SACDmods.com--Modifications and Repair of Audio Research Equipment

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Audio Research Modification and Repair

SACDmods has built up years of experience modifying and repairing Audio Research equipment for the Reference System and for friends and customers at home. Most equipment from Audio Research features timeless circuit designs that are still the state-of-the-art to this day. The advantage that new equipment often has is the benefit of newer parts, applied to the tried and true circuits. When older equipment is rejuvenated with the best of today's components, the sound will far outshine today's cheapened electronics.

SACDmods modifications feature:

Audience Auricaps

IXYS High Current FRED Rectifier Bridges

International Rectifier HEXFRED Diodes

Why an older Audio Research preamplifier or power amplifier will benefit from the new components:

Capacitors:

ARC typically used a combination of RelCaps paralleled with a small value WonderCap for all coupling applications. The RelCaps by themselves tend to have a dull, somewhat waxy sound, so the WonderCap bypass is installed to compensate for this. Often the values are 5.0µF RelCap and a 0.01µF WonderCap. A capacitor stores and releases charge over time so that only the ever changing audio signal will pass through it on the way to the outputs, blocking the DC from the tube. Differing values of capacitor charge and discharge in different times. The two different values are said to have different time constants. The small bypass capacitor charges and discharges faster than the larger value cap, thus it affects the higher frequency sounds. The effect of this is the render the highs brighter since they have been stretched over the two different time constants. While these bright highs may help sell equipment in the dealer's showroom, it is detrimental to imaging and the enjoyment of your music. I would not necessarily call this a design flaw, but rather a way of compensating for the capacitors available 20 years ago; however, old habits die hard and ARC still retains RelCaps with some bypass. In a modification, all coupling bypasses will be removed so that the circuit only has one time constant.

Capacitors also degrade over time. The better materials of today offer longer lasting capacitors than the RelCaps or WonderCaps from two decades ago. When a capacitor ages, the connections between the metalized film and the leads often oxidize. The effect builds gradually over time, and most people will not notice it until they hear their equipment with new capacitors. Old capacitors lose detail.

Rectifiers:

HEXFRED diodes are installed in all preamps on the B+ power supply. These diodes noticeably lower the noise floor on every piece of equipment I've tried it on. They are especially effective in preamplifiers with high-gain phono stages like the SP-10.

IXYS high current bridge rectifiers can be installed in ARC power amplifiers. With the transistor power amps that require significant current during transients, these bridges make a really big difference in the perceived power of the amplifier. Your amplifier will sound, smoother, cleaner, and more powerful.

Other Modifications:

Owners of the SP-10 preamplifier may or may not be aware that the automatic muting circuit is very detrimental to the sound of the finest preamplifier Audio Research ever built. The SP-10 automute passes the signal through a device called an optocoupler before it reaches the outputs. An optocoupler is a device that conducts when a light emitting diode built in the the package is glowing. Otherwise, the device acts like a high impedance resistor, effectively disconnecting the outputs. This was installed to keep users from damaging their solid state amplifiers and speakers during the warm-up period if the user failed to use the mute switch. (The muting toggle switch connects the outputs to ground, and has nothing to do with the automute or optocouplers.) Over time, the optocouplers degrade, rendering them an even worse detriment to sound quality than they were in the first place. The solution to this design flaw is to bypass the coupler with a wire and remember to use the mute switch.

Tubes: Preamplifiers and Amplifiers can be retubed with either matched Electro-Harmonix, SED, or Tung-Sol tubes. All tubes will be aged and biases properly set.

All Audio Research modifications and/or repairs are handled on an individual basis, price is dependent on the extent of the work required.

SACDmods has direct experience with the following models:

Preamplifiers: SP-6, SP-9, SP-10, SP-16/L, LS-15/16

Amplifiers: D-120, D-350, D-250

Most others are accepted, such as the: D-100, D-125, SP-8, SP-11, PH-3, PH-5, etc.

If your model is not listed here, feel free to inquire.

SACDmods can also handle most repairs, and can purchase parts directly from ARC. In most cases, original ARC parts are used, especially on tube amplifier plate resistors. SACDmods repairs are affordable, well below the ARC shop rate of $80/hour.

SACDmods is not an authorized ARC servicer, nor does ARC really have any authorized service centers.

Click here for the SACDmods email address and phone number.

SACDmods modified SP-16:

6x 1.0uF 450V AuriCap

2x 2.2uF 400V AuriCap

1x 2.0uF 600V AuriCap

4x IXYS 1200V 11A FRED Diodes

Coupling bypass capacitors removed

Price for SP-16: $336.00

Price for SP-16L: $284.00

(prices as of March 2007, subject to parts cost increases)

The modified SP-16 had an extremely noticeable improvement in clarity, imaging, and detail from the modifications. Highs were significantly more articulate and less grainy. Noise floor also drops due to the FRED diodes.