PSU caps for tweeter only GC

Nuuk · 28th February 2006, 09:31 AM

I have done a search but and can't seem to find if this has been discussed before.

I want to build a pair of LM3875 Gainclones that will only be used to power 8 ohm tweeters crossed over no lower than 6 kHz. And I am wondering what the optimum value would be for the power supply capacitors (on the pins of the chip).

My first thought is to stick with 1000 uF but is there anything to be gained in going a bit lower?

And I am also thinking of bypassing the electrolytics with 0.1 uF film caps!

Vikash · 28th February 2006, 10:26 AM

Well if you can go low enough, then you could use better than electrolytic caps I guess. I certainly found that bypassing with 0.1 polys has huge impact.

I guess it also would depend on what PSU you're using, as you could go real small for the caps on the pins anyhow.

edit: assuming this is for a multi-way active setup, then personally I would like all amps used exactly the same. But this is just me.

Nuuk · 28th February 2006, 12:04 PM

Quote:

I guess it also would depend on what PSU you're using, as you could go real small for the caps on the pins anyhow.

You just reminded me! I will be using them with the Skynet SMPS modules. I am currently running the full-range drivers with such a set-up and the sound is wonderful so I'm going to use the same for the full-range drivers (that effectively become mid-range in the new set up) and tweeters. Woofers will also be GC (LM3886) but with linear PSU.

1000 uF works very well for the full-rangers at present so I'll probably stick with that but it should be possible to go lower with the tweeters. And as you point out Vikash, that would allow something more 'exotic' to be used if (I feel the need)!

carlosfm · 28th February 2006, 02:16 PM

Nuuk, to power the tweeters you should be better using the LM3886.
The LM3875 has no mute circuit, and it produces a small turn on/off thump.
Not good if you are using the tweeters without any protection, like a series cap.

Nuuk · 28th February 2006, 05:11 PM

Quote:

Nuuk, to power the tweeters you should be better using the LM3886.

Thanks Carlos but I am planning on using protection.

28th February 2006, 09:31 AM	#1
Nuuk diyAudio Member Join Date: Feb 2003 Location: Somerset, SW England	PSU caps for tweeter only GC I have done a search but and can't seem to find if this has been discussed before. I want to build a pair of LM3875 Gainclones that will only be used to power 8 ohm tweeters crossed over no lower than 6 kHz. And I am wondering what the optimum value would be for the power supply capacitors (on the pins of the chip). My first thought is to stick with 1000 uF but is there anything to be gained in going a bit lower? And I am also thinking of bypassing the electrolytics with 0.1 uF film caps! __________________ The truth need not be veiled, for it veils itself from the eyes of the ignorant.

28th February 2006, 10:26 AM	#2
Vikash diyAudio Moderator Emeritus Join Date: May 2003 Location: UK	Well if you can go low enough, then you could use better than electrolytic caps I guess. I certainly found that bypassing with 0.1 polys has huge impact. I guess it also would depend on what PSU you're using, as you could go real small for the caps on the pins anyhow. edit: assuming this is for a multi-way active setup, then personally I would like all amps used exactly the same. But this is just me. __________________ "The human mind is so constituted that it colours with its own previous conceptions any new notion that presents itself for acceptance." - J. Wilhelm. (But I still think mine sounds better than yours.)

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28th February 2006, 02:16 PM	#4
carlosfm Banned Join Date: Mar 2003 Location: Lisbon, Portugal	Nuuk, to power the tweeters you should be better using the LM3886. The LM3875 has no mute circuit, and it produces a small turn on/off thump. Not good if you are using the tweeters without any protection, like a series cap.

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