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DIY Simple Active Preamp

Grainger49 said:
The 100 ohm needs to be on the other side of the capacitor. Where it is the Op-Amp doesn't interact with it.

The 100k does the same thing your amplifier input resistor would do with the DC that leaks through at turn on. But if your amp is on the thump is heard.
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Thanks for your advice on this Grainger and Steve.

I have since moved the 100r inside of the capacitor.

With the 100k, it may be redundant in most systems but it's a "just in case" thing.

The DC blocking cap could probably go as well but it doesn't affect the sound as I tested it with and without but some op amps have higher DC offset than others so rather than take the chance. One side of the AD823 has 1.1 mv and the other around 0.8 mv, so if you have an op amp that goes awry, it will save the day.

SimplePreampV3.jpg
 
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This is amazing. Great thread fella's. I really need to remove my Rane splitter pre-amp from my system and this is exactly what I want.

I have basic soldering skills and limited knowledge on circuits. I am tempted to try building this on a rat shack board.

At any rate, subscribed and love where this is headed.

Walker
 
Dudeman258 said:
This is amazing. Great thread fella's. I really need to remove my Rane splitter pre-amp from my system and this is exactly what I want.

I have basic soldering skills and limited knowledge on circuits. I am tempted to try building this on a rat shack board.

At any rate, subscribed and love where this is headed.

Walker
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Hi,

FYI, there is another version of PCB for same layout designed by me using same BOM.

attachment.php


Contact sachu888 if you need board, I think he has some available. It was discussed along with CNC phono stage stage here.

Regards,
 
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so I just stumbled onto this thread, any chance of purchasing a circuit board and parts ?I'd love to assemble one and give it a try!
 
I know I read the PS requirements earlier today, but I can't find it now. I have a +/- dual 15V supply, am I good to go? I know the IC spec sheet says it's ok up to 18 dual volts. Anyone using 15?

Sorry, I know this has been covered somewhere.
 
skywave-rider said:
I know I read the PS requirements earlier today, but I can't find it now. I have a +/- dual 15V supply, am I good to go? I know the IC spec sheet says it's ok up to 18 dual volts. Anyone using 15?

Sorry, I know this has been covered somewhere.
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A well filtered supply of +/- 15v will be fine, the current draw with an AD823 and a LED is only around 10mv's so batteries will last a while also.
 
Very interesting thread. I never read where anyone gave a total cost of this pre. My biggest question is how does it sound... LOL or doesn't sound since it's a pre. I guess I just wondering if this is actually worth the average person to build instead of just buying an exsisting pre or a pre packaged kit.
 
HypnoToad said:
A well filtered supply of +/- 15v will be fine, the current draw with an AD823 and a LED is only around 10mv's so batteries will last a while also.
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Thanks! It will be fun. :thmbsp:

Sovereign said:
Very interesting thread. I never read where anyone gave a total cost of this pre. My biggest question is how does it sound... LOL or doesn't sound since it's a pre. I guess I just wondering if this is actually worth the average person to build instead of just buying an exsisting pre or a pre packaged kit.
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I posted a list of prices I got today from DigiKey here:
http://www.audiokarma.org/forums/showpost.php?p=5320603&postcount=835
The list is from HypnoToad originally.
 
Sovereign said:
Very interesting thread. I never read where anyone gave a total cost of this pre. My biggest question is how does it sound... LOL or doesn't sound since it's a pre. I guess I just wondering if this is actually worth the average person to build instead of just buying an exsisting pre or a pre packaged kit.
Click to expand...

I wanted something I could run between my phono stage and power amp to control the volume.

I tried the Pass B1 Buffer Preamp and although it sounded really good it was too sterile for me. So I decided to work on an op amp based simple preamp. After some fiddling and trial and error this was born, it sounds better than the preamp section of my Yamaha CR-1020 by a long way IMO. It will run on batteries for a long time and is very cheap and easy to build.

So if you have a power amp you can use this instead of a dedicated preamp for little money and have performance that will embarrass expensive preamps IMO.
 
Just ordered my PCB board, I can't wait to get this thing up and running!

If you don't mind I have a few very amateur questions regarding the construction of the preamp.

I plan to grab as much as I can off of digikey when I order the components. Would any of you have a suggestion for a potentiometer to use? I read the issues you had HypnoToad and your end result sounded fine. I am not looking to spend a fortune. Would digikey have something at a reasonable price? If you could direct me with keywords to search for that would be great.

With that, I am assuming the CCW, CW, and W spots are for the potentiometer? If so is there somewhere I can read about what these abbreviations stand for? (I only have basic electrical under my belt as I am a Mechanical Engineering student).

Lastly is there anything else I should be weary of when constructing this circuit past basic soldering skills and polarity of components? I have soldered a fair amount and recapped systems so that is of no worry to me.

Thanks so much to all of you who have contributed and for making such a great piece attainable for such a small sum of money.

Walker Clark
 
You can use any 25k pots 2 x single (Mono) or 1 x dual ganged (Stereo). They sell stepped pots on that auction site, a dual gang stepped pot of 20k or more would be fine IMO.

CCW stands for Counter Clock Wise

CW stands for Clock Wise

W stands for Wiper

If you look at the pot from the front, where the knob goes with the connections at the bottom the left hand side connector is CCW, the middle one is W and the right hand side one is CW. The wiper is the contact that is connected to the shaft.
 
HypnoToad,

Would you mind posting your final revised schematics of your basic pre. What kind of power supply do i need now - can i just use a wallwart. Thanks
 
cuthien said:
HypnoToad,

Would you mind posting your final revised schematics of your basic pre. What kind of power supply do i need now - can i just use a wallwart. Thanks
Click to expand...

The finalized PCB is at post #123 of this thread. It is easier to run it off a couple of nine volt batteries as the current draw is low, other wise you need a filtered PSU that provides between +12v, 0, -12v up to +18v, 0, -18v to run it. You can't simply use a wallwart as it will be too noisy and not have a ground, or positive and negative rails. If you ask Sachu888 he may have some PSU PCB's left.
 
HypnoToad said:
The finalized PCB is at post #123 of this thread. It is easier to run it off a couple of nine volt batteries as the current draw is low, other wise you need a filtered PSU that provides between +12v, 0, -12v up to +18v, 0, -18v to run it. You can't simply use a wallwart as it will be too noisy and not have a ground, or positive and negative rails. If you ask Sachu888 he may have some PSU PCB's left.
Click to expand...

If you're using batteries won't you be running +/- 9V? I was planning on using a +/- 10V filtered PSU that I have but now I see the 12V recommendation.
 
dodog said:
If you're using batteries won't you be running +/- 9V? I was planning on using a +/- 10V filtered PSU that I have but now I see the 12V recommendation.
Click to expand...

I think this can be run from 3V to 18V.I may be wrong here.

Regards,
Sachin
 
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