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Ampeg SVPCL preamp low output advice

#22
There may be significant differences between the versions. Somebody familiar with the Ampeg line AND the versions would be helpful. Maybe Jimmy has the info?
 
#24
agedhorse said:
There may be significant differences between the versions. Somebody familiar with the Ampeg line AND the versions would be helpful.
Click to expand...
It's been published here with serial numbers as to when the change was made. It will require some time using the search feature. What's much easier to find is this same problem mentioned over and over. I've used 2 of these preamps as well as own an SVT-IIP and none of them offer significant gain but both work OK with .775 V amp sensitivity.
I've owned this pre for over 10 years and use it once a week. I have used it with a variety of power amps. It is what it is.
 
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#25
Jim C said:
It's been published here with serial numbers as to when the change was made. It will require some time using the search feature. What's much easier to find is this same problem mentioned over and over. I've used 2 of these preamps as well as own an SVT-IIP and none of them offer significant gain but both work OK with .775 V amp sensitivity.
I've owned this pre for over 10 years and use it once a week. I have used it with a variety of power amps. It is what it is.
Click to expand...
The volume I get is practically unusable with out the boost from the spect
Jim C said:
It's been published here with serial numbers as to when the change was made. It will require some time using the search feature. What's much easier to find is this same problem mentioned over and over. I've used 2 of these preamps as well as own an SVT-IIP and none of them offer significant gain but both work OK with .775 V amp sensitivity.
I've owned this pre for over 10 years and use it once a week. I have used it with a variety of power amps. It is what it is.
Click to expand...
The volume I get is so low its practically unusuable without adding the spectracomp to the pedal board. And if the difference between .775v or 1.1v to 1.16v is insignificant then theres something else amiss
 
#26
Davi said:
The volume I get is practically unusable with out the boost from the spect

The volume I get is so low its practically unusuable without adding the spectracomp to the pedal board. And if the difference between .775v or 1.1v to 1.16v is insignificant then theres something else amiss
Click to expand...
Agreed.

Are you using a 1/4" 6.36mm) TS or TRS cable?
 
#28
Davi said:
The volume I get is practically unusable with out the boost from the spect

The volume I get is so low its practically unusuable without adding the spectracomp to the pedal board. And if the difference between .775v or 1.1v to 1.16v is insignificant then theres something else amiss
Click to expand...
It sounds like there is something wrong with your pre.
Lately I've been using an Ampeg SVP 1500 which is 1.5 VRMS and in mono with the pre input and master volume at 1/2, there is plenty of power to gig with a 2x15 cabinet. Granted the signal light are just barely illuminated but it's plenty loud. If you power amp is of equal power, one would think that you would get close to the same volume all things considered.
I'm really interested in what your find with T/R vs. TRS with 1/4" cables. I don't remember any volume change with the SVP-CL, but my memory isn't what it used to be! That rig is at our rehearsal space and I won't be back there for a week.

[Invalid or Expired Link Removed]
 
#30
Davi said:
Ive been using the 1/4" TS im going to try the 1/4" TRS tonight
Click to expand...
TS is the correct cable to use, a TRS cable won't work properly into a balanced TRS input because it looks like Ampeg floats the ring (most common way to do it).

I checked my documentation and the SVT PRO shows a full +20dBu line level output from the two main 1/4" TS output jacks.

Other versions may very well be different.

BasturdBlaster said:
The svp 1600 power amp has a 0.5v input sensitivity according to the manual, maybe this model was intended for the OP's model pre?

https://ampeg.com/pdf/SVP1600.pdf
Click to expand...

Might be helpful as that's a 6dB improvement in effective sensitivity.

It's also possible that there's a problem with the preamp. A tech would be able to verify the overall gain and maximum output level quite easily.
 
#31
BasturdBlaster said:
The svp 1600 power amp has a 0.5v input sensitivity according to the manual, maybe this model was intended for the OP's model pre?
Click to expand...

This is correct, the SVP 1600 was the matching amplifier. I bought the 1500 as I found a great deal on a used one about 10 years ago and never thought to check about input sensitivity / compatibility.

Is .5V used anymore or even used by anyone other than Ampeg back then? Seems like .775V is the lower industry standard these days.
 
