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Cmoy components/gain

post #1 of 50
Thread Starter 
I want to build a cmoy √° Tangentsoft. To be honest, my headphones don't even need it, but I still want to make one. It'll be my first cmoy so I won't do anything special, proper sq would be nice though. I'll be using 0.6w metal film resistors, opa2132pa and a stripboard.

1. What gain should I use for 40-60ohm headphones?

2. Is there any point at using big capacitors rated for high voltages, does it improve sound? (220uf,50v electrolytic and 100nf,1600v film cap's)

3.Is there any point at using audio grade caps and pots in a cmoy?

4.How can I tweak frequency response of the cmoy? Different size caps?
post #2 of 50
Quote:
Originally Posted by UnknownAX View Post

my headphones don't even need it, but I still want to make one

 

If nothing else, a headphone amp gives you a volume knob at arm's length. That's not nothing.

 

The direct alternatives to that have their own problems.  Cable-mounted passive volume controls hurt the sound, and the newer digital sort popularized by the iPhone require special headphones and compatible sources.

 

Quote:
What gain should I use for 40-60ohm headphones?

 

Headphone impedance only loosely correlates with required gain. Before I broke one of them, I had a 64 ohm set and a 300 ohm set that required exactly the same gain to achieve the same loudness level. I also had a 120 ohm set that also wanted the same voltage!

 

You probably don't actually need any gain, but if you make me give a wild guess, I'd go with g=2.

 

Quote:
Is there any point at using big capacitors rated for high voltages, does it improve sound? 

 

Voltage tolerance has nothing to do with sound quality.

 

In electrolytics, using a too-high voltage tolerance merely risks breakdown of the electrolytic barrier between the conductors, eventually causing the cap to fail. Since low-voltage electrolytics are widely available, there's simply no reason not to pick as low a voltage as you can get away with.

 

Film caps are a different story. Again, using too high a voltage won't help, but because plastic is such a good dielectric, getting a cap with a voltage tolerance anywhere near your actual signal level is basically impossible. Someone could make it, but no one does. Still, given a choice between a 0.22 uF 50V cap and a 0.22 uF 100V cap in the same product line, go with the 50V cap. All you'll get by going with the other is more bulk for no gain.


Edited by tangent - 3/27/13 at 8:56am
post #3 of 50
Quote:
Originally Posted by UnknownAX View Post

1. What gain should I use for 40-60ohm headphones?

3.Is there any point at using audio grade caps and pots in a cmoy?

4.How can I tweak frequency response of the cmoy? Different size caps?

 

Good reply from Tangent.

 

1. I would add that you should choose the gain based on the max voltage from your source and the max voltage output of the amp. If you were to use a 9V cell for example and could get the opamp to go up to the rails the max output would be 3.18 Vrms. Therefore a gain of 2 could take an input signal of 1.6 V before clipping, which is about in line with most sources.

 

3. caps in the signal path probably should be audio grade.

 

4. some designs have a bass boost (jdslabs) but I'm not sure how they're implemented. Some caps may have an effect on sound, in particular coupling caps as these often act as high pass. I don't know enough about that though.

post #4 of 50
Quote:
Originally Posted by UnknownAX View Post

I want to build a cmoy √° Tangentsoft. To be honest, my headphones don't even need it, but I still want to make one. It'll be my first cmoy so I won't do anything special, proper sq would be nice though. I'll be using 0.6w metal film resistors, opa2132pa and a stripboard.

1. What gain should I use for 40-60ohm headphones?

2. Is there any point at using big capacitors rated for high voltages, does it improve sound? (220uf,50v electrolytic and 100nf,1600v film cap's)

3.Is there any point at using audio grade caps and pots in a cmoy?

4.How can I tweak frequency response of the cmoy? Different size caps?

While you are over at Tangentsoft, read the Audiologica section...every question you asked is covered there PLUS a ton of other good stuff you will want to know...wink.gif

post #5 of 50
Thread Starter 
Yeah, I found the audiologica site just shortly after posting this thread.... Thanks a lot for your help! I'll go for 35v electrolytics and 40v film caps. Sadly, the shop doesn't sell any 0.1uf audiograde caps, only >1uf.

