[Pavel Macura]

Anything new?

 

[fewtch]

Quote:

Originally Posted by ryssen I tried my new headphone amp today,http://www.pha.inecnet.cz/macura/buffer_en.html I tried it with OPA627 and OPA637 and I must say that OPA637 was the best! The OPA627sounded dark not so detailed as OPA637,I thougt it was funny as evrybody say`s OPA627 sounds best

Well, it's all about synergy. I like the OPA627s with my Beyer DT880s, because otherwise they can be detailed to the point of analytical as well as a little too bright (at least with some music), and the OPA627 is just about perfect for them. They work out pretty well with the K501 too, which can also be a bit overly detailed and a little lean. Congrats though on finding a sound that goes well with your setup.

 

[Pavel Macura]

I have added my recommended headphone amp schematics to the page.

http://www.pha.inecnet.cz/macura/buffer_en.html

 

[ryssen]

I tried it wis this bias arrangement http://home.swipnet.se/~w-50719/hifi/qrv04/index.html
I did a switch,bias on/off ,I use a bias of 4mA It´s hard to tell the differenece on
AD8610 maybee a little more room info,did notice a difference on OPA627,better details,but no in class with AD8610.

Quote:

They work out pretty well with the K501 too, which can also be a bit overly detailed and a little lean. Congrats though on finding a sound that goes well with your setup.

Maybee OPA627 work better with K501.

By the way,I ordered 2 PCB´s for this buffer http://home.swipnet.se/~w-50719/hifi/qrv05/index.html
just to try for fun,thouhgt I leave the BUF634 in there an use QRV 5 after the
OPA,how about the feedback if I use QRV 5, any thouhts?

 

[ryssen]

Hai,it´s me again I got some EL2125es and they sounded quite nice,but I get DC
at the output 350-500mv and the OP get´s hot!!It says "stable for gain´s of 10 and greater" is it oscilating?should I raise the gain,will the DC dissapear then?
http://www.intersil.com/data/fn/FN7045.pdf
I tried gain 11,DC went down a bit to 200mv that´s high isn´t it?What does gain 10 and greater mean,that I can use it at gain 6?
That Ic almost sounds like a AD8610.Great!
--------------------------------------------------------
Must have been oscilating,one Ic stopped working after a while.How to fix this??

 

[ryssen]

I tried this:http://hififorum.knaak.dk/Ryssen/Pic/H%f6rlur/1a.jpg
http://home.swipnet.se/~w-50719/hifi/qrv05/index.html
http://hififorum.knaak.dk/Ryssen/Pic/H%f6rlur/2a.jpg
And it is a little edgier than the BUF634,better?Different.i am going to built this in box with 2 headphonejacks just to chose...

My next project:http://hififorum.knaak.dk/Ryssen/Pic/H%f6rlur/3a.jpg
http://home.swipnet.se/~w-50719/hifi/qrv08/index.html .......

 

[ryssen]

I realy must ask,I got 2pcs of LT1468 and tried them with The QRV5 buffer,and i must say they beat the AD8610 they sound more com,more natural.Any one tried them,or any other good op from Linear?

 

[steinchen]

you cannot directly replace AD1820 with LT1468, the first one has jfet inputs while the second one is bipolar, thus their input bias currents differ by magnitudes. That is where your DC offset results from, it's not the gain or unity gain stability. You need to carefully select the resistor values (lower values for bipolar) to null the bias currents.

 

[ryssen]

There´s 7mv and 19mv after the QRV5 is it to much?You mean I should lower the gain or?

 

[steinchen]

less than 20mV is just fine

I recommend to read
http://tangentsoft.net/audio/hs-opamp.html
http://tangentsoft.net/audio/calc.html#offset
before dropping bipolar opamps into circuits designed for opamps with jfet inputs. You cannot just swap opamps and expect the comparison to be fair (if it works anyway)

 

[ryssen]

Thank´s I´ll read that.But it sounds damn good...

 

[ryssen]

So l lovered the input resistor to ground,to 82K and got a little lower dc offset,4mv lover,whould it be whise to lover the resitors value bu1/10 to lower it further?That would be 8.2k input to ground,100 ohm,470 ohm in the feeback.
I don´t use a input cap.

 

[steinchen]

generally speaking lower is better with bipolar opamps, but I don't have the experience to give concrete advice

a good starting point are the application examples in the datasheets of bipolar opamps, or take a look at existing amps based on bipolar opamps:
LM6171 http://www.meier-audio.de -> Projects / Headamp
NE5532 http://www.semiconductors.philips.co...otes/AN142.pdf
AD797 http://headwize.com/ubb/showpage.php?fnum=3&tid=6101

and search head-fi and headwize for LM6171 / AD797 / NE5532

with careful resistor value selection input and output caps are not needed

 

[ryssen]

It turnd out that this one (LT1468)had offset trim,bur I can´t get it to zero any way the lowest I get it is to 2,4 and 4,4mv.Maybee I should lower the resistor values anyway?

 

[Andrea]

ryssen,


So do you clearly prefer the LT1468 to the AD8610 and OPA627 ? Thanks