VTA ST-120 amp driving B&W CDM 9NT mains

First of all Happy Holidays to all.
Im a newbie here. Been reading though a lot of the forums. As a kid I can remember many a night listening and watching the warm glow of the Dynaco ST-70. My father was a DIY builder nut. He was bitten badly by the endless pursuit of perfect reproduction of sound.
I cant tell you all the projects he had started using innovative ideas for speaker design and amplification. After all the systems in his life that he changed and bought he ended up going back to his beloved ST-70. He had many modification to his amp that he changed and I can see a lot of his mods that are being used on these amps today. Mind you this is way before the internet and literature of today that is widely available to everyone now. Even with my exposure to his obsessions I am still ignorant to it.
I ran across this site and saw the VTA products and I now find myself thinking about buying the VTA ST-120.
Can anyone share your thoughts as to how I would fair driving my B&W CDM 9NT's? I currently have more of a home theater setup
with my Outlaw 5000 amp 5.1 and using my Anthem MRX-300 as a prepro driving two more channels for 7.1 along with 2 Outlaw Ultra-X12 subs. I know this is comparing apples and oranges but you got to start some where right?

Thanks

I would not hesitate to recommend the combo. Having recently retired my B&W Matrix 803s (same 90 db "efficiency" rating and pretty analogous to the CDM 9NT) I would say that you will not regret the choice of the VTA ST-120. An unofficial yet useful rule of thumb is that "tube watts" are at least twice as powerfully perceived as SS watts - in other words the ST-120 at 60 WPC will give the equivalent EXPERIENCE to at least 120 WPC from most SS amps.

Oh, and welcome to our humble forum. Here you will find information, conjecture, and humor to fill even the darkest and coldest winter's night with cheer.

Kentley,
Thank you for the kind reply. It is definitely a cold and dark night here in Michigan. I would say that Im pretty sure Im going to purchase the VTA ST-120. Im very fond of the beautiful tube glow and from what I can remember as a kid the warmth and detail of the fine sounds that I just dont hear from the SS equipment Ive owned in the past. While I will never be able to understand the circuitry to level my father did I will still very much enjoy the sound and experience of the Amp. One other question if I may.
I have built some speaker systems and I do know the benefit of quality Caps and resistors in the speaker crossovers.
Knowing this I have read on B&Ws web site that they actually design the crossovers taking the Caps and resistors characteristics into consideration with their drivers. Part of me still wants to upgrade to higher quality components in the CDMs but dont want to end up with undesirable results. Do you or anyone else have any experience with the B&W crossovers? Any suggestions?

Thank you
Fred

I have no first-hand experience of the CDM 9NTs but it is quite likely that you could improve the crossovers by upgrading the caps. Even well-regarded speaker makers have been known to skimp on these components, especially in "budget" lines like the CDM Series.
If you do decide to upgrade, make sure to use the EXACT equivalent. My old B&Ws had odd value caps; I could locate only one manufacturer who supplied them all - Sonicap. {Unfortunately, I waited too long, and when a 25 year old cap finally drifted too far, I blew a midrange driver, which is unobtanium even used.}
Unless the design of your speakers has diverged greatly from the older models, at least the X-overs are readily accessible.
You might have to purchase a tech manual in order to get the correct values:
https://www.tradebit.com/filedetail.php/199402546-bowers-wilkins-bw-cdm-9-nt-service
Good luck. If you proceed cautiously and in an orderly fashion, I can see little chance that you would screw anything up. Famous last words....

ImFritz wrote:
....I do know the benefit of quality Caps and resistors in the speaker crossovers.
Knowing this I have read on B&Ws web site that they actually design the crossovers taking the Caps and resistors characteristics into consideration with their drivers. Part of me still wants to upgrade to higher quality components in the CDMs but dont want to end up with undesirable results. Do you or anyone else have any experience with the B&W crossovers? Any suggestions?

