The new Coda S5.5 amplifier: It's a "Petite Beast"!


I have in-house the New Coda Technologies S5.5 amplifier for review for Stereo Times website. It will be awhile before I write the review. However, I'm so impressed by the performance of this petite amplifier, it only weights 45 pounds, that I wanted to give a heads up to you GON members if you are in the market for a balanced pure class A amplifier, delivers 50 watts @ 8 Ohms, and can drop 100 Amperes of current on a peak!

The world class build quality of Coda amplifiers is on display with the S5.5, along with the most beautiful purity of tonality, precise sound-staging, complete liquidity offered by pure class A design, and what might be the best top end regarding details, decays, and a natural shimmering without brightness or any edge at all.

The S5.5 uses extremely wide bandwidth output transistors instead of the usual TO3 devices used in most transistor designs. I own the Coda #16, which is great, but the midrange/high end is taken to another level of musical enjoyment with the S5.5. The S5.5 has a sense of speed/aliveness that is exciting to listen to that you experience in live music. The amp is dynamic as hell, has driven with ease any speaker I have tried it with, hence my nickname of the "Petite Beast". Remember, 50 watts pure class A, can drop 100 amperes of current and only weights 45 pounds.

Teajay (Terry London)

johnah5

Hey paoz,

The 07x is a great preamplifier. When I reviewed it, and bought it, I put it on the Stereo Times "component of the decade" list. It was the first solid state preamp that rivaled my tube based line-stages in tonality/color and spatiality. The combo of the S5.5 and 07x would be the heart of a reference level system.

Teajay

I’ m not asking about sound quality.

I was asking about the technical data.

the two coda preamps have different outputs.

how many ohm outputs should a preamp have to have a good match with the s5.5 (which has an input of 10k ohms)

100ohms output should be good?

Ok, I am going to borrow from Wikipedia, and also add some things I have found to work.

If you think of your preamp as a source, and your power amp as a load, then you may consider that maximum power transfer can occur when the output impedance of the preamp matches the input impedance of the power amp. However, in high fidelity audio, it is typically considered optimum to have a source with low impedance connected to a load with high impedance. In that case, the power that can pass through the connection is limited by the higher impedance (so power transfer is not maximum), but the electrical voltage transfer is higher and less prone to corruption than if the impedances had been matched.

When matching preamps to power amps, a general rule of thumb is for the load (amp) input impedance to be at least 10 times higher than the source (preamp) output impedance to provide a suitably flat frequency response. Many prefer using a minimum ratio closer to 20 to 1, or having an amp with input impedance 20 times or more greater than the preamp output impedance.

With solid state preamps, this is generally not a problem since most have output impedance of only a few hundred ohms or less, while most SS amps have input impedance of at least 10K ohms. However, you must pay much closer attention when trying to match tubed preamps to SS amps, since many tubed preamps have an output impedance of several thousand ohms or greater. Another thing to watch is how the output impedance spec is reported, since it is sometimes limited to a measurement at a given frequency such as 1K Hz, while the actual output impedance may vary with frequency. It is not unusual for the output impedance of tubed preamps to rise significantly as the signal approaches a lower frequency of 20 Hz, because of the size of coupling capacitors used in the preamp. In these cases, a low frequency roll off can occur whereby, for the same power output, the lower frequencies drop in output compared to the rest of the frequency range, resulting in a loss of deep bass.

The good news is that most tubed amps have sufficiently high input impedance to allow the use of most preamps, tubed or SS. Also, for SS power amps, input impedances of around 50K ohms and above are common and these amps should work well with the vast majority of tubed and SS preamps.

Only a couple of manufacturers make SS amps with input impedances of 10K ohms (e.g., McCormack DNA500), and a couple (such as Pass) make SS amps with input impedance of 20K ohms. These lower impedance amps would require careful matching with tubed preamps. If you are trying to match a preamp with one of these lower input impedance amps, you should try to find information on your preamp’s output impedance throughout the entire frequency range. Some manufacturer’s report this information and some do not. A good source is a Stereophile review, since JA commonly provides the information as part of his measurements. Others will likely have good suggestions I have missed, but this information should give you a good starting point.

Which begs the question...why do some manufacturers design amps with such low input impedance in the first place? Is it to limit equipment that can be used from other companies?