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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.
Follow Ups:
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.
What pre-amp did you get?
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.
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.
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.
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.
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?
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.
Thanks.
I will look forward to some upgrades.
I'll post some pics in the fall!
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.
What is the "discrete MOV"?
see above
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
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.
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
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