Buffer headphone amp

[Granholm]

I just received the 2 PCB's from Damian! Looking just fine! Now I just have to source tha last components to complete the project and fire up my MDR F1's ;o)

Anyone with an availabel partlist? Or recomandations for capacitors/Diodes etc??

Rgds.

 

[kalin oleg]

I have just today finished similar project.
it is OPA 2134 buffered with 2x BUF634P.
very nice sounding, glad of this choise.

some pictures here
http://kalin.euweb.cz/index.html

 

[Granholm]

I have just today finished similar project.
it is OPA 2134 buffered with 2x BUF634P.
very nice sounding, glad of this choise.

some pictures here
http://kalin.euweb.cz/index.html

Sure looks nice! What impedance are the headphones the amp will be driving?

Rgds.

 

[kalin oleg]

Granholm,

16 Ohms

 

[TB]

Hello, I would like to build LT1210 buffer amp based on schematic posted on website mentioned by Chumi. The only difference would be not to use current source. I understand that without use of current source I will have to protect inputs and outputs with caps, what really do not mind. Could someone advised me how to change the circuit to accomodate that change? Which parts are not necessary with use of only LT chip?
Thanks for the help.

 

[Granholm]

Hello, I would like to build LT1210 buffer amp based on schematic posted on website mentioned by Chumi. The only difference would be not to use current source. I understand that without use of current source I will have to protect inputs and outputs with caps, what really do not mind. Could someone advised me how to change the circuit to accomodate that change? Which parts are not necessary with use of only LT chip?
Thanks for the help.

Why not contact Damian that made the layout? I got a pair of PCB,s from him after reading this tread and have only positive experience with the information and fast responce from Damian.

Have Fun

 

[peranders]

Since you already have an opamp (OPA627) driving the buffer I'd imagine the buffer would be within the feedback loop of the opamp ?

The LT1210 is a current feedback amp so it's not possible to use it with no local feedback but if you have so local feedback you can also use global feedback too.

I have designed four current feedback headphone amps and I really like current feedback. I wonder why so few have tested current feedback?

 

[Dxvideo]

Hi all,

I plan to make a good headphone amplifier for myself. And I have some LT1210. So I want to use them. I've searched a lot of site to find a good design with it but I couldnt.
Youre talking about the "backdoor" however there is no schematics of LT1210 head amp in this site.
Does anybody know a working good schematics. I have never made a headphone amp and as my supposition it should be like a gainclone. But I saw more complex circuits on web, like DC servo, pre buffer etc..
May anybody give me some tips to make a good headamp pls?

Best regards,
Ozgur

 

[endia]

Hi Ozgur,

backdoor has the schematic;
http://www.unisonus.com/pdf/lt1210_sch.pdf

i built lots of headamps (opamp based, mosfet, tube hybrid) but lt1210.
glad to share them. also i have some spare headamp pcbs..

by the way building headamps are more fancy than gainclones imho

hope these help; for projects:
http://headwize.com/projects/index.htm
http://tangentsoft.net/audio/

and for discussions:
http://headwize.com/ubb/forumdisplay.php?fnum=3
http://www.head-fi.org/forums/forumdisplay.php?s=&forumid=6

also sent you an e-mail..

selamlar,
naim

 

[Dxvideo]

Thank you Naim,

I've already examined that sites. Thats interesting but I couldnt see the schematics of LT headamp in backdoor.
Anyway,
What kind of headamp PCBs you have? I can buy one of them from you if possible.
By the way; why youre not one of our members?
forum.diyaudiotr.com

Best regards,
Ozgur

 

[Dxvideo]

Thats the Damian's circuit for LT1210;

An externally hosted image should be here but it was not working when we last tested it.

But I am confused that whats OPA604 for? Its a kind of POSITIVE FEEDBACK or what? If so he has a big trouble!
Does anybody have any idea?

 

[endia]

Hi Ozgur,

i have some cmoy, a47, meta42 and sijosae design zen headamp pcbs, plus a few but can't remember their names now.. they all single sided and etched in a small pcb house. i'm not planning to use most of them and of course free for you..

also, i have not an excuse and as soon as joining the forum.

naim

 

[gfiandy]

The OP604 is eing used as a DC servo so that the design does not need any coupling caps and won't have any bias DC offset on its output.

Regards,
Andy

 

[Dxvideo]

Hi Naim,
What a nice proposal! Thank you. I will contact you about that matter in next week.
Looking forward for your membership to our club.

And for GFiandy,

Its interesting. I have never had any experience with DC servo circuits. Op-amp choosing is important on this design? I mean does this feedback carry any kind of signal? If its important for just its precision then I can use another more available alternative like TL071?

Thx.

 

[ybserge]

Theres another way to get rid of DC at the output when working with 1210. One has to change the feedback resistor value from
2K to 1K. However the gain is reduced. In this case some nice sounding previous stage should be added before 1210, possibly an opamp, that OPA604 might happily do.

 

[Dxvideo]

Is it a rule to put a buffer before headamp? I can run a 80W power LM3886 without any buffer, and it works fine! But I did not see any kind of "nude" and good sounding headamp.
Whats that? Somebody like to make things more complex?

 

[gfiandy]

The servo opamp carries a very heavly low pass version of the signal. This means that you get minimal interaction from the DC opamp on the main path. However for best sound quality a good opamp here will out perform a cheap one.

The most inportant characterisitic of the DC servo opamp is the input offset. However it will carry signal upto 1K at very low levels this can interact with the main path.

I have also noticed in listening trials that the quality of the low pass capacitor (C4) significantly affects the sound quality of the main path.

Also note that this circuit has significant noise gain if the input to the main opamp is not driven from a low impedance source.

Regards,
Andrew

 

[Dxvideo]

So if we use the DC servo to cancel input cap. because of the input cap is important on sound quality and the C4 is still critical on sound quality even while DC servo exists:
The DC servo idea is not effective as guessed.
Am I true?

 

[gfiandy]

I think this is rather over stating the case. When AC coupling the cap is directly in the audio path and can introduce measurable distortion.

The DC servo works to much lower frequency using a much higher quality dielectric than can be used for AC coupling. All I am saying is that the type of capacitor is still significant to the sound quality.

If cost is not a problem I would go with a DC servo as you will get a better result.

If you want a simpler or cheaper solution then AC coupling makes sense.

Regards,
Andrew

 

[steppler]

I have a small question.
What is better quality please:
Damians LT1210 or SDS Labs HeadAmp ?

Thank You very much.