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Clipping problems (still!!!)

Discussion in 'Amps and Cabs [BG]' started by rockstarbassist, Oct 16, 2005.


  1. rockstarbassist

    rockstarbassist Banned

    Apr 30, 2002
    The Woodlands, TX
    Endorsing Artist: HCAF
    Ok, so I really don't understand what's going on here.

    I'm seeing if I can maybe get some help here, but if not, I'm calling Peavey or something cause this to me just seems crazy.

    I just recently, like this week, finally got my new speaker cable (from Todd @ ProCables N Sound) so I could bridge my power amp into my Schroeder 1210.
    My preamp is a Demeter VTBP-201s (tube pre) into a Peavey PV1500 power amp. I run an unbalanced line out from my Demeter via a 9" Monster Bass Instrument cable, into the regular input on channel A of my power amp. I run banana plugs from the poweramp into a Speakon on the Schro.

    So, last night was our first gig with this type of setup for me. I had been running it just @ 4 ohms stereo as I didn't have a bridgeable speaker cable yet, and had some clipping issues even back then, and I thought (possibly wrong) that this would fix the problem-
    Wrong.

    I don't know if it's just my preamp being extra hot or the poweramp too sensitive or what, but I CANNOT for the life of me turn up what you would even consider "loud" and NOT clip! On the Peavey's they have that DDT compression thing, which from what I've read is the same thing as clipping, or supposed to keep the amp from clipping... Regardless, the red lights are comin' on, and that bugs me.
    Last night I had my preamp on about 1:30 and my poweramp on about 2:45/3:00 and it was in the red most of the time. I had to keep cutting back and back so it wouldn't constantly stay in the red...

    I'm totally lost here. I play active (but hardly "high output") basses, and just go like normal into the "Active Input" of my preamp.
    Am I doing something totally wrong, or am I just expecting too much from my cabinet, possibly? But it's not like the cab was hurting really from what I could even tell. I was getting decent volume, but nothing that would constitute "crazy" or anything.
    Should I look to upgrade to a 410, or would switching out poweramps maybe help??

    I'm just really lost, so any input or suggestions on stuff to try/test out will be greatly appreciated...
    thanks.
    rsb
     
  2. murphy

    murphy

    May 5, 2004
    Toronto, Canada
    Is the light telling you it is clipping, or just that the DDT is kicking in?
    I always find the DDT very heavy handed and kills all the dynamics.
    Is the ddt defeatable?
    You might also have a lack of power in that amp....Peavey seems to exaggerate their specs.
    Murphy
     
  3. rockstarbassist

    rockstarbassist Banned

    Apr 30, 2002
    The Woodlands, TX
    Endorsing Artist: HCAF
    Yes, from what I remember (without being able to look at it right now), the DDT is enabled, but defeatable as well. I just thought (from what the manual in a round-about way says) that the DDT was just a form of clipping; they just called it something different.

    Because I remember borrowing a Mackie power amp before I got this one, had the thing CRANKED, as well as my preamp, about 400w/channel @ 4 ohms and it never got into the red... Not really even close!

    So maybe I'll turn off that feature and see what I get. I'm looking for a new poweramp as we speak anyhow (Stewart 1.6 or 2.1), so I guess I'll try that for a bit and see what happens.

    Thanks for the input!

    But for lack of power... it's rated at 1500W bridged @ 4 ohms... so even if it were a tad exaggerated, I'd still be looking at 1100-1300W, yeah?
    My cab (Schroeder 1210) isn't even sweating with this much power, so it's gotta be an amp problem somehow...
     

  4. Do you know this to be true, or are you just repeating somebody else's opinion?

    I've personally tested several Peavey products on a dummy load and have ALWAYS found them to meet or exceed their published specs.

    Either back up your statements with proof, or please refrain from slandering a manufacturer.
     
  5. the peavey amps ive used have always seemed loud as they are stated, could be you have a problem with yours tho, have you tried turning down the pregain/gain on your preamp a bit ? might work
     
  6. murphy

    murphy

    May 5, 2004
    Toronto, Canada
    No slander intended.
    This has just been my experience in live situations with Peavey bass amps....keeping a clean sound at high power outputs.
    When I used more speakers I always got better results, but do always find DDT compression too heavy handed for bass guitar.
    I would choose Peavey over Yorkville.
    Just not higher end stuff......Peavey is ok
    Murphy
     
  7. brooklynbassguy

    brooklynbassguy Supporting Member

    Feb 8, 2004
    maplewood, nj, usa
    Dude, I would take your whole rig to an amp repairman. It could be something minor, or something major like a blown output transistor.
     
  8. What's another name for a dummy load? Peavey customer? :D

    Just kidding, never been a fan of Peavey's, but my last bad experience was 30 years ago, so maybe they've cleaned up their act... They're affordable, wouldn't accuse them of being hifi.

    Try another power amp, make sure you don't have input gains, EQ boost, etc too high, maybe the clipping is happening in the preamp.

    When you "turn up", what are you turning up? The power amp? Or bass/preamp input/preamp output?

    If you get clean tone at lower volume, leave everything alone and just increase the power amp input gain. That ensures the only thing that changes is the power amp output.

    Otherwise it could be you turning up the bass, clipping the input, turning up the preamp, clipping the preamp output. For a good test, you want the bass and preamp to remain unchanged. Only up the power amp volume and see if the distortion occurs.

