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Re: PMD660 preamp problems

Subject: Re: PMD660 preamp problems
From: "oryoki2000" <>
Date: Thu, 02 Jun 2005 05:20:47 -0000
Dan Dugan wrote:

> How can I tell if my friend Scott's 
> PMD660 needs the mods?

The PMD660 preamp problems seem to be of two sorts:
1. lots of clipping of mic input, even with the record level turned
down, and 

2. -20dB pad setting provides much more than 20dB reduction.

For a fix, contact Marantz Tech Support at 866-405-2154.  

Below are comments from PMD660 owners who experienced pre-amp
problems, as recorded at,



audio sounded clipped regardless of the input gain or value indicated
on the level meters. Even the waveform of the test audio was looking
clipped with all the peaks truncated

experiencing clipping on manually set levels using the internal
preamps. Clipping was audible at all set levels. I then tried the pad
and just got a whoosh of soft white noise, and no real audio signal.

Speaking into a shure sm58 at loud vocal volumes produced clipping
regardless of where the level controle was set. I tried a variety of
mics and setting to no satisfaction. The -20db pad makes so much hiss
that it is as well, unusable

I started pluging various mics into it, and got clipping before -0 all
over the place. I placed the signal peak at -12, -8, and -6, and could
get clipping at all 3.

I was recording with an AT-3032, a pretty hot condensor mic. It was
definitely clipping with the input meters reading no higher than
-12dB...The so-called 20dB internal pad in the 660 is more like 35dB. much attenuation a Sennheiser MKH416 would need to work well
with the 660, and we settled on -10dB, but even then there's clipping
before well before 0dB

the built-in pad is so knocks the inputs back WAY more
than 20dB, doesn't fix the clipping, and makes everything hissy.

We tested out the -20dB pad on the PMD 660 and came to the mesure of
exactely -40dB! Thats then nearly line level, and why there is
suddenly so much hiss.

Got a PMD660 and connected it to ME66 shotgun mic, running off of
phantom power from the PMD660. Unacceptable clipping and distortion at
normal conversational levels-turning down the input does nothing. Same
problem everyone else has been having with the -20dB pad: it helped
with the distortion but had to turn up with input to the point that we
got a crazy hiss.


and the result of the Marantz repair:

my 660 was one of the ones afflicted with both the pad problem and
clipping issues. marantz said they were only addressing the pad
problem, but i figured i'd send it in anyhow and see what happened.

it was returned within days and i'm happy to report that everything
seems to be working perfectly now. on test recordings, with the
internal pad set to 0 db, i'm getting sound that actually correlates
with what's happening on the meters. it's not clipping prematurely and
works the way it should.

and even though i'll probably never use it, the -20 db pad seems to be
doing it's job properly as well. 


"Microphones are not ears,
Loudspeakers are not birds,
A listening room is not nature."
Klas Strandberg
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