Pass D1 I/V for Sabre DAC

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khundude

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Joined 2006
Fran,
What cans are you listening to with the Aikido and Buffalo? I will be using the HD650 and was interested in whether or not it has too much or not enough gain with the IVY? The high output of the D1 is of great news to me. I am building a 24v balanced Aikido as well(just bought some 6N27P, got Telefunkens), Buffalo is on the way. The issue is that I want to use the volumite controller for the headamp and Firstwatt F1(need boards). The F1 will drive a pair of AN Cast Super 12's. I was thinking that if the gain was good for the headamp it would be too low for the F1, or visa versa. I have two sets of boards so i could wire one for the headamp and one for the F1. I could then get a couple of TP OTTO's to switch them. could use same PS. What do you think?
 
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woodturner-fran

Member
Joined 2006
650s and K701 - theres plenty of gain, I never go past 12 on the control which is only half way. Its loud at that level. In fact I even use the same setup with a monica NOS dac which only outputs at 0.5V and there is enough gain for that too. I have bought a volumite for my buffalo but haven't tricked about with gain settings on the IVY yet.

Why don't you use the aikido as a pre into the F1 and then also as a headphone amp. The aikido is a great pre, one of the best. Only thing you might need to do is wire in a mute switch so that the the preamp outputs are muted when you are using the headphone amp. Thats what I do with mine.....


Fran
 
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Yunick

Member
Joined 2006
relder said:


It's a wee bit easier to mod the D1 than the DAC.

The D1 should be adaptable to most any DAC current output, you probably just need to tweak the resistor values. The IRF610s aren't wimpy little FETs and could handle more current if need be (properly heatsinked). The lower resistors (R26/R33) control the current bias (~9ma). The upper ones (R27/R34) control the voltage gain. The combo of the upper and lower resistors sets the DC voltage bias point (~15V) of the input to the voltage followers (Q2/Q5) (VOL+/VOL-). I'd probably try to keep that 15V bias point.

So, if the Buffalo puts out twice the current of the PCM63 of the original D1 (I don't know much more the Buffalo puts out) then to cut the gain in half, cut the upper resistors by half, to 750. If that's all you do your VOL+/VOL- bias point becomes 22.5 volts. To lower that back down to 15V cut the bottom resistors by half to 1.65K, which will raise the current bias to 18ma.

Don't know how it will sound, but it seems Nelson tends not to object to more current through a FET.
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Hi Relder,

Thanks for your reply! This is what I was looking for. I tried as you described and lowered the gain and raised the bias. I have only listened for a little while, but i'm afraid the sound is somewhat flat and not so exciting.. I'll keep testing for a few days, maybe it's the loss of gain that fooling me..


Fran,
Thanks for sharing your experiences. I bought only the buffalo with the intention to mate it with the D1. I tried it also with just a cap on the output (voltage mode), but wasn't to excited over the sound..

Best Regards
 
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