Hi David, Lonnie and I pulled in the 305 and ran it in the lab early on. We were astounded by its performance. One of the technicians said, "be careful you can't load a tube amp on the test bench for very long without damage", I said, "that's not what Bob told me, watch this".
Now listen, this is s TUBE amp with very low feedback and it the "classic" mode it maintains a THD+N of about 0.5% across the spectrum at rated output, which is EASILY exceeds! It's bulletproof. It doesn't really care what you do to it.
Now if you get really nuts with low impedance loads at high power levels for a long time it'll pop a fuse, but you can't really hurt it. Thow a new fuse back in a start playing!
In the "modern" feedback more TH+N is around 0.25% across the band. This is amazing performance for a tube amplifier. And its noise floor is around -115dB. Really impressive.
Lonnie commented during the testing that it performed like a modern SS amp, in many respects, and this is a real accomplishment.
There is a reason they sound so good, they are incredibly well designed; thank you Bob!
IMO, they are worth every penny. When you see one made you'll know why they have to cost what they do. They are hand made here in the USA with premium parts, sourced from the USA whenever possible, and they take a long, long, time to build.
Not for everyone, and we understand this, but they are worth it if you love tube gear. Cheers, Big Dan
I know Sir, that your post needs no backup, but I can attest to everything you have stated above. These amps easily find themselves in the top 5% of tube amps ever built. The ciruit was co-designed by Bob and Tim DeParavinci of E.A.R. fame, and from the outset was meant to be among the world's elite. They do everything right, including driving the most demanding loudspeakers with absolute prescision and authority. The sound is as glourious and detailed as can be described and still words come up short.
I have had a custom version of the 305 in my rig for more than a year now and have had zero issues with regards to reliabliity, and mine se near daily use.
If there is anybody in SoCal that wants to experience them first hand, my door is open.
Nice to chime in here! Could you please describe the customizations you had for your 305? Also do you drive it with demanding speakers and if so, what would be their lowest impedance ans stated efficiency? What transformer tap do you use for your speakers(8/4 or 2 ohms).
One of the reviews i read (Tone Audio or 6moons?) said the bass was good but not excellent like a SS amplifier. What is your honest opinion of its bass performance in your system?
Sorry for the many questions but "inquiring minds want to know" :-)
I went with upgraded power caps and 1% resistors wherever possible. They were tweaked by Bob to deliver 353 wpc@ 8 and 446 wpc@4 ohms. I have also upgraded the 12ax7's and 12 AT7's to vintage Bugle Boys from 1958 and 1961 respectively, they had a dramatic impact in improving the low end and highs. Also in the loop is a Dodd MLP tube preamp and SimAudio Moon phono stage.
I have an affinity for Magnepan speakers, and they drove my MG-20's with ease. Bass response from them is very tight, fast and accurate, but as with all Maggies, a sub was nice but not required. Currently they drive a pair of Polk SDA SRS, and I find much the same. Bass is fast, tight and controlled, never sloppy, even at concert level volumes, which is well above my reference levels. The big difference here is that no sub is needed, as this setup digs deep, well into the sub 15htz range. I have not tested that personally, but the sound is so deep I can feel the bass being transmitted through a concrete floor 40 feet away when I unleash the beasts. I use the 8 ohm taps for the Polks, 4 ohm for the Maggies.
The highs are dramatic and detailed, without appearing to be rolled off or too bright. The shimmering decay of a cymbal tap and the taking of a breath by a sax player between notes can be heard as if they were in the room with you, and all the special information is there, also in lush detail.
I have made a few cosmetic enhancements as well, including us of non-traditional materials for the chassis cover, so they won't be mistaken for a production piece any time soon, but they do look very much like the High-End performers they are supposed to be.
Last Edit: Jul 17, 2013 18:57:47 GMT -5 by luvtubes
Thanks for the great detail and review luvtubes!!! And to have Bob personally tweak the amp for more power is precious indeed! Very interesting that changing out the stock tubes to vintage ones improved the low-end and highs. I wonder how that could happen?...Just curious.
I have electrostatics from Martin Logan (Spires) which dip down to 0.5 ohms at 20KHz since the Xstat panel is seen as a capacitor. I hope when I save up the enough cash for the 305's, I'd perform the same tube change you did.
Again thank you very much for the review on its bass and treble performance. It seems it has no lack in these areas after the tube roll you did.
BTW, I live in Camarillo for now and plan to move further south closer to work for the 3 hour commute is a killer!