Discussion in 'Amps [BG]' started by Geezer Brown, Dec 30, 2012.
I have an SVT CL
I also have an SS poweramp
Can I run the pre from my CL into the SS power amp?
Yes but you still need a speaker load on the SVT.
On the power section, right?
Yep. But since after the power section is the only place in the chain you can plug in a cab...
So I need a cab on the SVT power section and (obviously) the ss power section.
You could also get a dummy load for the SVT power section, that way you won't have to tote an extra cab. The trick is finding one that will take the power.
YOu could also make one with a "Non-Inductive Dummy Load Resistor". Actually several and make sure the master vol. is all the way down.
Dummy loads that size are going to be pretty darn huge and cumbersome, plus you'll likely have to build it yourself. Might as well just bring a cab if you ask me.
What if he pulled the power tubes?
If you want to burn the power transformer up.
I really don't.
Series 2 of them and you're good to go. Weighs about 3 lbs.
Or you can trade me your SVT for my Streamliner 900 and then you have the best of both worlds
Unfortunately the aluminium plate that they need to be mounted to will weigh considerable more!! Sorry, there's no free lunch.
What if he ran the signal from the CL's preamp out, put a shorting plug in the Power Amp Input jack and also insert a shorting plug in the speaker jack?
Tube amps don't hate short circuits like solid-state amps do and there will be no input signal to the power amp anyway.
I built a dummy load out of two of those eight ohm non-inductive resistors that Parts express sells. Below are a few pics of one way to do it.
Connect to the amp via a speakon, 1/4" jack, or banana plugs. The resistors get a big warm but not too hot. If I were running it as a dummy load for a long time, I'd add a fan to the box which draws the heat off.
There is another option that hasn't been mentioned. You can add a line out similar to what is shown in the last two pics. You add a pot resistor and a jack to the dummy load to tap off the signal. This allows you to take advantage of having the tone of both the SVT's pre and power amp and feed it into the solid state power amp. You have to be careful how hot the signal going to the SS amp is otherwise it will be quite distorted. I've done this with smaller amps and the distortion and sustain are amazing. Never tried it with an SVT. Similar circuits are found on some Mesa (as in the last pic) as well as other amps. Add a transformer and you can have a 600 ohm balanced line out to go to a mixing board.
You can short the out for short periods of time without harming the amp. Some techs do this when working on amps like when setting the bias. It isn't such a good thing to do when playing though. Some amps short the output when a speaker isn't connected. In the short term, it protects the amp till you go "oh no, what have I done" and shut down. As was mentioned above, you can disable the power amp on the SVT by pulling the driver tubes. It isn't good to keep installing and pulling the tubes. No harm in doing it just to see if the pre into the SS amp delivers the goods.
EDIT: I checked the SVT-CL schematic, if you plug a shorting plug into the power amp in, the pre-amp out will still work and the input to the power amp will be shorted shutting it down. An errant spike in the power amp could cause a problem without a dummy load in place. As Charlie said below, just a little extra insurance to have it in place.
I've done this for many many gigs with one of my old guitar amps. The key part is the input shorting jack at the power amp in, and that input jack being normalled such that it cuts signal when something is plugged in. If the power amp isn't seeing signal it's not going to cook the output transformer. If you want to be really safe, use a dummy load anyway. Doesn't need to be a high power one, and this way the power tubes are not getting unnecessary wear. Of course, you only get the preamp section mojo then though.
If I owned an SVT I wouldn't mess with any of this, frankly. I'd use it where it worked for me and just use something else the rest of the time.
Ya, really...what's the point of lugging 85 lbs of SVT only to use the preamp? Just get an old SVP-CL if that's what you want. They're $300 or so used and much lighter, and they're the same pre.
yep, worst. preamp. ever.
if you're gonna lug it out, might as well use its power.
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