Want to build chimp amp

coolhead · 25th August 2011, 05:09 AM

Hi,
I am new to chip amp and I am not an electronic engineer, please correct me if some you found something not right in my description.

I got a 150VA toroidal trans to start with, it written 24-0-24, 12-0-12 and 6-0 secondary.

For ease of build, I narrow down to 2 chips LM1875 or LM3875, it look really easy to build and both have a lot of reference on line.

Here is my question:
1. Because of so many design out there, I am really confuse which should I use. For example:
- default circuit from datasheet LM1875 datasheet
- 60W Power Audio Amplifier circuit using LM1875 | Basic Electronic Circuit Design

2. My area the AC supply is about 240Vac, the trans secondary will give out about 26-0-26Vac and after rectification will give out ~37Vdc. Is it too high?

3. LM1875 is a class B while LM3875 is a class AB, which one more suitable for a pair of 8ohm Castle Eden speaker? Music type mostly vocal and jazz. The system will be in a small room of about 10' x 18'

4. I have some good result with Light Dependent Resistance volume control + Tripath amp. Will LDR work with chimp amp also?

sofaspud · 25th August 2011, 07:04 AM

A chimp amp?
To play APE files?

sofaspud · 25th August 2011, 07:49 AM

I would choose the chip that best fit my transformer.
That appears to be the LM3875, but 150VA may not suffice for full power output.
With the LM1875 you'll need to stay at or below the maximum +-30V.
As far as I know, the LDR will work anywhere in place of a standard potentiometer.

coolhead · 25th August 2011, 08:05 AM

Quote:

Originally Posted by sofaspud

A chimp amp?
To play APE files?

Sorry it is typo mistake.

coolhead · 25th August 2011, 08:12 AM

Quote:

Originally Posted by sofaspud

I would choose the chip that best fit my transformer.
That appears to be the LM3875, but 150VA may not suffice for full power output.
With the LM1875 you'll need to stay at or below the maximum +-30V.
As far as I know, the LDR will work anywhere in place of a standard potentiometer.

In LM1875 spec, supply voltage rage can be from 16V to 60V. What will happen when supply voltage is above +-30V?
Thanks.

abraxalito · 25th August 2011, 08:16 AM

The chip will fry. Sometimes it will let you know by emitting what's colloquially called 'the magic smoke'. Other times you may see nothing untoward from the outside at all.

sofaspud · 25th August 2011, 08:22 AM

Just having fun.
As you said, both have a lot of support. They would both sound good IMO. A lot of the best online reference material is right here at diyAudio.

bcmbob · 25th August 2011, 01:15 PM

coolhead

Have you considered the MyRef-C?. Most believe it is a cut above the rest of the chipamps. It is though a PCB approach and it sounds like you may want to roll your own design. I have one pair running on 24V-0-24 and another pair on 22V. The results may be worth swapping tour trany.

Bone · 25th August 2011, 02:11 PM

You havent said what speaker impedance you are driving. This will determine the maximum voltage to use. Having said that the LM1875 will NOT give you 60 watts in any impedance. 25 maximum is all. Have you thought of the LM3886 gainclone as an alternative?

bcmbob · 25th August 2011, 03:21 PM

Not to be obnoxious, but the MyRev-C (LM3886) is nominally rated at 68 watts.

25th August 2011, 05:09 AM	#1
coolhead diyAudio Member Join Date: Mar 2010	Want to build chimp amp Hi, I am new to chip amp and I am not an electronic engineer, please correct me if some you found something not right in my description. I got a 150VA toroidal trans to start with, it written 24-0-24, 12-0-12 and 6-0 secondary. For ease of build, I narrow down to 2 chips LM1875 or LM3875, it look really easy to build and both have a lot of reference on line. Here is my question: 1. Because of so many design out there, I am really confuse which should I use. For example: - default circuit from datasheet LM1875 datasheet - 60W Power Audio Amplifier circuit using LM1875 \| Basic Electronic Circuit Design 2. My area the AC supply is about 240Vac, the trans secondary will give out about 26-0-26Vac and after rectification will give out ~37Vdc. Is it too high? 3. LM1875 is a class B while LM3875 is a class AB, which one more suitable for a pair of 8ohm Castle Eden speaker? Music type mostly vocal and jazz. The system will be in a small room of about 10' x 18' 4. I have some good result with Light Dependent Resistance volume control + Tripath amp. Will LDR work with chimp amp also?

25th August 2011, 07:04 AM	#2
sofaspud diyAudio Member Join Date: Nov 2005 Location: San Antonio TX	A chimp amp? To play APE files? __________________ It is error only, and not truth, that shrinks from enquiry. - Thomas Paine

25th August 2011, 07:49 AM	#3
sofaspud diyAudio Member Join Date: Nov 2005 Location: San Antonio TX	I would choose the chip that best fit my transformer. That appears to be the LM3875, but 150VA may not suffice for full power output. With the LM1875 you'll need to stay at or below the maximum +-30V. As far as I know, the LDR will work anywhere in place of a standard potentiometer. __________________ It is error only, and not truth, that shrinks from enquiry. - Thomas Paine

25th August 2011, 08:16 AM	#6
abraxalito diyAudio Member Join Date: Sep 2007 Location: Hangzhou - Marco Polo's 'most beautiful city'. 700yrs is a long time though... Blog Entries: 46	The chip will fry. Sometimes it will let you know by emitting what's colloquially called 'the magic smoke'. Other times you may see nothing untoward from the outside at all. __________________ I think ideas are what you want to get rid of. I don't really like songs with ideas. - Leonard Cohen

25th August 2011, 08:22 AM	#7
sofaspud diyAudio Member Join Date: Nov 2005 Location: San Antonio TX	Just having fun. As you said, both have a lot of support. They would both sound good IMO. A lot of the best online reference material is right here at diyAudio. __________________ It is error only, and not truth, that shrinks from enquiry. - Thomas Paine


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25th August 2011, 01:15 PM	#8
bcmbob diyAudio Member Join Date: Dec 2009 Location: Bay City, Michigan	coolhead Have you considered the MyRef-C?. Most believe it is a cut above the rest of the chipamps. It is though a PCB approach and it sounds like you may want to roll your own design. I have one pair running on 24V-0-24 and another pair on 22V. The results may be worth swapping tour trany. __________________ Bob M. "Arrange Whatever Pieces Come Your Way."

25th August 2011, 02:11 PM	#9
Bone diyAudio Member Join Date: Jun 2004 Location: Dorset, UK	You havent said what speaker impedance you are driving. This will determine the maximum voltage to use. Having said that the LM1875 will NOT give you 60 watts in any impedance. 25 maximum is all. Have you thought of the LM3886 gainclone as an alternative?

25th August 2011, 03:21 PM	#10
bcmbob diyAudio Member Join Date: Dec 2009 Location: Bay City, Michigan	Not to be obnoxious, but the MyRev-C (LM3886) is nominally rated at 68 watts. __________________ Bob M. "Arrange Whatever Pieces Come Your Way."

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