Jump to content

Audio Research D-70 shut-down *thump* with Quatro's

Recommended Posts

My ARC D-70 MkII causes a low-frequency *thump* when it shuts off. I have been told this is normal for this amplifier, and is not harmful. However, I am concerned because the Quatro amplifiers boost the gain of the low frequency, in compensation for the high-pass input filter. Because this thump is coming from the power amp, not the preamp, it's not being filtered, and therefore is being *amplified* by the Quatro's! I measured 9V/21 DBu peak at the output taps.

I'm investigating possible solutions, including a mod published by ARC. I wanted to know if others have experience with this pairing, as I know ARC + Vandersteen is a popular combination. I know Richard is very concerned about excessive low-frequency signals being sent to the woofer section...

Link to comment
Share on other sites

Wouldn't the internal crossover reduce the amps output to what the Quatro requires to produce the proper level of sound?

If so, then it shouldn't be as high as you measured at the output taps.


But, as I am a humble gardener, I might have it wrong.


Link to comment
Share on other sites

6 hours ago, Richard Vandersteen said:

This "thump" is not a problem.  9V is not that big compared to the low bass on some recordings.  You should still investigate the ARC mod as it may improve other aspects of the sound.  RV



Thanks Richard, that puts my mind at ease.

The mod just shorts the output to ground on power-off, so the stray voltage doesn’t go to the speakers. I’m waiting on a response. Even if they don’t have the original parts, it’s just some wire and a couple relays, I can source that.

  • Like 1
Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
  • Create New...