ajcllc Posted January 13, 2007 Share Posted January 13, 2007 I currently own a tube preamp that has a high gain problem in the right channel and am running it through my Behringer DEQ2496 Ultra Curve Pro to correct this. My solid state Sherbourn amplifier will not allow me to adjust the volume, as I won't be able to do so until I get my new TAD-60 tube amp for two channel listening. Also, 12 DB attenuators do not work, because the gain is very excessive. I want my system to sound as neutral as possible from the line stage, because I am trying different tubes to see what sounds best. How do I ensure that my Behringer settings are 'flat'? What settings do I go into in my Behringer to have the correct balance? Do I go into the DEQ menu, WIDTH menu, or both? Basically, I want a 'flat' response with even balance in both speakers. Please advise. Thanks! Quote Link to comment Share on other sites More sharing options...
DrWho Posted January 16, 2007 Share Posted January 16, 2007 I have no clue...but have you tried reading the manual? That'd be the first place I'd start. Quote Link to comment Share on other sites More sharing options...
ajcllc Posted January 16, 2007 Author Share Posted January 16, 2007 I have read the manual, and the only thing that I can come with are the DEQ and WIDTH modes. All I want to do is get a correct balance in the speakers and a flat response, and the manual gives no answers. Quote Link to comment Share on other sites More sharing options...
Arkytype Posted January 17, 2007 Share Posted January 17, 2007 To bypass all the signal processing functions of the DEQ2496, press the BYPASS button. From there you can "X" (bypass) each of the five internal modules (GEQ, PEQ, DEQ, DYN, & LIMIT). To adjust the output level, go to Page 1 of the UTILITY menu and select Gain Offset. You can then boost or attenuate the output level of the DEQ2496 in half dB steps from + to - 15 dB. Unfortunately, there doesn't seem to be a provision to adjust the output channels independently whether the unit is in dual mono or stereo mode. Here's a site for those who might want to roll their own pads. http://www.uneeda-audio.com/pads/ Lee Quote Link to comment Share on other sites More sharing options...
ajcllc Posted January 17, 2007 Author Share Posted January 17, 2007 Lee, I seem to have had some success as suggested by Behringer technical support by adjusting each channel independently in the dual mono mode. I will also try your suggestion to see how it differs from what I did. Thanks, Andy Quote Link to comment Share on other sites More sharing options...
Arkytype Posted January 17, 2007 Share Posted January 17, 2007 Andy, Although my McIntosh MC 502 amp has input level controls, I'd sure like to know how to adjust output levels of the DEQ2496 separately. Lee Quote Link to comment Share on other sites More sharing options...
mikebse2a3 Posted January 17, 2007 Share Posted January 17, 2007 Andy, Although my McIntosh MC 502 amp has input level controls, I'd sure like to know how to adjust output levels of the DEQ2496 separately. Lee Hi Lee In dual mono mode if you scroll the curser over to 20khz band using the upper small data wheel then press the knob you will be able to adjust left and right gains independently. mike tn[] Quote Link to comment Share on other sites More sharing options...
mikebse2a3 Posted January 17, 2007 Share Posted January 17, 2007 I currently own a tube preamp that has a high gain problem in the right channel and am running it through my Behringer DEQ2496 Ultra Curve Pro to correct this. My solid state Sherbourn amplifier will not allow me to adjust the volume, as I won't be able to do so until I get my new TAD-60 tube amp for two channel listening. Also, 12 DB attenuators do not work, because the gain is very excessive. I want my system to sound as neutral as possible from the line stage, because I am trying different tubes to see what sounds best. How do I ensure that my Behringer settings are 'flat'? What settings do I go into in my Behringer to have the correct balance? Do I go into the DEQ menu, WIDTH menu, or both? Basically, I want a 'flat' response with even balance in both speakers. Please advise. Thanks! Because the Pre-Amp has a gain problem in one of it's channels something has gone wrong and you most likely have other audible problems(ie: distortion) besides gain/balance issues between channels. Trying to correct this with the Behringer will probably have very limited sucess. Will the pre-amp also be replaced with the TAD-60 tube amp(I'm not familiar with it) that you mention or are you going to continue to use this pre-amp? mike tn Quote Link to comment Share on other sites More sharing options...
ajcllc Posted January 18, 2007 Author Share Posted January 18, 2007 Mike, I'd like to continue using this pre-amp, because when it was working correctly it produced really good results...great sound stage...very musical...really open sound. The Behringer is just a temporary fix until my tech is able to figure out what the problem is. (bad or wrong volume pot?) As far as distortion goes, the Behringer does an excellent job at removing it, and the amp that I am getting also has input level controls. Here is the link to the amp: www.angelfire.com/biz/bizzyb/TAD-60.html Andy Quote Link to comment Share on other sites More sharing options...
