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Blueberry Audio + Upgrades

post #1 of 9
1/19/11 at 8:56pm
Thread Starter 

Hi Guys,

 

 

I'm looking to upgrade the OPAMP's, Buffers, and Capacitors in my Blueberry Audio Headphone amp. I've added photos to the post and tried to make them as clear as possible. Any suggestions on what I may be able to upgrade (cables, OPAMPS, Caps, RCA jacks, POTS, and headphone port) to would be greatly appreciated.  Prices are not a limiting factor, although I know availability might be.

 

Currently it's fitted with 3 x BUF634P buffers, 2 x OPA228PA, and 1 x OPA2604AP (on the ground)

 

Thanks in advance.

 

Tom

 

2011-01-19_23-38-53_776.jpg2011-01-19_23-39-29_108.jpg2011-01-19_23-39-58_503.jpg

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post #2 of 9
1/19/11 at 9:19pm

Can certainly switch out those OPA228s for better opamps, I'd recommend AD825.  The Wima MKP10's are nice, but there are certainly better caps as well, I'd recommend Sonicap Gen1.  The pot can also be switched, I'd recommend Alps RK27.

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post #3 of 9
1/19/11 at 9:46pm
Thread Starter 

Thanks a bunch for your reply. In your opinion, would that POTS make a good fit (without heavy tweaking to the case)?

 

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post #4 of 9
1/20/11 at 8:16am

Looks like it should fit... but look at datasheet to confirm.

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post #5 of 9
1/20/11 at 6:21pm
Thread Starter 

Does anyone else have some more suggestions regarding other parts?

 

Thanks

Thomas

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post #6 of 9
1/21/11 at 5:56am

You can change out the power caps for the largest ones that will fit in the case.

The BUF634s can be stacked. Add three more on top of the three already there.

As FallenAngel suggested, swap out the OPA228s for something else.

Be careful of Bi-Polar input op amps with this design, you could get a bad

DC offset. Try and stick with JFet op amps if you can.

If your sources are free from DC offset, you can bypass the input caps all together.

 

Always make sure to test for DC offset whenever you make a change.

Test with cans you don't mind frying when you test a change.

Only use your good cans when you are sure your modification is safe.

 

What are you using for a power supply? There may be a chance for

improvement there too.

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post #7 of 9
1/21/11 at 6:03am

Remove and jumper the resistor at OG.

You can add a switch to jumper the other two output

resistors and see which way it sounds better.

Some cans like a resistor, some sound better

without.

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post #8 of 9
1/21/11 at 6:14am

How much height is there inside the case for the power caps?

 

I'm thinking something like this if you have the room.

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post #9 of 9
1/22/11 at 4:32pm
Thread Starter 

Thanks for all of your input Avro. It's much appreciated.

 

Regards

Thomas

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