hey kenpeter,
It´s your circuit that doesn´t work not mine, so take it easy!
You can E-mail me if you want some help with LTSpice.
Say thank you instead
. Maybe you haven´t gotten so deep into LTSpice yet. ".four" command is fourier-analyze. You can check the figures under "View"/"Spice error log". www.revintage.se/Draft14.asc
It´s when you bypass/or substitute with LEDs you get the severe THD!!!! Off coures I tried your schematic first and as I suspected it did not work to well. One of the reasons was that you bypassed the "unused" cathode to ground! But if you like 2%THD it´s OK.
About the added 12V you already have it for heating your 12AU7 so there are no extra parts!
And if you want a low-mu tube go for 6H30.
And for this circuit DN2540 or whatever you got at hand is good enough.
Sunrise: You are so right, it´s in the ballpark of 5mA/triode.
Why add distortion and tube noise? Just use one side (the hot, or +). You will lose 6 db but if your inputs are unbalanced then it should be ok; there nominal input should be 14 db lower than the 2volt out (not sure why you want a gain of 1) In pro recording studios you usaully drop the level 14 db as well as go from balanced to unballanced. This is usaully done with a resistor pad (3 or 4 resistors, thats it) the cheapeast easiest cleanest quietest flatest (you get the point).
revintage said:
Yes, you will only be able to listen to music if you buy $250 worth of transformers. Edcor makes a 1:1 nickel core transformer for $20, or a steel core for about $10. As good as the Lundahl? Probably not. But probably closer than you think. Otherwise, tie the negative signal to ground and call it a day.
A mic input maybe won´t be able to cope with the 2Vrms level. Couldn´t find at what level they measured distortion?
But surely Edcor and many american manufacturers have transformers at low prices that will work and will be likable to play music through.
A somewhat cheaper alternative is LL1544A(max 2V before core saturation) at 160USD/pair. Thank godness I live in Europe where Lundahl prices are lower.
If you want to tie the negative signal to ground, you must do it through a cap.
But surely Edcor and many american manufacturers have transformers at low prices that will work and will be likable to play music through.
A somewhat cheaper alternative is LL1544A(max 2V before core saturation) at 160USD/pair. Thank godness I live in Europe where Lundahl prices are lower
.If you want to tie the negative signal to ground, you must do it through a cap.
oh boy.... a lot of answers again.....guys thanks .... you are very helpfull.....
@kenpeter - "If low parts count is going to be a consideration here at all?"
yes - it is in consideration....but most of all what i would like is to have a tube out of that Wolfson dac. and not to loose to much voltage when doing that.... so i would like at the output of the dac to have a minimum od 1Vrms if possible.....
and quality - in my opinion WM8740 is a very nice dac that deserves to have a tube output that can match its quality....
@revintage - i like that 6H30 tube circuit better...... less complicated and with a nice tube in it too.....
so is it the one to go????
@kenpeter - "If low parts count is going to be a consideration here at all?"
yes - it is in consideration....but most of all what i would like is to have a tube out of that Wolfson dac. and not to loose to much voltage when doing that.... so i would like at the output of the dac to have a minimum od 1Vrms if possible.....
and quality - in my opinion WM8740 is a very nice dac that deserves to have a tube output that can match its quality....
@revintage - i like that 6H30 tube circuit better...... less complicated and with a nice tube in it too.....
so is it the one to go????
I like the 6H30 that is so neutral, some call it laid back......
C2 must be adjusted in circuit with load as it seems critical.
About the circuit I am sure it can sound OK. But I have never tried anything like that myself, nor had I seen anything like it until kenpeter showed the embryo yesterday.
C2 must be adjusted in circuit with load as it seems critical.
About the circuit I am sure it can sound OK. But I have never tried anything like that myself, nor had I seen anything like it until kenpeter showed the embryo yesterday.
don't worry - i am waiting for WM8740 to come home - to try them in a cheap dac concept.....
i have some E88CC at my home and also maybe i can find some 6N23P (they are very similar but it seems to me that they are more linear in 5mA region)......
6H30 is the one i would like to try the most..... but actually don't have them - so i will have to buy them.,....
will see.....
if the design works i think it is the one to go...... one or the other.....
i have some E88CC at my home and also maybe i can find some 6N23P (they are very similar but it seems to me that they are more linear in 5mA region)......
6H30 is the one i would like to try the most..... but actually don't have them - so i will have to buy them.,....
will see.....
if the design works i think it is the one to go...... one or the other.....
Kenpeter,
You have to add it yourself to dmtriode.inc! There are no updates to rely on. This one I borrowed from Andrei:
.subckt 6H30 P G K
Bp P K I=(0.391133693m)*uramp(V(P,K)*ln(1.0+(-0.0187352739)+exp((5.147858602)+(5.147858602)*((12.74287762)+(-184.3951189m)*V(G,K))*V(G,K)/sqrt((23.72646407)**2+(V(P,K)-(13.80558026))**2)))/(5.147858602))**(1.205889167)
Cgp G P 6.0p
Ci G K 6.3p
Co P K 2.5p
.ends 6H30
Lots of useful models at www.intactaudio.com/forum/viewforum.php?f=15&sid=59139eebb3c8e1c9ce4eef777da4d3e7!
You have to add it yourself to dmtriode.inc! There are no updates to rely on. This one I borrowed from Andrei:
.subckt 6H30 P G K
Bp P K I=(0.391133693m)*uramp(V(P,K)*ln(1.0+(-0.0187352739)+exp((5.147858602)+(5.147858602)*((12.74287762)+(-184.3951189m)*V(G,K))*V(G,K)/sqrt((23.72646407)**2+(V(P,K)-(13.80558026))**2)))/(5.147858602))**(1.205889167)
Cgp G P 6.0p
Ci G K 6.3p
Co P K 2.5p
.ends 6H30
Lots of useful models at www.intactaudio.com/forum/viewforum.php?f=15&sid=59139eebb3c8e1c9ce4eef777da4d3e7!
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