Behringer Problems

[PrestonTom]

I recently got a Behringer DEQ2496 Ultra Curve to use as an equalizer etc.

I am running the digital out from a CD player to the digital in on the Behringer. I built the cable (unbalanced RCA to XLR) and it works fine (in spite of the potential problems of impedance mismatch and AES vs SPDIF). I use the analog output of the Behringer to go to a passive preamp (balanced XLR to unbalanced RCA using a short & shielded 75 Ohm cable).

The problem: At idle there is quite a bit of high frequency hiss coming out of the Klipschorns (mostly the tweeter but some from the mid-range) This hiss is audible (at 6ft away) when the volume control is at max but not when it is at a "listening level" position.

1. The CD player is not the problem. When using the analog ouput from the CD player and going directly to the pre-amp there is no hiss.

2. If the CD player is switched off (and the Behringer is ON and in the circuit), the hiss is still present. If the Behringer is switched OFF, the hiss is absent.

3. The "bypass" mode on the Behringer has no effect

4. The input cable is not the problem (CD digital out to Behringer digital in) - I can disconnect this and the hiss is still present.

5. I contacted SameDayMusic (nice folks) and they shipped a replacement. Same problem with the new unit. Maybe I had a bad luck twice .....

6. I put in a cheater plug on the Behringer. When the ground is lifted - no improvement. When I swapped the polarity - no improvement.

7. This is not an AC hum. All the outlets are properly grounded and this occurs if the Behringer is plugged into the wall or into power strip (common with the rest of the equipment).

8. I do not think this is an issue of using unbalanced connections, since the hiss is so audible. The regular connections (without the Beringer) are not balanced and there is not a problem. Also the cable lengths are short and well separated from power cords etc

Have others used a Behringer DEQ (or even DCX etc) with high efficiency speakers? Was there a clearly audible hiss?

Suggestions?

-Tom

[JohnA]

Easy. The source of your hiss is the Behringer. The extreme

efficiency of K-horns lets you hear what could not be heard in "normal"

speakers. Since it is NOT audible at normal listening levels, it

is not a problem, enjoy your system. It is normal for all electronics to display more noise then the gains are at maximum.

[sfogg]

Tom,

"This hiss is audible (at 6ft away) when the volume control is at max but not when it is at a "listening level" position."

If you hear no hiss with the volume control in your normal position why worry about it?

I haven't used that unit but I assume you are just hearing normal self noise from the Behringer. What is the output voltage on that model? On the DCXs the outputs are hot, as a result for best performance some attenuation between them and the amps they are connected to is a good idea.

Since you have your pre-amp behind the Behringer it in effect is acting like the attenuation. When you turn up the volume all the way on your passive you are no longer attenuating the signal/noise from the Behringer. So with your efficient speakers the noise is audible.

If you really wanted to get rid of it you could add some additional attenuation between the Behringer and the pre-amp or between the pre-amp and the amp. Since you are running a passive pre-amp though you shouldn't over do the attenuation. And of course if you do this where ever your normal SPL level is will be at a higher position on your volume control. If you add too much attenuation you would get to the point of not being able to turn the control up high enough for whatever SPL you wanted.

With the DCX they have around 8v of output a 0dBfs. The connect straight to my amps. I put attenuation between the DCXs and the amps as well as altered the gain of the amps they are plugged into. In my setup the DCXs are dead silent. No difference in noise with them on or off standing right up close to the speakers.

Shawn

[mikebse2a3]

I recently got a Behringer DEQ2496 Ultra Curve to use as an equalizer etc.

I am running the digital out from a CD player to the digital in on the Behringer. I built the cable (unbalanced RCA to XLR) and it works fine (in spite of the potential problems of impedance mismatch and AES vs SPDIF). I use the analog output of the Behringer to go to a passive preamp (balanced XLR to unbalanced RCA using a short & shielded 75 Ohm cable).

The problem: At idle there is quite a bit of high frequency hiss coming out of the Klipschorns (mostly the tweeter but some from the mid-range) This hiss is audible (at 6ft away) when the volume control is at max but not when it is at a "listening level" position.

