Audio Research VT100 MK1 and LS15 HELP!!!


I recently bought this set VT100MK1 and preamp LS15 and while I was at this seller house he demonstrated the sound from his online Tidal on TV connect optical to the DAC Luxman DA - 06 then this go to the preamp LS15 and out into the VT100. This set up sounds amazing at his house. However, when I came home play CD from the Sony X1100ES Blu-ray player RCA output into the LS15 and out to the VT100 and it sound horrible - no bass at all in any type of music.  The sound sometime muffle and not clear and most importantly the bass missing tremendously. Im using a pair of KEF R900 Speakers. What is wrong here? can anyone help me correct the sounds? it is because I didn’t have the Luxman DA - 06 DAC? or it is because I don’t have those fancy hundred - thousands of dollars cable?  or the CD source is playin at 41khz /16 bit not high enough signal?  

This is my first system and I don’t know why I can’t get that high fidelity sound from the ARC equipments.  I'm waiting for the Audioengine B1 to arrive so I can stream Spotify into the LS15.   What is wrong with my set up?  Thank you in advance for helping me solve this.
kentrent
So...  Just a polite correction.  The jumpers do not go in the XLR socket.  The receptor is separate and apart.  See the manual.
To clarify my earlier post, test the preamp without a load.  No input cables attached.  No output cables attached.  See if the sparking stops.

If not, steal a 6922 from the VT100.  It has 8.  Swap it in for the sparking LS15 tube.  See if it fixes the sparking problem.  If so, put it back in the VT100 and go tube shopping.


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

chip_29508 posts

08-29-2019
8:02pm

So... Just a polite correction. The jumpers do not go in the XLR socket. The receptor is separate and apart. See the manual.
@chip,
Thanks for the shorting pins info.

The OP is using balanced ICs. But with that said are the jumpers removed?

~ ~ ~


@almarg,

What if the jumpers are still installed? The OP is using balanced ICs. Would the jumpers not be shorting out one side of the balanced outputs of the LS15 preamp? That might explain why the OP said he had to crank up the volume so high to reach the desired volume level he wanted.
Wouldn’t shorting the outputs cause problems with that section of the balanced output circuitry of each channel of the preamp? Could that cause the 6922 tube damage?

Back of VT100
https://www.manualslib.com/manual/907956/Audio-Research-Vt100.html?page=3#manual

Al,

Here is a PDF for the SP15 preamp manual. Read the warning about muting the preamp with the volume control turn up.
https://audioresearch.com/ar-package/ls15_manual-pdf/

Jim


chip_29508 posts

08-29-2019
8:15pm

To clarify my earlier post, test the preamp without a load. No input cables attached. No output cables attached. See if the sparking stops.

If not, steal a 6922 from the VT100. It has 8. Swap it in for the sparking LS15 tube. See if it fixes the sparking problem. If so, put it back in the VT100 and go tube shopping.

If not, steal a 6922 from the VT100. It has 8.


Bad idea. If the 6922 tube is damaged he will have a bigger headache than he has now. First he will have to buy two new closely matched pairs, and I mean each section of each pair closely matched, 6922 tubes and pay a qualified Tech to re bias the 6922 tubes in that channel of the amp.