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Old 23rd August 2010, 06:24 PM   #1
Monomen is offline Monomen  Netherlands
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Default Dual mono-amp with seperate psu and pre-amp

I'm thinking about building myself a Gain-clone LM3886 amp. Now I'm interested in making something that have a good quality of sound and looks nice.
Tube-amp is my dream, but i don't have experience so start simple.

What are the recomendations about:
2 monoblocks with 1 seperate PSU.
Next to that I like to build a simple pre-amp with Riaa input for my record player (philips 212) and 2 or 3 inputs for cd, pc, dvd.

Is it a stupid idea to make everything seperate in seperate casings?

What is a pre-amp idea that works good with a Gain-clone for Riaa input and 3 normal inputs?



[IMG]file:///C:/Users/Monomen/AppData/Local/Temp/moz-screenshot.png[/IMG]
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Old 26th August 2010, 12:34 PM   #2
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Quote:
Originally Posted by Monomen View Post

What is a pre-amp idea that works good with a Gain-clone for Riaa input and 3 normal inputs?



[IMG]file:///C:/Users/Monomen/AppData/Local/Temp/moz-screenshot.png[/IMG]
For my preamp, I use an opamp circuit with the TLE2082CP from TI, with a BUF634T in the feedback loop, 3 gain. This is powered with +-15V regulated PSU.

For my chipamp I use one LM3886 per channel, 25 gain, powered with +-24V regulated. This is the schematic to my regulated PSU: Mini-MosFet Audio Amplifier - RED - Page123 its near the bottom. Obviously I used a transformer and regulator adjustments appropriate for my project. Also, for C2 in the schematic I use a 50V 10000uf.

I cannot seem to find the schematic for the preamp. I know it is around here on the forum, but it uses an OPA134 (i think) instead of the TLE2082. I love the way the TLE2082 sounds in this configuration. I hate the way it sounds without the BUF634, though. The OPA134's are also great sounding.

For the chipamp, I use a slightly modified application circuit from the datasheet.

For inputs, I use something similar to this: http://sound.westhost.com/p97-f6.gif, Without the phono, and less # of inputs.

For a phono pre, maybe you could use this: Hi-Fi RIAA Phono Preamp It is quite simple, you could even get PCBs.

Last edited by odysseybmx414; 26th August 2010 at 12:48 PM.
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Old 26th August 2010, 02:08 PM   #3
AndrewT is offline AndrewT  Scotland
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Hi,
save the cost of the third case for the separate PSU and use that money to buy a second transformer.
That way you can build two monoblocks.

If you use one transformer to power two separate amplifiers, at some point you have to connect the Main Audio Ground in one amp to the other. Once that connection is made you have a two channel amplifier in three connected cases.
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Old 1st September 2010, 07:22 PM   #5
Monomen is offline Monomen  Netherlands
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hey people,
Is this a useable transformer for a gainclone? Or is to much?

van het merk ILP
zover ik de gegevens heb kunnen opzoeken is het:
Type 61017
s no V27228
secundair 2 x 30 Volt 2 x 3,75Ampere
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Old 1st September 2010, 07:32 PM   #6
AndrewT is offline AndrewT  Scotland
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the 30Vac secondary is the rating when loaded to full AC current through a resistor and when fed with rated mains voltage, probably 230:30Vac.

This will give anywhere between 35Vdc and 45Vdc depending on mains and loading.

Too high for a <=42Vdc chipamp.
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Old 1st September 2010, 07:37 PM   #7
Monomen is offline Monomen  Netherlands
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So a 2 x 25 V 5 A transformer would be better?

(thanks for the fast reaction again ;-) )
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Old 1st September 2010, 07:49 PM   #8
AndrewT is offline AndrewT  Scotland
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safer to use a 230:25+25Vac transformer with chipamp driving 8ohm speaker.
depending on how it is specified you can use slightly higher.
I suggested a long while ago using a 230:28+28Vac 4% regulation on 220Vac+-supply tolerance and got shot down in flames for such blasphemy.
I still stand by that, for experienced builders who are prepared to test/measure before setting to work.
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Old 4th September 2010, 10:02 AM   #9
neeraj is offline neeraj  India
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Quote:
Originally Posted by AndrewT View Post
safer to use a 230:25+25Vac transformer with chipamp driving 8ohm speaker.
hi Please specify VA rating for single LM 3886 /8 Ohm load

thanks
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