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Need advice on making first portable DIY amp

post #1 of 19
8/30/05 at 4:21pm
Thread Starter 
I tried searching a little but it’s like looking for a needle in a haystack, because I’m not even sure what I need.

I want to build a cheap (cmoy I guess) portable amp. Just point me to an website or a previous post please, with instructions on how to build one (from parts available in Canada if possible).

I’ll use it with (most likely) DT770-80, from an MP3 player headphone out, and I’d like volume control on the amp too.
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post #2 of 19
8/30/05 at 4:34pm
www.tangentsoft.net/audio
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post #3 of 19
8/30/05 at 4:44pm
I have only built a tiny cmoy as suggested by Shijosae. Never have I seen anything as simple or lightweight for the simplicity and amount of work put it. As he says in his guide, if you can handle this much complexity, you should start looking for a new hobby
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post #4 of 19
8/30/05 at 5:11pm
Thread Starter 
Thanks! Sounds fairly easy...

I couldn't find anything becuase I was searching in the wrong forum May I should find a new hobby
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post #5 of 19
8/30/05 at 9:53pm
Quote:
Originally Posted by MikoLayer
I have only built a tiny cmoy as suggested by Shijosae. Never have I seen anything as simple or lightweight for the simplicity and amount of work put it. As he says in his guide, if you can handle this much complexity, you should start looking for a new hobby
Hey mikolayer, do you have an instructions link? I copied one of sijosae's realllly tiny cmoys a little while ago, and sort of stared at his layout pictures (which were pretty blurry) 'til i could match his parts to the layout...

Thanks!
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post #6 of 19
8/30/05 at 9:53pm
Hey there fellow torontonian!

Skip the cmoy, in my opinion it is for people who have little experience in working with electronics. You will get a much better sound for hardly any more difficulty if you build an A47.

For parts, head down to Supremetronics on queen street and get their 1% metal film resistors. For the input caps you can use 1uF film, but for the power caps I found some great slightly stubby 680uF capacitors down the street at Active Surplus, there should still be a bin there. When i replaced poor quality 700uF caps with these 680uF, it made an astounding difference.

Good luck!
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post #7 of 19
8/31/05 at 3:31pm
Thread Starter 
Quote:
Originally Posted by moeburn
Hey there fellow torontonian!

Skip the cmoy, in my opinion it is for people who have little experience in working with electronics. You will get a much better sound for hardly any more difficulty if you build an A47.

For parts, head down to Supremetronics on queen street and get their 1% metal film resistors. For the input caps you can use 1uF film, but for the power caps I found some great slightly stubby 680uF capacitors down the street at Active Surplus, there should still be a bin there. When i replaced poor quality 700uF caps with these 680uF, it made an astounding difference.

Good luck!
Yup, I know Supremetronics . Is this the site with instructions to buid the A47?
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post #8 of 19
8/31/05 at 4:28pm
How much of a difference in sound is there between a Cmoy and an A47? I have built a few Cmoys, but I've never tried or heard an A47.
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post #9 of 19
8/31/05 at 5:15pm
I found it a big struggle to get my cmoy to sound decent, it would always clip at high levels because i'm using very small headphones, i dont have any fancy expensive ones. I built an A47, and even on a relatively cheap amp (OPA2227) it improved the sound. I'm now using 2 AD8620s. For your first amp I reccomend you take advantage of the free samples program that TI and AD offer, but dont abuse it.

My A47 is slightly different than that. I fit it in a square altoids tin with one 9v battery, but I didnt use the BUF634s (too expensive). It still sounds fine. I also have a PCB design for it if you would like to etch your own, although its pretty crude and bulky.
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post #10 of 19
8/31/05 at 5:49pm
Quote:
Originally Posted by moeburn
I found it a big struggle to get my cmoy to sound decent, it would always clip at high levels because i'm using very small headphones, i dont have any fancy expensive ones. I built an A47, and even on a relatively cheap amp (OPA2227) it improved the sound. I'm now using 2 AD8620s. For your first amp I reccomend you take advantage of the free samples program that TI and AD offer, but dont abuse it.

My A47 is slightly different than that. I fit it in a square altoids tin with one 9v battery, but I didnt use the BUF634s (too expensive). It still sounds fine. I also have a PCB design for it if you would like to etch your own, although its pretty crude and bulky.

Sure. Go ahead and post the layout.
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post #11 of 19
8/31/05 at 6:00pm
I'm also about to build my first amp and have been debating between a CMoy and an A47. From what I've read, the A47 is only good for low impedence phones. Is this really the case? Is it worse than the CMoy for high-impedence phones? or does it just really shine on low-impedence ones?

I'm currently using ER-6's (which are low impedence I believe), but haven't decided on my next pair yet.

Thanks,
Garron
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post #12 of 19
8/31/05 at 7:17pm
Quote:
Originally Posted by garrontmo
I'm also about to build my first amp and have been debating between a CMoy and an A47. From what I've read, the A47 is only good for low impedence phones. Is this really the case? Is it worse than the CMoy for high-impedence phones? or does it just really shine on low-impedence ones?

I'm currently using ER-6's (which are low impedence I believe), but haven't decided on my next pair yet.

Thanks,
Garron
Low impedance phones need more amps than voltage, high impedance phones need more voltage than amps. When low impedance phones arent properly fed, they clip and distort. When high impedance phones dont get enough voltage, they just sound quiet.

Either way, an A47 doesnt deliver less voltage than a cmoy, so they would both be the same.

My amp and schematic are both ere:
http://www6.head-fi.org/forums/showp...&postcount=654
In the pic i have two different types of input caps, both 1uF, the red one worked better.

Also I reccomend you pick up half a dozen of the cheap (70 cent) 9v batteries at supremetronics, they seem to last just as long as the expensive ones and you will want more than one laying around when building/testing.

And dont use a blue case, nobody in toronto sells socketed blue LEDs!
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post #13 of 19
8/31/05 at 11:43pm
Quote:
Originally Posted by headchange4u
How much of a difference in sound is there between a Cmoy and an A47? I have built a few Cmoys, but I've never tried or heard an A47.
i liked my a-47 ALOT. as i understand it the guy i sold it to (with a set of headphones) likes it lots too. it always served me quite well on my litttle harrem of grados, and was good on my hd-595's (120 ohm) i think the guy i sold it to also ran his hd-600/650's off of it with much delight.

the a-47 had an "effortless" feel about it. it just did as it was asked, and then it did nothing. a simple amp for a simple task.

i HIGHLY reccomend using 1 chip for gain, and 1 chip for "pseudo-buffer" rather than having left and right chips. i think a large part of the quality of my a-47 was using a diferent opamp for gain and pseudobuffer. also bypass psu caps with film.
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post #14 of 19
9/1/05 at 2:16am
A47 XP




Total cost was like $35
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post #15 of 19
9/1/05 at 3:38am
Quote:
Originally Posted by diredesire
Hey mikolayer, do you have an instructions link? I copied one of sijosae's realllly tiny cmoys a little while ago, and sort of stared at his layout pictures (which were pretty blurry) 'til i could match his parts to the layout...

Thanks!
Forgot to mention his instructions are in korean only as far as I know.. most of it is self-explanatory once you look at the diagrams. I will do some research on it once I am done with my E-mag homework...
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