Acoustat X amp schematic - diyAudio
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Old 7th April 2003, 10:02 PM   #1
Milo is offline Milo  Italy
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Default Acoustat X amp schematic

Hi all,

who knows where to find the Acoustat X schematic diagram?

Thanks in advance

Milo
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Old 8th April 2003, 10:56 AM   #2
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i believe this is what you are looking for

http://gilmore.chem.northwestern.edu/accoustat1.gif
http://gilmore.chem.northwestern.edu/accoustat2.gif
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Old 8th April 2003, 12:36 PM   #3
Milo is offline Milo  Italy
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Default Acoustat X schematic

Many thanks Kevin,

It was what I was looking for.

Thanks again

Milo
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Old 8th April 2003, 12:47 PM   #4
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Does anyone have any experience trying to build these? I had a set of the III's with the tube amps and hey were great to listen to as long as the amps ran. If they could be improved and made more reliable it would be a nice piece of 'history" to have. I still have a set of II+II's that would be fun to drive with this amp.
rt
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Old 8th April 2003, 02:33 PM   #5
SY is offline SY  United States
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I haven't tried the X design yet, but I'm deep in the design phase for a DD amp of my own. Mid-summer ETA. When it's up and running (assuming my design concept proves out), I'll post details.
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Old 8th April 2003, 03:23 PM   #6
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Default DD Amps

SY,
Great...I had a lot fo fun with the III's...bought them used in 1979...eventually bought the transformers and later regretted it...should have kept the tube amps even though they were always blowing up....just should have learned to fix them.

They were not perfect but they sure did sound sweet and imaged well when they were set up right and being fed good source material. I was doing a lot of live recording then..all acoustic small groups...folk...chamber music etc......two NAK CM-300's into a reel to reel 1/2 track....the tapes sounded sweet out of the III's!

rt
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Old 8th April 2003, 05:17 PM   #7
SY is offline SY  United States
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Yeah, I've heard a lot of negative buzz about the reliability of the Acoustat amps. One of the things I'm trying is the use of TV sweep tubes- you can get a lot of watts dissipation for not many $$$. Tubes like the PL509/519 can take 4000 volts on their plates, yet swing enough current to move the diaphragm without breaking a sweat.
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Old 8th April 2003, 06:04 PM   #8
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I have repaired and modified dozens of these amps. In fact, at one time we offered a complete new all tube driver stage (replaced the op-amp front end that was, at best, equal to a Dyna PAT-4 in sonic quality). We don't offer the work any longer due to the amps two fundamental problems:

1) the HV power transformer fails frequently and with the trail of owner changes over the years, replacements are near impossible to find. Some customers have resorted to either buying another amp or pair for spare parts or having the transformer rewound - both expensive propositions.

2) The 6HB5 output tubes are are operating near boderline voltage rating. It is common for them to flash and ark until everything stabilizes immediately after turn-on (which by the way must be after the filaments have reached 50 % operating temp to avoid complete destruction). I haven't checked recently but the 6HB5 may have materialized into unobtainium.

That having been said and even with the poor front end they sound much better than any of the transformer interfaces.
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Old 8th April 2003, 07:48 PM   #9
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Joe,
Many thanx for posting your experience. Guess I will not attempt to recreate an original tube amp for the Acoustats. I have to agree on all counts...I was tired of the amps blowing up so I went for the transformer interface and I was really dissapointed by what I heard. However, as i stated previously, I still have a set of II+II's and would like to run them with a tube amp like the Acoustat but with better reliability and of course better sound.

SY's project sounds pretty interesting.

I also someday would like to pick up a set of III's (I still know where mine are.) just because I had so much fun with them...they were neat speakers and that alone makes it easy for me to rationalize...they had a high fun factor...especially when used for playback of my live tapes...

Any advice?

Thank you,
rt
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Old 8th April 2003, 09:13 PM   #10
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If you are willing to accept the reasonable possibility that you may lose the (non-replaceable) HV transformer - my advce would be to try to find an original pair with working tansformer(s). There are 3 proprietary transformers in addition to the HV transformer. Two feed the filaments in the "upper" tubes and therefore need to have at least a 5KV insulation rating. The remaing transformer feeds the bottom output tube filaments and provides the lower voltages for the screen grids and op-amp supply lines.

Then change the output tubes to PL-509's as suggested earlier. I have recently redesigned the original Beveridge esl amp (using all tubes in the driver stage) using this tube in the output. There are absolutely no problems with arc-over even when the filaments are powered up at the same time as the HVB+.

You could also try better op-amps in the driver circuit. Be careful - the original op-amps were 741 vintage and the current crop of op-amps are sure to oscillate without necessary provisions.
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