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Jazzed and excited ...

99.6.55.49
Posted on January 22, 2016 at 09:29:18
Sondek
Audiophile

Posts: 9632
Location: Fort Worth
Joined: May 17, 2000
Contributor
  Since: April 5, 2002
 Well, after a bit longer than I'd hoped, I'm making the drive to OKC on Sunday to retrieve my newly rebuilt Acoustat servos from my friend and amp builder, Mike Savuto, of Analogue Associates. Too many changes to detail them all, but new caps in several places, Ohno wire where it counts, magnetic/hydraulic circuit breakers, and larger up-rated high-voltage trannies. Although Mike has installed these updates in other amps individually before, this is the first set of amps he's done incorporating them all. I can tell by the echoes of glee in his voice when he describes their sound to me that I am in for a real treat. The servos had been substantially modified (older mods) before this latest bout of updates, and I thought they delivered among the very best sound I'd ever experienced. He tells me that I aint heard nuthin yet. This is gonna be FUN!

 

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Pics Please! nt., posted on January 22, 2016 at 19:46:48
Barry
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Posts: 1003
Location: PA
Joined: November 24, 1999
Contributor
  Since: January 18, 2009
 : )

 

RE: Jazzed and excited ..., posted on January 23, 2016 at 15:01:57
dogwan
Audiophile

Posts: 871
Joined: December 16, 2004
 Kudos!

I have some servos with only most, but not all, of Mike's mods. They are absolutely marvelous. Really only thing left to do is the High and low voltage resistors, and then all the smaller caps.

Although, I have not heard about the circuit breakers. Probably time I check in with Mike and see what else is new for these.

Mike is great to work with..... have fun!

 

Way cool !, posted on January 23, 2016 at 16:24:35
E-Stat
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Posts: 37666
Joined: May 12, 2000
Contributor
  Since: April 5, 2002
 I second the notion of showing pics of the new amps. Does it still use op amps on the input section? I remember updating the original Fairchilds(?) with TL084s which was easy to do since they were socketed.

I still have a sweet spot for the Acoustax X with servos as they were my first stats purchased in '77. I moved to the Monitor 4 a year or so later when they became available.

 

RE: Way cool !, posted on January 23, 2016 at 17:11:31
Sondek
Audiophile

Posts: 9632
Location: Fort Worth
Joined: May 17, 2000
Contributor
  Since: April 5, 2002
 I'll get some snaps of them posted as soon as I can. Yes, they still use an op amp. When Mike started to upgrade Strickland's design, he had the choice to as much as possible work with what he had, or go completely off the reservation. He opted to upgrade/uprate the op amp rather try to rig up some kind of tubed driver setup. One of the issues with the amps is that there is not much free space around the input to mount an input driver board, etc. The one Joe Curcio came up with was probably the most elegant one I've seen, but I kind of worry about his design layout because long-term exposure to the heat generated from the output tubes. Anyway, I'll try to get a good close up of what Mike has done with the op amp and input section. A tubed input is potentially a further mod, but I have a feeling I'm not going to see a need for more upgrades for quite a long while.

 

Servo Rebuild pics, posted on January 25, 2016 at 09:03:10
Sondek
Audiophile

Posts: 9632
Location: Fort Worth
Joined: May 17, 2000
Contributor
  Since: April 5, 2002
 Okay, first pics of the servo rebuild. Keep in mind that these amps are going on 40 years old. In that time they've been used, abused, disused and kept in storage for who knows how long. During their life Roy Esposito had done work on these, Mike Savuto had done some work on them, the guy I bought them from had messed with them, and who know how many other guys before him had tinkered with them. It took quite a while after I got them to smoke-out and fix all the issues and make them stable and playable. I will be the first to admit that they have a look that only a mother could love, but then they were never designed to be seen anyway. They were meant to be heard, and I can tell you that they sound fantastic! The amps grab the panels by the gonads and have absolute control of them. Improvements in dynamics, resolution, and bass are all stunning. The speed of them is mind boggling. The pics are of the top of one of the amps only. I'll pull them out of service at some point in the next few days and get a snap or two of the underside of them as there's almost as much going on there as on top.

 

Pic #1, posted on January 25, 2016 at 09:05:16
Sondek
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Posts: 9632
Location: Fort Worth
Joined: May 17, 2000
Contributor
  Since: April 5, 2002



 

Pic #2, posted on January 25, 2016 at 09:07:46
Sondek
Audiophile

Posts: 9632
Location: Fort Worth
Joined: May 17, 2000
Contributor
  Since: April 5, 2002



This shows a close up of the op amp input.

 

Nice, posted on January 25, 2016 at 13:35:01
E-Stat
Audiophile

Posts: 37666
Joined: May 12, 2000
Contributor
  Since: April 5, 2002
 You can tell that virtually everything in the signal path except the tubes has been updated! Are the Burr-Brown op amps in the TO-99 case the OPA-627?

I'm still enjoying 1+1s in the HT system. :)

 

RE: Nice, posted on January 25, 2016 at 13:41:51
Sondek
Audiophile

Posts: 9632
Location: Fort Worth
Joined: May 17, 2000
Contributor
  Since: April 5, 2002
 Correct. They are OPA-627's.

 

RE: Way cool !, posted on January 28, 2016 at 07:11:29
Satie
Audiophile

Posts: 5426
Joined: July 6, 2002
 I think you are right, a well done OPA 627 stage is hard to beat so that further upgrades are likely to provide better bang for the buck elsewhere in the amp and speaker.

 

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