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Cavalli EHHA Embedded Hybrid Headphone Amp - Page 2

post #16 of 1813
5/1/09 at 11:42pm
Runeight! Welcome back from across the river styx!

As I mentioned, i'm thinking of an active ground or balanced version - has one been attempted?

I'm actually leaning toward BJT...

For balanced, I reckon I'll need a CL gain of less than 7.5 - is there a formula available for determining R13 or should I buckle down and try to understand the circuit?
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post #17 of 1813
5/1/09 at 11:49pm
Quote:
Originally Posted by wiatrob View Post
Runeight! Welcome back from across the river styx!

As I mentioned, i'm thinking of an active ground or balanced version - has one been attempted?

I'm actually leaning toward BJT...

For balanced, I reckon I'll need a CL gain of less than 7.5 - is there a formula available for determining R13 or should I buckle down and try to understand the circuit?
If I could only get you guys to look at the website.
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post #18 of 1813
5/1/09 at 11:52pm
Thread Starter 
Ok, I'm confused... and excited. What mods are needed for the higher power version? I want names and addresses!

I have some insanely hard to drive phones which need all the power they can get (though not 100w ). Is this something easy to do?
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post #19 of 1813
5/2/09 at 12:00am
Quote:
Originally Posted by runeight View Post
If I could only get you guys to look at the website.
OK, I promise to read the pages of the site OTHER than the parts list!
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post #20 of 1813
5/2/09 at 12:16am
Quote:
Originally Posted by smeggy View Post
Ok, I'm confused... and excited. What mods are needed for the higher power version? I want names and addresses!

I have some insanely hard to drive phones which need all the power they can get (though not 100w ). Is this something easy to do?
I believe the implementation would have to be a bit different to support those levels of power, so modding the current EHHA to perform to that spec may not be possible. Just a guess though...
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post #21 of 1813
5/2/09 at 12:23am
Quote:
Originally Posted by smeggy View Post
Ok, I'm confused... and excited. What mods are needed for the higher power version? I want names and addresses!

I have some insanely hard to drive phones which need all the power they can get (though not 100w ). Is this something easy to do?
If you use a s22 supply with 30V rails you'll get all the power you need for headphones. Many watts in fact. But to drive speakers needs some resistor changes. I don't remember what they are anymore, but I can go back and figure it out if someone really wants to do this.

And, I should add, because of the different ways bjts and fets work, the bjts will be the higher power version.
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post #22 of 1813
5/2/09 at 12:25am
Thread Starter 
Well this will do just as it is, no need complicating what I'm already over my head with

I've already bumped into hurdle number one.. trying to figure out all the values of all these resistors. They're nearly all identical looking brown Dale RN55D resistors with different numbers/letters above and below that. How can you tell what they are?

I guess this is one reason it's not a beginners amp.
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post #23 of 1813
5/2/09 at 12:46am
The RN55 line is very easy to read. Turn the resistor so that you can read the words, rotate it so you go to the bottom (big gap before the top, as you turn it). That's the resistor value. Put it on a DMM, and you'll figure it out, I'm sure.

Small DIY advice. When populating boards, I always put the RN55 resistors so the value is visible right on the top. This way you can read the values right off the resistors as you troubleshoot. It's much easier than decoding color bands.
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post #24 of 1813
5/2/09 at 12:47am
Quote:
Originally Posted by wiatrob View Post
OK, I promise to read the pages of the site OTHER than the parts list!
wazzat? There are other pages?
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post #25 of 1813
5/2/09 at 1:07am
Quote:
Originally Posted by holland View Post
wazzat? There are other pages?

Quite edifying too, 'though I think I'm going to need more brainpower to figure setting the relationship/values for R13/22/23.
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post #26 of 1813
5/2/09 at 1:28am
Quote:
Originally Posted by holland View Post
The RN55 line is very easy to read. Turn the resistor so that you can read the words, rotate it so you go to the bottom (big gap before the top, as you turn it). That's the resistor value. Put it on a DMM, and you'll figure it out, I'm sure.
dang... all this time I thought those were just part numbers!

I'm such a noob.
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post #27 of 1813
5/2/09 at 1:51am
Thread Starter 
you and me both...

so it looks like the first three are the value numbers and the fourth digit is the number of zeros at the end.
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post #28 of 1813
5/2/09 at 2:02am
Quote:
Originally Posted by smeggy View Post
you and me both...

so it looks like the first three are the value numbers and the fourth digit is the number of zeros at the end.
With V-D RN-type resistors, the fourth digit is the exponential notation. So "1001" is a 1K resistor - 100 x 10. "1000" is actually a 100R resistor - 100 x 1. Note that V-D's CMF-type resistors that you can buy at DigiKey are identical, but use a more traditional notation.

Quote:
Originally Posted by holland
Small DIY advice. When populating boards, I always put the RN55 resistors so the value is visible right on the top. This way you can read the values right off the resistors as you troubleshoot. It's much easier than decoding color bands.
This should be made a LAW.
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post #29 of 1813
5/2/09 at 2:05am
Thread Starter 
Thanks, I will abide by it
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post #30 of 1813
5/2/09 at 2:07am
I had a lot of fun building the CTH, and finally finished one of the SOHA+JISBOS I've had on the shelf for a while, and now my bro-in-law has asked for his drill press back..(It was such a pleasure using it to do the case work) What was my first reaction? Where can I get one for myself cheap.. and I'm picking up a good used one tomorrow.

Is this the beginning of the end.?
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