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marshall jubilee-out of phase ?
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 4/24/2000 3:30 PM |
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dale |
marshall jubilee-out of phase ? someone here told me i would find that my marshall silver jubilee is out of phase with most other amps. is this true, and how can i tell/rectify this problem? i run it in stereo with a pv classic 30 as the effects amp, and while i havn't noticed it sounding like it's fully out of phase, it does seem to have a certain quality when i gig with it that could possibly be described as sort of out of phase. you might say it sounds like it's 20% out of phase. i noticed this, but wrote it off as just the way the amp sounds. i know what out of phase speakers sound like, and o.o.p. p/u's, but this doesn't have that thin sound, just a certain small aspect of the out of phase sound. tho i have only run it stereo, so maybe if i ran it w/o the 2nd amp i may hear an even better sound. but thats not an option as i love running stereo by the way, the speakers are in phase, as i checked then with a battery. any thoughts on how to tell and rectify this? thank you,-dale ps--as i said, i don't know this amp is out of phase w/ others. just want to be sure after reading the post that mentioned it. [can't seem to find that post by the way] |
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| 4/24/2000 3:50 PM |
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| Trace |
Who ever told you that was correct! That amp is out of phase with nearly every other amp out there but it's not a big deal if you are not running it with another amp at the same time. You can take your speaker cable and simply flip (or reverse) the positive and negative (ground) leads on one end only. This will flip the phase. Now with that being said we are using one of those amps in the studio now and even after flipping the phase it still sounds wacky in the phase department. I think it's the actual design to be perfectly honest with you. It sounds better with the phase reversed but it's still a bit wacky.
The entire amp will not be completely out of phase with another. Usually you notice it on the lower mids and low-end more than anything. The low-end starts to shrink up or disappear. Flip the phase with the speaker cable and you'll hear the difference in the low-end and the lower mids. 
It's not a drastic as speakers being out of phase with each other. Speakers will sound far worse when they are out of phase with each other.
If you run both amps in mono and send the same signal to them you should the phase cancellation even more.
Dale, I'd be willing to bet that the Marshall is out of phase with the Peavey. Simply reverse the speaker wire as described above and you should be fine after that. Trace
I think I was the only one who made mention of it recently  | ||||||
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| 4/24/2000 4:12 PM |
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| dale |
thanks trace, i'll try reversing the speaker leads, but you say it'll still be out?! geez, i can't win. finally find the amp i've always wanted, and theres a problem. just can't win. do you know what feature or the circuitry causes this, and can it be reversed? why would they do this in the 1st place? thanks,-dale |
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| 4/25/2000 1:41 PM |
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| Trace |
In theory you'll be in phase but to me it still sounds a tad funky with something like a Vox AC30. The phase meter on a Neve VR console also shows it as being a "little" out of phase with some other amps but nearly as bad as before.
Realize that if it sounds good to you then THAT'S all that counts!! I know many engineers who love to set up multiple mics and get a cool tone buy literally causing phase cancellations in certain frequencies.
Without getting inside of one of those amps with the expressed purpose of correcting the phase, I really couldn't tell you. I suspect that when they got the amp done it sounded fine so they ran with it and rightfully so since they had no plans of running that amp with any other amp(s). On it's own it sounds fine and that's what really counts. I'm sure when they designed it that they didn't think anyone was going to use it with a Vox, Fender, Peavey, or any other amp. Trace | |||
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| 4/24/2000 5:19 PM |
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| dale |
trace, i just did a test. i rigged up an adapter so i could quickly A/B the stereo setup with and without one of the speakers out of phase. but it sounded fuller with both speakers in phase ! could it be that only certain jubilees are like that? or maybe some were shipped with speakers that were either hooked up out of phase or with incorrectly labeled terminals? i know that sounds impossible, but i can't understand why yours sounds out of phase but mine doesn't. the thing i mentiond before is probably just the way the amp sounds compared to my old 900. it's not a bad thing, just different. but i would expect a out of phase sound to definatly be worse. so apparently either mine is in phase, or theres something in the amp that makes it out of phase in a way that can't be resolved with a speaker reversal. what are your thoughts? dale |
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| 4/25/2000 1:53 PM |
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| Trace |
I'm not sure what you mean by "both speakers"... do you mean two different speaker cabinets? (I>E> one for the Peavey and one for the Marshall?)
That could be although every time people used those with another amp at the same time it was out of phase with the other amps but that's just my experience.
It's all possible but I would suspect that the it's the actual amp. We tried several different speaker cabinets and it was the same thing each time which is how we determined it was the amp head.
I couldn't answer that unless I could actually hear your set up. Again, it's just been my experience with those amps when used in a multi amp set up (and being run at the same time).
It's not that it's really bad or something that most people notice. We noticed it in the studio and it was not super obvious but you could tell the low-end was out of phase when you used the Marshall with any other amp. We reversed the phase and it was better.
That does seem to be the case. Again it's pretty darn close to being 100% perfect but even the phase meter on the Neve VR shows it as being out a tiny bit. Most people wouldn't really notice it but we do since it's under mics. Trace | ||||||
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| 4/24/2000 5:24 PM |
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| dale |
oh, i forgot to mention that the amp seems to have more low end than the other marshalls i've had.[don't forget, i use this one and all the other marshalls i've had in stereo with the same pv C30] certainly this can't be if it's got a phase problem, or can it? dale |
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