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Ampeg SVPCL preamp Low output advice


Davi
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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 :) 

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2 hours ago, la bam said:

I think these are notorious for struggling to drive a power amp I'm afraid. Hopefully someone will know a bit more.

It does seem that way, if it wasnt for the boost from spectracomp compressor on my pedal board it would be completely useless for band rehearsal

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11 minutes ago, NAS Bass said:

Try a power amp with a lower input sensitivity 

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 1.5v

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Hmmm.... with the RMX1850 you've got plenty of watts available, so it's a problem at the amp input or amp output.

 

What cabling method are you using? This could be a cabling issue.

 

I'd connect amp ch1 to one 8R cab and amp ch2 to the other 8R cab (the other option is the two cabs paralleled to 4R and connected to the amp in mono bridge mode - this will give max amp power).

 

As to the amp inputs you've got the option of bal XLR, mono jack or screw terminals - as the preamp outs are unbal mono I'd go jack-to-jack to the amp's jack ins with two mono jack cables.

 

If things are still not loud enough it's either the preamp's out is low level (-10dB?) or the power amp (at +3.5dB) is not very sensitive, (and/or speakers are low efficiency).

If it is a case of low levels then you need to make up an extra 13.5dB approx - you could use a HPF (Broughton)  or compressor (dbx 166xs, Drawmer DL241) between pre and power amps to make up the gain...

or it might be cheaper to swap the power amp.

 

 

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18 minutes ago, Bigguy2017 said:

Hmmm.... with the RMX1850 you've got plenty of watts available, so it's a problem at the amp input or amp output.

 

What cabling method are you using? This could be a cabling issue.

 

I'd connect amp ch1 to one 8R cab and amp ch2 to the other 8R cab (the other option is the two cabs paralleled to 4R and connected to the amp in mono bridge mode - this will give max amp power).

 

As to the amp inputs you've got the option of bal XLR, mono jack or screw terminals - as the preamp outs are unbal mono I'd go jack-to-jack to the amp's jack ins with two mono jack cables.

 

If things are still not loud enough it's either the preamp's out is low level (-10dB?) or the power amp (at +3.5dB) is not very sensitive, (and/or speakers are low efficiency).

If it is a case of low levels then you need to make up an extra 13.5dB approx - you could use a HPF (Broughton)  or compressor (dbx 166xs, Drawmer DL241) between pre and power amps to make up the gain...

or it might be cheaper to swap the power amp.

 

 

Or use an active unbal to bal converter like the Sonifex RB-UL1, Alice MatchPack or cheapo Art CleanBox to make up the levels (if you fancy some DIY the Sonifex has loads or room to add two jack sockets parallel to the phonos in).

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7 hours ago, agedhorse said:

There are several versions of the SVP, it’s very possible that this is common with all SVP models.

I used to run an SVP-PRO into a QSC PLX 1602 and had no problems with levels - plenty of signal level with preamp out put on like 1/3rd volume.

 

Id be tempted to get the preamp checked out for faults. 

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2 minutes ago, bassman7755 said:

I used to run an SVP-PRO into a QSC PLX 1602 and had no problems with levels - plenty of signal level with preamp out put on like 1/3rd volume.

 

Id be tempted to get the preamp checked out for faults. 

In the past I've run quite a few different pre-amps (not an SVP PRO though) into a QSC PLX 2402 without problem

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1 hour ago, Bigguy2017 said:

What cabling method are you using? This could be a cabling issue

Im using a speakon to jack for the first cab then daisy chaining the next cab speakon to jack to get a 4ohm parallel connection.

 

1 hour ago, Bigguy2017 said:

As to the amp inputs you've got the option of bal XLR, mono jack or screw terminals - as the preamp outs are unbal mono I'd go jack-to-jack to the amp's jack ins with two mono jack cables.

The manual also gives the option of balanced jack. Ive been using unbalanced jack, tonight I will try a balanced jack to see if the 20kohm (balanced) to 10kohm (unbalanced) makes much difference.

 

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If it helps - and it may just be my unit - but I tried running my svp pro with a crown xls1500 power amp. Switched it to .775 and it was still way way underpowered.

 

I then tried it with a bass amp, via the send/return, and it worked perfectly.

 

Also worked great going out of the svp and into the input on the bass amp.

 

Edited by la bam
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17 minutes ago, la bam said:

If it helps - and it may just be my unit - but I tried running my svp pro with a crown xls1500 power amp. Switched it to .775 and it was still way way underpowered.

 

I then tried it with a bass amp, via the send/return, and it worked perfectly.

 

Also worked great going out of the svp and into the input on the bass amp.

 

The effects return is usually more sensitive than the input on a dedicated power amp. Interesting that your SVP pro struggled with the crown amp, maybe these ampeg preamps have some poor quality control or something where the output isnt consistent between units or something.

Edited by bassman7755
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39 minutes ago, bassman7755 said:

 

The effects return is usually more sensitive than the input on a dedicated power amp. Interesting that your SVP pro struggled with the crown amp, maybe these ampeg preamps have some poor quality control or something where the output isnt consistent between units or something.

Looks like the Ampeg pre output is low level (-10dB or less ? - not stated in the manual) and better suited to FX returns

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6 minutes ago, Bigguy2017 said:

Looks like the Ampeg pre output is low level (-10dB or less ? - not stated in the manual) and better suited to FX returns

There is very little technical information in the SVP-CL manual, it doesnt mention anything about the output level

Screenshot_20211202-124431_Samsung Notes.jpg

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9 hours ago, agedhorse said:

The preamp output must be -10dBu nominal then. The sensitivity difference between .775V and 1.16V is insignificant in this context.

 

There are several versions of the SVP, it’s very possible that this is common with all SVP models.

Would a boost pedal between the pre and power amp solve the volume issue ? 

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TUBE ULTRAGAIN MIC100 User Manual
5. Specifications
XLR Input
Connector balanced/unbalanced
Type transformerless, DC-decoupled input
Impedance approx. 2 kΩ
Max. input level +7 dBu / -20 dB with pad
¼" TRS Input
Connector balanced/unbalanced
Type transformerless, DC-decoupled input
Impedance approx. 1 MΩ
Max. input level +16 dBu / -20 dB with pad
Audio Outputs
Connectors XLR connector + ¼" TRS jack
balanced/unbalanced
Type transformerless, DC-decoupled output
Impedance approx. 700 Ω balanced,

approx. 350 Ω unbalanced
Max. output level approx. +26 dBu @ 100 kΩ

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