    Randy
     
  9. jerry

    jerry Doesn't know BDO Gold Supporting Member

    Dec 13, 1999
    Hawaii
    You might be running the Demeter a little hot, I've never used mine past 11 oclock.
     
  10. Nightbass

    Nightbass

    May 1, 2001
    Seattle, WA
    Something doesn't click about your speaker cable situation. You say you ordered a new cable so you could bridge the Peavey. You mentioned banana on the amp end. Isn't the Peavey like any other amp such that the bananas are inline and to use it in bridged mode, you simply use the center red jacks and flip a bridged switch? Why couldn't you use your first cable, if it had bananas on the end? The same cable is used for both stereo and bridged operation. The only difference is which banana jacks you use on the amp.


    Is your new cable wired 1+ and 1- ? You didn't get a 1+ and 2+ at the Speakon end, did you?
     
  11. rockstarbassist

    rockstarbassist Banned

    Apr 30, 2002
    The Woodlands, TX
    Endorsing Artist: HCAF


    To first address this question, no, my old cable was a regular 1+ 1- on the Speakon end, and a regular 1/4" on the other. I'd ordered it a while back, b/c the Mesa Diesel cab I had at the time only had 1/4" inputs, so I went that route.
    My new speaker cable is just a regular Banana/Speakon cable, with no special additions, like being 1+/2+ or anything.

    At our next gig I'll try boosting the poweramp to full, and then start the preamp around 9-10 and see where I get. I could possibly be running the Demeter hot, but I don't know- it's my first tube preamp! Anyhow, I was using this as a temp anyhow, but this problem just seems to be bugging me. As said before, with other amps I've tried I never encountered this, as the Peavey would clip/DDT would come on when I would be running in stereo/Channel A only as well. I just figured when bridged the amp would have enough headroom/power to turn up and just blast away. Apparently not. Sucks, but oh well.
    Would anyone suggest killing the DDT as well and seeing what happens, or use that as a last last resort??

    Also, I plan on buying a compressor here soon, and would it help any if I ran the signal preamp-comp-amp instead of the Demeter's FX loop?
     
  12. Dan1099

    Dan1099 Dumbing My Process Down

    Aug 7, 2004
    Michigan
    Your preamp volume seems quite high. Try backing that off, and increasing your peavey's gain. You might be overloading the inputs on the Peavey.
     
  13. Ah, everybody's a comedian!!! :D

    Actually, I've been a satisfied Peavey customer for 25 years...I'll agree that their products may not have a "boutique" tone (though it's acceptable for my tin ears). But they are built like a brick s***house (and about as heavy) and their customer service, the few times I've contacted them, has been superb (for replacement knobs, they sent them to me free, and schematics, also sent free).

    There are some people who may not know what a dummy load is, and I've seen other threads that inquire about "why isn't there a standard way to test the power of an amp?" So here's the simple way to test and compare amps, called RMS power:

    Start with the amp. Hook a resistor to the amp's outputs, a big honkin' resistor with lots of power handling and preferably no inductance. I use a 4 ohm with a fan blowing across it.

    Hook an oscilloscope in parallel with the resistor. I use an old HP that I bought of the Evilbay. Now put a sine wave into the amp's input--I use a HP 200CD sine wave generator, at 1000 Hz. Turn the amp's tone controls flat if applicable, then turn the amp's volume or gain up, looking at the scope. The amp's output will be a sine wave up until the amp clips, then you can visually see the tops and bottoms of the sine wave being "clipped" off. At this point, measure the RMS voltage (this is an AC signal), and calculate the power (since we know the resistance of the dummy load). Easy, straightforward, and at least it gives us some indication of an amp's power.

    Now there are many more thorough and informative tests, like specifying a certain distortion level and a frequency range to examine the amp's response over.... but I don't have a distortion analyzer.

    However, the RMS power at 1000 Hz is a good start. If the amp manufacturer claims 500 watts, but it clips at 200 watts...well, we can draw our own conclusions about the manufacturer's claims.
     
  14. rockstarbassist

    rockstarbassist Banned

    Apr 30, 2002
    The Woodlands, TX
    Endorsing Artist: HCAF
    Yeah that's what I'm gonna attempt next time I get a chance to "turn up" really loud, as people in my apt. complex bitch about my damn computer speakers being too loud, much less busting out the Schro rig and rockin' out.

    I just figured on a tube preamp, it was like a tube amp, and the more you turned it up, the hotter they ran and the better they sound.

    Also for any Demeter users out there- if/when using the Jensen DI on the pre, do you usually set it Flat or EQ??
     
  15. jerry

    jerry Doesn't know BDO Gold Supporting Member

    Dec 13, 1999
    Hawaii
    I send the DI on my Demeter flat to the P.A.
     
  16. If your planning on running the power amp at full and control the volume with the pre amp, id recommend you keep your DDT on, it may not be much but it'll stop you frying your speakers if it clips, especially at full power on the power amp
     
  17. rockstarbassist

    rockstarbassist Banned

    Apr 30, 2002
    The Woodlands, TX
    Endorsing Artist: HCAF

    Yeah I plan on leaving that as-is for at least the next time I try this out. If it's still being dumb, I'll cut the power to about half and then cut out the DDT as well and see what happens...
    If it's still being unfriendly, it's gone next month sometime...
     
  18. Dan1099

    Dan1099 Dumbing My Process Down

    Aug 7, 2004
    Michigan
    Tube preamps will sound different at higher gains, not necessarily "better." The worry i have is that you are sending a signal that is too hot for the poweramps input to handle, which is setting off your protection circuit.