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Sgheadphones DIY A47 pocket amp kit


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#91 jasonhanjk

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Posted 15 July 2004 - 09:51 PM

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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#92 Q00

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Posted 15 July 2004 - 11:36 PM

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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#93 mukegile

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Posted 16 July 2004 - 10:20 AM

QUOTE
slow down the 20Hz to 100Hz
phase shift ?
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#94 digi01

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Posted 16 July 2004 - 05:31 PM

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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#95 jasonhanjk

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Posted 18 July 2004 - 07:56 PM

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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#96 tropicalrips

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Posted 21 July 2004 - 01:08 AM

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, 21 July 2004 - 01:14 AM.

user posted image + user posted image = user posted image
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#97 Q00

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Posted 21 July 2004 - 04:57 AM

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

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Posted 21 July 2004 - 10:07 AM

QUOTE (tropicalrips @ Jul 21 2004, 01:08 AM)
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

#99 digi01

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Posted 21 July 2004 - 10:57 AM

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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#100 Mackie

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Posted 21 July 2004 - 02:39 PM

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

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Posted 21 July 2004 - 03:41 PM

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, 21 July 2004 - 03:42 PM.


#102 mukegile

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Posted 21 July 2004 - 04:03 PM

QUOTE
maybe we can use opa627-->

huangyong.....why dun u pass it to tropical for some test and comparison ?

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#103 huangyong

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Posted 21 July 2004 - 04:33 PM

sure.. i just get my opa627BP yesterday.
headphone.gif headphone.gif

#104 huangyong

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Posted 21 July 2004 - 04:37 PM

tropicalrips ,
you got PM.


#105 bpribadi

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Posted 21 July 2004 - 05:32 PM

QUOTE
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, 21 July 2004 - 05:34 PM.