Slave Out vs. Preamp Out on SVT CL?

I never use them, but I believe the difference is the slave out breaks the preamp's path to the CL's power amp and the preamp out doesn't.

 

http://www.ampeg.com/pdf/SVTCL_OM.pdf

Look at page 6, item #21. The Power Amp In allows you to "slave" the SVT-CL's power section to an external preamp source or other device. The Slave Out then sends the signal to wherever you want. Doing so breaks the signal that was present at the Preamp Out jack. IOW, I'm just as confused as you are. It does appear as if this configuration may act as an effects loop: Preamp Out > Compressor, for example > Power Amp In > Slave Out to send affected signal to external component (amp, mixer, etc.). Why don't you throw something in the loop and see what happens?

I'll be standing over...........................................here.

Riis

 

I doubt you'll have to wait long for a definitive answer. The former head engineer of Ampeg and the guy who puts together the Heritage series amps are regulars here, and they'll likely see this thread.

 

Looking at the schematics for the SVT-CL (wiring same as the 2Pro) and SVT-VR I see the following:

The signal from the pre-amp goes out the pre-amp out jack when something is plugged in.

The pre-amp signal is also routed through a switch in the power amp in jack then out to the power amp. So when you plug into the pre-out, the power amp is still functioning.

If you plug into the power amp in jack, the jack switch opens and disconnects the pre-amp signal going to the power amp. The pre-amp signal is still available at the preamp out jack. Whatever signal you feed into the power amp in jack will be sent to the power amp.

The slave out shares the same signal, from either the pre-amp or the power amp in, that is going to the power amp. It is intended to go to another power amp.


SVT CL:

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SVT-VR:

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I think that you meant to say "into the SVT's power amp in jack" rather than "into the SVT's preamp in jack". But yes, you've got it now.

That switch in the power amp in jack can be a problem. The signal pathway from the pre to the power amp goes through this contact. If it is dirty, the amp's performance is going to suffer. Good reason to apply some DeOxit to this switch contact at least once a year to keep it in top form.

 

I've usually sprayed it right in there and then done the jack in and out (I'm talking about cleaning the jacks on amps, sickos!), but I guess either way would work as long as it gets in there and cleans.

 

I use the deoxit 100% liquid with the needle applicator.

As Jimmy said, it needs to get in there. In and out with a plug will clean the plug contacts but it may not get into the switch contacts on the jack. The switch contact needs to be broken and the liquid applied to the contact point.

Just my preference but I think that it is better if the amp is opened. A small brush (see below), Q-Tip, or pipe cleaner works well. I apply it, let it sit, after a few minutes the oxides and other gunk are loosened, then I wipe it off. When it is clean, I then reapply and leave it.

If you use a spray it will seep in to the contacts and work its magic. Problem is, the gunk tends to stay in place. Even still a lot of people do it this way. It is a lot quicker and safer than opening the amp.

For tube sockets I use a small interdental brush that you can get at a drug store. Anything more than cleaning a jack and you need to be very careful.

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I use the slave out of a VR to the power amp in on a CL. I allows me to use the single pre of the VR for both amps. Easy peasy. No Y cables or messing with 2 amps required ('course if you want the singular tone).

 

Getting back to an earlier question I asked: can the Preamp Out / Power Amp In be used as an effects loop?

Riis

 

Yes.

 

Thanks for the clarification.

Riis

 

Great thread, very helpful!!!
Is the above explanation also valid for SVT3 Pro? I guess it is, but there might be some differences in the schematic.
I'm planning to use the slave out of my SVT CL to feed the power amp in of SVT 3 PRO. I suppose that the SVT 3 PRO EQ will be disconnected (no adjustments will be possible) and changes will be possible only through the SVT CL EQ. Is that correct?
Also, my plan is to use the 3 PRO with some distortion, while the SVT CL will provide clear signal (both amps will run different cabinets ) - do I need to place the drive pedal between the SVT CL slave and the SVT 3 PRO power amp in, or there is more accurate way to engage the drive effect to the SVT 3 PRO?
Another question – is it possible to use the SVT 3 PRO as a slaved amp but connect it through the guitar input in order to engage the preamp as well? I know that using two preamps is not a good idea but not sure.

 

The power amp in and pre-amp out are wired the same on both amps.

Yes. The CL preamp will be fed into the 3 Pro's power amp. You will be running two power amps fed by the CL's pre. The only problem with inserting an effect here is the input levels into the effect and does it have enough output to drive the power amp. Depending on the pedal there could be impedance issues. Try it and see. Start with the volume levels low.

I've never tried that but it should work. When a plug is in the power amp in jack, the 3PRO'S pre-amp is disconnected so that signal can be fed into another power amp. Hopefully there won't be any ground loop issues between the three amps which would cause a hum.

 

Thank you! Again!
Actually, would it be possible the drive pedal to be engaged through the effect loop of the slaved amp, or this chain will be also isolated, considering the fact that the signal will be delivered through the power amp in jack?