1. The CD player is not the problem. When using the analog ouput from the CD player and going directly to the pre-amp there is no hiss.

2. If the CD player is switched off (and the Behringer is ON and in the circuit), the hiss is still present. If the Behringer is switched OFF, the hiss is absent.

3. The "bypass" mode on the Behringer has no effect

4. The input cable is not the problem (CD digital out to Behringer digital in) - I can disconnect this and the hiss is still present.

5. I contacted SameDayMusic (nice folks) and they shipped a replacement. Same problem with the new unit. Maybe I had a bad luck twice .....

6. I put in a cheater plug on the Behringer. When the ground is lifted - no improvement. When I swapped the polarity - no improvement.

7. This is not an AC hum. All the outlets are properly grounded and this occurs if the Behringer is plugged into the wall or into power strip (common with the rest of the equipment).

8. I do not think this is an issue of using unbalanced connections, since the hiss is so audible. The regular connections (without the Beringer) are not balanced and there is not a problem. Also the cable lengths are short and well separated from power cords etc

Have others used a Behringer DEQ (or even DCX etc) with high efficiency speakers? Was there a clearly audible hiss?

Suggestions?

-Tom

Hi Tom

When I was using the Behringer DEQ2496 with my Khorns I never had any problems of hiss or noise of any kind.

I never tried mine with the digital out of the CD player feeding the Behringer so I can't say anything about that specific use.

I used the Variable Audio Out from my CD player into the Behringer and then sent the signal either through a Cary SLP98L Pre-Amp into a Cary CAD2A3i Amplifier or Bypassed the Cary SLP98L with the Behringer Feeding straight into another input on the Cary CAD2A3i Amp. All Cables were (XLR to unbalanced RCA) going into and coming out of the Behringer.

Not sure if this will apply when using the Digital Input and you might have already tried this but there is a switch on the back of the Behringer Location (20) on page 7 of the manual which affects input/output gain and this has caused noise for some people I've talked to until they get it in the right position for the system they are using the Behringer in.

mike tn[]

[PrestonTom]

Thanks for your comments.

Yes, you are correct that if it is not audible at a listening level then there is no problem.

However at max gain it is quite audible and I was concerned that the unit was defective (Behringer does not have a strong reputation for quality control) and that is why I had a second unit shipped.

The DEQ is putting out a hot signal probably close to 8-9 volts full scale, although I lose about half that when I go from balanced back to unbalanced.

The other issue is that the self noise seemed to be high. Although it will not be audible, I will "know" that it is there. It's a neurotic compulsion ....

Thanks,

-Tom

[sfogg]

"Although it will not be audible, I will "know" that it is there. It's a neurotic compulsion ...."

Then put 3 or 6dB of attenuation between the pre-amp and your amps. That will lower the level of hiss by the same amount if you compare at the same volume position on your passive.

Doing this will also expand the range of you volume control that you use which in turn will give you finer control.

Shawn

[PrestonTom]

"Although it will not be audible, I will "know" that it is there. It's a neurotic compulsion ...." Then put 3 or 6dB of attenuation between the pre-amp and your amps. That will lower the level of hiss by the same amount if you compare at the same volume position on your passive. Doing this will also expand the range of you volume control that you use which in turn will give you finer control. Shawn

This is great therapy. Mix a few resistors together and cook up a voltage divider and presto my compulsion is cured. I will probably go down that path.

But I am still curious. Others who have used Behringer 2496 products with high efficiency speakers - was there a clearly audible hiss when the circuit was at a max (I have a 100 watt amp with probably a typical input sensitivity).

Thanks,

-Tom

[mark1101]

You say you are using it as an EQ.......what does the curve look like? Do you have the high frequencies boosted, and has the gain been corespondingly reduced?

[PrestonTom]

You say you are using it as an EQ.......what does the curve look like? Do you have the high frequencies boosted, and has the gain been corespondingly reduced?

Mark,

Good question but no quick answer.

