Acrosound UL-II rebuilt with photos.

trainbuftony

Electron Herder
Subscriber
So the story Begins 2 or 3 years ago, when a new friend, Nick introduced me to a fellow hifi enthusiast pal of his. I met the the guy and he definitely had the bug and had it bad. He brought me some gear to check out which I did free of charge. ( i think i cleaned a few switches and pots with DE-oxit) He mentioned having bought and Acrosound Ultralinear 2 at an estate sale with the matching Dynakit mono preamp and a Giant BOZAK speaker. At that time I mentioned that should he decide to sell the amp that I would like to make a serious offer. He is after all a solid state type of guy... Several months later I got a call and he indicated that the time may be right to make that serious offer. I took cash and came home with this beautiful Acrosound, unrestored and working, and in beautiful shape for its age.



I Had some Idea of what I was getting my self into, I own a magazine somewhere where this amp was explained and bragged about by its designers. I knew it was Top of the line tube gear, and I had to have it. I got to work doing as much research as I could about the amp and the options for bringing it up to date. It didn't take long to find the info Brice has posted on his set. I sent A PM to Brice and he had a set of extra prototype boards available for me to purchase. I Immediately went to work ordering the best parts I could afford, to rebuild these unique monoblock amps. Somewhere in the mean time I bought another on Ebay for within $5 of what I paid for the first. The other one is so damn ugly that it broke my camera, hence: No pictures of it!


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One cool feature of this Amplifier design is that it only uses 2 coupling caps. I do not like to argue, so fewer coupling caps is a better choice, fewer things to argue about. I chose the typical low end caps to start with, and ordered a few sets of audiophile types to roll in when the mood suits. I honestly doubt that they will have any affect on the performance of this lovely sounding amplifier.


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I used some special reserve old production 9 pin triodes for these. I pulled a set of Telefunken Ribbed plate 12AX7s and a pair of Raytheon Blackplate 12AU7s from my private stash. Given the feedback loop around the entire amp, I have my doubts that any measured performance difference could be found between good tubes of the same type. I'm just showing off... The power tubes are Russian 6550s from Jim McShane. Rectifier is a Vintage Mullard 5AR5 Bypassed with Diodes. Again, just showing off.


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I may be trying to find another set to restore for a club member friend of mine who has expressed interest in owning a pair. These are the biggest and by far the most powerful tube amps I've ever owned. They are a definite step up from the HH Scott 299D which was my main amp prior to these. I need to find a preamp that I am in love with and the conclusion that I'm coming to is that I may need to build that preamp. Perhaps more on that later... As for these Acrosounds, they just drive rich beautiful and dynamic sound from top to bottom and at as loud of a volume as you can stand to listen at, with headroom. I am very happy with the result.

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:banana: I am not the only one crazy about this amp ! Ha ha. Congrats on your rebuild Tony. Looks awesome.

I also feel good about helping fellow AK member with their Acrosound gear, and knowing that now these great amps are going to outlive us with modern components.

Thank you for posting your result.
Brice.
 
Nice amp. I've heard a lot of good things about these, would love to actually hear one sometime.
 
Gadget,

If you are going up north, please feel free to swing by. I have the whole Acrosound family and more :) to listen to.

Brice.
 
These amps truly are special and after a year they still sound beautiful and really drive the music deep into your soul. I ended up building the preamp which i had been planning in my mind for a while. The Acrosound amps sound really deserve something better than a PAS3, and i ended up building just the circuit. An HH Scott Riaa phonostage coupled to a shunt regulated push pull line stage, with DC heaters and 100% point to point construction. Anyway, im listening right now and this combo really doing it for me right now. I don't feel the need to buy any equipment, maybe some records instead...
 
I agree with you regarding these amps. Congrats.
What preamp did you build? I am curious.
 
Yes they are the same amps i had hooked up. They sound rather good after a rebuild and the new preamp helps.

Brice, this is the preamp i built. Not a kit but a true scratch build, which has been brewing in my head for a long while. Its 100% point to point, dc floating heaters, chassis separation between power supply and signal sections. I even hooked up the inputs on relays. It turned out great.
https://audiokarma.org/forums/index...be-preamp-new-photos-up.852210/#post-12361127
 
Nice work Train, and superb amps indeed! Watch out for Brice however -- He is absolutely beyond help when it comes to Acrosound gear!! :)

Dave

Agree with both of Dave's comments here. Really well done and Brice is sick with Acro fever!

I think Brice got his 1st pair of UL II's from me which he promptly redid the boards on. I have the pleasure of owning 2 pair, (1 pair still to be rebuilt), along with a pair of Stereo 20-20's and a Stereo 120 waiting for the rebuild. They are ALL amazing amps. The little Direct Coupled EL84 Stereo 20-20 is my/our favorite of these Acro's.

Acro all the way!
 
Brice has been a great help, and his passion for these amps is understandable. The world in general is desperately in need of more passionate people. Thanks for the kind words everyone. This has been a long, expensive, and laborious process and the reward should last a lifetime. Im 34 years old and i feel like i have reached a destination in my audio journey. Im content to enjoy what ive got for a while. Life is good, take time to stop and appreciate it once in a while. All of the hard work is done now, and all i have to do is hit the bliss switch (Actually 3 switches) and drop the needle, and the BS of the day just slips away...
 
Ah ! You see :whip:Dave. I am not the only one ! :banana:

I am so happy when I see Acro gear been restored/saved with little involvement on my part.
It is like saving a piece of history.

And as Antoine said: Acro all the way!
 
The next set of big power amps on my horizon is a complete rebuilt of the McIntosh MC30. I have one right now in very poor shape, and eventually ill have a pair, restored and sitting in between my ultralinear 2s, and my Grommes 260As Which are also coming my way... (WISHFUL THINKING ON MY PART)
 
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