Synthesis Roma 753AC Valve Amplifier

Synthesis Roma 753 AC valve amplifier is the middle model in the Roma range, and like the Roma 96DC+ features EL34 valves but boosts power from 25W to 50W per channel.

This is a stereo valve, integrated amplifier featuring a pair of ECC82 dual triode drivers followed by four EL34 power tubes in a push-pull configuration. Synthesis are renowned for their no compromise valve amplifiers. This amplifier has a classic design with all modern components and a stylish Italian design.

There are five analogue inputs and a pre out connection. Additionally, the output transformers are custom made with modern materials, for superior performance.

Powerful class A valve amplifier

With the 753AC sound quality and performance take priority. The ECC82’s have a DC stabilised heater circuit. To reduce hum and noise pickup. Normally the heaters are powered from 6.3V AC which can introduce hum. The power and output transformers are mounted on a very rigid platform. This eliminates mechanical and electrical noise.

Additionally, sockets are gold plated to stop oxidization and reduce connection resistance. Premium components are used and the result is incredible musicality. Purity of voice is stunning as is the accuracy of instruments reproduction. Synthesis also make their own output transformers for superior performance.

Specially designed output transformers

The output transformers are specially made by Synthesis. Transformers can now be made that outperform older designs. Modern materials such as high grade iron silicon cores optimise the frequency response. Additionally modern copper wire is much purer than in the past, reducing resistance and improving reliability.

Output transformers are needed to match the high impedance output from the valves to the low input impedance of the speaker. Valves work by having a heated cathode that emits electrons. The electrons are attracted to a positively charged plate or anode. Next, a grid is placed between the cathode and anode. This is normally held slightly negative to block electron flow. An audio signal placed on the grid will be amplified.

Why valve amplifiers?

Amplification valves have been around since 1903. In fact they were the only way of providing amplification until transistors came along in 1947. Most amplifiers used valves well into the 1960’s. Today valves still have a following among audiophiles. This is due to several factors. One of them is that they look cool. However, the main factor is the “warm” sound.

Valves also run at a much higher voltage than transistor amplifiers. As a result, the current draw is much less for a given power than with transistors and the loading on the power supply is much less. This leads to less ripple and noise.

Another advantage is linearity. Valves are inherently linear. Whereas transistors have to be carefully biased to prevent non linearity causing intermodulation distortion. Finally, modern materials results in better performance from valve designs.

Who are Synthesis?

Synthesis are an Italian company that specialise in high-end valve audio. The Roma range comprises integrated amplifiers that have either analogue or digital preamps. Some have a built-in DAC for streaming and CD playback. They also have a stand alone Phono preamp as well as CD players that use valves. Their ethos is making no compromise audiophile equipment that looks amazing and sounds clean and pure.