Audio Research VT100 MK1 and LS15 HELP!!!

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.

@newbee you said it right out of my mind and I couldn’t have said it better.  Yes, i love the vintage tube sound of warm and low soft bass response from vintage MAC1500 but i needed more details.  I thought this ARC equipments would give me that sound im seeking for but its so flat and no bass.  I can understand these equipments are not colored or has any tone control but i feel that the bass should be a little more fuller.  The sound doesn’t feel full like it should coming from a floor stand speakers.   I compared the ARC sound with the 2 Devialet Gold Phantom speakers and the ARC has about 50% less bass.  The gold phantom has good soft bass response i want but it doesn’t has the holographic sounds and details like from the tube amp system.  My goal is to have both in this system but i guess the r900 and Arc don’t work synergistically...?

Just right now, i used another old 80s preamp from Sony and the sound is boomy boost of full bass and tone control was on neutral (imagine if i crank that bass up).  So this confirmed the vt100 is working and my LS15 preamp is not giving that sound.  Perhaps because of the faulty V3 tube? I already ordered the new tube on the way.   I’m hoping replacing this faulty tube will fix my bass response problem.  

You guys has been so helpful and awesome... Thank you so much. 

Just right now, i used another old 80s preamp from Sony and the sound is boomy boost of full bass and tone control was on neutral (imagine if i crank that bass up). So this confirmed the vt100 is working and my LS15 preamp is not giving that sound. Perhaps because of the faulty V3 tube? I already ordered the new tube on the way. I’m hoping replacing this faulty tube will fix my bass response problem.

@ kentrent

I assume you used RCA single ended ICs to connect the Sony preamp to the VT100.
Read my post above ( page 2 ) about if the shorting jumpers were removed on the VT100. If you were using balanced ICs the jumpers must be removed.

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

@jea48 yes. The shorting jumpers were removed.  I used RCA interconnect.  This will effect the sound if jumper not removed?