Thank you
Fred

Welcome Fred

If you so fancy as to go to the spiraling abyss that is capacitor upgrade research there is Tony Gee's Humble Homemade HiFi cap shootout page:
(pray tell, hold on to your wallet)
http://www.humblehomemadehifi.com/Cap.html

If nothing else, it's a listing of most everything on the market all in one place with one person's subjective opinions.  Some of the caps he tests and rates are stupid expensive, but there are usually whole ranges for most manufacturers.  (Did I mention this is a spiraling abyss??)  

Personally, in various projects I have tried a couple models of Clarity and Mundorf, some Jantzen Superior Z's and the super good deal Cornell Dubliers he rates highly with good results.
My apologies in advance if visiting his page gives you a headache or induces a bout of cap rolling fever.

ImFritz,

I am probably one of a very few that has an original VTA ST120 kit in its original factory issue state.  I bought one of Bob's very first VTA ST120 kits almost 9 years ago without factory upgrades.  I will tell you that you can not go wrong with this kit in any form.  The amplifier as it comes without the upgrades is in a word "spectacular".  I have never had any urge to change any of the capacitors because I do not feel the need to diddle with perfection.  I will say that my amp being a very early one also came the higher output VTA board, and again I have not felt any need to change a thing. My speakers are ESS Heil AMT-10B rated to 90-91db and greater than 150 watts and this amp drives them with ease.  So whatever you throw at it should be just fine.

ImFritz wrote:Kentley,
Thank you for the kind reply. It is definitely a cold and dark night here in Michigan. I would say that Im pretty sure Im going to purchase the VTA ST-120. Im very fond of the beautiful tube glow and from what I can remember as a kid the warmth and detail of the fine sounds that I just dont hear from the SS equipment Ive owned in the past. While I will never be able to understand the circuitry to level my father did I will still very much enjoy the sound and experience of the Amp. One other question if I may.
I have built some speaker systems and I do know the benefit of quality Caps and resistors in the speaker crossovers.
Knowing this I have read on B&Ws web site that they actually design the crossovers taking the Caps and resistors characteristics into consideration with their drivers. Part of me still wants to upgrade to higher quality components in the CDMs but dont want to end up with undesirable results. Do you or anyone else have any experience with the B&W crossovers? Any suggestions?

Thank you
Fred

If you're willing to ship one of them I know a guy who can measure your speaker and optimize the crossover for them. www.gr-research.com

At the very least you could swap out the tweeter caps as those tend to make the biggest difference.

I used to own a pair of CDM-1SE's years ago and drove them nicely with an ST70.

Kentley,
Thanks for the Tech Manuel info. I downloaded it and after reviewing I found that B&W used cheap slip on connectors for the internal wiring. That bothers me. Id rather see soldered connections. I believe you are correct stating they are budget line and cutting corners.
Based off of that Im going to find mid line capacitors (Sonicap) for the crossovers and change them out. Also change the internal wiring.
I plan on ordering the VTA ST-120. I may end up ordering a speaker kit as well. I would like to get the best I can with that amp.

IMHO, you are taking a good course of action. Keep us updated. It's always nice to have someone new here [to abuse ].

ImFritz wrote:Kentley,
Thanks for the Tech Manuel info. I downloaded it and after reviewing I found that B&W used cheap slip on connectors for the internal wiring...

As the servicer in a now-closed B&W dealer, I can confirm this. The intents were for quick assembly, and replacement of failed drivers by untrained personnel in the field.

Thanks for the reply guys. That confirms my suspicions. Its like watching a commercial on TV advertising WHERES THE BEEF! Showing a huge roast beef sandwich loaded with roast beef and then when you go buy it and get it home all you see is the bun! LOL
I am going to order the SoniCaps for the HF and the MF. They already have the air coils and wire wound resistors. Also ill replace the cheap wiring with better and solder all the connections. That will keep me busy till I order the st-120.