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Cmoy as pre-amp?

post #1 of 23
1/16/11 at 11:12am
Thread Starter 

Well I'll be ordering the parts for a cmoy soon and since the company I'll be ordering from doesn't accept small orders I'll have enough parts for 2 CMOYs. One will be for my hd 650s. Now I got this idea about using the other one in a home stereo setup using this denon amp http://denon.de/de/Product/Pages/Product-Detail.aspx?Catid=4983297a-4f3b-4d8d-b83f-fb7b49f8b0a6&SubId=382959a5-3966-49af-8d66-cc751e41b0ad&ProductId=312e9560-08a8-4eea-952e-943fbe2907cb I realize that that already has a pre-amp built in(I think so anyways), but would the sound quality be improved or be able to be altered more towards my liking with the adition of a cmoy between the amp and DAC?

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post #2 of 23
1/16/11 at 11:59am

In a word...no.

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post #3 of 23
1/16/11 at 1:04pm
Thread Starter 

Thanks for the clear answer ^^, but anyways concerning the amp I'd be using for the 650s would these caps be good?

 

http://be02.rs-online.com/web/search/searchBrowseAction.html?method=getProduct&R=0824200

 

and

 

http://be02.rs-online.com/web/search/searchBrowseAction.html?method=getProduct&R=3150726

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post #4 of 23
1/16/11 at 3:11pm

The 0.33uF cap for the input is too small.

Something more like this will give much

better low frequency response.

 

The Panasonic FC is a good choice for the power caps.

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post #5 of 23
1/16/11 at 3:15pm

This is probably a better value for the power cap.

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post #6 of 23
1/16/11 at 11:08pm
Thread Starter 

The panasonic I posted comes from tangensoft's liust of reccomended parts is there a reason he would have reccomended that one above the one you mentioned?

 

And pretty much the same question for the input cap where tangent reccomends 0.1uF with a tolerence of 5%, you reccomend 2.2uF with a tolerence of 10%, so why would'nt he reccomend that aswell if it his better low frequency response? Are there also any other parts you'd reccomend over the ones reccomended by tangent?

 

I would like trying to optimize this cmoy for my 650s so if its possible to buy parts specialised for that it would be nice.

 

I will be ordering the following op-amps because I read the first was the best to begin with and the other two are very good:

opa2132PA

LM6172IN

AD823AN

What do you think?

 

and lastly how do you think this kind of cmoy would stack up to a nice commercial amp(lets say around the 100usd price range)?

 

Thanks for your great input so far.

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post #7 of 23
1/17/11 at 3:35am

Tangents guide is great and has helped many people

enjoy their first headphone amp but it is a guide, not

a bible. Many people build these to go inside small

cases like mint tins. Small part are needed in this case

and Tangents parts are picked with this in mind.

If you have the room, larger parts will give you better sound.

The LM6172IN is a fast Bi-Polar op amp and you might

find it hard to use for a first time build. Try and stick with

JFET input op amps for now, Bi-Polar input op amps

are trickier to use. You could add OPA2227, OPA1642

and AD8620 to your list to try as well. For op amps that

only come in SIOC case you can use an adapter like this.

 

There are a couple of well respected "commercial" designs

that are little more than well designed "CMoys".

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post #8 of 23
1/17/11 at 9:36am
Thread Starter 

I can't seem to find a soic adapter to DIP of rs components so I just figured I'd stick with DIP op-amps.

 

So here's what I came up with(basing my self largly on majkel from this thread http://www.head-fi.org/forum/thread/243642/best-sounding-cheep-op-amp-for-cmoy-s-opa2227-opa2228-ad8066-other )

 

op-amps: opa2132, opa2228(According to rs components it's bipolar, but so is the 2227(which majkel says isn't nearly as good as the 2228) you reccomend so it's fine right?), TLE2142

 and TLE2082(again Majkel says they are good and well they're dirt cheap).

 

For caps I'll get the input caps you mentioned, but for the power caps wouldn't this be better if I wanted to go with 2 9v batteries http://be02.rs-online.com/web/search/searchBrowseAction.html?method=getProduct&R=0572075 ?

 

and again thanks A LOT for your help

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post #9 of 23
1/17/11 at 10:07am

The OPA2227/2228 have a balanced input bias so you can use

it where you would use a JFET op amp.

 

The power caps each see 1/2 of the total supply voltage.

It is good practice to rate the caps twice the voltage they

will see. So, in your case, two 9 volt batteries will give you

18 volts total voltage. 16 volt caps would due, but 25 volts

would be safer. On the other hand, I have one amp where

the power cap is rated only one volt higher than the supply

voltage and it's been happy for months now...

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post #10 of 23
1/17/11 at 10:37am

Here are a couple of pictures for inspiration...

 

This one is three OPA227 and a TLE2426 rail splitter

Power is two Li-ION cells

OPA227.jpg

 

This one is a LT1364 and LT1363 with a TLE2426 rail splitter.

Power is an eight cell AAA NiHM pack

 

LT1364.jpg

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post #11 of 23
1/17/11 at 11:53am
Thread Starter 

considering the millions of things that could go wrong I guess it's best to be on the safe side with the power caps and go for 25v.

 

Seems like I'm good to go so thanks again for all your help I hope I can post some pics in the coming weeks with the results

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post #12 of 23
1/17/11 at 11:54am
Thread Starter 

Nice builds, but what is a rail splitter? ^^

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post #13 of 23
1/17/11 at 2:34pm

Tangent explains it quite well...

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post #14 of 23
1/18/11 at 9:13am
Thread Starter 

Sorry to trouble you again. but could you link me a power switch from rs components? I've tried to find one myself, but I seriously don't understand a damn thing of it.What does an on-on switch config mean? ANd what about contact rating or contact resistance?(you don't really have to answer the questions I'm just making clear that I don't get it ^^)

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post #15 of 23
1/18/11 at 9:29am
Thread Starter 

also what would be a good A and V rating for a power supply if I intend to use one? I have 12Vdc and 1A power supply lying around would that be adequate?

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