@lowrider57 from preamp to amp is XLR cable. Everytime i turn on the preamp one of the tubes sparks. That seems like one of the tube is defect?
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.
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.
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what were the speakers that the seller had? could it be that you liked the bass on those speakers more than the ref's? different speakers will do different things in the bass department. Also the seller might have a really good dialed in set up. Are you sure there is an actual problem or that you are just disappointed from the sound of your setup? |
@akiravelvet the speakers he has is Pure audio project - Quintet 15 ive tested the r900 speakers with another amp and its sounds wonderful much bass and strong. Switched to the ARC i just bought its missing about 60% bass compared to the original amp i have (MAC1500). And tonight I discovered the LS15 one of the tube (V3) has white sparks when i turn on. So now i can only conclude that either the preamp LS15 or VT100 amp is defects. I contacted the seller and he’s not responding- avoiding me. So I’m kinda bumped and feel down that this happened to me. I wanna ask him for money back but i doubt he’ll give back. |
kentrent OP31 posts In your case, imo, no kentrent OP31 posts The preamp protection circuit was/is shutting down the unit.I would not power up the preamp again until you install the new tubes. Hopefully the bad tube didn’t take out a resistor. As for why the 6922 tube shorted, went bad? I have had new 6922 short after just a few hours of use. It happens. Just curious approximately how many times have you turned on, and turned off, the preamp since you brought it home. Repeated power up can cause stress on a tube. Did you read the owners manual for the preamp? |
FWIW, Some European sourced small tubes do flash on turn-on. Not at all unusual and it is not significant. I suspect, as others, that your problem may be speaker location (set up in your room) combined with the basic difference in the sound of your new electronic’s. Audio Research components are not known for warmth and unless your system and speakers set up are synergistic and properly set up they can sound cold and clinical, much as you describe, especially compared to your old Mac. I’m an old ARC advocate but I dropped out of that line some years ago for just that reason. It is also possible that your ARC amp is just not one that works well with your KEF’s. Take a break from your assumption that your components are faulty and that someone has lied to you. Think more about speaker set up and trying to get them (and your listening position) to sound better by properly locating them in your room, Do some research on set up. If you think you need help with that issue, just ask. Many folks here would be happy to help. Good luck. |
I called ARC and asked them about the tube flashing/sparking and they said that’s not normal. As for the set up, i placed the speakers about 7-8 ft apart in a 18ft x 20ft room. Same set up, I switched out the arc and use the mac1500 and has a lot of bass response especially low. Switched back to arc and it has about 60% decreased in bass. All speakers wires are all properly connected. Can someone here explain this? |
If you’re hearing 60% more bass by only switching the amps, then the issue is not speaker/room set up. Assuming the tubes are fine, I would suggest trying to borrow a preamp or an amp from someone and try to isolate the bottleneck systemically. Interconnects, power cords, or speaker cables can affect bass quality but not anywhere close to +/- 60%, in my experience. Keep at it and good luck. |
Same set up, I switched out the arc and use the mac1500 and has a lot of bass response especially low. Switched back to arc and it has about 60% decreased in bass. All speakers wires are all properly connected. Can someone here explain this? https://classicreceivers.com/mcintosh-mac-1500 http://sportsbil.com/mcintosh/Receiver/MAC1500/MAC1500_ser.pdf But what about the LS15 preamp? You didn’t just switch out the VT100 amp. You switched out the preamp, amp, and balanced ICs. Just curious, what do you have the tone controls set at on the MAC receiver? Flat, ( 0 )? How about the loudness button? In, on? Out, off? You need to find someone to come into your home to help you to resolve your problem. |
Firstly, I overlooked your comments about the LS15 going into protection frequently. This could well be the result of the V3 6922 flashing/sparking. If the LS 15 doesn't require re-biasing you can easily change this tube yourself with like kind and quality. ARC is correct, this Sovtek 6922 doesn't flash on turn on. FWIW I don't think this tube needs to be re-biased. Ask ARC. Re the loss of bass response, as stated earlier, I think it is a fundamental difference between your Mac, an old vintage tubed receiver known for overblown low frequency response, and a modern amp/preamp known for its more linear, cool, and for many, clinical response. The basic difference between the two is huge! I suspect that you have just made a fundamental beginner mistake, and we all make them, of assuming that what we hear elsewhere will be what we hear in our own homes, but to our disappointment it does not. Been there, done that! This is especially so when the seller has taken great care to match and set up his audio system. A good audiophile can obtain excellent results from fairly ordinary stuff because of his basic understanding of his stuff, how it all synergizes, and the requirements of his room for proper set up. That said, in order to optimize the bass response of your current stuff, I would run your speakers off the 4ohm taps. I would buy a SPL meter and a test disc and insure that you speakers are not located in a bass null (and at the same time help pin down getting the best overall frequency response). I would also buy Robert Harley's book on audio for a good primer about audio. |
@newbee thanks for your explanation. But the different is so huge. It’s like the ARC has no bass at all. The Mac1500 does have tone control but i flat them just to compare and it still boost a large amount of bass. I called ARC and they said that tube 6922 doesn’t requires re-baised but that’s not normal for it to sparks. I called Kef and they said not recommended to use the speakers in 4ohm when the speakers are rated at 8ohms. |
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 |
Also speakers are rated at 8ohms thoughAs I stated before, KEF may rate the speaker as a 8 ohm nominal load, but you look at the impedance curve to determine which tap to use (to start with). The frequencies in the bass and mid-bass range are at approximately 4 ohms. This is the critical area of the frequency spectrum because it is harder to drive the speaker to reproduce good low-end response. |
Well I did a little on line reading regarding your speakers which causes me to suspect the combination of your ARC stuff and the KEF may be your problem. Your speakers seem to be considered ’neutral speakers’ (at best). You seemed to like them when driven by a (very) warm vintage receiver). You are hearing the results of you amplification choices quite clearly. You seem to like a warmer toned system’s sound but with better resolution than you get with the old Mac.. Very common in audio. Now you change to electronic’s which, tonally speaking, might be voiced to be neutral (at best, IMHO, very cool). So you are doubling down, so to speak, and get the sound inherent in both. For you this sound is not synergistic in that it doesn’t produce the tone you want, not that either the electronics or the speakers are wrong, they just don’t sound as you would like when combined. I would suggest that most of us have been there and done that. I certainly have. That is why most folks will recommend ’matching’ your speaker and electronics. Arbitrary buying will not get you there. BTW, regarding 4 ohm taps. I’m a bit put off by KEF’s ’recommendations re using only the 8 ohm taps. I could understand why they think your speakers might sound best a 8 ohms (perhaps they think the 4 ohm tap might unbalance their preferred sound) but I know of no reason you should not try them. Your speakers may have have a nominal 8ohm rating but this is far from indicating that they have a minimal 8ohm ’curve. Reviews point out that they have a minimal ohm droop to 3.8 ohms. Were I you, I would research this issue before I just walked away from it based on someone from KEF’s opinion. I like warm toned systems and have most always operated off 4ohm taps. |
The balanced input impedance is 200K. SE is 100K. Big difference. IMHO. Check that first. Do you have a multi-meter with spring-loaded hook clips? If so, check the amp bias to make you have power. As to the LS15, disconnect it from the amp (power off). Power it back up and see if the sparking goes away. Let me know and we can go from there. Have had a lot of ARC gear over the years. |
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@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 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. |