First, equalizers are the work of the devil! There is no getting around that when you have so many knobs and dials you will spend extraordinary amounts of time adjusting things. I picked up an ECM measurement mic at the same time to do the RTA. This is correcting in the frequency domain based on long term averaging. This is not a good idea to do in a blind fashion, nor in isolation. Fortunately, Behringer protects the user from himself by not automatically doing any adjustments in the lower frequencies. That you need to do manually, and the devil will again be at work. I very sparingly apply the equalization, no more than 2 or dB at most per 1/3 octave band. Yes, it is mostly augmenting the highs and making the overall sound a bit brighter. Utlitimately I will use it even more conservatively once I get some time domain measurements done and apply absorption, bass trapping and diffusion. That is a longer term project, since I need to get educated on various topics.

Regardless of the room "correction," the unit is pretty neat (in spite of the noise floor). It can also perform many things including expansion and could clean up some compressed recordings. And it has an endless number of adjustment, again this can be a true time-waster. The reason I say this is that it is very easy to "change" the sound, even with very modest adjustments. Especially when you re in the mid-frequencies, simply adding or subtrating a 2 or 3 dB in a narrow band can do all sorts of things. Eg, the horns, and vocals can sound "brassier" or honier, or more "mello" or " warmer". Go up an octave or two, and the strings can have "more air" or "transparency". The words are difficult and one starts to sound like those audio idiots that write magazine reviews....

The point is that it is easy to change the sound and put labels on that change. However, it is exceedingly difficult (and time consuming) to decide whether the change is for the better, This is even true when you set some firm goals of accuracy or "musicality" (again the words and labels are probably also the work of the devil).

Yes, it is a great toy!

Once I get the measurement issues down and combine a small bit of equalization with a large dose of room treatment, then I will post a bunch of pictures and DIY projects (the room treatments are hoplessly expensive, but they can be replicated).

Until then I will worry about the noise floor.

-Tom

[D-MAN]

I do remember my EV T-35 tweets hissing with the old Crown amplifier (back in the day).

However, my current system is dead silent at idle, even with your ear right in the horn!

So I think it's the amp. Impedance mismatch or possibly noise floor is just too high?

DM

[Duke Spinner]

voltage gain mismatch .....

the Behringer is looking for a Pro level signal in ...

like +4 db

[Jim E]

Correct as usual Duke...consumer audio is typically around -20 dBu at 50% modulation isn't it? I would think the EQ should be the last item in the chain before the amps. Set the input and output gain with a 1 kHz @ -20 dBu tone and be done with it.

[mas]

Yes, simply constructing cables is insufficient.

You need a device like the Rolls MB-15 ProMatch to convert levels and balanced and unbalanced signals

http://www.music123.com/Rolls-MB15--Promatch-i11845.music

Also, you cannot correct for room response anomalies with an EQ. All you can do is adjust the direct ('minimum phase') signal. Any apparent changes in the room response are due to small changes in phase introduced by the EQ which, during the process of superposition (the summation of the direct with reflected signals), results in small changes to the polar response and the corresponding frequency of the comb filter nulls.

Rolls MB15 ProMatch Manual.pdf

[Erik Mandaville]

Shawn:

Then put 3 or 6dB of attenuation between the pre-amp and your amps.

Are you referring to in-line attenuators? I'm glad this thread came up, since it applies indirectly to some of our own situation. Do you know of a source U.S. source for them?

It's something that might work really well between the DC-1 and 300B Moondogs. I also have some gain related hiss, but don't want to alter the circuitry in the amps because it sounds so good the way it is.

Erik

[PrestonTom]

voltage gain mismatch .....

the Behringer is looking for a Pro level signal in ...

like +4 db

Duke,

I understand what you are saying, but this is not the problem. I am not using the ADC on the Behringer so I do not need to boost the analog input. I am going digital into the Behringer. Although the Digital (Behringer) is AES (higher voltage and slightly different impedance) it can handle the SPDIF digital from the Denon. If there were a problem, it would be much more drastic. Remember even with the digtal input disconnected the hiss remains.

Thanks,

-Tom

[PrestonTom]

Yes, simply constructing cables is insufficient.

