LM1875 schematic...

[w00t]

Hi all,

I would like a LM1875 schematic other than that provided in the first page of the datasheet. Have tried Google but only found those related to that in the datasheet.

I need about 20W-30W to drive my KEF Cresta1. Already have a 18-0-18 300VA trannie. Refraining from LM3875 due to past disappointments with it. (Rebuilt 3 times with boutique parts, and it had probs 3 times... P2P wired...)

Thanks!

[PauSim]

Quasar Electronics sell an LM1875 kit wich use quite different values from what I´ve seen here for the NFL resistors. Check the 25 W mono amp. It´s very easy to build. Sometime ago I started two of these kits to drive my KEF Cresta 2s with good results. In the end I returned to the "traditional" configuration, which I believe sounds much, much better.

http://www.electronic-kits-and-projects.com

http://www.electronic-kits-and-proje.../3000/3050.pdf

[w00t]

Originally posted by PauSim
Quasar Electronics sell an LM1875 kit wich use quite different values from what I´ve seen here for the NFL resistors. Check the 25 W mono amp. It´s very easy to build. Sometime ago I started two of these kits to drive my KEF Cresta 2s with good results. In the end I returned to the "traditional" configuration, which I believe sounds much, much better.

http://www.electronic-kits-and-projects.com

http://www.electronic-kits-and-proje.../3000/3050.pdf

Hi,

Thanks for the reply. By "traditional" configuration, I suppose it's the one on the first page of the LM1875 datasheet?

Thanks once again!

[Greg Erskine]

Originally posted by w00t
Refraining from LM3875 due to past disappointments with it. (Rebuilt 3 times with boutique parts, and it had probs 3 times... P2P wired...)

I can't see an advantage of using a LM1875 when you weren't happy with the LM3875. I have built a few IGCs with LM1875 and LM3875 using exactly the same circuit and components. Very similiar results except the LM1875 wasn't powerful enough for very inefficient speakers.

What problems did you have with the LM3875 that you think the LM1875 will solve?

Anyway, here's a couple of circuits.

http://sound.westhost.com/project72.htm
http://gainclone.com/inv_gainclone_1.gif

[demogorgon]

I think you'd be better off trying the lm3886 instead of a much less powerfull IC. maby even teh lm4780.

as for alternate scematics: there are only so many ways to use a op-amp to amplify a signal...

[w00t]

Originally posted by grege


I can't see an advantage of using a LM1875 when you weren't happy with the LM3875. I have built a few IGCs with LM1875 and LM3875 using exactly the same circuit and components. Very similiar results except the LM1875 wasn't powerful enough for very inefficient speakers.

What problems did you have with the LM3875 that you think the LM1875 will solve?

Anyway, here's a couple of circuits.

http://sound.westhost.com/project72.htm
http://gainclone.com/inv_gainclone_1.gif

Hi,

My LM3875 had no problems and were extremely silent (hear a very very soft radio broadcast with ears right next to the speakers), but once I turned on my tube preamp, it started acting funnily and it can't be tamed after that!!

BTW, for the inverted gainclone you have given me, can I use a 1/4W for the 0.22ohm at the output pin? Thanks!

Cheers!

Originally posted by demogorgon
I think you'd be better off trying the lm3886 instead of a much less powerfull IC. maby even teh lm4780.

as for alternate scematics: there are only so many ways to use a op-amp to amplify a signal...

Hi,

The LM3886 has much too much pins to handle (2 pins of one rail IIRC). BTW, If I sub a LM3886 in place of a circuit designed for LM3875, would the power output be higher? (Supposing the same rail voltages for both) Thanks!

Cheers!

[PauSim]

Hi w00t,

<<...By "traditional" configuration, I suppose it's the one on the first page of the LM1875 datasheet?...>>

Yes

Cheers

[richwalters]

<I would like a LM1875 schematic other than that provided in the first page of the datasheet. Have tried Google but only found those related to that in the datasheet>

Hi there.......I've tampered with the original National circuit to the extent that What's shown in the data sheet is prettywell optimised. I've attempted altering the gain with poor results.
I use this op-amp for headphone apps because it has a nice low S/N ratio and good B/W. Like all these power op amps, it is layout sensitive and best used with a ground plane. I've even put this chip in a console and everyone remarked how brill the sound was without realising it.

rich