LM3875 audiosector kit - Optimum DC cable length - power & amp PCBs?

GAH · 24th August 2009, 04:43 AM

How critical is the length of cable (DC power) between the Power and Amp PCBs of a LM3875 or LM4780 audiosector kits?

I'm building one these kits and wish to include a separate chassis each for the amp and power supply. Would 1.5 metres be ok?

Nuuk · 24th August 2009, 12:16 PM

1.6743 metres would be optimum!

AndrewT · 24th August 2009, 12:31 PM

0.6m would be OK, 0.3m would possibly be better.
The speaker cables also fall into a similar length compromise.

GAH · 25th August 2009, 10:08 PM

Quote:

Originally Posted by Nuuk

1.6743 metres would be optimum!

Thanks. Nuuk, your reply is so precise!

Atilla · 28th August 2009, 09:43 AM

1.6743 metres of which wire gauge ?

mrevie · 28th August 2009, 10:07 AM

Three strands of precisely braided 17.98 guage cadmium wire.

N.B. Best results obtained if braiding is done by rare south americian mountain gerbils.

H3nry · 28th August 2009, 03:27 PM

Serious answer: as long as the chips are bypassed well on the amp board, which means put your big electrolytics there, and maybe bypass them with small high quality film caps, you're covered. Then the only concern is the voltage drop / current carrying capacity of the cable. With a meter or more cable, I'd probably put something larger than the 10 uF filters that come in the kit on the rectifier PCB.

My own amps have 3300 uF + 10 uF on the rectifier board and 4700 uF + .047 uF on the amp board. I like solid bass, so I go for lots of energy storage in the power supply. Peter Daniel prefers a lighter supply, I believe. That's a nice feature of chip amps. The circuit is so simple it's easy to tune to your own taste.

lanchile · 28th August 2009, 03:43 PM

Quote:

Originally Posted by H3nry

Serious answer: as long as the chips are bypassed well on the amp board, which means put your big electrolytics there, and maybe bypass them with small high quality film caps, you're covered. Then the only concern is the voltage drop / current carrying capacity of the cable. With a meter or more cable, I'd probably put something larger than the 10 uF filters that come in the kit on the rectifier PCB.

My own amps have 3300 uF + 10 uF on the rectifier board and 4700 uF + .047 uF on the amp board. I like solid bass, so I go for lots of energy storage in the power supply. Peter Daniel prefers a lighter supply, I believe. That's a nice feature of chip amps. The circuit is so simple it's easy to tune to your own taste.

The shorter the better!.and I am also using big caps on the power supply
10000uf on the rectifier and 1000uf on the amp board.Nice bass!

H3nry · 28th August 2009, 04:02 PM

Quote:

Originally Posted by lanchile

Nice bass!

Indeed! My amps are DC coupled and my preamp is flat to 1 Hz, and the bass is incredibly natural, smooth and alive. My previous amps were decent JBL pro studio monitor models, and the Audiosector amps are amazingly better. Not only bass - mids and top are much clearer, more relaxed and natural.

AndrewT · 28th August 2009, 04:18 PM

Lanchile,
please stop posting in that almost illegible colour.

24th August 2009, 04:43 AM	#1
GAH diyAudio Member Join Date: Apr 2009	LM3875 audiosector kit - Optimum DC cable length - power & amp PCBs? How critical is the length of cable (DC power) between the Power and Amp PCBs of a LM3875 or LM4780 audiosector kits? I'm building one these kits and wish to include a separate chassis each for the amp and power supply. Would 1.5 metres be ok?

24th August 2009, 12:16 PM	#2
Nuuk diyAudio Member Join Date: Feb 2003 Location: Somerset, SW England	1.6743 metres would be optimum! __________________ The truth need not be veiled, for it veils itself from the eyes of the ignorant.

24th August 2009, 12:31 PM	#3
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	0.6m would be OK, 0.3m would possibly be better. The speaker cables also fall into a similar length compromise. __________________ regards Andrew T.

28th August 2009, 04:18 PM	#10
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	Lanchile, please stop posting in that almost illegible colour. __________________ regards Andrew T.

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28th August 2009, 09:43 AM	#5
Atilla Soldering Gun Fanatic diyAudio Member Join Date: Jul 2008	1.6743 metres of which wire gauge ?

28th August 2009, 10:07 AM	#6
mrevie diyAudio Member Join Date: Jan 2009	Three strands of precisely braided 17.98 guage cadmium wire. N.B. Best results obtained if braiding is done by rare south americian mountain gerbils.

28th August 2009, 03:27 PM	#7
H3nry diyAudio Member Join Date: Aug 2009 Location: Austin, TX	Serious answer: as long as the chips are bypassed well on the amp board, which means put your big electrolytics there, and maybe bypass them with small high quality film caps, you're covered. Then the only concern is the voltage drop / current carrying capacity of the cable. With a meter or more cable, I'd probably put something larger than the 10 uF filters that come in the kit on the rectifier PCB. My own amps have 3300 uF + 10 uF on the rectifier board and 4700 uF + .047 uF on the amp board. I like solid bass, so I go for lots of energy storage in the power supply. Peter Daniel prefers a lighter supply, I believe. That's a nice feature of chip amps. The circuit is so simple it's easy to tune to your own taste.

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