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Beginner's Gainclone, HiFi LM1875, The Amplifier Board
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Old 22nd August 2017, 04:31 AM   #761
danielwritesbac is offline danielwritesbac  United States
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Quote:
Originally Posted by AndrewT View Post
+32dB (40times) is quite a high gain. Do you have a reason for going this high?
A stable amplifier won't cause a rush to purchase an ineffective tone control.
A rather weak modern source performs better when not run to max.

Other than those two things, I can't imagine why the amp gain is that high.
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Old 14th September 2017, 03:14 PM   #762
vj_audio is offline vj_audio
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Mr. Daniel

Please see the picture.

Thank you
Vijay
India
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Old 20th September 2017, 12:13 AM   #763
danielwritesbac is offline danielwritesbac  United States
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Originally Posted by vj_audio View Post
Mr. Daniel

Please see the picture.

Thank you
Vijay
India
Two cheap 10R 1/4w cost much less than a 5R 1/2w resistor.
This can be replaced with one 1/2w resistor; and, there are many other options (most of which won't be needed if the amp is stable).

Two cheap 220u caps sum to 440u and result in maximum quality.
This cannot be replaced with a single part because it would cost either a higher gain setting resulting in lower resolution, or cut the power voltage (not slightly) to increase stability. I say, make room on the board for duplicate power caps, run tandem. It probably will be worth doing that for all of audio amplifiers.
Edit: Don't go nuts--I said two, not fifty.
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Old 11th October 2017, 12:54 AM   #764
plgsekip is offline plgsekip  Indonesia
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Default inverting vs noninverting LM1875

hi guys,
any of you tried inverting LM1875 instead of the noninverting?
some said it sounds better in the inverting mode.
any comments and thoughts you could kindly share here?
thanks

ps. hope this question is ok in this thread
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Old 13th October 2017, 02:15 PM   #765
Ivo-Cici is offline Ivo-Cici  Macedonia
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Hi luq
Visit: T-network: the better feedback solution?
Ivo-Cici
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Old 13th October 2017, 03:02 PM   #766
plgsekip is offline plgsekip  Indonesia
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Hi Ivo-Cici
Thanks. I'll have a look at it and will try it. I am currently collecting some materials on the inverting 1875. I have built one according to my taste but eager to check other solution. I am using a single 2SK170BL per channel as a buffer and quite happy with the result. The same resistor value as in the database for non-inverting but configured in inverting mode.
I have DCB1 and connect it to my non-inverting LM1875 per datasheet. They do sound a bit different and difficult to tell. Thanks.
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Old 17th October 2017, 11:12 PM   #767
plgsekip is offline plgsekip  Indonesia
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Default Trying a simple LM1875 with 2SK170BL

Hi,
Attached are simulations of a simple LM1875 with a single 2SK170BL (left-overs from a DCB1 Buffer project). Is it stable based on the schematic?

I have built it with resistors and cap values, they are available with me currently. It does not show an excessive temperature raise and it's been two weeks operating. DC out is about 1 mV or so, similar to my non-inverting LM1875.

I have not tried the T-network because as I read it, the T-network is useful if we build without buffer. Please correct me if I am wrong.

PSU is a 18-CT-18 transformer with simple 2x2200 uF per rail.

Any comment on the bode-plot?
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File Type: jpg bode_inverting_lm1875.jpg (569.3 KB, 390 views)
File Type: jpg inverting_lm1875.jpg (792.9 KB, 379 views)
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Old 14th November 2017, 04:12 PM   #768
vj_audio is offline vj_audio
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Mr. Daniel

There are three pinouts on a 200R trimmer. How do I attach it to the schematic? Eagle has 3 pins for all trimmers.

1 Pin = Input

2 Pin = Ground

3 Pin = Output

Am I right?

Thank you
Vijay
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Old 14th November 2017, 04:54 PM   #769
adason is offline adason  United States
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Quote:
Originally Posted by plgsekip View Post
hi guys,
any of you tried inverting LM1875 instead of the noninverting?
some said it sounds better in the inverting mode.
any comments and thoughts you could kindly share here?
thanks

ps. hope this question is ok in this thread
Yes, it does. But it needs input buffer.
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Old 15th November 2017, 02:46 AM   #770
vj_audio is offline vj_audio
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Can I use it for small subwoofer?
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