You need a device like the Rolls MB-15 ProMatch to convert levels and balanced and unbalanced signals

http://www.music123.com/Rolls-MB15--Promatch-i11845.music

Also, you cannot correct for room response anomalies with an EQ. All you can do is adjust the direct ('minimum phase') signal. Any apparent changes in the room response are due to small changes in phase introduced by the EQ which, during the process of superposition (the summation of the direct with reflected signals), results in small changes to the polar response and the corresponding frequency of the comb filter nulls.

MAS,

Again the issue is not an analog signal with too little voltage going to a Pro ADC. I am goint digital between the Denon and the Behringer.

Yes, I agree with your coments about Eq and Room correction. That is why I noted some caveats in an above post.

Thanks,

-Tom

[Duke Spinner]

what happens of you "short" the analog inputs w/ say, 3k ohms ..???

[mas]

From Behringer Online Support:

http://behringer-en.custhelp.com/cgi-bin/behringer_en.cfg/php/enduser/std_adp.php?p_sid=AKCS_wji&p_lva=&p_faqid=58&p_created=1078145639&p_sp=cF9zcmNoPSZwX2dyaWRzb3J0PSZwX3Jvd19jbnQ9MjQmcF9wcm9kX2x2bDE9NDYmcF9wYWdlPTE*&p_li=

Q: Can I send a S/PDIF signal from a CD player to the digital XLR input on the CX2496 / DEQ2496 ?

A: Yes - under most normal circumstances this will work. The two transmission standards are similar but not identical - you may find that under certain circumstances the AES/EBU input to the DCX2496 does not automatically recognise the SPDIF signal coming from the consumer device. This is due to the physical properties of the SPDIF transmission, and is not a defect in the DCX2496. The best solution to this situation is to use a universal format converter - eg our SRC2496. The DEQ2496 allows you to select the incoming format. However, if you do decide to use an adapter cable it is important to use a cable which is suitable for digital data transmission.

http://behringer-en.custhelp.com/cgi-bin/behringer_en.cfg/php/enduser/std_adp.php?p_sid=AKCS_wji&p_lva=&p_faqid=58&p_created=1078145639&p_sp=cF9zcmNoPSZwX2dyaWRzb3J0PSZwX3Jvd19jbnQ9MjQmcF9wcm9kX2x2bDE9NDYmcF9wYWdlPTE*&p_li=

Q: Which are the main differences between the digital format standards ?

Effectively, SPDIF (consumer format, unbalanced, normally characterised by the RCA co-axial connectors) is digitally simpler, whose basic information id unit utilises 4 bytes, (each byte being 8-bit).

A: AES/EBU (professional format, balanced, normally characterised by the XLR-type connectors) is digitally more complex, the basic information id unit being a differently structured 6 byte format (again each byte has 8 bit). The differences in impedance are not critical, but the fact the AES/EBU is both digitally more complicated and generally of a higher operating voltage means that AES/EBU signals will not be recognised by SPDIF (consumer) equipment.

It is however possible, although not guaranteed, that an SPDIF signal may be recognised by AES/EBU (professional) equipment. You can always test this on your own equipment by constructing an adapter cable (RCA - XLR). Because of the lower operating voltage of the SPDIF signal, this will not distort the signal or damage your equipment. (good reason for not trying it the other way around!)

[PrestonTom]

From my understanding, if the SPDIF to AES does not work, the incompatibility is not subtle, the results would be drastic. My problem is subtle, in fact the music plays fine and there is no evidence of missing bits on the playing.

Again, even if the digital input is disconnected, the hiss is there. I like Duke's idea about a shorting input plug on the analog in of the Behringer. Certainly that sort of trick can work other places. However, the analog input is the input to an ADC (all processing is digital). So this may or may not work.

Thanks for your thoughts,

-Tom

[pzannucci]

I also have a DEQ2496 and it is more quiet with a toslink connect from the player along with balanced out to the preamp than my Denon 3910 running RCA's direct to the preamp. Slight hiss is typical but my DEQ is very very quiet.