SVT 3-Pro: Difference between Preamp Out/Power Amp In and Effects Loop?

[the_fooj]

I've got an Ampeg SVT 3-Pro and I've never used any effects before, but I've been thinking of picking up a compressor (dbx 166A, to go in the loop).

I noticed on the back of the amp there's jacks for Preamp Out and Power Amp In as well as Effects Loop Send and Return. I always thought these were the same thing? Or does it have to do with where they're placed in relation to the Line Out? What's the difference?

Any Ampeg gurus here that can help me out?

http://www.ampeg.com/pdf/SVT-3PRO.pdf here's a link to the user manual (pg 4) to see what I'm talking about.

[billfitzmaurice]

My guess is that's to allow you to use effects and output/input at the same time, rather than just one or the other.

[jaspercbass]

Preamp Out: This is to be used if you are using a separate power amp with the SVT 3 Pro. This signal comes directly from the amp's preamp section and bypasses the power section. So if you like the sound of the preamp but need more power, you can run a line from the preamp out to a power amp of your choice. You would then have the sound of the SVT 3 Pro, but with a different power section.

Power Amp In: This bypasses the preamp/eq section. If you have a different rack preamp, or stompbox preamp that you prefer over the SVT 3 Pro, you can use this input to bypass the onboard eq and just run the SVT 3 Pro as a power amp essentially. This is handy if you have a sound you like without your amp, but still need something to power it.

Effects Loop: This is a loop inserted in between the preamp section and the power amp section of the SVT 3 Pro. Generally this is used for any line level effects that you are running with your rig. This is probably the spot you would want to run the 166a in, as usually rack mounted effects tend to use line level. The effects send comes directly from the preamp section, giving you a post-eq line level output. You'd then go from there to your compressor and compressor back to the Effects Return.

Hopefully that made sense.

*Edit* Sorry, I misunderstood the question. I guess technically they are essentially the same thing. However, the Preamp out and Power Amp in can't be used as an effects loop, as once you plug in to the power amp in, the internal signal is disconnected.

[the_fooj]

Originally Posted by billfitzmaurice

My guess is that's to allow you to use effects and output/input at the same time, rather than just one or the other.

So what would the difference be between:

using the effects loop for effects and sending the SVT preamp to a separate power amp?

AND

SVT Preamp Out > effects > separate Power Amp
or
separate Preamp > effects > SVT Power Amp In

[stiles72]

Both the effects loop send and preamp out are post EQ, and can essentially act as line outs. But the effects loop itself is probably before the preamp out in the chain. That way, effects inserted into the loop will still make it to the preamp out which can be feeding a slave amp, mixer, front of house, recording device, etc... Someone like Jerrold Tiers could confirm for sure.

[the_fooj]

Originally Posted by stiles72

Both the effects loop send and preamp out are post EQ, and can essentially act as line outs. But the effects loop itself is probably before the preamp out in the chain. That way, effects inserted into the loop will still make it to the preamp out which can be feeding a slave amp, mixer, front of house, recording device, etc... Someone like Jerrold Tiers could confirm for sure.

Yeah this is what I what thinking/hoping for. Makes sense and allows for the maximum amount of flexibility.

[jaspercbass]

Originally Posted by stiles72

Both the effects loop send and preamp out are post EQ, and can essentially act as line outs. But the effects loop itself is probably before the preamp out in the chain. That way, effects inserted into the loop will still make it to the preamp out which can be feeding a slave amp, mixer, front of house, recording device, etc... Someone like Jerrold Tiers could confirm for sure.

Yep, according to the schematics if I'm reading correctly, the effects loop comes before the preamp out.

[Jerrold Tiers]

Effects loop is before master, so the master does not affect it. Whatever you put in is getting same level at any volume setting.

And it goes to the DI, if that is set "post".

Pre out/power amp in obviously gets the signal the power amp gets, after tha master. And it does NOT go to the DI.

Pre out does NOT interrupt signal, but power amp in does. Same for effects send vs return.