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Most recent Acoustat upgrade

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Posted on July 27, 2014 at 11:12:42
dogwan
Audiophile

Posts: 871
Joined: December 16, 2004

Just installed new output coupling caps and discrete MOV replacements on my Servo amps.

Did the MOV's first and it was subtle, but really did remove a haze on the upper registers. They are the little white bulb like things between the big resistors.

Did the caps second and they are sooooo much smoother.

 

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RE: Most recent Acoustat upgrade, posted on July 28, 2014 at 13:26:48
Roger Gustavsson
Audiophile

Posts: 2058
Location: Huskvarna
Joined: February 12, 2010
 What is the "discrete MOV"?

 

RE: Most recent Acoustat upgrade, posted on July 28, 2014 at 13:42:16
dogwan
Audiophile

Posts: 871
Joined: December 16, 2004
 Replacement for the MOV built out of discrete parts. Not sure the actual components, but pretty sure it's made up of caps and diodes.

 

RE: Most recent Acoustat upgrade, posted on July 28, 2014 at 13:46:07
dogwan
Audiophile

Posts: 871
Joined: December 16, 2004
 see above

 

RE: Most recent Acoustat upgrade, posted on July 28, 2014 at 18:24:03
john65b
Audiophile

Posts: 326
Location: Chicago
Joined: July 19, 2005
 Varistor - A Metal Oxide Varistor. What is "Discrete" about it? You made a Metal Oxide Varistor out of caps/diodes and inside that little container?

MOVs are Voltage surge supressors. You see them a lot on switches and power supplies.
I VOID WARRANTIES

 

RE: Most recent Acoustat upgrade, posted on July 28, 2014 at 19:13:30
pictureguy
Audiophile

Posts: 22597
Location: SoCal
Joined: October 19, 2008
 MOVs are also the 'sacrificial' device in surge suppressors.
As such, they have a limited capacity to absorb abuse and should be replaced periodically. This is not a bad thing, since they are commodity cheap.
Too much is never enough

 

RE: Most recent Acoustat upgrade, posted on July 28, 2014 at 21:54:44
dogwan
Audiophile

Posts: 871
Joined: December 16, 2004
 Perhaps I should've phrased it differently. It is a replacement for the MOV in the circuit and it is made of discrete components.

I did not make it. It was made for me by someone who has devoted a lot of time and energy into increasing the dependability and performance of the Acoustat servo amps. And, he has done his research. I trust him.

In this case the MOV's are in the signal path and as such have an effect on the sound. I can't tell you what they actually do in this position. What I can tell you is that doing the swap removed a haze on the upper frequencies that was most noticed once removed. A subtle, but cheap tweak.

 

RE: Most recent Acoustat upgrade, posted on August 3, 2014 at 22:55:06
benie
Audiophile

Posts: 1851
Location: Alberta, Canada
Joined: October 24, 2004
 I understand them caps are very good in the servo amps.
I ended up picking up some huge Dearborn P/O caps, had to mount them under.
What brand are your 4 black caps at the front that you replaced.
Going to be some more upgrading in the very near future.

 

RE: Most recent Acoustat upgrade, posted on August 3, 2014 at 23:47:19
dogwan
Audiophile

Posts: 871
Joined: December 16, 2004
 Those are F&T caps (80uf/450v) that Mr. Savuto put in when he did my 1st round of upgrades.

Next thing I want to do is replace all the HV resistors. But, those are expensive and hard to find in the right values. I think Analogue Associates uses Caddock MG series.

 

RE: Most recent Acoustat upgrade, posted on August 4, 2014 at 12:47:42
Sondek
Audiophile

Posts: 9626
Location: Fort Worth
Joined: May 17, 2000
Contributor
  Since: April 5, 2002
 I lost one of my servos yesterday. Transformer shorted. Can you believe it? The danged thing was only 35 years new! Talked to Mr. Mike this morning. Have to drive through his town in the near future anyway, so will probably swing by and drop it off with him. Aside from the drag of it being broken, I just got a new preamp a couple of weeks ago and was really starting to dig the way thing were sounding.

 

RE: Most recent Acoustat upgrade, posted on August 4, 2014 at 15:19:54
dogwan
Audiophile

Posts: 871
Joined: December 16, 2004
 What pre-amp did you get?

 

RE: Most recent Acoustat upgrade, posted on August 4, 2014 at 15:28:39
Sondek
Audiophile

Posts: 9626
Location: Fort Worth
Joined: May 17, 2000
Contributor
  Since: April 5, 2002
 I bought a CAT SL1. It's the current version of the SL1, but it's 2 years old. Got a very good buy on it. It sounds, or rather sounded, AWESOME with the Acoustats! Bummed.

 

RE: Most recent Acoustat upgrade, posted on August 4, 2014 at 22:54:18
dogwan
Audiophile

Posts: 871
Joined: December 16, 2004
 Oooohhh, that looks like a good one!

I'm running a highly modified Dynaco PAS3. Tubes and especially a tubed phono stage are magic through the Acoustat servos.

 

RE: Most recent Acoustat upgrade, posted on August 4, 2014 at 23:34:52
benie
Audiophile

Posts: 1851
Location: Alberta, Canada
Joined: October 24, 2004
 Thanks for the info.
Did you upgrade the OP-amp or did Mike do it.
I know you have done some of the work yourself, but if remember right, Mike did some to?

 

RE: Most recent Acoustat upgrade, posted on August 5, 2014 at 09:12:11
dogwan
Audiophile

Posts: 871
Joined: December 16, 2004
 Mike did that. It actually looks pretty simple with just a couple of caps and TO-99 style op-amps (can't remember off top of head which ones). But, looks can be deceiving. Parts of the original OP-11 operated the auto turn-on circuit which is no longer used and a number of other parts in that circuit were removed.

 

RE: Most recent Acoustat upgrade, posted on August 8, 2014 at 21:35:13
benie
Audiophile

Posts: 1851
Location: Alberta, Canada
Joined: October 24, 2004
 Thanks.
I will look forward to some upgrades.
I'll post some pics in the fall!

 

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