Copland CTA 408 Integrated Amplifier

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Active member
Jul 26, 2017
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Madison, Wisconsin
Does anyone on this forum have experience with this Copland CTA 408 Integrated Amplifier?

It is designed around the KT 150 tube (4 of them) plus it has a built in phono stage that is solid state. It has received rave reviews.

I came across a YT video of it driving ML CLSII and realized since my 13A already has amps in both speakers to drive the 4-10" woofers all that I need is to drive the panels, so perhaps my dream of tubes with ML will come true.

There is a Conrad Johnson owner's site and of course they are partial to CJ gear but there are sooo many people using CJ on ML but what was eye opening was they are using the CJ Classic amplifer meaning their smallest not the biggest.

I really thought I would need VTL mono blocs 200+ watts per channel to make the ML come alive but it is only at the very top end that it can get rolled off if the amplifier does not show something like .05 output capacitance meaning very low, something you rarely see on tube amps and yet 40 years ago when I fell hard for CLS it was being driven by an all tube system; at that time it was Audio Research and it worked out of this world.

Here from PS Audio:

Here's what's important: whatever you are trying to ask the output amplifier to drive must be at least 10 times higher in impedance and preferably 100 times or more. Why? Because you don't want to lose any of the musical energy being sent to the receiving device and you don't want to stress out the amplifier that's sending the music in the first place.

So here are some practical examples. If the input impedance of your power amplifier is 10k then the output impedance of your DAC or preamp feeding it must be at least 1k and better if it's 100 Ohms or less. If it's 100 Ohms you'll only lose a tiny amount of signal at the junction between the preamp and the amp - 100th of what you are sending, just for understanding sake (not entirely accurate but you get the idea).

Here's another example: a loudspeaker. Let's say your loudspeaker is an 8 Ohm speaker whose impedance dips as low as 3 Ohms at its lowest point (speakers don't have flat impedance). That means the output impedance of your power amplifier should be at least 0.3 Ohms and probably better at 0.03 Ohms to really have very little affect.

Tubes generally have higher output impedance than solid state products. One piece of evidence you see in most tube power amplifiers is the output transformer of the tube amp. This is there to more closely match the high output impedance of the amplifier with the low input impedance of a loudspeaker.

Bottom line: output impedance is always better lower.