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Topic: Baffled by loss of volume. Help!!! |
Ron Sodos
From:
San Antonio, Texas USA
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Posted 9 Oct 2011 2:26 pm |
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Maybe one of you electronics wizards can help me. I bought a small rack and want to use it sealed, so I don't have to open the back. I installed a jack plate, a fan, a power connector. I am using a couple of PA100b Stewart power amps. The inputs are 1/4" female jacks. So I installed female 1/4" jacks in my jack plate and soldered a short cable to the jack and to a 1/4" male plug on the other end. I lose about 30% of my volume. When I go direct out of my preamp (PODXT) to the input on the back of the power amp the volume comes back up. If I use the jack I installed in the jack plate i am back to volume loss. I thought I had a short so I recreated the cables. I have cut and soldered a dozen times changing cable and jacks and resoldering. I also own 2 power amps and it does the same thing to both amps. I have 2 separate jacks with 2 separate cables. It happens on both setups which are completely independent of each other. No matter what I do there is a volume loss to the input when I use my jack plate. I know lots of guys have sealed racks with plugs going into the side of the rack. Anybody have any ideas. I am truly baffled.
Ron Sodos
Albuquerque NM |
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Tim Marcus
From:
San Francisco, CA
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Posted 9 Oct 2011 4:07 pm
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do you have a weird balancing or phase related issue with the connector on the plate?
if its a mono jack you should not have a problem - make sure you are using Tip Sleeve only - not a TRS jack, because if the amp has a balanced input you may be causing a phase cancellation which would definitely cause a problem.
What jack are you using?
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Milkmansound.com |
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Ron Sodos
From:
San Antonio, Texas USA
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Posted 9 Oct 2011 4:57 pm totally mono plug, jack and cable
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As I said it does the same thing on 2 completely separate amps, plugs cables, jacks etc. Everything is mono. Plug, cable, jack and the amp is bridged so I am going in the mono jack. When I go in with the cable directly from the output on the pod it doesn't do it at all. The minute I plug into the jack in the jackplate and it is run through a mono cable into the mono male and plugged in to the mono input on the amp I lose about 30% volume. I again I can't understand.
Ron Sodos |
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Brett Lanier
From:
Hermitage, TN
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Posted 9 Oct 2011 6:17 pm
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| Ron Sodos wrote: |
and soldered a short cable to the jack
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Are you using a shielded instrument cable where you should have a speaker cable? I don't know if that could cut off 30% of your volume but it's a thought. |
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Ron Sodos
From:
San Antonio, Texas USA
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Posted 9 Oct 2011 6:22 pm When I change the input cable the volume loss goes away.
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| When I change the input cable to the direct line in from the POD I do not change the speaker cable and the volume loss disappears. Thus, it can't have anything to do with the speaker cable. |
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Brett Lanier
From:
Hermitage, TN
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Posted 9 Oct 2011 6:35 pm
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| I guess I'm reffering to the short cable that is between your power amp and your patch bay; on the inside of the rack. |
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Ron Sodos
From:
San Antonio, Texas USA
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Posted 9 Oct 2011 6:54 pm That is a shielded cable.
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| The small cable from the plug to the jack is shielded. So is the cable when I go directly from the POD to the input. |
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Dave Grafe
From:
Hudson River Valley NY
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Posted 10 Oct 2011 8:38 am
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Sounds to me like a cold solder joint or really cheap jacks, plugs and/or cables, but you say you have re-soldered a bunch of times so maybe it is something else. If you are running the amp mono bridged then the amp's ground is electrically situated midway between the two output poles, if this ground appears on the chassis and is then transferred to the back plate your signal may be compromised.
Try removing the female jack from the back plate and see if that makes any difference, if it does you can replace it with an insulated jack which should solve your problem. |
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