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.
What you are describing is a conventional passive bi-amp arrangement. It won't do any damage. The crossover circuits in each of the two sections of the speaker will filter out frequencies that should not be applied to the corresponding drivers, just as they do in your present configuration.

I believe that your preamp has a transformer coupled output, which results in a low output impedance across the entire audible frequency range. If so, there won't be any impedance compatibility issues driving the DNA-500's relatively low input impedance (10K iirc).

Given that, the major question as I see it is how coherently the sonics of the two different amplifiers will match. But since you already have the McCormack amp, there would be nothing lost in giving it a try.

Obviously, when you do this any connections that presently exist between the two sections of each speaker, either directly or through bi-wire cables, should be removed.

-- Al
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 Fplanner2010,

if you got a pair of Vac's Statement 450's you would not have to worry about this Ha! Ha!

Very interesting what you posted above in relation to the tubes in your Vac, are those the only ones you have changed.

Do you have the stock fuses or did you go with ...

I'm at the stage now to try some different things such as tubes, fuses, power cords etc.

I'm truly enjoying my current set-up but when I read from other owners such as your self really peaks my interest specially when the cost of trying really is not too costly.

Where did you get you Seimens NOS 7308 tubes
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?
I see what you are doing but no solid state amp that I have tried to date provides the sonic characteristics of what these tube amps can.

I have had Boulder 2050's, Karan 1200,s, MBL 9008's and 9011's, Bryston 28 Squared just to name a few all with the same speakers.

Using these amps with my speakers ya there was bass but know way sounded like it does as with my VAC 450's, not in the same universe. I'm not just saying that because I own them, it's a fact.

F.Y.I. Amount of power isn't everything, it's "The QUALITY" that matters :-)

I think my speakers might possibly be a little less efficient when it comes to this area than your also and when I tried a pair of 300.1 on my speakers just didn't do it.

Heck by the time you deside to buy a pair they will be $100K Ha! Ha!, they are now @ $80K and Kevin continues to get orders so you know he will continue to raise the price.

My pre-amp doesn't have that switch either so our pre's must be the same besides except mine has the built-in phono added.

I just ordered a pair from Sam who had listed on Gon saying;

Siemens and Halske grey plates 7308 E188CC NIB/NOS best of the best!

These grey plates tubes are the best Simens made E188CC/7308 tubes. According to the date code engraved on the metal plates inside the glass, these two tubes were made in 1967 with the same G7/1C date code. They scored 92/104 and 102/92---almost 100% matched! For Simens 7308/E188CC tubes, these are good as you can get.

So we will find out soon enough.

Cables; that's a whole story on it's own.
Fp, are you sure about the DNA-500 being 500 w/ch in Class A? If we are talking about the amp made by McCormack I believe it is an Class AB design although I don't know how many watts are in Class A? A buddy of mine owned one a while ago and I don't remember him advising it was all Class A power. If you are speaking of another manufacturer then never mind....
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.
Steve McCormack as quoted in this review:
The DNA-500 is a Class A/B amplifier that's biased fairly rich. Because I don't have to use extremely high voltages, it runs only warm at idle and I don't need a huge amount of heat sink surface area. If it were pure Class A, I would have had to use a huge heatsink to dissipate all that continuous heat. The heat sink in the DNA-500 is actually quite generous and can handle extreme operating conditions, including very low-impedance speaker loads.
As Steve explains elsewhere in the review, the need for extremely high voltages is avoided by incorporating two amplifier circuits, bridged together, for each signal channel (left and right).


-- Al
Fplanner- yes I look forward to hearing those tubes.

The DNA-500 is an okay amp but really nothing special to me. Your passion speaks volumns, if you feel the 500 is that great why do you have your VAC 300.1's.

I have never heard any solid state period provide the same bass as a top notch tube amp can, once you get the 450's and experience such you will know what I talking about and all will be history.
Al- Thanks for clarifying on the DNA-500 - I feel a bit embarrassed to have caused this mess-up.

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!! :-)
... 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).
I suspect that if you connect the sub you would be connecting it to your Integra processor, and using the preamp's cinema (home theater bypass) mode. If, however, you ever find yourself wanting to connect the sub via its speaker-level inputs, an important point to keep in mind is that the sub's negative speaker-level input terminals must not be connected to the negative output terminals of any of the amplifiers.

Since the DNA-500 is fully balanced, and the 300.1's are being operated in bridged mono mode, all of their negative output terminals have full-range, full amplitude signals on them, rather than being grounded. Connecting the sub's negative input terminals, which presumably are grounded, to the negative output terminals of the amps risks shorting those output signals to ground (depending on the internal grounding configurations of the sub and the amp), and causing damage.

If you want to connect the sub to the outputs of the DNA-500, either of the negative input terminals of the sub should be connected to a circuit ground point on the amp. Chances are that a chassis screw is such a point. That could be verified by using a multimeter to check for continuity between the screw and the ground sleeve of one of its rca input connectors, or between the screw and pin 1 of an xlr connector (while nothing else is connected to the amp).

