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jasonhanjk

Sgheadphones DIY A47 pocket amp kit

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Wow, Mackie really know how to explain things... ohmy.gif

Another "bad" thing having a cap in the signal is it will slow down the 20Hz to 100Hz frequency by 10 degrees. Meaning sound is distort a bit and the tempo maybe slow.

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cool...thanks for the info Mackie...

 

So a cap would be a 'bad thing' in the signal path? Does the current design have a cap then?

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Hi jason,have you plan to offer a all parts kit?including the case?

 

if thus,I agree with Mackie,the budget $30-40 is realistic wub.gif

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Ya. $40 will be a max out version. I had done a calculation using cheap opamp and without pot and casing will be less than $25. Will update first page.

 

Currently still creating the alps pot symbol in eagle as it is not available. Find some PCB manufacture and will contact them next week.

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got the amp today from jason laugh.gif

user posted image

 

initial test is very promissing, drives Grado without any problem, design a layout also seems to be very stable, don't hear any noise even with an expose board

 

user posted image

 

i hav tried a few op-amps for the left/right channels changing out the opa2134 that jason left on the amp, AD823 , LM881 , opa2604 & opa2228.

 

user posted image

 

the LM881 was unusable, it has a lot of distortion, and one of the chip heats up, i'm guessing the speed of this op-amp thats causing this.

the AD823 sounds good, with very good drive, but i feels its a little too full-bodied, lossing some details, this chip still sounds better with EL2001 or BUF634 as buffer smile.gif

my fav op-amp with this board is the opa2228, this was very surprising to me as the chip didn't sound good on a Cmoy or A47. The opa2228 sounds the most balanced of the 3 op-amps i tried, with good details and mid-range

the opa2604 sounded weak, i think this chip needs a high voltage to sound good, still trying it out

Edited by tropicalrips

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Ooh...you guys are at the final few development stages... i cant wait!

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my fav op-amp with this board is the opa2228, this was very surprising to me as the chip didn't sound good on a Cmoy or A47. The opa2228 sounds the most balanced of the 3 op-amps i tried, with good details and mid-range

Hi Tropicalrips,

 

I thought you guys built an A47? So what circuit is good for the OPA2228?

 

I would like to try one, let us know when you guys ready with the 'production model' yes.gif

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tropicalrips,good PCB layout.those components looks balance and neat.I think what you need is a sexy case now laugh.gif

What power supply do you use for? and have you do the high frequency compensate in feed back loops?

 

 

congratulations beer.gif

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I can almost hear it as interest in this project flares up following tropicalrip's post.

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NICE work.. tropicalrip.... happy.gif

uses audio grade components too...

blackgate and WIMA. am i right??

 

would you guys condsider using opa627 for this amp?

though it's expensive ( $40+ in farnell ), but we have a lobang king here, can get it

for around half price.

 

maybe we can use opa627-->opa227/228.

whahahahah...it will be great then... mini high-end.. party.gif

Edited by huangyong

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Huangyong wrote:

...though it's expensive ( $40+ in farnell ), but we have a lobang king here, can get it for around half price.

 

Hi Huangyong,

 

Where? where? I want a pair to w00t.gif

 

Does your 'lobang' can get the OPA637 as well? If you don't mind, please let us know where to buy OPA627/637 with half of Farnell price biggrin.gif

 

Thank you so much!

Bram

Edited by bpribadi

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