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Old 13th February 2012, 02:08 AM   #1
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Default Separating the bias & audio portions of Acoustat Servo?

Was just thinking.....is it possible or even desirable to physically isolate the bias voltage circuit from the audio circuit in an Acoustat Servo amp and go with two enclosures?
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Old 14th February 2012, 09:58 AM   #2
tyu is offline tyu  United States
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Man i did like the sound of the old Acoustat X...even if it was a littel dark sounding...But thay were in a box an canted back....the frist Acoustat i owned back in the 80s... I would not deal with the Sevos i would just add a bias an leve the SevoAmps stock or as thay are...have fun an goodluck
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Old 14th February 2012, 11:54 PM   #3
ehous is offline ehous  United States
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I intend to do this my self, my reason is to keep the panals charged. In the Interface design, the bias has nothing to do with the passive transformers. Based on this, I assume it will work just fine. How ere you going to build the power supply?
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Old 15th February 2012, 07:14 AM   #4
tyu is offline tyu  United States
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Here is the MK121 setup ....tranfourmer is 750vac
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File Type: gif MK-121C_Xovr[1].gif (39.5 KB, 131 views)
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Old 15th February 2012, 02:45 PM   #5
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Thanks, guys. I'm eventually going to do a full rebuild of the Servos using Analogue Associates parts. I was thinking about getting/making new circuit boards, which then got me wondering if there is any advantage to keeping the two portions apart.
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Old 15th February 2012, 03:57 PM   #6
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I am not sure if there would be in benefit to separating them ,unless the bias voltage is common to the amplifier plate supplies.
I will have to look up the info as maybe I am thinking of the wrong amplifier system.

jer
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Old 15th February 2012, 07:21 PM   #7
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Quote:
Originally Posted by geraldfryjr View Post
I am not sure if there would be in benefit to separating them ,unless the bias voltage is common to the amplifier plate supplies.
I will have to look up the info as maybe I am thinking of the wrong amplifier system.

jer
The plate supply and diaphragm bias are fed from the same supply, as there is only one high-voltage transformer. Making the two supplies seperate might offer some sonic benefit, plus having the diaphragm bias as a seperate supply does offer the highly advantageous benefit of allowing the panels to remain charged even when the amplifier is in the 'sleep' mode.

The circuit shown above for the MK-121 bias supply should work well. I do see the 750-VAC Acoustat bias transformer for sale on eBay occassionally, and possible other sellers. Part number is TTA-117 for the 110/120 VAC input model. Other transformers with different output voltage could be used by adjusting the number of stages in the voltage multiplier (within reason, of course). So nice to see a schematic that I drew so many years ago, still getting good use. Who knew?
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Old 15th February 2012, 07:41 PM   #8
tyu is offline tyu  United States
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Wow I would think you Knew....An may i say, thanks for some of the best ESLs i have ever had! I know it was jims deal but ...you were there...I have had a lot of esl Quad....SoundLab....MartinLogans ...But thay come an go.......Along with the Magnepans B&W thiels ADS Apogee...Got have one pr of every thing ....Once..But i well die with Acoustat panels in my home.
Thanks for your time an the info on Acoustats thay just keep going an going..
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Old 16th February 2012, 05:57 PM   #9
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Quote:
Originally Posted by tyu View Post
Wow I would think you Knew....An may i say, thanks for some of the best ESLs i have ever had! I know it was jims deal but ...you were there...I have had a lot of esl Quad....SoundLab....MartinLogans ...But thay come an go.......Along with the Magnepans B&W thiels ADS Apogee...Got have one pr of every thing ....Once..But i well die with Acoustat panels in my home.
Thanks for your time an the info on Acoustats thay just keep going an going..
Wow...that's the nicest comment I've heard all week. Your comparison of Acoustats to all the other manufacturers is a very strong testimonial, and there isn't much I can add to that! Acoustats do seem to just keep on running year after year, and that is one of the reasons I spend time helping owners maintain their speakers - because both the speakers and their owners deserve it! I also try my best to erase the ill effects of Rockford's bone-headed move (IMHO) in selling the brand to an Italian firm. I truly believe that a US buyer could have been found, and if that had been the case, I believe that Acoustat would still be a strong contender in the market, and would still offer support to the thousands of speakers still in service. And who knows, I might still be enjoying the most rewarding job I ever had. What a shame! Color me bitter? - you bet!

I too, will die with my Acoustats!
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Old 5th May 2012, 03:02 AM   #10
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I have a pair of Acoustat X with servo amps that have been working fine all these years, but time to downsize and sell them (my wife loves them, but can't live with anything that big anymore). Any idea what they are worth?
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