LM1875 transconductance amp

[Clueless but avid]

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

 

[Clueless but avid]

Just finished my first LM1875 Transconductance Amp and it sounds great! Just one channel, just one 5" speaker, but it sounds like much more 🙂.

 

[Clueless but avid]

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:

 

[Clueless but avid]

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.

 

[kking85743]

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)

 

[Sype]

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.

 

[padamiecki]

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?

 

[Sype]

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.

 

[padamiecki]

would you send the link for ebay pcb you moded?

 

[Sype]

would you send the link for ebay pcb you moded?

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

 

[Amit Ghosh]

Can I get 10 Watts output from this circuit using LM1875 I'm sending here as attachment ?

 

[Panelhead]

Should

Can I get 10 Watts output from this circuit using LM1875 I'm sending here as attachment ?

You will need to series two batteries. The chip requires 20 volts(+/- 10 volts). Output will require more supply voltage.
With 8 ohm load it will 1.1 amps. 1.6 amps with 4 ohm. But jacking up the rail will help.
15 volt single rail is really low.