LM338 regulated snubberized PSU for audio amplifiers - Page 3

XELB · 26th April 2005, 03:17 AM

Carlos, you have 8 Ohms speakers. Don't you ?

Mine are 6 Ohms, and normally I test the amp with 4/2 Ohms speakers(this ones have 5 drivers but 98dB sensitivity).
Do you think 10,000uF per rail will work fine with this speakers?

cjd · 26th April 2005, 03:47 AM

Quote:

Originally posted by metalman
Let me see if the XGC likes it!

Quote:

Originally posted by carlosfm
Do that, try it.

The only reason I want to parallel before the X (SuSy) circuit is the speakers will be rather low impedance... between 2 and 3 ohm I think very likely.

May dip below but I think I can keep it above 2. I also have a few of the LM3886 to mess with, and will likely wire up one with those before the LM4780's. There I can obviously go with this circuit as-is. Looking forward to it.

C

neutron7 · 26th April 2005, 05:05 AM

carlos, why dont you try a tracking pre-regulator version . It is a cheap way to get quite improved noise performance. since the pre regulator is referenced to the output of the main regulator. the main regulators input also benefits from the regulation of its output,. (and who knows maybe the snubberization as well

) and the error amplifiers in those things need as much help as they can get, they are about the quality of a 741!

i hope that makes some kind of sense.

you need to have a bit more of a voltage drop though.

you just need another 338, a cap and 2 resistors per rail.

its on page 12 of here
http://www.national.com/ds/LM/LM138.pdf

Mikett · 26th April 2005, 06:29 AM

Try some LT1083s which have better HF impedance characteristics than the LM338 which are not as high performance. The snubber values will need to change I imagine. The LT1083 is unfortunately more expensive though.

Here's one example with no snubbers.
http://shine7.com/audio/gainclone.htm

Alcaid · 26th April 2005, 07:30 AM

Carlos

Secondary on T2 is shorted in the diagram.

Nuuk · 26th April 2005, 09:30 AM

Carlos, does the regulated 3886 still run hotter with your latest regulated supply?

nina · 26th April 2005, 09:49 AM

The LM338 reg Ic is more expensive than the LM3875 power IC !

Carlos,

Seems we also put the chipamp to its limitation now. Just wonder what next innovation you will contribute to this forum

How about this:

- Parallel chip amps with IC driver/buffer
- Chipamp as driver to Mosfet power stage
- Integrated (Chip)amp with NOS DAC
- Chipamp with High WAF ** Important*
( WAF = Wife Acceptance Factor )

Hee hee hee

NealG · 26th April 2005, 10:32 AM

Hey Carlos, thanks for sharing this!

It's been a while since I changed my clone, I will dust off the soldering iron and get to work!

All the best

NG

Nuuk · 26th April 2005, 10:53 AM

Yes, I'm going to try it as well. I'll sell the Krell to raise money for the extra parts!

(Only joking Uncle Carlos but I will need to order the extra caps)

shusha · 26th April 2005, 01:03 PM

Quote:

Originally posted by nina
The LM338 reg Ic is more expensive than the LM3875 power IC !

I don't know. LM338 cost me less then LM3886, while both of them cost practically as one LM3875. In my local store(s).

LM338 = 4,4€
LM3886 = 5,3€
LM3875 = 9,3€

26th April 2005, 03:17 AM	#21
XELB diyAudio Member Join Date: Dec 2004 Location: Lisboa	Carlos, you have 8 Ohms speakers. Don't you ? Mine are 6 Ohms, and normally I test the amp with 4/2 Ohms speakers(this ones have 5 drivers but 98dB sensitivity). Do you think 10,000uF per rail will work fine with this speakers? __________________ If you want power you must add control

26th April 2005, 09:30 AM	#26
Nuuk diyAudio Member Join Date: Feb 2003 Location: Somerset, SW England	Carlos, does the regulated 3886 still run hotter with your latest regulated supply? __________________ The truth need not be veiled, for it veils itself from the eyes of the ignorant.

26th April 2005, 10:53 AM	#29
Nuuk diyAudio Member Join Date: Feb 2003 Location: Somerset, SW England	Yes, I'm going to try it as well. I'll sell the Krell to raise money for the extra parts! (Only joking Uncle Carlos but I will need to order the extra caps) __________________ The truth need not be veiled, for it veils itself from the eyes of the ignorant.

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26th April 2005, 05:05 AM	#23
neutron7 diyAudio Member Join Date: Dec 2003 Location: Toronto Canada	carlos, why dont you try a tracking pre-regulator version . It is a cheap way to get quite improved noise performance. since the pre regulator is referenced to the output of the main regulator. the main regulators input also benefits from the regulation of its output,. (and who knows maybe the snubberization as well ) and the error amplifiers in those things need as much help as they can get, they are about the quality of a 741! i hope that makes some kind of sense. you need to have a bit more of a voltage drop though. you just need another 338, a cap and 2 resistors per rail. its on page 12 of here http://www.national.com/ds/LM/LM138.pdf

26th April 2005, 06:29 AM	#24
Mikett diyAudio Member Join Date: Aug 2003 Location: Toronto	Try some LT1083s which have better HF impedance characteristics than the LM338 which are not as high performance. The snubber values will need to change I imagine. The LT1083 is unfortunately more expensive though. Here's one example with no snubbers. http://shine7.com/audio/gainclone.htm

26th April 2005, 07:30 AM	#25
Alcaid diyAudio Member Join Date: Nov 2003 Location: Klepp	Carlos Secondary on T2 is shorted in the diagram.

26th April 2005, 09:49 AM	#27
nina diyAudio Member Join Date: Apr 2005 Location: Earth	The LM338 reg Ic is more expensive than the LM3875 power IC ! Carlos, Seems we also put the chipamp to its limitation now. Just wonder what next innovation you will contribute to this forum How about this: - Parallel chip amps with IC driver/buffer - Chipamp as driver to Mosfet power stage - Integrated (Chip)amp with NOS DAC - Chipamp with High WAF ** Important* ( WAF = Wife Acceptance Factor ) Hee hee hee

26th April 2005, 10:32 AM	#28
NealG diyAudio Member Join Date: Dec 2003 Location: .	Hey Carlos, thanks for sharing this! It's been a while since I changed my clone, I will dust off the soldering iron and get to work! All the best NG

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