Arkytype Posted January 18, 2007 Share Posted January 18, 2007 Mike, Doesn't the GAIN in the EQ mode allow each of the 1/3-octave bands to be boosted or attenuated depending on where the cursor is? Lee Quote Link to comment Share on other sites More sharing options...
mikebse2a3 Posted January 18, 2007 Share Posted January 18, 2007 Mike, Doesn't the GAIN in the EQ mode allow each of the 1/3-octave bands to be boosted or attenuated depending on where the cursor is? Lee Lee, Yes the Gain will adjust wherever you have the curser located and as you know in the upper right box(freq) will display the frequency the curser is on but if you will scroll all the way to 20khz band and then press the knob it will jump over to the overall gain band next to the 20khz band and the box(freq) in the upper right corner will now read full and you can adjust the gain for both channels(in stereo link mode) or independently for the left and right channels (in the dual mono mode). This gain adjustment is best used to adjust for the best optimised signal to noise ratio after a frequency curve has been decided on but within reason a person might use it for some channel balance issues in a system. mike tn[] Quote Link to comment Share on other sites More sharing options...
mikebse2a3 Posted January 18, 2007 Share Posted January 18, 2007 Mike, I'd like to continue using this pre-amp, because when it was working correctly it produced really good results...great sound stage...very musical...really open sound. The Behringer is just a temporary fix until my tech is able to figure out what the problem is. (bad or wrong volume pot?) As far as distortion goes, the Behringer does an excellent job at removing it, and the amp that I am getting also has input level controls. Here is the link to the amp: www.angelfire.com/biz/bizzyb/TAD-60.html Andy Nice Amp Andy So what Pre-Amp do you have? Do I understand you correctly that one channel has to much gain? and if so will the volume control adjust that channel all the way down(ie: no or very litle sound) like the good channel when you try to lower the volume? If not one possible problem you could have is a bad control or possibly a bad connection to ground( ie: bad solder joint or if circuit board is used possibly a copper trace broken in the circuitry from the volume control terminal to signal ground. Other possible problems I could think of assuming you have already tried other tubes is a resistor has changed values causing the circuit perimeters to have changed. mike tn Quote Link to comment Share on other sites More sharing options...
Arkytype Posted January 19, 2007 Share Posted January 19, 2007 Mike, Thanks for the tip. Looks like I need to update my firmware. My unit has version 1.2B. Lee Quote Link to comment Share on other sites More sharing options...
ajcllc Posted January 19, 2007 Author Share Posted January 19, 2007 Mike, Right. The left channel has way too much gain, and the replacement volume pot barely goes to 8 o'clock until it is too loud. It's an Audcom AP100...out of business for almost two years. (I only paid $170 for it, but am wondering if that was too much, since I already put about $100 in unneeded repairs.) The volume control was replaced (as well as the tube sockets), because one channel was not going all the way down with the volume off. Since the volume control was changed, the volume goes all the way down, but there is too much gain in the left channel. My tech is trying to locate another volume potentiometer to replace the one the he already installed. Do you think that could be the problem? By the way I took out the old Chinese tubes, and replaced them with Western Electric 396A's...much warmer and revealing...less harsh and brittle. Do you think these replacement tubes might have caused this as you said "a resistor has changed values causing the circuit perimeters to...change(d)"? Thanks, Andy Quote Link to comment Share on other sites More sharing options...
mikebse2a3 Posted January 20, 2007 Share Posted January 20, 2007 Mike, Thanks for the tip. Looks like I need to update my firmware. My unit has version 1.2B. Lee Lee mine has V1.3 and here is an old picture showing the gain being adjusted for one channel. I found this ability to adjust gain by just playing around because it seemed to be there but I couldn't seem to get the curser over there until I found the need to press the button. I've never seen this ability to control the channel gains in the EQ mode mentioned in the manual but it is there. By the way once you are scrolled onto the channel gain position you use the larger wheel.(if you turn the small wheel it will jump back to 20khz and you will need to press it again) mike tn[] Quote Link to comment Share on other sites More sharing options...