#32
Jim C said:
This is correct, the SVP 1600 was the matching amplifier. I bought the 1500 as I found a great deal on a used one about 10 years ago and never thought to check about input sensitivity / compatibility.

Is .5V used anymore or even used by anyone other than Ampeg back then? Seems like .775V is the lower industry standard these days.
Click to expand...
There is the consumer -10dBu unbalanced standard which is around .250V, when balanced this would represent .5V so maybe that's where the concept originally came from.
 
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#33
agedhorse said:
TS is the correct cable to use, a TRS cable won't work properly into a balanced TRS input because it looks like Ampeg floats the ring (most common way to do it).
Click to expand...
TRS = balanced TS = unbalanced, is that correct ?. I was under the impression that a balanced lead would give an extra 6db and raise the sensitivity slightly. Sorry im not very technical clued up with this stuff :)
 
#34
Davi said:
TRS = balanced TS = unbalanced, is that correct ?. I was under the impression that a balanced lead would give an extra 6db and raise the sensitivity slightly. Sorry im not very technical clued up with this stuff :)
Click to expand...
A balanced signal with a balanced input will give you an additional 6dB, but because the output of the SVP's 1/4" output is unbalanced, the (maximum) signal level is reduced by 6dB.

Another interface that would work is a step-up audio transformer between the unbalanced output of the preamp and the balanced input to the amp. Because the output impedance is low on the preamp, it can drive a step-up transformer well.

Here's an example of one, marketed for going the opposite direction but the transformer process is bi-directional (just that the connector gender is wrong and it uses an RCA rather than 1/4" ):
Link Removed

Here's something that should work right out of the box:
Morley Ebtech LLS-2-XLR Line Level Shifter -10dBu <-> +4dBV Voltage Converter
 
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#35
agedhorse said:
A balanced signal with a balanced input will give you an additional 6dB, but because the output of the SVP's 1/4" output is unbalanced, the (maximum) signal level is reduced by 6dB.
Click to expand...

https://ampeg.com/pdf/SVPCL.pdf
Page 5
Would using the transformer balanced line out offer more output? I completely forgot it had one.
 
#36
agedhorse said:
A balanced signal with a balanced input will give you an additional 6dB, but because the output of the SVP's 1/4" output is unbalanced, the (maximum) signal level is reduced by 6dB.

Another interface that would work is a step-up audio transformer between the unbalanced output of the preamp and the balanced input to the amp. Because the output impedance is low on the preamp, it can drive a step-up transformer well.

Here's an example of one, marketed for going the opposite direction but the transformer process is bi-directional (just that the connector gender is wrong and it uses an RCA rather than 1/4" ):
Link Removed

Here's something that should work right out of the box:
Morley Ebtech LLS-2-XLR Line Level Shifter -10dBu <-> +4dBV Voltage Converter
Click to expand...
I've had a svpcl that I should've never sold, its not as low as an alembic f2b but with a plx3602 and good cabs it's plenty loud for gigging.

Would the Morley have helped the output of both amps? Would the preamp go to the +4 and -10 to the power amp or vice versa?

Would a pedal with a buffered output help with this issue?
 
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#37
I have an SVP Pro. It too has a low output. I was able to resolve this by putting a BOSS GEB7 Equalizer in the effects loop. It's perfect because it'll cleanly bump up the output signal and you can tweek the EQ based on the room acoustics if like.
 
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#38
Jim C said:
https://ampeg.com/pdf/SVPCL.pdf
Page 5
Would using the transformer balanced line out offer more output? I completely forgot it had one.
Click to expand...
Depends on the drive circuit and how it's configured, but maybe. I believe it's pre-master volume though.

Laklandfan said:
I've had a svpcl that I should've never sold, its not as low as an alembic f2b but with a plx3602 and good cabs it's plenty loud for gigging.

Would the Morley have helped the output of both amps? Would the preamp go to the +4 and -10 to the power amp or vice versa?

Would a pedal with a buffered output help with this issue?
Click to expand...

The Morley level shifter would certainly help.

A pedal with a buffered output wouldn't help without enough gain and it would still need to have a maximum output level of >+4dBu (typically around +10dBu is adequate, and hard to achieve unbalanced from 9V)
 
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