Looking for help finding a zero feedback amp, not megabuck
- Thread starter donnrut
- Start date
Hello donrut
Welcome to the What's Best Forums.
What are the specs of new speakers?
What makes you think your current amp is not up to the task?
Why not try your amp first to get acquainted with your speakers and then try different amps in comparison?
Where are you located and what is your budget?
Cheers,
Christoph
I have owned Vandersteens for 40 years. I would suggest an Ayre amp. Richard Vandersteen used Ayres before he built his own.
You don't need a zero feedback amp for it to work really well on Vandersteens. We've been making zero feedback amplifiers for nearly 50 years so take that for what its worth; we've had lots of Vandersteen customers over the decades and shown with Vandersteen at shows.
The reason feedback has a bad rap is because of several problems in amplifier design. One common problem is the point in the amplifier where the feedback is applied is not linear. So the feedback signal gets distorted before it can even do its job! Another problem is that all tube amps and most solid state amps made in the last 70 years lack the gain and bandwidth to really support the feedback properly across the audio band- so at some point in the audio band the distortion rises with the frequency. Both of these problems lead to harshness and brightness.
There are two ways to overcome this problem. The first is to make sure that the feedback node as as linear as possible. An example of this is the old Dynaco ST35, which used a 7247 tube for the voltage amplifier and driver. The feedback was applied to the cathode of the first section of that tube, which is the same as a 12AX7 section, so the tube was fairly linear. In this way the feedback signal was distorted less, causing less higher ordered harmonics to be generated by the feedback as a result. Since the ear perceives higher ordered harmonics as harshness and brightness and since the ear is keenly sensitive to these harmonics since it uses them to sense sound pressure, the result in this case was a very smooth and musical amplifier. The output power might be a problem on the Vandy 2s unless you're in a smaller room though.
The other way to overcome this problem is to use a self-oscillating class D amplifier. With this topology so much feedback is being applied that the amp goes into oscillation the moment its turned on and the oscillation frequency is used as the switching frequency of the amp. With this much feedback the non-linearity of the point in the circuit where the feedback is applied is ameliorated to quite an extent. There is also enough gain/bandwidth product to support the feedback at all frequencies. While I can't speak for all class D amps of this type, I can say with direct experience that such amps can be every bit as smooth and musical as any zero feedback amplifier whether tube or solid state.
You might also want to read this thread from the Vandersteen forum since it addresses your concerns:
Ampifiers for Vandersteen 3s
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