[setmenu]

Has anyone had any experience with these :


http://www.analog.com/en/prod/0,,759...8055%2C00.html

The reason I ask is that my previous portable dac was up graded to the 8056
by the person who did the mods to it a few years back, and I think the
sound is rather nice.
Thus they seem a good candidate for a headamp I wish to build for my partner,at the moment she is using a sony 2000 pcdp to drive a pair of
HD25 phones but being a euro model this player has a crippled output,
and has to be run very close to the limits with many cds.

My usual preferred amp configuration is an HA 5002 buffered 3 channel Ad 8610 setup.
But this time around I wish to go for something that consumes less power
as large battery packs are out of the question here.
The amps 60ma plus drive capabilities and the fact I like the sound of this chip are the driving force behind this choice.

I am presuming the 8055/6 is a bipolar input amp, and that adapting the 'cmoy' circuit shown in Tangents 'working with cranky opamps' section
is the way to go.

This is my first foray outside 8610 territory so any views or tips would be welcome.


Cheers

Setmenu

 

[morsel]

A quick glance at the pdf reveals the maximum power supply operating range is ±6V, or 12V total. I would not use it.

 

[setmenu]

Hi morsel
Thanks for your reply.
I appreciate the max supply voltage is fairly low compared to the supply range
usually recommended.
The headphones this amp will be driving do not really need a lot of voltage swing, Er4,s and HD25,s .
My current portable dac/amp combo uses an 8 cell nimh battery pack for the amp section , this averages at about 10v and supply's more than enough to drive all my 'normal' phones admirably.
A fully charged pack unloaded makes about 11.6 v so no danger of exceeding the chips max rating.

Perhaps this chip is not the best choice for my purposes, but the sound is
one that is familiar and likable, so I thought it would make a good starting point.
If the power consumption was not an issue I would build an AD 8610/HA 5002
based amp again, I love this combo, but 3 of those buffs add around 25ma to the power consumption as you are well aware. [plus, no output protection would also be an issue for the amp destined to drive the HD25 with its easy to pullout 3.5mm plug]
As for the Buff 634, well that one is protected and can be economic but, I just cannot stand the sound of them.

Any other suggestions you might have would be most welcome.


Cheers

Setmenu

 

[morsel]

You could try discrete BJT outputs instead of buffers.

 

[setmenu]

Quote:

Originally Posted by morsel You could try discrete BJT outputs instead of buffers.

Hi morsel
I guess discrete outputs are something rather close to your heart at the moment eh?

In fact I am interested in learning more about discrete amp design, as I am
currently investigating discrete designs for I/V conversion with my portable
dac designs, but at present I still have a long way to go before I start
to understand and appreciate the subtleties of such designs.

But for the time being I would like to concentrate on ic based designs for this
current application.

As I am pretty sure a +-60ma output ought to be enough current for the intended headphones.
So, I am wondering as I am quite a fan of the AD8610, whether I could
connect a couple of these per channel in parallel [using the 8620] to
increase the load current capability?
I would presume there are downsides to such an approach, but it
does have a great deal of appeal due to size and power consumption.





Cheers


Setmenu

 

[setmenu]

Quote:

Originally Posted by setmenu So, I am wondering as I am quite a fan of the AD8610, whether I could connect a couple of these per channel in parallel [using the 8620] to increase the load current capability? I would presume there are downsides to such an approach, but it does have a great deal of appeal due to size and power consumption.

Hmm, I have just done some searches on parallel opamps and it seems that
it is not such a good idea unless one uses some resistance on the outputs
to prevent the amps from 'fighting'...



Setmenu

 

[ppl]

i have not used these to drive headphones directly however the below are some you might look at
http://www.analog.com/UploadedFiles/...12AD8021_d.pdf 60 mA output current not unity gain stable without external compensation. Great sound

http://www.analog.com/UploadedFiles/...81AD8022_a.pdf
Dual 75 mA output smooth sound more like the Burr Brown sound.

http://www.analog.com/UploadedFiles/...960AD825_e.pdf
A classic around Head-fi Fat sounding puncy Bass somwhat silbelent Jfet Input. 50 mA output current 100 mA short circuit output current

 

[bpribadi]

I love it

Now the AD8066 stays in my HeadAmp.

My small review:
http://www.sgheadphones.net/index.php?showtopic=2628

 

[setmenu]

Quote:

Originally Posted by ppl i have not used these to drive headphones directly however the below are some you might look at http://www.analog.com/UploadedFiles/...12AD8021_d.pdf 60 mA output current not unity gain stable without external compensation. Great sound http://www.analog.com/UploadedFiles/...81AD8022_a.pdf Dual 75 mA output smooth sound more like the Burr Brown sound. http://www.analog.com/UploadedFiles/...960AD825_e.pdf A classic around Head-fi Fat sounding puncy Bass somwhat silbelent Jfet Input. 50 mA output current 100 mA short circuit output current

Thanks for your suggestions,opamp choice seems a bit of a minefield for the inexperienced, so I greatly appreciate you sharing yours.

I realize that you have not used it in a standalone configuration but how would
you compare the sound of the 8022 with that of the 8610?
I like the apparent transparency of the 8610 and would definitely wish to avoid anything dark or veiled.


Cheers

Setmenu

 

[setmenu]

Quote:

Originally Posted by bpribadi I love it Now the AD8066 stays in my HeadAmp. My small review: http://www.sgheadphones.net/index.php?showtopic=2628

Thanks for your suggestion.
I do have some samples of these, but think the current output when used unbuffered may be a bit on the low side.


Setmenu

 

[Earwax]

Quote:

Originally Posted by setmenu So, I am wondering as I am quite a fan of the AD8610, whether I could connect a couple of these per channel in parallel [using the 8620] to increase the load current capability?

Like in aphered's A47 design? That should work.

 

[setmenu]

Quote:

Originally Posted by Earwax Like in aphered's A47 design? That should work.

Thanks
I just took the briefest look at the A47 design, interesting.
I would be curious as to what sort of source R/Z a headphone would see from
this configuration ? [not sure how to calculate this at the moment

]


Setmenu

 

[morsel]

Historically, these opamps have been popular for directly driving headphones:

LM6171 90mA single
NJM4556A 70mA dual

You could also try this. National says it is an improved version of the LM6171:

LM7171 100mA single

 

[setmenu]

Thanks to everyone for their suggestions and advice.

I look forward to experimenting with some of these chips and
seeing what results.
I think I now need to find a good quick way of producing little test pcbs, as
some of these chips seem to be fairly fussy about layout.


Cheers

Setmenu

 

[bpribadi]

Just a reminder, those op-amps with high output current suggested above are not jfet input, means you will have to deal with DC output offset. So design wise you need to be really carefull with the resistor values.

CMoy, Pimeta, PPA, they are all for Jfet input op-amps.

Easy solution for the DC offset will be output capacitor which will make the bass weak.

30 mA output might seems low, but in fact they are sufficient to drive most headphone. Tested, CMoy with AD8610 drives DT880 (250 ohms) very well.