aguilar db750 problem!!!

foxo661 · #1 07-06-2010, 01:39 PM

Hey guys, i need help! Just recently bought a used aguilar db750... I've been experiencing some nasty distortion/clipping at moderate volumes. This distorting happens when i'm playing, and i "dig in" to the bass. And i have come to believe it is a preamp issue, because when i plug into the back "poweramp in" input, there is absolutely no distortion, and i can play at higher volumes and intensity with no problem. At first i thought it's a tube issue, but i changed out ALL the tubes and the problem persists. (but i did notice that when i changed out the tubes, the distortion begins to vary. With certain tubes put in or taken out, the distortion is a higher frequency or lower, more or less etc...

settings are very reasonable: gain 11-12 master 11-12 all eqs are flat. the active/passive switch makes no difference, neither does the groud switch. the only way i can get rid of this is to plug in the poweramp in, but i would really love to plug in the normal input and play.

I dropped a heavy dollar on this baby, and i really want to solve this problem! the distortion is very noticeable, so i don't want to start gigging with this amp until i fix it. any response would be greatly appreciated!

BigOldHarry · #2 07-06-2010, 01:48 PM

I'll say it first: Take it to a qualified tech. It's probably something simple.

Sliderbass · #3 07-06-2010, 02:12 PM

Call Aguilar FIRST! They are great to deal with and can assist you with your issue. They are also the best choice to service that amp.

naturalkinds · #4 07-06-2010, 02:14 PM

Sounds like you've got to join a doom metal band now.

(Kidding. +1 to calling Aguilar.)

msquared · #5 07-06-2010, 02:25 PM

In addition to the excellent "contact Aguilar" suggestion, I suggest buying some electrical contact cleaner and cleaning out the tube sockets. Also, you didn't say if you swapped out your tubes with new or known good tubes but if you didn't then that's another thing to check.

You should also make sure you have all of the tubes in their proper places. The 12AU7 in the V4 slot is physically interchangeable with the 12AX7s in V1, V2, and V3 slots. The 12AU7 has a lot less gain than the 12AX7 (see http://thetubestore.com/gainfactor.html) so it could be that you are overdriving the power amp. What you're describing could be a gain staging issue.

I agree that it's something simple. If it was a serious problem, the amp wouldn't even power up.

BassmanPaul · #6 07-06-2010, 03:50 PM

Sounds like you are overdriving the front end of your amp. Try putting your master to max and using the gain to control volume. If you still get distortion get it checked out by a tech.

Paul

Growly Lytes · #7 07-06-2010, 06:58 PM

Maybe your bass is very hot & overloading the front input.I have a Lyte bass which is very very hot & it overdrives the input depending on how i play & have the levels. I notice i get that bit of distortion when i dig in even when i have no overdrive dialled in. So i think `maybe` your p/u are hot & overdriving the input though it could be as simple as some contact cleaner & giving it a little clean.

hasbeen · #8 07-06-2010, 07:06 PM

what are all of your settings on the amp?...please denote in "o clock" format.

Also, what is your bass? If active, what are your settings there? As a previous poster mentioned, you may be hitting the front end too hard.

Lastly, it very well may be a dirty pot etc......and "cleaner" might help. However, a quick call to Aguilar will tell you which cleaner they prefer.

akaTRENT · #9 07-11-2010, 05:31 PM

Thread bump.
I seem to have gotten some clipping(751) on my last gig sparingly, in oclock gain: 11, treb: 12 mid: 2 bass: 12 volume: 11-12 oclockish

I do dig in, and use a jaguar bass (passive) with all the pickups in the on position, and volume/ tone all the way up. Possibly a compressor to even out the peaks?

msquared · #10 07-11-2010, 07:29 PM

Quote:

Originally Posted by akaTRENT

I seem to have gotten some clipping(751) on my last gig sparingly, in oclock gain: 11, treb: 12 mid: 2 bass: 12 volume: 11-12 oclockish

What did Aguilar say when you contacted them about it?

akaTRENT · #11 07-11-2010, 07:45 PM

Quote:

Originally Posted by msquared

What did Aguilar say when you contacted them about it?