If you want to connect the sub to the outputs of the 300.1's, since there are two of them one of the negative input terminals of the sub should be connected to a circuit ground point on the preamp.

The two negative speaker-level input terminals of the sub are most probably connected together in the sub, so only one of them would need to be connected externally. The positive speaker-level input terminals of the sub would be connected to the positive output terminals of the amp.

-- Al
Hi Fplanner- no worries it's just a discussion of agree to disagree which is okay and nothing else meant by my replies.

Let us know how it works out for you.

Visiting Kevin to hear the 450's, don't think that's going to pan out, reason I mention such is becuase someone else whom I know was wanting to do such but was referred by Kevin to best go to a dealers or someones place.

Even doing is far from being ideal, if they just happened to have the identical speakers you have that would be amazing but what's the chance of that happening, slim to non.

I know of a guy who has two pairs of 450's and is bi-amping his speakers, absolutely crazy but has me wondering what my speakers would sound like.

Never ending journey.
Al- YIKES!!! Now I'm scared to turn anything on!! Just kidding - thanks for the heads up and insightful analysis.

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!! :-)
Hi Fplanner,

Yes I did, I actually owned one. Tried it with Focal Salon's and Andra 2's which I both owned.

I'm waiting to receive my tubes and I'll pass along my thoughts once I log in some time.
I'm running a similar biamp setup with VR5-Annis. Double Kronzillas on the top and monoblock Spectron Musician III Mk2s on the bottom. Very tight, fast, articulated bass and the Kronzillas doing their thing on the top. A friend is installing a VAC 300.1a this week. He has the same Spectrons as mine and will be comparing running his system full range vs biamped.
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.

Kronzillas, I like those amps. That would be an intersting set-up to hear. How are you dealing with matching, what's the rest of your system?

Does your friend have the same speakers also.
I had been using Spectron monoblocks full range for a couple of years. When I had an opportunity to get the Double Kronzillas (two output transformers on each monoblock), I couldn't resist. The Krons do some amazing things, but the Spectrons shine on the bass with their grip and definition on the woofers. In monoblock mode, the Spectrons have a 100k bandwidth, so they have the speed to seamlessly blend with the Krons.

I would not recommend touching the internal crossovers nor adding an external crossover. I suppose I could pick up a bit more headroom by putting a high pass filter in front of the Krons, but so far I've never run out of volume and why add more stuff in the signal path? On the VR5-Annis, the Spectrons need to be attenuated by about 3 to 4 dB when both amps are driven by my ARC REF3-- there are lots of options out there for attenuators. The net impedance of the amps is lower than the REF3 published specs recommend, but I've not noticed any audible rolloff of the highs.

I tried the biamping route when I auditioned the Krons just to see if it was worth keeping the Spectrons instead of taking the price hit on the used market. Well, I was amazed how well they worked together and have never looked back. The result is definitely more than the sum of the parts. By the way, my friend is using VR5-Annis also. I don't know if he's going to keep the Spectrons or go full range with the VAC 300.1a.
Interesting, you are using a ARC REF3 pre. I recall reading a thread discusion some time back that the owner owned a REF3 also and paired it up with the Spectron mono blocks and was a desaster, I then read from others whom tried and also did not favour.

I'm still not getting is because both amps are totally different and you are bi-amping such just pluged into the REF3, Correct?

I have personally never heard positive results in doing such so I'm kinda left scratching my head with this one and I personally owned a REF3 for 4 years.
Thanks Bob - Enjoy The Music!!!
Mixing different amps for biamping

Dev, sure the Spectrons and Krons are very different amps. So are the woofers and midrange drivers in the VR5-Annis. I don't understand why that matters. The Spectrons have tremendous control over the magnesium woofers with a very high damping factor as well as being very fast. They generate righ, deep bass with lots of information, not just weight. This information-rich bass mates very well with the Kron's similarly information-rich, open, wide & deep delivery through the VR5's mid/tweeter module.

The combo has no hint of discontinuity throughout the frequency spectrum. I was surprised by how well they work together. One thing, the Spectron amps got a major performance upgrade when I installed VonSchweikert/Delphi_Aerospace Masterbuilt Signature powercords. I wouldn't expect anyone to believe the qualitative jump in quality that this provided-- I know I wasn't expecting it to make that much difference. Every time I demo the difference (vs Shunyata Python or Anaconda CX) folks are amazed.

What type of problem would you expect to see "just plugged into the REF3"? The only thing one needs to do is to adjust the volume to the Spectrons with an in-line attenuator of some type to reduce their volume by 3 or 4 dB.
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
Kernelbob- Can you shed any additional light?
attenuator info... again

I've tried submitting this post several times, but here's a 6-Moons article with links to various attenuator sources.
Thanks - sorry for the trouble.