Paul Stubblebine listening room

[microstrip]

I have read a few comments of fortunate audiophiles who had the pleasure of  listening to master tapes at Paul Stubblebine listening room. "I have never heard anything as good as this " is a  typical reaction. Although I now know that the speakers were Magico driven by Bottlehead amps, I am looking for more information, such as type of amplifiers and details about the active filters. Do you know if this system was ever reviewed?

 

[ironbut]

That system is actually Paul's monitoring system he uses while mastering.
It's almost totally custom/purpose built so I'll leave it to Paul and Doc (who built the amps/crossovers) to go into the detail.
It is amazing!

[High and Outside]

I have moved the Magico/Bottlehead system home, and now we're using something else at the mastering studio (Focal Grande Utopias.)

The Magico is a four way system. It's from the time before Alon was making his own drivers, so it uses commercially available units. The bass, mid-bass and midrange are Focal cone drivers. The tweeter is an Aurum Cantus ribbon. I decided from the beginning to quad-amp it. Dan and PJ took a Marchand crossover and totally re-engineered it. Now of course it has the current-sourced active loads everywhere, plus they redesigned the filters and chose different tubes as needed for each part of the circuit.

The amps were designed and built by eXemplar, and have now been modified and rebuilt by Bottlehead for better sound, more consistency and higher reliability. The bass, mid-bass and midrange amps are differential 300B's. The tweeter is powered by a single ended 45. All amps use Magnequest iron. It's all connected with First Impression Music cables: power, interconnect, and speaker cables.

Besides the gear itself, there are two other stories: the acoustic design of the room, and the extensive tweaking of the system in place. These are longer stories than I want to detail here...I just mention them because those aspects are of equal importance to the final result. The tweaking in place is now being repeated for the system in its new location in my living room.

I don't recommend such a complicated approach for anyone else. But I wanted to push a certain idea to its limits, and I felt I had the resources available to do it. It took a lot of work to dial it in initially, and it takes quite a bit of work on an ongoing basis to keep it operating at peak performance.

[docb]

I'll just throw in here that I have taken a similar, complex approach with my own system after hearing the results of Paul's system. These systems are indeed rather high maintenance because of the sheer complexity of the setup. That complexity allows one to build an amp that is designed specifically for a given driver and a given box. And the active crossover allows for fine tuning and also for the use of a passive compensation network on a driver. Separating the compensation and the crossover slope sometimes solves interaction problems that can occur when both of those functions are performed in the same realm, i.e. both a passive crossover and a passive zobel.

[Studer Fool]

Thanks for the description!

But, you state: "differential 300B's"
What's that?  Push-pull with common-mode long tail CCS or ?

-cdw

[microstrip]

Thanks Paul and Dan for your very interesting answers. I have always had the feeling that a properly done active system would be the right way to go for low power amplifiers.
Paul, are you using the new Grande Utopia EM or the older Be? Still with Bottlehead tube amplifers? 

[High and Outside]

Christopher,

Yes, you've got it about right. The circuit for the 300B amps is single ended through the driver stage, then the 300B's are configured as a differential pair with a current source in the tail. It's an unusual circuit, the only other designer I've heard of using something similar is Allen Wright.

Francisco,

They are the Grande Utopia EM's. They need a bit more power, so we are running  them with Pathos Adrenaline amps.

[Studer Fool]

Thanks Paul,

You state:  "the 300B's are configured as a differential pair with a current source in the tail"
Well that would make it a very, very, cool design and I can't help but wager that it provides very mellifluous sound, and could even take much of the credit for the excellent sonics attributed to your system!  (good room acoustics allowing it to be better "heard")

You state:  "the only other designer I've heard of using something similar is Allen Wright"
Yes, though he is not so straight forward about what he calls it.  See also the Audio Express 2006 May issue where Sears applies the concept with MOSFET constant current sources to 6AS7 balanced P-P.

It is very satisfying to know that such pinnacle audio fruit is enjoyed by a professional who obviously has great ears!

Thanks for explaining & sharing,

-cdw

[ironbut]

Hey, I wanta see pictures of it in your house!

And then I wanta hear,.. Pot-Luck at Paul's!