Audio Research VT100 MK1 and LS15 HELP!!!

@jea48  Wow! Yes, it appears you were right that you were wrong :-)

And between Chip's comment earlier and my not looking closely enough at the rear panel photos I mentioned it appears that I was wrong as well. What I assumed were separate connectors for the jumpers were just printed symbols.

Thanks for catching that.  

Best,
-- Al

P.S: I'm signing off for the night.

The jumpers install into the balanced output jacks.... They would have to be removed before the balanced cables could be plugged in.

@jea48  Jim, no, I'm pretty certain that you were right the first time. The OP said that his amp is a VT100 MkI (which I would think is the same thing as a VT100 that has no Mk designation indicated on it). Your comment that I quoted would apply to the MkIII, and perhaps to the MkII, but rear panel photos of the VT100 with no Mk designation show connectors for the jumpers that are separate from the XLR input connectors.

Best,
-- Al
 

Would it damage the system if i dont have jumper connected while using rca?

No.  It just wouldn't be sonically optimal, and it might result in a bit of hiss and/or hum.  

Regards,
-- Al

@Kentrent, the jumpers must be present on the rear of the amp (in the two places where it says "use jumper for single-ended") if and only if the connections between preamp and amp are made with RCA cables. The jumpers must be removed if the connections between preamp and amp are made with XLR cables.

@jea48
Jim, it looks like I provided an answer to some of the questions you directed to me in one of your recent posts while you were composing that post. So as I said it seems very possible that if the jumpers are installed while the amp’s balanced inputs are being used it "could make the preamp very unhappy." And the caution you found in the manual about not using the mute function while the volume level is high would seem to add credence to that.

Regarding your question about the volume difference, the OP had said earlier that:

At the seller house setup, he only turn on 30% and i can hear music pretty loud. But when my setup i had to crank up to about 70% to hear loud.

... And I note that the seller’s speakers are spec’d as being 6 db more efficient than the OP’s speakers. I’m guesstimating that would account for about 1/3 of that 40% difference. And perhaps differences in the source components and source materials that were used, room effects, and differences in listening distance might be contributing to some extent as well. But in any event it would seem that all bets are off until the issues of the sparking tube and the shut-downs of the preamp are resolved.

Best,
-- Al

The jumpers do not go in the XLR socket.  The receptor is separate and apart.  See the manual.

Excellent point about the jumpers, Chip. Since the OP has been using balanced interconnections between the preamp and the amp he should verify that jumpers are NOT installed on the rear of the amp in the two connectors labelled "Use Jumper for Single-Ended."

If jumpers are installed there while balanced connections are being used one of the two signals in the balanced pair of signals the preamp is providing for each channel would be shorted to ground. Which could make the preamp very unhappy.

Regards,
-- Al

Assuming that the sparking is occurring most of the time (which would not be normal), rather than just briefly during the first minute after turn-on (which might be normal, as has been said), it is conceivable that both the sparking and the shut-downs are being caused by poor contact between some of the pins on that tube and its socket.

If you haven’t already done so I repeat the suggestion I and others made earlier of taking off the top cover and checking that the tubes are securely inserted in their sockets, and that they don’t seem so loose in their sockets that they come out with essentially no resistance.

When you do that, be sure to follow the cautions Jim (Jea48) stated earlier: Unplug the component from the AC, and wait for a while after doing so before touching anything inside. He suggested waiting for 30 minutes in the case of the amp; somewhat less than that would probably be ok in the case of the preamp (although keep in mind that the tubes will be hot for a while after the component is turned off). And be sure that any tubes which are lifted out of their sockets are returned to the exact same socket.

(Jim, thanks for stating those cautions, which I should have thought of saying myself in my earlier post).

We know in this case that the amp and the preamp were working before they were transported from the seller’s house to yours, at least for the amount of time you spent listening to them at his house. Which reinforces the possibility that something happened during transportation, or during setup at your house. Such as a marginal contact between the pins on a tube and its socket turning into a problem.

Good luck. Regards,
-- Al

One thing I would do is to remove the top covers of the two components and make sure that the tubes are securely inserted in their sockets.  Especially in the case of the amp, given that all of its 16 tubes are mounted horizontally, which might have made them susceptible to coming loose when the amp was transported.

Regards,
-- Al