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Buffalo II & transformers

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Dear Tyimo

Sory for late answer but for some time I was not looking hire.
As for LL1517 conection diagram I did use serial primary and serial secondary connection exactly as per http://www.lundahl.se/pdfs/datash/1517.pdf datasheet. I did experiment with diferent resistor at trafo output and end up with about 1kOhm, but this could greatly depends on Your next stage. In any question Please ask.

Rosedndorfer
 
Hi Tyimo

So Some answers:

Pin no 9...no connection... I did listening tests with my headphones and my Power Amp and did not find any differences so I have left it with no connection.

Volume pot.....Who needs expensive pots when you have buffalo..and Volumite... OK I know that there are guys that do not like this solutions but I'm personally big fan of Buffalo+Volumite this combo solves so many problems and works so nice that right now I even do not look at my precious AlpsPots and even more expensive hand made attenuator made out of military grade resistors with silver solder ...

If I could recommend go with Volumite...this will save You lot of problems...

And then You can go directly from trafo to Your Power Amp..no Pre.../OK with Volumite Pre is in the dac.../.

And this starts to be bit tricky...
I hope some wise guys will tell something about this if I'm relay wrong ..but ....

At output of Buffalo and as mather of fact the same is at output of LL1517 as this is 1:1 trafo You will have plenty of power please see my post #44 and see my scope shots with different resistors at trafo primary....And with 1kOhm this is about 4vp-p at 0dB. You can go lower with resistors but somehow I did not like the results of this and below 300-200 Ohm I did find that "dynamics" get cut...but this is just me and other guys could thing/listen diferent... .

So we have got 4V p-p and...this is too much to connect to "regular/standard" power amp @usualy about 20 times amplification...
So actually there are two solutions ...or use Volumite or Pot "hard way" about -40to -60 dB but this is just waste of dynamics....and no good...
Or... cut Your PowerAmp amplification...
Thing about...
Your Dac+LL1517 with PowerAmp should be set up to work together in "optimum" configuration...Buffalo is giving You 4Vp-p Pure Music/Dynamics so do not waste this by 300W Power Amp ....with -80dB Pot..@.input.
What for 20x amplification when all you need is 2-5 times in "normall" listening situations...

So back to Your questions ..... next stage input impedance...

In my system it is about 10kOhm and my PowerAmp has amplification about 4x and then Volumite is set at 8 or 9..out of 10max..at usual listening level ..

OK and very nice Trafo feature is that You can remove Caps at Your Amp Input...No DC ....

Vell I hope that will answer some of Your questions...

If I could help please ask...

Rosendorfer
 
195 ohms for each phase, so it's 390 ohms total .... higher than ideal for most transformers, not that it can't still sound good of course. :)

Hi Tyimo

Well from Russ White informations that he shares on this forum, Buffalo output impedance is about 195 Ohm in stereo mode..if I understand him correctly.
If LL1517 likes this or not I did not ask, but I know that this is working realy nice...

Greets
Rosendorfer
 
Hi Rosendorfer!
Well from Russ White informations that he shares on this forum, Buffalo output impedance is about 195 Ohm in stereo mode..if I understand him correctly.
If LL1517 likes this or not I did not ask, but I know that this is working realy nice...

Thanks for the info!!
May be your load resistance (1K) is optimal in this situation.

greets:
Tyimo
 
Hi Tyimo

Regarding load resistance just to to make this clear I've never told that 1KOhm is optimal for LL1517 and Buffalo. I did few measurements and they clearly showed that load resistance has really big influence on this how this combo works..mainly for THD but also other measurements. And please know that from my measurements 1KOhm in this setup could be too much and we should go for much lower value maybe about 300-200Ohm, as this trafo load values gives much better measurements for THD. But again based just on my sbjective listening tests I did find that load less than 600-700Ohm seems to kill bit of dynamics IN MY Setup, but this is just my subjective opinion. So I definitely recommend you to test also different load values..there is no proof that 1kOhm is optimal.

Dear Alex..

As for Input caps I definitely through them out... With Trafo caps at input are no use..there is no DC at trafo... And as for me no caps was definitely impovment..
All I can say is it is worth to try..

Dear Spartacus

Well You could be right that 195Ohm is for one phase... so between phase connection makes 390Ohm ...

And this could even explain me bit more why Russ "recommend/suggested" that for Buffalo he wouldn't use typical "current output"/"low imput impedance" trafos like for other current output dacs, as there is no chance to force Sabre to work in current output mode with any Trafo..but he "suggested" interstage trafo with 600:600Ohm...And 600Ohm could be probably "more optimal" for 390Ohm than 20Ohm from our LL1517.
But as I've mentioned few months back in this thread I'm not trafo/dac specialist and I really could use somebody with much greater knowledge in this subject...As there is lot of different ideas and probably with Sabre all this configurations are working but what is the best/optimal solution I really would like to know...

And I hope that Russ will correct me if anything I said He said is not what He said.... :D


Regards
Rosendorfer
 
Hi Rosendorfer!
Thanks for all the help!
I tried my LL1517 with another DAC and works super!
The ideal for this transformer: 10 R primary source impedance and 600 R Secondary load.
You should paralell the secondary windings to get 2:1 turn ratios. That would be good for you high voltage output DAC.

Greets:
Tyimo
 
Hi Fedor

This is the beauty of this situation, as far as I know there is no "provern" circuit ...
But on other hand it seems that with Buffalo moust of transformers "just" works..prety well.
As for and RC filter it seems that You are on Your own, just trust to Your ear...

It would be great to hear Your coments regarding this connection, as 600Ohm Trafos seems to be more siutable for Bufallo.
Do You have standard IVY or Legato to make any comparision..??

Regards
Rosendorfer
 
Hi Rosendorfer, thank you for your answer.

Seems that I'll have to experiment with different circuits :) Buffalo II is 2-3 days away from me, so when it gets here, I think first I'll try straight out from dac to the primaries. And then will try some other circuits found in this thread.

I'll post the results, when I'll get this thing running.

As for the conversion board - alas, I don't have one, but maybe will get later.

Thanks,
Fedor
 
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