• TalkBass has been independent since 1998. Add your voice.
    Create a free account to reply to discussions, view embedded media, and browse with fewer display ads.
    Join free Log in
    Want zero display ads or expanded classifieds tools? Compare plans.

Ampeg SVPCL preamp low output advice

Davi

Davi

Jan 13, 2010
29
13
UK
#1
Hi,

Im currently using an Ampeg SVPCL preamp into a QSC 1850hd power amp, into 2x8ohm cabs daisy chained single channel with parallel switches engaged on the power amp, ive noticed the output of the Ampeg is very low and is possibly due to a voltage mismatch. What would be a good solution to this problem ?

Maybe adding an EQ between the preamp and power amp or perhaps a boost pedal at the end of the pedal chain, im not sure.

Any help would be appreciated.

Many thanks
smile.png
 
  • Like
Reactions: DJ Bebop
#2
You could use a volume pedal as a quick fix. The SVP-CL was known to have low output sensitivity and will need to be matched with a power amp in the same range.

However, there are a couple of threads you can search on how to mod the output for use with a wider variety of poweramps.
 
Last edited:
  • Like
Reactions: DJ Bebop
#3
You must have an earlier SVP-CL like I do. Gerald once posted that the early one want to see a power amp with a .775 Volt input sensitivity. With an amp with a higher sensitivity (1 Volt or more), you can't get full power. There is a mod that I have a copy of somewhere but it is a fair amount of component swap out. I've use a compressor for increasing gain (with sensitivity set so it didn't compress). I have used an MXR boost guitar pedal between the pre and amp, but the S/N ratio wasn't great. A used Behringer rack mount compressor for $35 works far better.
 
  • Like
Reactions: DJ Bebop and Wasnex
#4
Jim C said:
You must have an earlier SVP-CL like I do. Gerald once posted that the early one want to see a power amp with a .775 Volt input sensitivity. With an amp with a higher sensitivity (1 Volt or more), you can't get full power. There is a mod that I have a copy of somewhere but it is a fair amount of component swap out. I've use a compressor for increasing gain (with sensitivity set so it didn't compress). I have used an MXR boost guitar pedal between the pre and amp, but the S/N ratio wasn't great. A used Behringer rack mount compressor for $35 works far better.
Click to expand...
The serial number is D5LUR5005, im not sure if this is one of the effected units or not. Also would the fact that im using an unbalanced jack from the pre to power make any difference ?
 
#5
When the volts are correct the pairing is seamless like an amp head. There's nothing like a good match. I speak from experience. I tried everything with an XLR out. DIs, DI outs of heads, studio Pres/eqs, etc. First real preamp I got with the program. Try, not buy, try a good matching preamp and know the bliss and get on with the music. Wishing or make do fixes will leave you unsatisfied. Your SVP tone goals are available in other preamps. Enjoy!
 
#7
Davi said:
The serial number is D5LUR5005, im not sure if this is one of the effected units or not. Also would the fact that im using an unbalanced jack from the pre to power make any difference ?
Click to expand...
I think I've tried it both ways with a Ampeg SVP1500 and there was no difference in output.
Crown and Crest both have amps that have adjustable input sensitivity and I think many QSC's do too.
Just as a goof I bought a Crest CA6 for cheap. Sounds so good and is so heavy.
 
  • Like
Reactions: packhowitzer and DJ Bebop
#8
Davi said:
Also would the fact that im using an unbalanced jack from the pre to power make any difference ?
Click to expand...
Yes, you do give up sensitivity and 6dB of maximum output level when going to unbalanced connections.

Your amp is ~1.1V rated sensitivity, but if operated in unbalanced mode your sensitivity drops IIRC. Be sure that the level controls on the power amp are fully clockwise.

You may also need to run your preamp master volume at a higher level than you think you should.
 
  • Like
Reactions: Laklandfan and DJ Bebop
#9
agedhorse said:
Yes, you do give up sensitivity and 6dB of maximum output level when going to unbalanced connections.

