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Super V/i converted (LL1684 )

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#282
analog_sa said:
You are welcome.

Again, not sure if the 9018 performs at its best when the bias voltage is disturbed. Otoh, introducing caps somehow spoils the entire idea of a transformer, doesn't it?
Click to expand...

For me it does unfortunately. I tried different caps for Super V/I and each time I got different sound signature, so for me it does matter. I tried polymer, ESA and copper foil. Copper foil was best in clarity. However now, no cap is best 🙂 especially in high frequencies. At least this observation works for ak4490.

Call for someone to test Super V/I LL1684 (no cap) with es90x8.

Otoh, I am wonder how Teramoto Finemet transformers handles bias voltage for es90x8 without the cap ...
 
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#283
A quick scan of the archives indicates the 1.65v is of no importance, or at least i cannot see a valid reason for trying to preserve it, no matter whether current or voltage operation is desired.

So the Teramoto does exactly the same thing as the Lundahl in its place does, only sounds much, much better
 
#284
kmajjo said:
Hello Guang Hao,
Sorry , but if i understand well, in this case i have a 4 : 1 transformer and not a 1 : 4 transformer for more gain.
I want to use LL1674 or LL1676 (1 : 2) in your dac converter.

LL1684 = 1:1 / Prim dc = 41 ohm/winding / Second dc : 41 ohm
LL1674 = 1:4 / Prim dc = 33 ohm/winding / Second dc : 605 ohm
LL1676 = 1:2 / Prim dc = 145 ohm/winding / Second dc : 605 ohm

Br
Jacky
Click to expand...


HI!

You can use LL1674 in the configuration 1+1 : 4 instead of 1 + 1 : 2

A my friend use this configuration without problems, some modifications on output pcb are necessary to use it!

no need by LL1684, thanks
quanghao
 
#285
quanghao said:
HI!

You can use LL1674 in the configuration 1+1 : 4 instead of 1 + 1 : 2

A my friend use this configuration without problems, some modifications on output pcb are necessary to use it!

no need by LL1684, thanks
quanghao
Click to expand...

Hello Guang Hao,
If i am not mistaken , connections are like this with LL1674 :
 

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#286
Vishay VAR-Series "naked" 18 ohm parallel to the output, then:
Lundahl LL1941

Trafo must be loaded by a reasonably high impedance (>25k)

Works very well.

//
 

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#287
TNT said:
Vishay VAR-Series "naked" 18 ohm parallel to the output, then:
Lundahl LL1941

Trafo must be loaded by a reasonably high impedance (>25k)

Works very well.

//
Click to expand...

Hello,
So , i understand well, ES9018 works in current mode , but output must be very low at the primary and gain partially offset by the output transformer ?
Could you give us some voltage level in this case ?
Br
Jacky
 
#288
The caps and the resistor in the primary side of the transformer as per kmajjo diagram form a low pass filter, this way you wont put subsonic frequencies in the trafo and create distortion 🙂

Since amorphous core transformers are very sensitive to dc offsets(if you apply a dc voltage across any of the coils you can magnetize the core and after the transformer will produce distortions) I don`t reccomend that you use in place of this filter a short wire to ground. LL1674 and LL1684 are amorphous core transformers.

There is another thread here where Joe Rasmussen presents some interesting things that you should check.
http://www.diyaudio.com/forums/twisted-pear/164294-buffalo-ii-transformers-19.html
See from post 185 and after.
I am using my es9018 with some LL1684 in the output connected as per diagram C in post 185 in the link above and the combo sound very good.

Regards.
 
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