aluminium conductors.

This is a major limitation for an audio amplifier.

T-Network Capacitor, equivalent circuit diagram

T-Network Capacitor, equivalent circuit diagram

The advanced circuit design of the new T Network Capacitor (TNC) uses four terminals to separate the input and output currents through the whole current pathway. They remain separate so the residual resistance and inductance are less critical.

Significantly most unwanted characteristics appear on each side of the TNC's bulk capacitance causing the capacitor to filter even more intensively.

The advanced circuit design of the TNC and Slit Foil plates combine today's two most advanced capacitor technologies to produce the ultimate audio capacitor.
For full technical specifications for the T-Network Capacitor, see our TNC Full Details page.

DNM Design hold stocks of T-Network Capacitors for quick access to this technology. For OEM and retail enquiries, to Denis Morecroft.

DNM Design stock the 4 terminal T-Network capacitor in these values and voltages :-
10,000 µF 63 Volt values with a case size of 40 mm. diameter and 55 mm. length.
10,000 µF 50 Volt (also 40 mm. diameter and 55 mm. length),
10,000 µF 100 Volt (40 mm. diameter and 105 mm. length).

You can either use our Online Shop
or post details of your order with a sterling cheque or bankers draft to DNM Design at :
18, Hartford Road,
Huntingdon,
Cambridgeshire PE29 3QD,
United Kingdom.

DNM Design also stock the 2 terminal Slit Foil capacitors in these values and voltages :-

10,000 µF 50 Volt (5 pin Din mount with a case size of 40 mm. diameter and 55 mm. length)

10,000 µF 80 Volt (2 pin Snap-In mount with a case size of 35 mm. diameter and 80 mm. length) and

1,100µF 63 Volt (4 pin Din mount with a case size of 30 mm. diameter and 45 mm. length).

Production enquiries for TNC and Slit Foil capacitors are particularly welcome.
Production orders of 1000 pieces or more can be custom designed in capacitance sizes and voltages dedicated to the amplifier including custom sleeving and printing.
Where required, technical assistance is available from DNM Design and BHC Components. For all T-Network and Slit Foil enquiries for details.)
See the full list of existing slit foil and T-Network Capacitors.

Manufacturer :

BHC Components Ltd
20-21 Cumberland Drive
Granby Industrial Estate
Weymouth
Dorset
DT4 9TE
Tel. 01305 782871

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