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Old 26th October 2011, 12:30 PM   #1
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Default WM8741 dual differential, output stage

Hello,

in my player I'm using 2x WM8741 DAC and have no idea which opamp I should use for output stage. The reference schema from WM is using a dual opamp OPA2227, but as I've read, this one is not really good. I would like to use single opamps, but which?

Can you help me or post a schema?

Thanks & kind regards,
Heinrich
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Old 29th October 2011, 04:43 AM   #2
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Quote:
Originally Posted by BMW850Ci View Post
Hello,

in my player I'm using 2x WM8741 DAC and have no idea which opamp I should use for output stage. The reference schema from WM is using a dual opamp OPA2227, but as I've read, this one is not really good. I would like to use single opamps, but which?

Can you help me or post a schema?

Thanks & kind regards,
Heinrich
Hola

which player do you use?
I get a Pioneer PD.D9 mk2 using two OPA2134 with WM8741 dacs.
I am planning change those with OPA1642s ( needed adaptors SOIC to 8DIP...)

Ciao.
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Old 30th October 2011, 12:33 AM   #3
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Quote:
Originally Posted by BMW850Ci View Post
Hello,

in my player I'm using 2x WM8741 DAC and have no idea which opamp I should use for output stage. The reference schema from WM is using a dual opamp OPA2227, but as I've read, this one is not really good. I would like to use single opamps, but which?

Can you help me or post a schema?

Thanks & kind regards,
Heinrich
Second opinion:

Why not go to PASSIVE option ?
I mean transformer coupled output.
Having used this option in my CA 640C mk2, I can say that is THE BEST option...
In shorts terms; no opamp at all, no need of very quiet analog psu, no coupling caps ( in my set up I mod the amp input suppressing inputs caps...
no DC OUT...)
Actually a couple PEAVEY TR are connected ( 20 years olds, from pro market...) in be twin dacmagic and my amp ( heavily modded CA 640A mk2 )

Ciao.
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Old 30th October 2011, 01:23 PM   #4
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My player is a DIY-development, here is a block diagram of them:

Click the image to open in full size.

Sorry, it is in German. It is a dauther board for Concert 1 radio, which is placed instead of tape drive, tape drive out and player in.

I found a schematic of Jumbo Dac, it is using dual differential WM8741 too, so I can use the output stage of them, it is using AD797 opamps.

Kind regards,
Heinrich
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Old 1st November 2011, 02:07 AM   #5
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Ola Heinrich

why don't explore the transformer option ?
Palmer, a German pro maker, has a couple of nice TR's, or Lundahl LL1527XL is very good indeed, for example.
May not the cheaper option ( you will save on opamps and opamp's PSU...some money )
but if you'll find the right one ( the best sounding in your system ) it will give you magical listening moments.
Usually they have a crystal clear, dynamic and distortion free sound character.
Generally speaking, the bass range is the harder task for TR's, but rightly impedance matched they are really astounding .
I have just received two 1+1:2 hight impedance matching transformers ( RS part #6675969 + #6675962 ) and will give them a run on next week...( few free time ...).
If you're interested I'll give you a "sonic" report when tested.

Cheers.

Marco
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Old 1st November 2011, 05:37 AM   #6
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Quote:
Originally Posted by bicefalo View Post
Ola Heinrich

why don't explore the transformer option ?
Palmer, a German pro maker, has a couple of nice TR's, or Lundahl LL1527XL is very good indeed, for example.
May not the cheaper option ( you will save on opamps and opamp's PSU...some money )
but if you'll find the right one ( the best sounding in your system ) it will give you magical listening moments.
Usually they have a crystal clear, dynamic and distortion free sound character.
Generally speaking, the bass range is the harder task for TR's, but rightly impedance matched they are really astounding .
I have just received two 1+1:2 hight impedance matching transformers ( RS part #6675969 + #6675962 ) and will give them a run on next week...( few free time ...).
If you're interested I'll give you a "sonic" report when tested.

Cheers.

Marco
I'd be interested to hear more about your results!

I'd also be interested to hear how you selected the transformer impedance to properly match. ie from the wm8741 datasheet it says min resistance load of 2kohm.

I'm trying for a similar passive output stage on my 8741 dac, but just starting the learning curve here at the moment.
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Old 2nd November 2011, 05:43 AM   #7
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Remark, waiting for the report of this RS transformer, if good, this will be a giant killer compare with something like Lundhal.
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Old 3rd November 2011, 10:52 AM   #8
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You could use this board to convert from differential to singel ended

Ray's Audio Shop
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Old 3rd November 2011, 10:56 AM   #9
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If you use a transformer, do you still have to filter?

Before or after the trafo?
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Old 5th November 2011, 01:14 AM   #10
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Quote:
Originally Posted by Marcelinho View Post
If you use a transformer, do you still have to filter?

Before or after the trafo?
Hola Marcelinho,

no you dont need more filtering..nor output coupling capacitors (no input caps in pre or amp after it too.. )
If transformers are Hight Impedance models, try them direct on Dac's outputs.
If you will use a 600ohm TR you can let the same resistors's value on dac`s output (R93/94,R184/185 left dac, R200/201,R208/209 right dac ) .
I will test RS transformers in a implementation like a direct box ( yes, to transform balanced to single ended, at my dacmagic output ) because I will not have free time right now, only to hear the sound "character" if any....
Will report..

ciao

Marco
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