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Looking for advice on an ampeg SVT 4 pro

wolfkeller

wolfkeller

Supporting Member
Aug 11, 2013
5,716
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detroit
#1
I just picked up a USA svt4p. I didn't get alot of time to play it as all my gear is in a trailer and I had a gig sat. So, I ran it onto 2 svt 810e cabs on stereo obviously. I have to say, it just didn't seem to be very loud. I have read about bass sucking power, I was mindful of that but it really sounded weak unless I used the ultra bass. I had the gain nearly maxed and the master at noon to get a decent level. Mind you, I play on a loud band with a very hard hitting drummer and no, theyre not gna turn down lol. I don't even bother with monitors since they usually screw it up.

So, I like a good drive and a nice thick tone, I play a variety of basses but it was IMO, weak. I just came from using 2 GK 800rb and they sounded better at 300w each.

My first thought is the preamp tubes. Maybe a new set with something more suited to overdrive? I need this thing loud and powerful and not sure how to proceed. Appreciate any input.
 
#3
I owned a 4-Pro for a bit, but I ran mine bridged into a pair of 4-10's. I absolutely loved it's sound, but I couldn't make it loud enough, either. I don't think I ever tried the Ultra Lo switch.

I've read a couple of SVT4-Pro threads here, where the same lack of volume concerns are stated , and there's longtime 4-Pro owners who shed light on how they set the preamp gain and how to eq the amp to get the most out of it.

Google SVT4-Pro lacks volume. I think you should be able to find the threads I'm talking about. I wouldn't change your preamp tubes until you read through the threads.

Take care.
 
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#4
What were your gain and master set at? Turn the gain up to as far as it can go before distortion. Last time I used a 4 Pro, it was with a PJ and I had the gain at somewhere around 3:00 and it wasn't distorting and it was blasting the 810e pretty darn good. Of course, I can't use it with the band at that volume, but I darn sure tried it at soundcheck!
 
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#10
It's an old amp and needs to be checked out by a tech to ensure that it is preforming to spec.. Low volume is not normal.

In particular, have them check the power supply voltages and caps, the tubes, the power tube bias. The tube sockets and jacks contacts should be cleaned (with Deoxit), especially the shunts in the effect send and receive jacks. This is all basic maintenance.
 
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#11
beans-on-toast said:
It's an old amp and needs to be checked out by a tech. Low volume is not normal.

In particular, have them check the power supply voltages and caps, the tubes, the power tube bias. The tube sockets and jacks contacts should be cleaned (with Deoxit), especially the shunts in the effect send and receive jacks. This is all basic maintenance. It will sound like a new amp.
Click to expand...
I will probably do that, but this is a 4pro, no power tubes or sockets
 
#12
wolfkeller said:
I will probably do that, but this is a 4pro, no power tubes or sockets
Click to expand...

Oops. I should know better.

The power transistor bias should still be checked to optimize performance and cleaning the jacks is very important. An oxidized jack contact in the signal pathway is like putting a resistor inline. It reduces the signal and prevents the amp from putting out the power that it should. Likewise for checking out the power supply.

Here is a link to the 4Pro schematics. It can help to have a set if your tech doesn't have a copy.

Ampeg SVT 4 Pro schematic needed
 
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#13
beans-on-toast said:
Oops. I should know better.

The power transistor bias should still be checked to optimize performance and cleaning the jacks is very important. An oxidized jack contact in the signal pathway is like putting a resistor inline. It reduces the signal and prevents the amp from putting out the power that it should. Likewise for checking out the power supply.

Here is a link to the 4Pro schematics. It can help to have a set if your tech doesn't have a copy.

Ampeg SVT 4 Pro schematic needed
Click to expand...
Highly appreciate it!
 
#16
Here is how it was sat. The ultra high and low are on as it sounded crappy otherwise. The limiter defeat is engaged as well.
IMG_20160912_152742808.jpg
 
#18
wolfkeller said:
Here is how it was sat. The ultra high and low are on as it sounded crappy otherwise. The limiter defeat is engaged as well. View attachment 948328
Click to expand...

Ditch the ultra High and Low. That is just scooping your mids. Turn the GEQ off. Turn your mid selector down to 1. Turn the gain up. After you get your volume sorted, you can turn the GEQ back on to adjust the final tonal changes.

JimmyM said:
Not near enough gain. Crank that puppy! With a Precision I have to crank to like 4:00 before I start hearing distortion. That's your problem...unused potential.
Click to expand...


Yep, turn that sumbitch up.
 
#19
I have an issue where my master is 12:00 and higher to get good volume too. It seems like it should be that loud at much lower knob positions. Also, try backing that compressor down. On mine that knob really cuts my volume.
 

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