Btw. how much input voltage can the cmoy handle? I'd like to use more than 9v.
post #6 of 50
Quote:
Originally Posted by UnknownAX View Post

Yeah, I found the audiologica site just shortly after posting this thread.... Thanks a lot for your help! I'll go for 35v electrolytics and 40v film caps. Sadly, the shop doesn't sell any 0.1uf audiograde caps, only >1uf.

Btw. how much input voltage can the cmoy handle? I'd like to use more than 9v.

The Tangent version can be powered by two 9 volt batteries. I would pay attention to the section that talks about voltage dividers...the TLE2426 is the way to go. Ebay is absolutely full of decent parts for the CMoy amp

post #7 of 50
Quote:
Originally Posted by joeyjojo View Post

 

Good reply from Tangent.

 

1. I would add that you should choose the gain based on the max voltage from your source and the max voltage output of the amp. If you were to use a 9V cell for example and could get the opamp to go up to the rails the max output would be 3.18 Vrms. Therefore a gain of 2 could take an input signal of 1.6 V before clipping, which is about in line with most sources.

 

I would not pick gain based on maximum voltage swing. This method quickly gets us gain in the teens which inevitably comes with a lot of noise and poor part matching. 

Rather I would pick gain based on how much voltage swing your headphones need, and whether your op amps will be stable. 

I do agree with gain of 2-3 as a starting point, just through different methods. 

 

Quote:
Originally Posted by UnknownAX View Post

Btw. how much input voltage can the cmoy handle? I'd like to use more than 9v.

 

Do you mean power supply voltage? 

You can find this info on the data sheets for the op amps you pick under "maximum supply voltage."

2*9V is OK for the VAST majority of op amps. 

post #8 of 50
Quote:
Originally Posted by nikongod View Post

I would not pick gain based on maximum voltage swing. This method quickly gets us gain in the teens which inevitably comes with a lot of noise and poor part matching. 

Rather I would pick gain based on how much voltage swing your headphones need, and whether your op amps will be stable. 

I do agree with gain of 2-3 as a starting point, just through different methods.

 

In the context of a cmoy it makes sense a the power supply is the limiting factor, but you're right it should be noted that a gain of 8 will probably cover every headphone (even power hungry ones like the HE-6).

post #9 of 50
Thread Starter 
Let's put it short. What would happen if i built this?
http://s2.postimg.org/8ut1bkqrd/cmoy_x2.jpg
Is there any real point at doing that? If it would work, should I use only one R4 and R5 for each dual-op amp? The component values should propably be modified...
post #10 of 50
Quote:
Originally Posted by UnknownAX View Post

Let's put it short. What would happen if i built this?
http://s2.postimg.org/8ut1bkqrd/cmoy_x2.jpg
Is there any real point at doing that? If it would work, should I use only one R4 and R5 for each dual-op amp? The component values should propably be modified...

 

you should draw a schematic... 

but it looks like you have 2 cmoys in parallel. 

you can do it, but you waste gain resistors. 

 

Look up "cha-47" for ideas of how to do what I'm thinking you want to do. 

post #11 of 50
Thread Starter 
Thanks for the tip with the cha-47! I cant get the TLE and the BUF right now, so I could build this exact design (same resistors and everything) with the tangent power supply (resistor divider), dual batteries and opa3134's, right? Or should i take opa3132's for maximum stability? I hope you can stand these noobish questions... smily_headphones1.gifA47.jpg
post #12 of 50
Thread Starter 
I've got a deadline for ordering the components (group buy) so I really need someone to confirm the stuff above. I have a major problem if I order the wrong parts. because shipping is expensive:)
post #13 of 50

Hope you don't mind for f I throw this in since you're discussing cmoys.

 

I'm looking to make a cmoy using tangent's schematic. Looking at the parts list it calls for one battery, but the schematic shows to 9v batteries. I'm using the 2107, so am I better with 9 or 18?

 

Thanks!

 

Mark

post #14 of 50
Quote:
Originally Posted by marksk View Post

Hope you don't mind for f I throw this in since you're discussing cmoys.

 

It costs nothing to start a new thread.

 

 

Quote:

Looking at the parts list it calls for one battery, but the schematic shows to 9v batteries. I'm using the 2107, so am I better with 9 or 18?

 

http://tangentsoft.net/audio/opamp-wv.html

post #15 of 50

FYI tangent the first link on that page is dead (redirects to FS subforum).
 

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