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Chip Amps Amplifiers based on integrated circuits

LM1875 transconductance amp
LM1875 transconductance amp
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Old 4th June 2018, 09:55 AM   #81
Clueless but avid is offline Clueless but avid  Germany
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I've got some LM1875 for free use to test several circuits and I'm building this one right now >
On the other hand I've got the complete output transistors, even the matched ones still matched, of a Rotel RA-06, and would like to get them to know a LM1875. Maybe there will/ could be love?


greetings
Jochen
Attached Images
File Type: jpg pano Trans-Amp Prasi 02.jpg (841.6 KB, 523 views)
File Type: jpg Transistoren Rotel RA-06 1000w.JPG (645.9 KB, 502 views)

Last edited by Clueless but avid; 4th June 2018 at 10:05 AM.
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Old 22nd June 2018, 09:31 AM   #82
Clueless but avid is offline Clueless but avid  Germany
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Just finished my first LM1875 Transconductance Amp and it sounds great! Just one channel, just one 5" speaker, but it sounds like much more .
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Old 25th June 2018, 06:24 AM   #83
Clueless but avid is offline Clueless but avid  Germany
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Still working on my 2 1/2-way active LM1875 speakers. 1st version with crappy wood and non inverting Amps I gave up for a new version built of MDF with triple Trans-Amp. Work is still in progress but Ihave got some pics:
Attached Images
File Type: jpg 1st contact 800w 01.jpg (163.6 KB, 402 views)
File Type: jpg triple LM1875 Trans-Amp 1000w 01.JPG (951.6 KB, 373 views)
File Type: jpg Box von hinten groß 02.jpg (205.4 KB, 387 views)
File Type: jpg Einbau Elektronik 1000w.jpg (170.6 KB, 115 views)

Last edited by Clueless but avid; 25th June 2018 at 06:28 AM.
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Old 28th June 2018, 01:44 PM   #84
Clueless but avid is offline Clueless but avid  Germany
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It's done and all three are running. Now some testing and then I got to see how I mount it in the box. Maybe a little drawer would be fine.
Attached Images
File Type: jpg triple trans amp läuft 1000w 04.JPG (601.2 KB, 108 views)
File Type: jpg triple trans amp läuft 1000w 02.JPG (656.4 KB, 96 views)
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Old 9th July 2018, 02:41 AM   #85
kking85743 is offline kking85743
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Quote:
Originally Posted by e_fortier View Post
Hi

Revisiting an old thread since I always wanted to try a transconductance amp. since I have full range speakers and the article from NP convinced me to one day give it a try.

Thanks to the good as built schematic of Bimbla and the great help from Prasi a PCB layout has been created. I will try to fire it up very soon and will keep you posted.

I attached some pics of the empty and stuffed PCB (need to find my LM1875

Once tested I'll have some PCB to sell at cost + shipping (cheap)

BR
Eric
I am even later to the party. I am using a pair of full-range speakers with an ACA, but was also intrigued by the TransConductance paper by Nelson Pass.

Do you still have any of the boards to sell? If not I can build one myself, but shipping from China takes foorrreeeevvvvveeeeeerrrrrrr.......

8)
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Old 17th December 2018, 06:42 PM   #86
Sype is offline Sype  Finland
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Here is my schematic for constant current amp. One prototype was made from modified (ebay) 2 ch amp. It worked very well with Scan-Speak Discovery 10F/8414G10.
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File Type: jpg 7273_current02.jpg (127.5 KB, 140 views)
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Old 18th December 2018, 07:45 AM   #87
padamiecki is offline padamiecki  Poland
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Great! :-)
but in fact this is mixed voltage/current drive.
Why are you using double Zobel?
What voltage are you using to power it?
what type of 40uF cap are you using?
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Old 20th December 2018, 07:22 PM   #88
Sype is offline Sype  Finland
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It is mixed design, only for stability and dc-offset if speaker wires are disconneted. Zobel network seems to be double, but one is in fact compensating gain for high frequencies in current feedback loop. I used metallized polypropylene film capacitors.
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Old 20th December 2018, 08:14 PM   #89
padamiecki is offline padamiecki  Poland
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would you send the link for ebay pcb you moded?
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Old 23rd December 2018, 12:21 PM   #90
Sype is offline Sype  Finland
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Quote:
Originally Posted by padamiecki View Post
would you send the link for ebay pcb you moded?



TDA7294 Audio Amplifier Board Amp Power Board PCB Dual Channel one Board | eBay
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