Is the U70 the best low wattage amp ever!?!?!?

simon wagstaff · « **on:** 25 Oct 2008, 12:04 pm »

This amp just doesn't seem to get the attention it deserves. I have had mine for over a year now and it continues to amaze me. I just feel compelled to post my experiences with it. In the right set up this amp is pure magic. Three dimensionality, midrange liquidity, top end extension in spades. I think the key to this performance is to not ask it to drive the ultra lower end. I run mine with a pair of Infinity Intermezzo 4.1s, the have built in sub amps, 850 watts, that cross over at 80 hz. I also use a pair of VMPs smaller subs just in case Phil Lesh decides to drop a bomb, as he is wont to do.

I get all the volume that I could want with this set up in an average sized room. This amp is definitely a sweet match for the Infinities and would probably also mate very well with the Mythos Towers or any other speaker that includes a built in powered sub.

though I haven't tried a bunch of amps with the Infinities I couldn't imagine anything better nor do I have any desire to try something else.

Just a great amp!

martyo · « **Reply #1 on:** 25 Oct 2008, 02:23 pm »

Thanks for posting your experience and I might add it comes with extra weight when you reference the PhilZone. aa

avahifi · « **Reply #2 on:** 25 Oct 2008, 02:34 pm »

Note that Bill Thomas is in the process of building and thoroughly documenting an Ultimate 70 at the Vintage Circle herein

http://www.audiocircle.com/index.php?topic=59784.0

You may be interested to follow along with his project.

Regards,

Frank Van Alstine

simon wagstaff · « **Reply #3 on:** 28 Oct 2008, 11:11 am »

Quote from: martyo on 25 Oct 2008, 02:23 pm

Thanks for posting your experience and I might add it comes with extra weight when you reference the PhilZone. aa

Perhaps I get some extra jollies knowing that I have 2,200 watts on tap for all the subs and 35 watts a channel for everything from 80 hz on up. All those Dead posters will really rattle around sometimes.....

G E · « **Reply #4 on:** 29 Oct 2008, 12:01 pm »

Quote from: simon wagstaff on 25 Oct 2008, 12:04 pm

This amp just doesn't seem to get the attention it deserves. I have had mine for over a year now and it continues to amaze me. ....

Just a great amp!

I have heard Wagstaff's system and can vouch for his comments. There is something magic here and it ain't coming from magic wires or caps. Amazing. Now if I can just convince him to get a turntable and some vinyl....

G E

Wayner · « **Reply #5 on:** 29 Oct 2008, 12:37 pm »

What's really fun is running the U70 on a vintage pair of Dynaco A25XLs. (listening to vinyl)

Wayner aa

simon wagstaff · « **Reply #6 on:** 29 Oct 2008, 01:31 pm »

Quote from: Wayner on 29 Oct 2008, 12:37 pm

What's really fun is running the U70 on a vintage pair of Dynaco A25XLs. (listening to vinyl)

Wayner aa

Geez, that is like a time machine!! All you would need is some schwag and it would be just like 1972 all over again!

Wayner · « **Reply #7 on:** 29 Oct 2008, 01:42 pm »

Brett Buck · « **Reply #8 on:** 29 Oct 2008, 05:46 pm »

Quote from: simon wagstaff on 29 Oct 2008, 01:31 pm

Geez, that is like a time machine!! All you would need is some schwag and it would be just like 1972 all over again!

The U70 doesn't sound like anything available in 1972!

gjs_cds · « **Reply #9 on:** 29 Oct 2008, 06:05 pm »

Hey Wayner,

The surrounds on your woofer looks to be in pretty good condition, all things considered. Are they original?

The A25XL was such a simple, yet great, design. It's always been interesting to me to see how fads change speaker designs over the years, as manufacturers seemingly ignore some simple, tried, tested and true designs (in lieu of a narrow-baffle multi-woofer .5 design that solves some problems at the expense of creating other ones...)

Wayner · « **Reply #10 on:** 29 Oct 2008, 06:13 pm »

Surrounds are like brand new. The "wet look" around the voice coil cap is from the glue that was used (it's just a stain). Yes, this design uses a simple 8 mfd cap in series with the tweeter, and I think a .75 or 1mh coil across the tweeter terminals. It also has a 3 position resistor ladder for tweeter level (I have mine on full). The woofer rolls off naturally and the cabinet is just a "loaded slot" with a bit of acoustical insulation. Insides have insulation on all interior walls except the front baffle. I'm lucky to have 2 pair of these.

Wayner

Dan Kolton · « **Reply #11 on:** 29 Oct 2008, 06:48 pm »

Wayner,
What does this mean? "An Audio by Van Alstine participant"

Wayner · « **Reply #12 on:** 29 Oct 2008, 06:56 pm »

I am required by the minds of Audiocircles to identify myself as an associate with Audio by Van Alstine as I occasionally do engineering work for Frank. Because of my relationship with AVA, AC considers my comments biased and therefore, I have to identify myself as being part of Frank's group. I'm not an employee, just a friend of Franks that helps out in the kitchen once in awhile, that's all. I have a very tiny role (but certainly Cherish it!).

Wayner

simon wagstaff · « **Reply #13 on:** 30 Oct 2008, 12:11 pm »

I first heard Frank Zappa's Hot Rats at my sister's boyfriend's place on those speakers around 1972 with an Ar turntable I forget the amp, maybe it was the schwag...

It was a memorable sound though!

Wayner · « **Reply #14 on:** 18 Jan 2009, 06:24 pm »

Yesterday, I hooked up the U70 to my Focal JMLabs speakers with the Insight EC Preamplifier. I also decided to do a bit of a wood project and give this proto-type a little face lift. It's a great amp for these speakers and vinyl. Enjoyed it all day on Saturday.

Wayner

avahifi · « **Reply #15 on:** 18 Jan 2009, 10:45 pm »

Be careful Wayne or you will find yourself designing wood enclosures too but how do you figure out all the bends and press breaks and welds with them?

Very nice looking!

Best regards,

Frank

P.S. Wayne just found out he was indispensable at his full time engineering job and thus was not dispensed with.

oneinthepipe · « **Reply #16 on:** 18 Jan 2009, 11:43 pm »

Wayner:

The enclosure that you built for your U70 is very nice.

Anyone:

What are the major differences between the U70 and the Super 70i, besides the sound?

carusoracer · « **Reply #17 on:** 19 Jan 2009, 02:13 pm »

Nicely done Wayne. It certainly enhances the aesthetics and WAF

Wayner · « **Reply #18 on:** 19 Jan 2009, 03:50 pm »

Thanks.

It's the best I can do with a power mitre saw and a drill press.

Wayner.

martyo · « **Reply #19 on:** 20 Jan 2009, 03:21 pm »

Nice clean look Wayne. I think a nice piece of wood improves the looks of just about anything.