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OLD THREAD DAC End by Andrea Ciuffoli

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mikelm

mikelm

Member
Joined 2003
How much for the full set ?

I joined this thread just recently and this DAC seems like just what I wanted so I ordered a full set of boards but I have no idea where in this big thread the details of the prices etc are.

I asked quanghao a couple of times how much I should send him but for some reason I did not get a reply . . . .

So I would be really gratefull if someone here can tell either the cost of a full set of boards including all extras or where in this thread this is explained

Many thanks

mike :)
 
apelizzo

apelizzo

Member
Joined 2006
Hi Adamus,

I'm back on this DAC for a little while as I'm working on a new SE amplifier.

As I said before I like your idea of replacing the cap with LED on I/V stage, but the LED IMO is not very linear. So I believe following you track try to use TLV431 instead of the LED... then let me know.... :)

It's linear from DC to 50KHz !!
 
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apelizzo

apelizzo

Member
Joined 2006
adamus said:
I guess so, which would lead us back to having to bypass with a electrolytic cap. thats the beauty of the LED's, no bypassing.
Click to expand...

Sorry I don't get it. Look at the first and second chart. Which one shows more dynamic impedance? LED looks more banana to me. Also I don't know what happens to the LED between DC and 50KHz.
 

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A

adamus

Member
Joined 2008
its so easy to try the mod, just go for it. 5 mins tops.

I have no idea how the tlv431 would behave in series (you would need to to get to 3.8v) and cant see that anyone has ever tried them. they could well work

MY guess is your electronics knowledge far outstrip mine, and we may be better to ask someone like Sy to comment, i dont want to get out my depth.
 
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apelizzo

apelizzo

Member
Joined 2006
adamus said:
its so easy to try the mod, just go for it. 5 mins tops.

I have no idea how the tlv431 would behave in series (you would need to to get to 3.8v) and cant see that anyone has ever tried them. they could well work

MY guess is your electronics knowledge far outstrip mine, and we may be better to ask someone like Sy to comment, i dont want to get out my depth.
Click to expand...

Well I tried the function on a little headphone amp using a 9pin direct heater tube.
I could not believe my ears. Very deep bass and clean details. Amazing. After that I feel any good cap for bias could go in the bin.

I don't think I'm better then you and I'm just here to share knowledge for improvement. It was your idea anyway, I just wanted to dig more into it.

Of course we gain something and we loose something at the same time. The self bias function of the valve in this case is lost so we need to be careful about maintaining B+ stable or the working point goes banana. Self bias is very safe but we need gain. Sometime a nice resistor is not enough and we put the cap which on AC AF is pretty unlinear (down and up) so we gain "gain" and we loose performance of the sound.
 
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tympani1d

tympani1d

Member
Joined 2009
Just for us newbies to this thread:
Could someone patiently re-list the link to order the boards?
Including the Salas HV regulator board?

I know we'll be reading and re-reading the whole thread... but a quick link re-listing pertinent reference links could help get newbies up to speed.
Thank you, all for a great thread-project-learning opportunity.
 
apelizzo

apelizzo

Member
Joined 2006
adamus said:
I could certainly try it at some point.

I still havent picked up the power resistors to drop the B+ and allow a sensible CSS, i need to try that too.

cheers for the tips!
Click to expand...

I will try it soon on this DAC.

Use TL431 as you LED. It''s like your LED but with three legs where you adjust the voltage. There is no TL431 tuned at 3.8V so it's just matter of adjust it.
It's the same but with better performance I believe. If nobody tried this it doesn't mean it's impossible. Just follow the rule.
 
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F

flocchini

Member
Joined 2004
apelizzo said:
I will try it soon on this DAC.

Use TL431 as you LED. It''s like your LED but with three legs where you adjust the voltage. There is no TL431 tuned at 3.8V so it's just matter of adjust it.
It's the same but with better performance I believe. If nobody tried this it doesn't mean it's impossible. Just follow the rule.
Click to expand...

What resistor values will you use to program?

Thanks

Bob
 
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