HELP- using Behringer DSP1124P for para EQ room correction - havenoise problem

[MD]

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?

[MINe 109]

In article >,
MD > wrote:

> 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?

Try it in the preamp-amp loop if you have one.

What does the 'gain' button on the front do? Is that for output or
something else?

Stephen

[Arny Krueger]

"MD" > wrote in message


> I use the unit on tape out of my int amp

The signal levels on a tape output are in the 0.100 mV to 1
volt range.

The DSP 1124 being designed for pro audio, its designed for
signals in the 1.3 to 6-8 volt range.

> 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).

You've nailed the problem - the signal at the tape outputs
is too low to optimise the noise performance of the DSP 1124

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

Those specs are probably referenced to +4 vu, which is about
1.25 volts. The signal coming out of your phono preamp could
be 10 times, or 20 dB lower.

> Is this because I am running single ended?

Not really, though driving the DSP1124 effectively makes it
6 dB more sensitive.

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

Boost the output of your inputs especially the phono preamp,
or as Stephen sugegsts, move the equalizer to a point in the
signal chain where the signals are larger.

[Robert Morein]

"MD" > wrote in message
...
> 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.

"Robert Morein" > wrote in message
...
>
> "MD" > wrote in message
> ...
>> 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

[[email protected]]

MD wrote:
> 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?

I have two Behringer equaliser units=both noiseless. One former unit
failed within two months of purchase. Behringer distributors in
Seattle-Edmonds first had it repaired and mailed there and back with no
expense to me and then when the repair failed replaced it with a brand
new unit- still no costs. Later without asking I was sent an upgraded
chip for the unit when it became available.
My experience with them was excellent. Why don't you contact them in
Edmonds Wa. instead of trying this and that?.
Ludovic Mirabel

[MD]

MINe 109 wrote:

> In article >,
> MD > wrote:
>
>
>>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?
>
>
> Try it in the preamp-amp loop if you have one.
>
> What does the 'gain' button on the front do? Is that for output or
> something else?
>
> Stephen
no pre out. gain is for each filter/freq chosen.

[MD]

Arny Krueger wrote:

> "MD" > wrote in message
>
>
>
>>I use the unit on tape out of my int amp
>
>
> The signal levels on a tape output are in the 0.100 mV to 1
> volt range.
>
> The DSP 1124 being designed for pro audio, its designed for
> signals in the 1.3 to 6-8 volt range.
>
>
>>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).
>
>
> You've nailed the problem - the signal at the tape outputs
> is too low to optimise the noise performance of the DSP 1124
>
>
>>The specs say noise is less than -94db. This doesn't
>>make sense
>
>
> Those specs are probably referenced to +4 vu, which is about
> 1.25 volts. The signal coming out of your phono preamp could
> be 10 times, or 20 dB lower.
>
>
>>Is this because I am running single ended?
>
>
> Not really, though driving the DSP1124 effectively makes it
> 6 dB more sensitive.
>
>
>>Is there a way to bump up the input level of the device
>>to increase the sig/noise ratio?
>
>
> Boost the output of your inputs especially the phono preamp,
> or as Stephen sugegsts, move the equalizer to a point in the
> signal chain where the signals are larger.
>
>
thanks - no pre out- I'm stuck I guess
shame - cause the unit does wonders on the bumps (I use a multitude of
test discs - including one with one hz steps from 20-300hz - and a sound
meter)

[MD]

Robert Morein wrote:

> "MD" > wrote in message
> ...
>
>>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.
>
>
OK - thanks - there goes the hope of "less is more"

[MD]

wrote:

> "Robert Morein" > wrote in message
> ...
>
>>"MD" > wrote in message
...
>>
>>>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
>
>
thanks

I will look

[Robert Morein]

> wrote in message
...
>
> "Robert Morein" > wrote in message
> ...
> >
> > "MD" > wrote in message
> > ...
> >> 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.