wrote in message
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"Robert Morein" wrote in message
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"MD" wrote in message
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I use the unit on tape out of my int amp


I have huge room bumps at 48hz, 68hz and 130hz- the unit works great to
fix these with no negative side effects - especially in the highs -
chan
separation - EXCEPT - it adds white noise on its output (I can tell
it's
the output because I can disengage the filters and the noise is there -
as well as try to use the filters to find the noise - which I cannot.
It is barely noticeable with a CD input - but there - and very obvious
when I use phono (lower level input).

The specs say noise is less than -94db. This doesn't make sense

Is this because I am running single ended?

Is there a way to bump up the input level of the device to increase the
sig/noise ratio?

This is a problem frequently encountered with equalizers, probably just
because they are the most common "inserted" appliance. An equalizer has
a
certain dynamic range, depending upon the design. There is some optimal
value for the voltage level of the signal input to the equalizer. If the
signal level is too low, the gain in components after the eq will
magnify
the internal hiss. If the signal level is too high, the eq will clip.

Depending upon the system and your personal preferences, the preamp may
be
operating either as an attenuator or a gain providing device. Let's say
the
setting of the volume control is such that it is providing gain. Then if
you
insert the eq after the preamp, it will be working with a high signal
range
than if it were inserted in the tape loop. This will reduce hiss, while
increasing the possibility of clipping. The lower the gain of your power
amp, the higher the signal will be at this point, and the greater the
possibility of clipping.

If you wish to retain the eq in the tape loop, there is another
possibility.
By inserting a preamp in series with the eq, both in the tape loop, you
can
adjust the signal level to suit the program material, thereby insuring
that
your eq always operates at the optimum signal level.

If you have a schematic diagram of the receiver, you might find that the
circuit that drives the tape loop output can have its gain increased---or
not. In any case, it's much better to add whatever gain you may need
inside
the receiver, where there is a power supply available.

Norm Strong

The problem is, the vast majority of equipment has a passive tape loop
buffer, merely a series resistor intended to prevent complete loss of sound
from a short.
I do have an old Heath receiver that has an active buffer, but the
arrangement is extremely rare.