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Amp Internals 2

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M4trix View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote M4trix Quote  Post ReplyReply Direct Link To This Post Posted: 02 April 2021 at 1:30am
Originally posted by JonB67 JonB67 wrote:

You must be an upper order magic smoke wizard if you managed to get the smoke back into that one. 


LOL
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Post Options Post Options   Thanks (0) Thanks(0)   Quote kedwardsleisure Quote  Post ReplyReply Direct Link To This Post Posted: 02 April 2021 at 1:42am
I'm sure the intact fuses and the ones missing from the adjacent (good) channel had something to do with it. It blew up - let's blow it up some more!
Kevin

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Earplug Quote  Post ReplyReply Direct Link To This Post Posted: 07 June 2021 at 11:10am
A friend dropped these beauties off yesterday for general clean up and renovation.   Smile




































They actually fired up and worked, which was quite amazing. Don't do 2 ohm bass - but will do 500 ohm stacks!  LOL LOL LOL

The smaller one still has original (and very rare) EL506 on the output, which I will change for the 7868 equivalent. One of the smaller valves was also dodgy, so will change them all. Even so, it sounded really good - which was not so with the other.

It was distorting early, so will definitely need a complete valve change - and then see where we are.


In any case, to be filed under "They Definitely Don't Make Them Like This Any More"!!  LOL





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Post Options Post Options   Thanks (0) Thanks(0)   Quote Sonic the hedge Quote  Post ReplyReply Direct Link To This Post Posted: 09 June 2021 at 4:14pm
Originally posted by Earplug Earplug wrote:

Mid and top, Class AB, MOSFETs on the o/p, with transformer coupling to speakers. Very odd choice for the design. I really don't see any advantage doing this.

DC doesn't go through transformers? 

Still a very odd way to do DC protection because a relay is surely cheaper.

As its class B O/P I guess the transformer will also smooth out any crossover distortion, but that doesn't say much for the design!


Edited by Sonic the hedge - 09 June 2021 at 4:23pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Earplug Quote  Post ReplyReply Direct Link To This Post Posted: 09 June 2021 at 5:29pm
Yes, who knows. Amp designers are always trying to do things differently. Sometimes over complicating what should be a fairly simple process. 


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Post Options Post Options   Thanks (0) Thanks(0)   Quote kedwardsleisure Quote  Post ReplyReply Direct Link To This Post Posted: 09 June 2021 at 10:54pm
probably more to do with impedance matching
Kevin

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Earplug Quote  Post ReplyReply Direct Link To This Post Posted: 10 June 2021 at 6:08am
The cab has 4 x 12", 1 x 8" & 1 x 1.4".

IIRC, the amp for the 12's was standard Class G. Mid and top with the transformer.


From the spec sheet:-

  • Active, high-output, wide dispersion 3-way system
  • 80° x 70° coverage pattern
  • High output, 133dB in High Pass Mode Operation
  • Four 12″ high-precision transducers
  • Low distortion, horn-loaded 8″ mid-range transducer
  • 3″ titanium diaphragm compression driver
  • 18mm birch plywood construction
  • 1500W high-effi ciency, high-current amplifier for woofers
  • 300W Trans-Fet amplifier for mid-range
  • 150W Trans-Fet amplifier for compression driver
  • On-board acoustic management control system

"Trans-Fet" sounds to me like marketing speak BS, like the Carver "Magnetic Field" stuff. The extra cost of those transformers is a bit crazy. These days, the 8" & 1.4" would just be driven by a couple or 3 3886's or 7293's!  LOL





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Post Options Post Options   Thanks (0) Thanks(0)   Quote imageoven Quote  Post ReplyReply Direct Link To This Post Posted: 10 June 2021 at 8:56am
Originally posted by Earplug Earplug wrote:

"Trans-Fet" sounds to me like marketing speak BS, like the Carver "Magnetic Field" stuff.


Now known as LBGTQ+ Fets...
Keep pushing on, things are gonna get better.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Earplug Quote  Post ReplyReply Direct Link To This Post Posted: 10 June 2021 at 9:10am
Originally posted by imageoven imageoven wrote:

Originally posted by Earplug Earplug wrote:

"Trans-Fet" sounds to me like marketing speak BS, like the Carver "Magnetic Field" stuff.


Now known as LBGTQ+ Fets...



You should be on the Mackie Marketing Team!   LOL LOL LOL


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