Under normal circumstances, modifications are often unnecessary and is not recommended on the brands which we carry.     We believe that a properly designed and faithfully implemented circuit will have a more substantial effect on sound quality than exotic part selection. You can spend hundreds of dollars on exotic capacitors or wiring, but if the equipment circuit violates the fundamental rules of audio design, it will never sound right.     You will find that we often discourage customers from installing exotic parts.

With certain DIY equipment or low cost equipment, upgrade and modification may be required depending the circumstances.   There are two levels of upgrade:

Basic upgrade replaces inferior or poor quality components in order for your equipment to meet specification. This is the prerequisite of high-fidelity.    In a perfect world upgrades would not be necessary, however in reality equipment can suffer from bad designs, cost reductions and corner cutting in the manufacturing process. Bad designs should be immediately corrected for reliability and safety reasons. 

Optional upgrade uses premium quality components to enhance sonic characteristics.  It may also include changes to certain circuit designs to improve performance. This service is offered for the customer who wants to bring out the fullest potential from his equipment.   Premium component upgrades should be taken only if the inadequate areas of a circuit have been corrected or modified in accordance with the fundamental principles of electronics, otherwise the money spent on exotic component upgrades will be useless.

When do you need Modifications ?

Audiophiles today have unlimited choices in equipment selection. However, the golden rule remains unchanged, You get what you pay for. There are many affordable tube amplifiers which offer good value for the money, but their full potential remains untapped due to budgetary constraints and sub-standard circuit designs.

Excel Stereo has been commissioned by several manufacturers and distributors of high end audio equipment (which shall remain anonymous), to rectify faulty designs (engineering change order) and suggest improvements before their products reach the general consumers.  In some instances, we rebuilt entire production batches from the ground up.  Through such experiences, we have learned the undeniable truth that, with the proliferation of OEM Brand Name products selling at jaw-dropping prices, Value for money has found itself a new meaning: Room for improvement.

When properly modified to meet specification, this equipment can outperform other brands costing significantly more money.

From our experience, these are the major areas for improvement.

Transformer windings – Some imported products do not comply to North American electrical standards and still use transformers which are originally designed for their local markets (110V / 50 Hz AC is typical). When plugged into a 120V / 60Hz outlet, the transformers produce unwanted buzz. The excess voltage will increase the load on the global circuit and affect the life expectancy of certain electronic components.   This can also lead to safety hazards.

Tube filament voltage – We have encountered many tube amplifiers with excess filament voltages due to the use of improper transformers. While changing the transformer is possible, a more cost effective remedy is to reduce the undesirable forward voltage by means of rectifier diodes and resistors. This will not only result in sonic improvement but also safeguard the usable life of the vacuum tubes.

Circuit board management – We have run into many tube amplifiers fitted with circuit boards originally designed for digital applications, which usually operate at low voltage. Bearing in mind that a typical tube amplifier requires anywhere from 400 to 600 volts to operate, these amplifiers take shortcuts and use light-duty traces (1mm or less) of copper on the circuit board to carry the high voltage.  We will rectify the situation by rewiring, point to point, the voltage carrying section with appropriate gauge wires. The improvement is safe and sound.

Component mounting - We have seen many amplifiers with components which are mounted improperly.   In many instances, components are simply "glued" onto  the chassis with glue guns.  While this may not necessary be a bad thing, it becomes a safety hazard when low quality or under-rated components are combined with aggressive designs.  The excessive heat generated by under-rated components can cause the glue to melt, which means the only thing which separates you from 500V of electricity is the melting glue as these components come into contact with the chassis.  

Safety check – Brand name equipment manufacturers need to make a fair profit. But why are some equipment brands more durable than others? How faithful is the implementation once the design has left the drafting table? We’ve been around long enough to know the inside stories.

Do you have problems with buzzes and excessive hum?   Is your amp burning a set of tubes every 9 months? 

We have measured tubes driven so hard (often 2 to 5 times over their dissipation limits) that it causes premature tube and transformer failure. This design flaw applies to North American, European, and Asian products. 

We have seen capacitors that physically self-expand over time to the point of bursting. We have witnessed transformers that are loaded significantly above the factory specification.    No matter how impressive the specs appear in the user’s manual, bring your equipment in for a thorough check up to avoid unpleasant surprises!  

Room for improvement ?

Some custom modifications we offer include: circuit re-engineering, bias tuning, power supply conversion, component replacement, and crossover enhancement. We provide for these services without altering the personality your equipment – only taking the sonic quality to another level.