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OLD THREAD DAC End by Andrea Ciuffoli

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apelizzo

apelizzo

Member
Joined 2006
adamus said:
I sorted my chattering by dropping the 2.2r to 1r, and the 1k to 700r.



Try just dropping less through the resistors, or get rid of them entirely and jumper, just watch the heat on the reg.

Edit - just noticed i misread your post. I'll whip the cover off and measure for you. Give me ten mins.
Click to expand...


Many thanks Adamus for your info,

I used E182CC and the PSU was fine but as you see 5687's heater is much more hungry.

Have you employed 5687 for your DAC? Do you experience microphonics?
E182CC is bad for that.

Please after half hour on and while is on please give "little slaps" to the tube with your finger nails and listen if the noise comes out from your speakers.
If I do that with the E182CC I can hear it.
 
A

adamus

Member
Joined 2008
apelizzo said:
Many thanks Adamus for your info,

I used E182CC and the PSU was fine but as you see 5687's heater is much more hungry.

Have you employed 5687 for your DAC? Do you experience microphonics?
E182CC is bad for that.

Please after half hour on and while is on please give "little slaps" to the tube with your finger nails and listen if the noise comes out from your speakers.
If I do that with the E182CC I can hear it.
Click to expand...

jan phillips 5687wb = not microphonic in my case

I also have some RCA 5687's, and one is badly microphonic.

If you fancy doing some board surgery, with the 6n6p you could take a sledge hammer to it and not worry about microphonics, they are super sturdy
 
A

adamus

Member
Joined 2008
**LED bias mod**

I found the dac ever so slightly 'soft'. incredibly natural but just softer than the dacmagic.

so mod time...

Pull out the 470r cathode resistors
pull out the bypass caps, including the film

Match cheap yellow or green leds to 3.8v for two in series (9v battery > 1k2 resistors > led, measure voltage over led, look for closest to 1.9v, then test them in series too for 3.8.

Solder in led units in place of 470r, led anode (long leg) nearest tube.


An externally hosted image should be here but it was not working when we last tested it.

switch on and you'll see them start to glow once the tube is warm.

Have a listen.....

to my ears, and in my opinion only, this has lifted a veil and turn this dac into a better beast. It now easily beats the dacmagic in everty department. Remember in a previous post i said the bass was big and almost too much? with the LEDs in place, the bass is still deep, but its more controlled.

Dont forget, with leds the dynamic impedance is a lot lower than the resistor, but we had the resistor bypasses, hence no negative feedback. The non-bypassed leds will be injecting a tiny amount of negative feedback. My guess is distortion will decrease because of this, hence the feeling of better bass control.

is it for everyone? maybe... if you are after that oldschool tube sound then stick with the resistor and lytics as a bypass. Want something with a bit more bite? LEDS. its not a subtle difference in my opinion.
 
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apelizzo

apelizzo

Member
Joined 2006
Adamus,

Very interesting mod. How did the mod affect the sound stage. As per personal taste I like large deep liquid sound stage with all details but not aggressive.

Also with regards to the bass what electrolytic caps did you use next to DAC chip, Oscon or something else?
 
A

adamus

Member
Joined 2008
Its such a quick mod i would have a go yourself and evaluate.

I tried oscons and panasonic FC's. I actually preferred the FC's. With the caps in place the sound was big and warm, with good depth but imho lacking sparkle.

LED's you loose some of that warmth (its still just on the warm side), but the sparkle is back, highs seem to go that little bit higher. Its not aggressive (i dont think you could make the ad1865 aggressive) but the detail is easier to pick out. I personally found the dac slightly too warm with the caps, it made me pull my speakers further from the wall to reduce bass a bit. bypass caps can have a big effect, i learned this building the baby huey el84 valve amp. I even went the lengths to try blackgates (££).

with LED's dare i say the soundstage width increases a little, that added 'air' just seperates things a bit.

its interesting, when i see you say 'large deep liquid' i equate that to some degree of softness, not sure if thats what you mean to imply?

I genuinely believe this has taken the dac up another level. Just listening to some of my favourite tracks. Cello's are simply stunning through it!
 
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A

adamus

Member
Joined 2008
agithegreat said:
I'm struggling to find suitable heat sinks for the salas board.

Can anyone recommend me any?
Thats all i need now and then i'm done too. :)
Click to expand...

you will be ok without for testing. They dont seem to get that hot if you stick to 27ohms.

i used these, just because i had them..
Rapid Electronics - Electronic Components

The pins didnt fit perfectly so i just drilled the holes slightly bigger.

i am very happy with the dacs performance now. with the led mod its very very pleasing to my ears.
I am bulding a couple of drop in CSS modules too ( cascode depletion mosfets) to test. will report back
 
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Ekkeri

Member
Joined 2008

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Agi

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