mikebse2a3 Posted January 20, 2007 Share Posted January 20, 2007 Mike,<?xml:namespace prefix = o /> Right. The left channel has way too much gain, and the replacement volume pot barely goes to 8 o'clock until it is too loud. It's an Audcom AP100...out of business for almost two years. (I only paid $170 for it, but am wondering if that was too much, since I already put about $100 in unneeded repairs.) The volume control was replaced (as well as the tube sockets), because one channel was not going all the way down with the volume off. Was your orginal problem just that one channels sound wasn't going all the way down or did you also have gain problems at this point? Since the volume control was changed, the volume goes all the way down, but there is too much gain in the left channel. My tech is trying to locate another volume potentiometer to replace the one the he already installed. Do you think that could be the problem? Doesn't seem likely to me since he has replaced it and you still have to much gain even though the sound does go all the way down at this point. If the volume control is wired in the circuit as is pretty much common then one leg of the control should run to signal ground and so when you adjust the control to all the way down you are basically taking the input of the tube's control grid to ground thus not allowing any signal to be applied to the control grid of the tube. The tech should be able to eliminate the control as a problem just by swapping the wires for the left and right sections of the dual ganged volume control and thus if the problem swaps channels(ie: right channel now has gain problem and left is normal) then you have control problems(or in the ribbon cable going to the controls) but if it stays in the same channel then the problem is still in the left channel's circuitry which is what seems most likely to me. Unless this problem is intermitent I don't believe this should be that hard of a problem for a good tech to find since he can easily compare circuit parameters for left and right channels. I googled the pre-amp and saw a couple of pictures and it looks to be pretty simple in design. Do you have a schematic for the pre-amp that you can post? If you do I might can offer a little more help. By the way I took out the old Chinese tubes, and replaced them with Western Electric 396A's...much warmer and revealing...less harsh and brittle. Do you think these replacement tubes might have caused this as you said "a resistor has changed values causing the circuit perimeters to...change(d)"? Well a bad tube could take out a resistor but you could just as easily have other problems for instance I noticed that it uses double sided circuit boards(copper traces on both sides) and I have seen many double sided boards develope bad connections between the upper and lower traces. You could swap the tubes from one channel to the other and again if the problem stays the same then the tubes aren't your problem. By doing this though you do risk damage to the good channel if a tube is bad. Thanks, Andy mike tn[] Quote Link to comment Share on other sites More sharing options...
Arkytype Posted January 20, 2007 Share Posted January 20, 2007 Mike, Looks like Behringer added the "GEQ global gain control" starting with software version 1.3. Here's a link to the software revisions for the DEQ2496. http://www.behringer.com/DEQ2496/DEQ2496_Software_Update_Information_V1_4.pdf Lee Quote Link to comment Share on other sites More sharing options...
ajcllc Posted January 20, 2007 Author Share Posted January 20, 2007 Mike, " Was your orginal problem just that one channelssound wasn't going all the way down or did you also have gain problemsat this point?"I didn't notice any gain problems at this point. I only noticed the volume problem. However, I do not have the schematic. "...then you have control problems(or in the ribbon cable going to the controls)" I have heard the ribbon cable going to the controls can also be a problem. The frustration lies within my tech not being able to reproduce the same gain problem that I am having. He is only noticing that the right channel is several decibels louder than the left, because he is running the preamp into a receiver as his amp for his testing, not an actual amplifier. The problem is not as noticeable for him, because he is able to adjust the volume through his receiver, while I cannot. Thanks for the input. It's really appreciated. Andy Quote Link to comment Share on other sites More sharing options...
mikebse2a3 Posted January 21, 2007 Share Posted January 21, 2007 Mike, Looks like Behringer added the "GEQ global gain control" starting with software version 1.3. Here's a link to the software revisions for the DEQ2496. http://www.behringer.com/DEQ2496/DEQ2496_Software_Update_Information_V1_4.pdf Lee Thanks Lee I'll check it out! mike tn Quote Link to comment Share on other sites More sharing options...
mikebse2a3 Posted January 21, 2007 Share Posted January 21, 2007 The frustration lies within my tech not being able to reproduce the same gain problem that I am having. He is only noticing that the right channel is several decibels louder than the left, because he is running the preamp into a receiver as his amp for his testing, not an actual amplifier. The problem is not as noticeable for him, because he is able to adjust the volume through his receiver, while I cannot. Thanks for the input. It's really appreciated. Andy Your welcome Andy. Andy the tech should still be able to find a volume setting on his receiver that pretty much duplicates your amps sensitivity and hear what you experience. Does your tech not have the ability to input a test signal into the pre-amp and measure the left/right channels output for the appropriate gain? mike tn Quote Link to comment Share on other sites More sharing options...
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