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SVP PRO help please

svp

svp

Mar 12, 2007
604
69
Atlanta
www.myspace.com
#1
I am running a SVP PRO pre-amp with a QSC PLX 2402. Running power amp channels bridged, the problem is with the volume on power amp at 12:00, master on svp on 12:00, I can't get the gain above 9:00 without pegging the red peak light. Also if anybody has suggestions on certain tubes to use to get a little more dirty tone out of the drive section that would be appreciated. Thanks for the help. I really like the tone so far through my Berg NV610, just trying to improve if possible.
 
#2
The red light is really kind of useless. If it's not on all the time your OK. Jimmy M may chime in on the ampeg gain staging & lights. I have main coming on every time I hit the strings, just not staying on or continuous. The SVP is a different bird as far as how interactive the gain/drive & tone sections interact from what I've read hear. It seems that way to my ears too.
 
#3
The thing is that if I get past 9:00 at all on the gain know the red peak led will stay on constant, what I don't understand is that I can only turn up the gain a quarter of it's total before the light stays on meaning peaked. I thought I had read somewhere about an issue with I believe it was relating to output sensitivity matching properly to the power amp, but then I was told should be ok with the model of power amp I am using, hopefully someone can shed some light on it.
 
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#6
To be clear I'm not having a problem achieving needed volume level maybe because of the wattage of the QSC PLX2402 but this just seems to be odd to me. Sure wish I could recall where I thought I read something about the output sensitivity rating(if that even has anything to do with it). Maybe someone familiar with QSC power amps and or svp pro pre-amps while chime in, thanks.
 
#8
svp said:
To be clear I'm not having a problem achieving needed volume level maybe because of the wattage of the QSC PLX2402 but this just seems to be odd to me. Sure wish I could recall where I thought I read something about the output sensitivity rating(if that even has anything to do with it). Maybe someone familiar with QSC power amps and or svp pro pre-amps while chime in, thanks.
Click to expand...
Here's how to gain-stage the set up correctly.

  1. Disconnect your speaker/cab from the PLX.
  2. Set your input gain on the SVT (until it flashes with strong playing per user guide).
  3. Turn down (minimum) SVT master, turn up PLX to max.
  4. Now, slowly turn up the SVT master out level - while playing - until the PLX clip light comes on. NOTE the LEVEL on the SVT.
  5. Back off the input levels on the PLX so you are not clipping the PLX input. NOTE the levels there also.
  6. Turn down SVT master, reconnect speakers/cabs.
  7. Turn up the SVT to the prior level.

You should be all set..
You are now gain staged properly for maximum output levels without clipping.

You can control the speaker volume using the SVT master (below the noted level in #4 above). If you go over that level you will clip the input levels on the PLX. If overall volume at those levels is too loud, turn down the SVT master until you are happy.
If it's not loud enough at gain staged levels, then you need more rig.

Couple of things to note.

NOTE #1: The "knobs" on the PLX are NOT volume knobs.. they are input attenuators. Meaning they control how much input voltage is required for the amp to produce rated power. You can get the PLX to produce rated wattage with those knobs almost completely "off" IF you crank up the SVT pro output level (theoretically, but it depends on how hot the SVT output is).

NOTE #2: Using steps 3-5 above, you can play with the levels on both the SVT and PLX to obtain the largest range of volume control over the main output. IOW replace steps 3-5 above with
  1. Turn down (minimum) PLX, turn up SVT to max.
  2. Now, slowly turn up the PLX levels - while playing - until the PLX clip light comes on.
  3. Back off the input levels on the PLX so you are not clipping the PLX input.
This will give you the greatest range of SVT volume control.
Hope this helps.
 
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#10
svp said:
To be clear I'm not having a problem achieving needed volume level maybe because of the wattage of the QSC PLX2402 but this just seems to be odd to me. Sure wish I could recall where I thought I read something about the output sensitivity rating(if that even has anything to do with it). Maybe someone familiar with QSC power amps and or svp pro pre-amps while chime in, thanks.
Click to expand...

I worked a bit on cableguy's SVP Pro a while ago, just a winter project to help a retired MI gear tech from going stir crazy. The clipping indicator is hilariously miscalibrated, but the front end is also quite hot and I liked it better with a little of that gain taken down a notch or two at the board level rather than via the pad and/or gain control. If you want more dirt, the Drive control can be your friend.

I've owned a bunch of PLX amps. Gain at noon or lower is not something I've ever found to work particularly well at all in any bass instrument or PA application unless biamping and just using the gain control to balance tweeter power levels. Somewhere in the manual there is a warning about running the gain controls too cold -- you can actually clip the circuit in front of the gain control if you run a hot enough signal into it. Just turning the gain control all the way up isn't necessarily the best solution either, you really need to suss best gain staging practice for your gear and your playing style.
 
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#14
svp said:
What power amp would you recommend that would have similar wattage and responsive to bass frequencies plus lightweight?
Click to expand...

You can get your QSC modded to a lower (numerical) sensitivity, not all all hard for a competent tech to do. The real problem is arguably the preamp, not the power amp though. One time honored band-aid is to use a pro audio EQ or compressor between the preamp and the power amp.
 
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#15
They're it's no problem with the output of the svp pro. You must be thinking of the svp cl.

I personally like the older carvin dcm amps. 1v input, torridal transformers, 10" deep. You can get them to your front door for around $200 or less.
 
#16
JimiLL said:
They're it's no problem with the output of the svp pro. You must be thinking of the svp cl.
Click to expand...

If it couldn't drive your QSC, that's a problem, no? As I posted in another thread though, that's situationally gain dependent. I didn't observe that problem with the one I had here, with my basses, even driving a power amp that needs 2+ volts RMS to drive it fully. I liked the way it sounded a lot too.
 
#17
JimiLL said:
They're it's no problem with the output of the svp pro. You must be thinking of the svp class.

I personally like the older carvin dcm amps. 1v input, torridal transformers, 10" deep. You can get them to your front door for around $200 or less
Click to expand...
You probably weren't getting full drive.

My carvin dcm 2000 was louder than the plx 3402 I had. .7 v difference in input sensitivity. My experiences are reflected by many here on tb
 
#20
JimiLL said:
Any setting. The carvin had more everywhere at 700watts a channel vs the plx with 1100 watts a channel.
Click to expand...

I could go through a big tedious post on gain matching, actual SVP measurements I've done on my bench, extensive experience at work with DCM2000s vs. PLX 1802s and 2402s, etc. If you and/or the OP really want that, please say so. Otherwise, it's a lot of work for little reward, especially given that it's already been done in similar form so many times here on TB. Link Removed
 
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