Quad II Valve Tube Amplifiers Restored By Icon Audio

This unique design set a very high standard in the 1950s. Their performance today is still on a par with modern valve and solid state counterparts BUT there are several issues that need expert attention in order to safely use them. The QUADS use a two core reversible mains plug without a safety "Earth" that is not up to modern safety standards. Also the old power socket was adjacent to the audio input and pre-amp, not ideal for minimising RF interference and hum Pick-up. There is no on/off switch. We fit a modern three core mains socket at the "power" end of the chassis with non-reversible plug and good quality power cable terminating with a fused 13A mains plug. There is no power switch as this was done by the QUAD pre-amp. We fit a double pole switch which isolates the power when switched off. The red glow of the KT66 heaters is a useful power indicator but we can fit a LED if preferred. The original audio input is via a non-standard WW2 multi-pin socket that also has 300V present. We Fit a good quality gold plated RCA phono socket ready for a standard interconnect and disconnect the dangerous voltage from the obsolete socket. To be sure that these amplifiers are working at thier best we do many tests including the following.

Distortion: Both tested less than 0.1% THD at 8 Watts. Maximum power: 18 Watts (into 8 Ohms) KT66. Noise and hum level: -75dB (2 mV).

These results would not be possible unless all components are working exactly as they should. One photo shows the amplifier at the point of clipping this is to show the symmetry of the output valves. Its no exaggeration that these legendary amplifiers helped to define the meaning of "domestic hi fi" from the early 1950s.

Manufactured without any change up the late 1960s. In good working order these amplifiers are capable of excellent performance with modern sources such as CD, vinyl, streaming etc with virtually any pre-amplifier. In most situations they will work with a "Passive" pre-amp.

With an output of 18 Watts they can provide a high sound level with speakers of 90dB or more in a medium sized room. They are an ideal upgrade for someone looking for a warmer more musical sound, less synthetic than many solid state amplifiers. The supplied valve set will be a new set of matched SG KT66s, JJ EF86d and SG GZ34 (5AR4). These amplifiers have been restored without any circuit changes exactly as originally manufactured. However there are a couple of topics worthy of discussion.

We can do this modification if required. The standard setting is 1.6V for full output. We can adjust this for a lower figure if required. Although designed for the KT66 a small modification will allow the use of either without any disadvantage. The more efficient EL34 allows an output of 26 Watts. The slight increase in in heater current is offset by not powering a pre-amp or tuner. The bottom plate has four metal studs which form the feet, This may not be ideal for your furniture. We can supply rubber feet at no extra charge. The paintwork of this pair is described as "good" for their age but they will inevitably have age related marks, see photo's.

Six months guarantee including valves is provided on a "return to base" basis. You are welcome to ask any questions. They may be auditioned at our premeses at LE2 in Leicester. They will be well packed with the valves removed.

Should you have a pair of these amplifiers we are able to service and test most vintage valve amplifiers. This item is in the category "Sound & Vision\Vintage Sound & Vision\Amplifiers & Tube Amps". The seller is "iconaudio" and is located in this country: GB. This item can be shipped to United Kingdom.

Type: Power Amplifier
Model: QUAD
Manufacturer warranty: 6 months
MPN: QUAD II
Unit Quantity: 2
Country/Region of Manufacture: United Kingdom