VAC Sig Ren MK2a Headscratcher


I am thinking about adding a solid-state amp (DNA-500) to my system to drive the bass cabinets of my VR-7se's. Currently I have 1 set of balanced outs going to 2 VAC 300.1s that are each driving a VR-7se speaker full range. The other set is driving my subwoofer.

If I disconnect the sub and hook up the 500 to these balanced outputs from the pre, with the 500 speaker outputs going to the bass cabinets of the VR-7se's, will this work? Only problem I can see is that both modules of each speaker will be receiving a full range signal, but only using a portion of it depending upon the drivers. Balancing will be a snap as the volume control will control the 500, with the attentuating knobs on the VACs available to balance the rest of the speaker to the bass.

Will I be doing any damage this way? Is there a better way to do this w/o complicating things with crossovers, etc? Does what I'm proposing make sense? The 7's love power and I had the DNA-500 sitting in a closet.... Seems like this way I can get the best of both worlds, with about 750w going to each bass unit and 300 VAC tube watts (50w+/- Class A) going to each mid/tweet/super-tweet module. On paper, seems like a great idea, BUT...Before I go very far down this path, I'd really like to get some feedback and answers to these questions above.

Thanks in advance for any light you can shine in the tunnel.. :-)

BTW- just replaced noisy Dragon 6dj8 pre driver tubes with Seimens NOS 7308's - quieter(obviously), better imaging, bigger soundstage, more air and a bit tighter bass - after 1 hour!! Will only get better - more expensive but worth it IMHO. YMMV.
fplanner2010

Showing 11 responses by fplanner2010

Thanks Al - you are correct about the transformer coupled output stage. I think/hope the sonic signatures between the amps will be more similar than not. If I can cable this properly, I'm hoping to achieve several orders of magnitude in sonic improvement, since the VAC's will be loafing and headroom should increase tremendously as well. Hopefully....:-). Thanks again.
Hi Dev-

Still stock fuses. Actually, it was thinking about the 450's that led me to my present plan! The DNA-500 I already own and is 500w of Class A into 8 ohms, 900w at 4. As you know, the first 50+w of the 300.1's is also class A. The VR-7se's thrive on lots of power and with only the 300's, are barely breaking a sweat. Time to see what they can REALLY DO!!

In effect, I will have MORE POWER THAN YOU, all class A, without killing my budget on the 450's. It should take away a lot of that "450 envy" you keep reminding me I have.. :-) (sorry - couldn't resist.. :-))

My preamp does not have the 6/12v switch, so I am limited to tubes of the 6dj8 line. I can't reveal my tube source yet until I get a backup pair - I'm sure you understand.. :-). I'm also sure there are better tubes for this application than what I got - its all about personal preference, what you are willing to spend, how much research you do, and what sound you are looking for. You really won't know until you start experimenting. I really wanted to try the 8416's, but was not able to due to the lack of the above switch. I just got very lucky in that I really like the first pair of 6v I tried in my system.

As you know, it is very easy to go nuts trying different tubes, fuses, etc. At this point, I am going to focus on the bigger picture of incorporating the DNA-500. As my friend Art mentioned this am, I may also need a buffer or in-line attenuator if the power of the DNA overwhelms the VACs. I will deal with that if it becomes an issue. The DNA is probably 1 of the best SS amps I could try to mate with the VACs, so I am glad I didn't sell it when it came out of my system several years ago.

I'm pretty sure I can reduce the cable quality, as long as silver prevails, in the chain from VAC pre to DNA to bass modules. I'm not sure I would hear the difference between $200. cables and $2500. cables for this bass-type chain. Thoughts?
Dev- The DNA-500 is the sweetest,most tube-like solid state amp I have ever heard, at any price. I used it in my prior system and am very familiar with how it sounds, especially in the bass area. It is very high quality sound and the rave reviews it received were accurate, IMHO. What I don't know is how it will sound with the VACs, but I suspect it will sound much better than it currently does, as the VR7se's crave power, especially in the less efficient lower bass cabinets, which is what the DNA will be feeding. Ran this past Albert VS last night and he also thought it was a great idea, being familiar with my VACs as well as the McCormack.

