SVT 2 Pro weirdness

StuartV · #1 06-03-2010, 09:37 AM

Last night, I was playing through my Promethean combo. I turned on my SVT 2 Pro at the same time I turned on the Promethean, so it could warm up.

After 5 minutes or so, I unplugged from the Promethean and plugged into the SVT. I turned it off Standy and the red light changed to green. And I had no sound at all.

The Mute was not on. I looked around back and made sure the cables were hooked up to both my Aguilar cabs and they were. I tried all the different buttons on the front. I put it back on on Standby, then took it back off again. Still nothing.

I put it back on Standby, went around back and unplugged both speaker cables from the amp and then plugged them right back in. I'm using both the 1/4" jacks, to 2 8 ohm cabs, amp set for 4 ohm operation. The cables were clearly visible that they were in fact both plugged in all the way before and again after I unplugged/replugged.

After doing that, I took it back off Standy and then it started working.

Also, it *seemed* like when it did start working, the volume was not as loud as it should have been. Like, maybe about 1/2 volume. After playing for a little bit, I went back to the Promethean briefly, than back to the SVT again and this time it seemed like the SVT was louder.

Any idea what was going on with all that?

kander · #2 06-03-2010, 09:46 AM

Was the SVT 2-Pro connected to a speaker when you had it turned on in standby? Tube amps can be damaged if they are on but not connected to an appropriate load (4 or 2 ohms in this case).

StuartV · #3 06-03-2010, 09:50 AM

It was plugged into both cabs the whole time except the few seconds where I unplugged and replugged them in.

StuartV · #4 06-03-2010, 11:12 AM

Also, not that it matters in this case, but it's my understanding that the SVT is fine to be on and not plugged to any speakers, IF and only if it is in Standby.

Oh, and when I unplugged/replugged, I did put it in Standby first.

BDL1991 · #5 06-03-2010, 11:21 AM

Nope, still can damage the tubes, due to the Nature of tubes, but it may just have been the leads weren't connecting properly, are you using instrument Leads or Speaker leads?

georgestrings · #6 06-03-2010, 11:28 AM

Quote:

Originally Posted by BDL1991

Nope, still can damage the tubes, due to the Nature of tubes, but it may just have been the leads weren't connecting properly, are you using instrument Leads or Speaker leads?

IME, this is incorrect - as long as the amp stays on standby, you won't harm it any that way... furthermore, it can even be switched off of standby, as long as a signal isn't sent thru it while a speaker load isn't present...

- georgestrings

StuartV · #7 06-03-2010, 11:30 AM

They're brand new speaker leads (1 3' and 1 5', both 1/4" - 1/4"). I bought them on Monday after I got back to town from picking up these new-to-me cabs, and the amp/cabs were working fine on Monday and Tuesday. All I did between then was turn the amp off and leave it sitting there. Had not moved anything or unplugged anything (except my instrument cable from the front).

BDL1991 · #8 06-03-2010, 07:37 PM

Quote:

Originally Posted by georgestrings

IME, this is incorrect - as long as the amp stays on standby, you won't harm it any that way... furthermore, it can even be switched off of standby, as long as a signal isn't sent thru it while a speaker load isn't present...

- georgestrings

a former guitarist bought a Peavey 6505 Head unit, which if I remember correctly is a full tube head, and the shop decided to warm up the Valves for him, just leaving it turning on to heat them I think he had it just on Standby, and come the day he got it and took it home, the amp worked about as well as a chocolate Fireguard.
Though if it is just the Specific amp this thread is about that does it fair enough, I just was lead to believe that not having the speakers connected is harmful to the head unit if done for more than a rather short period of time, but I accept I may be vastly wrong

georgestrings · #9 06-03-2010, 07:49 PM

Quote:

Originally Posted by BDL1991

a former guitarist bought a Peavey 6505 Head unit, which if I remember correctly is a full tube head, and the shop decided to warm up the Valves for him, just leaving it turning on to heat them I think he had it just on Standby, and come the day he got it and took it home, the amp worked about as well as a chocolate Fireguard.
Though if it is just the Specific amp this thread is about that does it fair enough, I just was lead to believe that not having the speakers connected is harmful to the head unit if done for more than a rather short period of time, but I accept I may be vastly wrong

Although I'm certainly no expert, I spent about 15 years as a gigging guitarist before picking up the bass - during that time, I played all tube amps by Marshall, Fender, and Dean Markley... AFAIK, what I posted on the subject is correct - maybe one of the resident experts will weigh in...

- georgestrings

Jerrold Tiers · #10 06-03-2010, 10:06 PM

With the amp on standby, there is no plate voltage, and no way to damage the 2 PRO by having no load.

You CAN damage a tube amp even with no input if it is OFF standby..... i.e. has all voltages and is ready to go.

There can be an instability with no load, that causes a high frequency oscillation... tubes turn red hot, and the cathodes may get stripped by a lot of plate current.

Typically takes a minute or so, a quickie pull--push of a plug won't generally be an issue.

StuartV · #11 06-03-2010, 10:19 PM

Thanks, Jerrold.

So, any idea on why it was giving no sound and then just started working? I really think unplugging and replugging the cabs was coincidence, but then again, I have no real understanding of the internal workings of the SVT to say whether it was really coincidence or not.

georgestrings · #12 06-04-2010, 08:00 AM

Quote:

Originally Posted by Jerrold Tiers

With the amp on standby, there is no plate voltage, and no way to damage the 2 PRO by having no load.

You CAN damage a tube amp even with no input if it is OFF standby..... i.e. has all voltages and is ready to go.

There can be an instability with no load, that causes a high frequency oscillation... tubes turn red hot, and the cathodes may get stripped by a lot of plate current.

Typically takes a minute or so, a quickie pull--push of a plug won't generally be an issue.

Thanks for clearing that up, Jerrold - you were one of the experts I was referring to earlier...

- georgestrings