We thought it may be a torn tweeter diaphragm so I replaced it. But same sort of noise, I think im just overloading the front end when I dig in.

edit: that wasnt about the clipping though, I had originally though I blew my tweeter, I realized afterword when I had some time with the amp it was just shy of clipping on harder hits, and thats probably causing the tweeter to react the way it is. So I think I need compression.

But I wanted to know your guys opinion before I hear back from them, Only because I do tend to call a good amount and dont want to be a bother haha, So I figured Id pick brains with you guys on tb before I hit them up so I can spare them what I feel can be my occasional non sense.

Its just hard because there is a great deal less info on aguilar gear than say Ampeg.

akaTRENT · #12 07-11-2010, 07:51 PM

Quote:

Originally Posted by BassmanPaul

Sounds like you are overdriving the front end of your amp. Try putting your master to max and using the gain to control volume. If you still get distortion get it checked out by a tech.

Paul

When you suggest this, about where on the gain knob should you even begin to get unwanted dist/clipping.

I know thats sort of a subjective question btw, But I know you are always pretty good with this stuff.

akaTRENT · #13 08-06-2010, 05:55 PM

Any one got some info on this thread? I was just looking through and seems no one has answered the op's question. Would love to see a fellow aggie user getting stuff right!

johnk_10 · #14 08-06-2010, 07:35 PM

IME, a stock jag bass has pretty hot pickups, and when run in series, it's even hotter (which is more likely to clip the front end). you can try using the 'active' switch which will pad the input, or try a 5751 tube where the first 12AX7 is in the preamp. both methods will lessen the chance of clipping the first pre-amplifier stage.

EricF · #15 08-06-2010, 07:54 PM

I don't know about the rest of you, but I find that 11-12 on BOTH the gain and master is a little more than MODERATE volume with a DB750/1.

jacohead · #16 08-06-2010, 08:03 PM

+ 1 on contacting Aguilar. They have great customer service and very helpful with technical issues

Queg · #17 08-06-2010, 08:18 PM

Quote:

Originally Posted by EricF

I don't know about the rest of you, but I find that 11-12 on BOTH the gain and master is a little more than MODERATE volume with a DB750/1.

+1
That's gotta be friggin loud. Unless your cab is very inefficient? Many cabs will fart out on transient peaks with that kinda clean volume. Do you have the low switch on?

With a DB750, I was hitting mechanical max of my speakers when I pulled a rack compressor out of my rig, but resolved it when I started using an overdrive pedal (which seems to make a natural compression)

msquared · #18 08-06-2010, 09:18 PM

Quote:

Originally Posted by akaTRENT

When you suggest this, about where on the gain knob should you even begin to get unwanted dist/clipping.

I know thats sort of a subjective question

That's the thing though, it's not even sort of subjective. You have to dial the gain in to the output of your bass, which changes based on where you have the volume, how hard you play, and how hot your bass's output is.

I'd say if you don't know what a good value for the gain knob is, run the XLR out into a mixer or preamp running at unity gain and listen with different speakers or headphones to get this "right". Then involve the rest of your rig.

akaTRENT · #19 08-06-2010, 11:50 PM

Quote:

Originally Posted by Queg

+1
That's gotta be friggin loud. Unless your cab is very inefficient? Many cabs will fart out on transient peaks with that kinda clean volume. Do you have the low switch on?

With a DB750, I was hitting mechanical max of my speakers when I pulled a rack compressor out of my rig, but resolved it when I started using an overdrive pedal (which seems to make a natural compression)

+1 on the compressor. I threw on a TLC after the tweeter wasnt the culprit and it really has alleviated most of the distortion problems similar to the op. I will say though going past 1 oclock on the volume with gain set at about 12, seems to be where the clipping really starts to happen, for me at least.

I do use a hot output bass, and play a with pick so im sure ill clip out a pre section faster than most.