Your amp is ~1.1V rated sensitivity, but if operated in unbalanced mode your sensitivity drops IIRC. Be sure that the level controls on the power amp are fully clockwise.

You may also need to run your preamp master volume at a higher level than you think you should.
Click to expand...
Ive got the power amp on full, the preamp gain at 12oclock and master full im also using a TC Electronic Spectracomp on my pedal board set at 11 oclock with the default setting engaged, with the pedal off there is hardly any volume at all and nowhere near enough for band rehearsal.
 
#10
Davi said:
Ive got the power amp on full, the preamp gain at 12oclock and master full im also using a TC Electronic Spectracomp on my pedal board set at 11 oclock with the default setting engaged, with the pedal off there is hardly any volume at all and nowhere near enough for band rehearsal.
Click to expand...
Be sure the pad is set off as well.

I don't know enough about the differences between the various versions of this preamp (there appear to be quite a few) to be able to confirm more.

When using the transformer balanced line out on the back, note that it's pre-master volume control.
 
#13
Ive got 2 QSC 1850hd Power amps, im considering selling them both and buying something that has the option of changing the input sensitivity from .775 to 1.5va I really like the sound of the Ampeg SVP-CL
 
#14
agedhorse said:
Yes, you do give up sensitivity and 6dB of maximum output level when going to unbalanced connections.

Your amp is ~1.1V rated sensitivity, but if operated in unbalanced mode your sensitivity drops IIRC. Be sure that the level controls on the power amp are fully clockwise.

You may also need to run your preamp master volume at a higher level than you think you should.
Click to expand...



Is this another situation where some sort of level shifter like a Radial J+4 is appropriate?

The J+4 is designed to bring -10dB up to +4dB. 1/4" input, XLR output. It has 17dB of gain and a variable level control. Max input is +17dBu and max output is +15dBu.
Ref: Radial-SmartSheetBook-Bookfile.pdf (radialeng.com)
upload_2021-12-1_15-16-51.jpeg

15VDC walwart included.


This is not a cheap solution as the street price of the J+4 appears to be about $259.

I think the better choice is to either get a power amp with compatible sensitivity, or get the mod performed so the SVPCL provides a hotter signal. Dealing with extra widgets is a hassle and also something else that can go wrong.
 
  • Like
Reactions: Davi
#15
Wasnex said:
Is this another situation where some sort of level shifter like a Radial J+4 is appropriate?

The J+4 is designed to bring -10dB up to +4dB. 1/4" input, XLR output. It has 17dB of gain and a variable level control. Max input is +17dBu and max output is +15dBu.
Ref: Radial-SmartSheetBook-Bookfile.pdf (radialeng.com)
View attachment 4490518
15VDC walwart included.


This is not a cheap solution as the street price of the J+4 appears to be about $259.

I think the better choice is to either get a power amp with compatible sensitivity, or get the mod performed so the SVPCL provides a hotter signal. Dealing with extra widgets is a hassle and also something else that can go wrong.
Click to expand...
Yes, this would help.

now the difference between.775V and 1.1V is almost insignificant, so the mismatch is likely much greater.
 
  • Like
Reactions: Wasnex
#18
Is the SVT-CL preamp a lot different from the SVP-Pro? I've used a SVP-Pro for years, into a variety of power amps, the last 10 years into a QSC PLX-1602. I run out the unbalanced output of the SVP-Pro, into the 1/4" TRS jack of the QSC and parallel the inputs of the QSC.

Never had ANY issues with level at all, using a 2 x 10" 4 ohm Carvin and a single 18" Carvin (also 4 ohms) for 1,000 watts if I had to turn the master output more than 10 o'clock it would have been deafening.

In fact the only time I even got close to halfway up on the master volume was on a really large stage in a venue that seated about 800 people and at 11 o'clock it was freaking loud on the stage.

Analogeezer
 
  • Like
Reactions: Laklandfan and SC Bassboy

Latest posts

Top Bottom
Back