Congrats on the tubes - let me know how you like them.

Rgd - I was TOLD by a friend who has had several McCormack amps that mine was all class A. I have a hunch it goes from A to AB at some point, but don't have the manual to confirm where that is. From my standpoint, having heard it extensively several years back, everything I heard sounded like A. In retrospect, I probably should have left out the sound rating comment, since I am *personally* not sure, so as not to unintentionally mislead anyone. Sorry if I caused any confusion by the McCormack "all Class A" comment.
Al- Thanks for clarifying on the DNA-500 - I feel a bit embarrassed to have caused this mess-up.

Dev-
Kevin talked to me about the 300 for over a solid year before I would even give the 300.1 an audition. I was THAT happy with the DNA-500. It is quite a bit more than an "okay amp", at least to me, all who have reviewed it and most who have owned it. It also obviously depends on the system it is in and what it is driving. It is very far from just "raw power", which is why I'm so excited about trying this little experiment.

I have never heard better midrange than the VACs produce and have come to really like the VAC "sound". The fact that I may be able to free up my VAC amps to only have to drive the glorious midrange and highs with 300 tube watts per speaker is something I really look forward to trying. The sound should be magical with ridiculous headroom :-)

In addition, the ability to finally drive the bass enclosures of my 7se's like they were made to be driven means I should no longer need my sub(except maybe for movies). Since the 500 is only driving the bass enclosures, there could be an enhanced positive effect there as well. The 7se's spec down to 18hz, which is probably more visceral and felt, rather than heard - can't wait to find out!!

I'm visiting Kevin in May - will hear the 450's if he's got a pair handy. Everyone I have talked to who has heard the 450's raves about them - I've yet to hear them. Quite honestly, I REALLY like my 300.1s, and may like them a whole lot more if my little experiment goes the way I hope it does. Thanks for your responses and enjoy the tubes!! :-)
Al- YIKES!!! Now I'm scared to turn anything on!! Just kidding - thanks for the heads up and insightful analysis.

Dev-
No problems. Already on other business near Kevin, so a visit to VAC is a no-brainer. I know its long odds they would have a pair of 450's to listen to, but you never know.

Bi-amping with 450's sounds like your next step. Its in effect somewhat similar to what I hope to be doing with the DNA-500 and my 300.1s. OF course I realize its nowhere near the same - hopefully yours would sound better :-)

What are your speakers again?
Hi Dev- Did you ever try the 500 in your system? If so, do you remember the speakers you were using? Just curious....

P.S. - chance to put the new tubes in yet? Mine just keep getting better, with about 12 hours on them. I'm told they will continue to do so until around 50-60 hours. Cool!! :-)
Kernelbob - That's quite a nice system you've got there. I heard a pair of 4 jrs bi-amped and fully driven this past weekend and the sound was literally amazing. I can only image how much even better your system must sound with the amps you are using. It gives me hope that maybe what I'm about to do might actually work!!

I have some questions, if you don't mind. How did you match the outputs between the top and bottom amps? Also, did you use an electronic crossover, or just the ones in the speakers? Have you always run them this way? Sorry for so many questions, but this is pretty new for me.

As far as your friend's system is concerned, not sure what speakers he's running but regardless, he should hear a significant improvement once those VAC tubes start to sing.

Thanks very much for sharing your experiences.
Thanks Bob. What kind of attenuators are you using? I'm using balanced cables between pre and amps. Scott Endler's 24 step variable looks best, but he's several months behind in production and I can't find any balanced used. Rothwell fixed at 10 is also an option, but they are literally out of stock in England and I can't find any balanced here. Find plenty of microphone attenuators and pads, but have been told they won't work for my application.

Any suggestions of balanced in-line attenuators that are actually available? WOn't now for sure I'll need them until this weekend - for now, I'm 90% sure I will. Thanks