Ultra Differences: Old Chassis ('05) vs. New Chassis ('06)

rockadanny · « **on:** 26 Apr 2006, 03:43 pm »

Ultra preamps first appeared in T7 chassis, I believe. Other than chassis size and faceplate, any differences internally? If so, are the differences noticably better (sonically) in the newer (larger) configuration? Or are they strictly production/assembly related?

rockadanny · « **Reply #1 on:** 26 Apr 2006, 06:01 pm »

The reason I ask is I've come across one of these (pre-Ultra) Ultras (serial number 102605). Reading past posts in this forum along with the first edition of "Inside AVA" I am trying to understand the differences between the two Ultra models. For example, the statement in Inside AVA, "In creating the new Ultra series of preamps we determined early on that the small SL chassis we have used in the past would not work with the new Ultra series". Then why were they sold in the T7 chassis? Or were they? I am confused (my wife will gleefully concur). Which of the following improvements (taken from Inside AVA) occurred in the larger chassis design but not in the T7 chassis design:
1. Enhanced power supply.
2. Isolated power supplies for each preamp section.
3. Dual-sided main circuit board.
4. Elimination of virtually all of the wiring.
5. Significant change in the inter-stage coupling between the tubes and MOSFETs.
6. Changed bias of devices for a more linear response.

I am just trying to figure this thing out.
Thanks.

elcaptain88 · « **Reply #2 on:** 26 Apr 2006, 06:20 pm »

I can't answer your question - but I've wondered this myself too. I have an early Ultra SL preamp from July '05 that is in the old SL chassis. It sounds phenomenal. I also read the remark in the recently posted AVA newsletter that the old SL chassis wouldn't work for the Ultra & was a bit confused. My guess is that AVA has now gone to standardized one-size boards for their new preamps and these new boards won't fit in the smaller old SL chassis. I could care more but I don't - because like I said before this one sounds great.

ricmon · « **Reply #3 on:** 26 Apr 2006, 07:01 pm »

Checkout this thread. It should help.

ricmon · « **Reply #4 on:** 26 Apr 2006, 07:02 pm »

Sorry about that. Here's the thread.

http://www.audiocircle.com/index.php?topic=25964

avahifi_lj · « **Reply #5 on:** 26 Apr 2006, 08:10 pm »

Hi:

Let me see if I can help out a bit: The Ultra preamps were put in the small SL chassis for short time. When we were designing the Ultra we were still selling the T7 , and actually used the T7 boards to design the Ultra. Once we finalized the circuit design, we made a decision to move to the larger chassis used for the EC. We made that decision for several reasons, such as more power supply sections, dual sided (ground plane) circuit board, integrated mute circuit, ease of building, additional features and new cosmetics.

Once we had the Ultra circuits finished, we decided to put the Ultra circuits in the unfilled T7 preamps orders. We did that because we knew the Ultra in the big chassis was going to be released soon, and we didn't feel it would be proper to sell the soon to be discontinued T7 (I know I hate buying a product only to find out a month later it's discontinued). Some of the T7 SL preamps sold last summer are actually the Ultra SL preamps.

We originally were going to keep the OmegaStar preamps in the small chassis, but later decided to move all the preamps into the bigger chassis; therefore, that left us with a pretty good stock of small chassis. Frank decided to sell the Ultra in the small chassis for the same price as the T7 to help us finish out the inventory of small chassis. Those that got that pricing/chassis got a pretty good deal.

There are some differences between the small and big chassis. The small chassis was limited to six power supply sections -- two heater/headphone supplies and four tube/Fet supplies. The big chassis has ten power supply sections -- two heater/headphone supplies and eight tube/Fet supplies. In the small SL chassis the phono section, if it was installed, shared tube/Fet power supplies with the line board. In the large SL chassis the phono section has its own power supply sections. So, if you have a small SL chassis WITHOUT phono you have the same six section power supply configuration as the large SL chassis.

The other sonic difference is the ground plane board and wiring. The small SL chassis did not have ground plane audio boards, but did have a ground plane power supply board. The ground plane board is quieter (shown on test equipment), but the Ultra in a small SL chassis is still very quiet (especially when you compare it to other preamps).

There is a slight sonic difference between the small SL and the big SL that has a phono section due to the shared power supplies, but in my opinion it's not worth getting rid of your small chassis (good to know since I have an Ultra in a small SL chassis).

Hope this helps.

Larry

mark funk · « **Reply #6 on:** 26 Apr 2006, 09:31 pm »

Thanks Larry, Now could you tell about the T5SLR to T8 upgrade in the small box. To the all new T8 in the big new box? Also with all the new upgrades, could you or would you use any of them with the Super Pas 3 kit?

rockadanny · « **Reply #7 on:** 27 Apr 2006, 11:51 am »

Thank you Larry and Ricmon for solving that mystery. Now, back to some groovy music ...

avahifi · « **Reply #8 on:** 27 Apr 2006, 08:33 pm »

The T5 was upgraded to the T8 in the small SL chassis by engineering a new active regulator for the B+ supplies inasmuch as it has worked so well in the Fet Valve amplifiers and Transcendence EC and SL preamplifiers. We had much less board real estate to work with on the original PC-149 board but were able to make a good fit of one regulator and that made a world of improvment in the preamp.

The sonic improvements made it obvious that we should plan on moving the T8 into the big SL chassis as soon as possible, this allowed us to look again at the T8 and design a new big mother board for it too, along the lines of the Ultra EC and SL. Actually, I could take the whole finished Ultra EC/SL big board and put it back into the PC card program, save the complete multi-regulator supply design, and just do new audio to match the supplies. This gave us the current Transcendence Eight, which is simply an awesome all tube preamp (which Larry and Dean like best, but I prefer the Ultra SL or EC - - - almost a matter of taste, both have such great dynamic range and transparency). Of course when the products migrated to the new big chassis this involved a price increase to cover all the new parts and work.

The units built in the small SL chassis are not upgradable into the new large SL chassis designs, nothing done to fit the old small chassis is appropriate for the new chassis layout. Don't dispare however, the small chassis T8 and flegling Ultra products remain outstanding performances and were well worth what you paid for them, and of course will be supported with service long term.

Frank Van Alstine

avahifi · « **Reply #9 on:** 27 Apr 2006, 08:37 pm »

The active regulators are not appropriate to the original Dyna PAS preamplifier chassis. The Dyna power transformer just does not have the current capacity to support the additional current draw to run the regulators and replacing the transformer and power supply board and all else necessary to make it work in that obsolete old chassis just would not be a cost effective project.

Frank Van Alstine