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Old 13th September 2005, 04:49 PM   #1
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Default Digitally controlled preamp/headphone amp

Hello all,

My good friend Mauro and others have pointed me towards the Cirrus CS3310 as a likely candidate for a very good preamp. This seems ideal as the specs are very impressive, and it is easy to interface.

The only thing I thought needed augmenting was the output current, as the CS3310 is limited to 25ma. So, I thought it a good idea to buffer the output with a good opamp that has low noise and good output current while still being fast and in general very good. I have come to really like the AD8620 for all those reasons, especially low noise.

So here I present my fist attempt at a PCB for my design. It is 2 sided, but pretty small. I would like to get some made, but I wanted to get some feedback from the folks here first.

The circuit is designed to be controlled by a single PIC 12Fxxx microcontroller. I am using a 12F683, but I think just about any of the 12F would work fine. Actually I think the 12F675 is probably ideal.

There is no pot in the signal path, the pot to the PIC is only used to feed an adjustable voltage to the PIC ADC to get a value for the volume control. I am trying to keep it very simple. No display, no complex interface, just a single linear pot.

This little amp would drive enough current for almost all headphones, and the output impedance is quite low making it exceptional for driving GCs, both inverting and non-inverting.

This is my first microcontroller project, so I will be asking for a lot of help.

Thanks for looking.

Cheers!
Russ
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Old 13th September 2005, 05:14 PM   #2
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Default Seriously Off-Topic

Jeeez Russ! You are designing stuff faster than I can build it. Still haven't found the time to finish my Free- and Yardbird amps.

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Old 13th September 2005, 05:33 PM   #3
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Default Re: Seriously Off-Topic

Quote:
Originally posted by GeWa
[B]Jeeez Russ! You are designing stuff faster than I can build it.[B]

I consider it my job to keep you swamped.

Cheers!
Russ
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Old 13th September 2005, 05:37 PM   #4
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Default Schematic

Forgot this, yes i know its a mess.
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Old 13th September 2005, 05:53 PM   #5
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I consider it my job to keep you swamped.
Ooh, thank you but if you don't mind I already have such a person in my life; this person is called "MY BOSS"
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Old 13th September 2005, 07:39 PM   #6
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Old 13th September 2005, 07:54 PM   #7
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Nice Russ, you could start like your own weekly online-magazine with new stuff

If I remember correctly the PGA2310/11 is pincompatible with the CS3310? as it has better specs, but if it's better I don't know.
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Old 13th September 2005, 10:21 PM   #8
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Quote:
Originally posted by tobias_svensk

If I remember correctly the PGA2310/11 is pincompatible with the CS3310? as it has better specs, but if it's better I don't know.
Hi Tobias.

Hah! See you learn something every day! I had actually looked at that device once (I actually think I have some samples), but I did not know it was pin compatible! Great tip! Thanks!

Cheers!
Russ
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Old 14th September 2005, 01:18 PM   #9
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Hehe Russ

I see that the PGA2320 also is compatible, a quick look shows that the THD is 0.0003 (PGA2310 0.0004 ) and the voltageswing is 1V higher, otherwise they seen the same?

Had'nt seen the 2320 before, must be quite new

Ch33rs
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Old 15th September 2005, 12:52 AM   #10
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Cool just ordered a few of those.

I am working on a single side board now since you can get the BB parts in DIP.
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