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Old 1st March 2010, 10:28 PM   #981
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Quote:
Originally Posted by adamus View Post
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.

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.
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Old 2nd March 2010, 05:25 AM   #982
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I show some member still need PCb of DAC so ,I will make about 10 set DAC_end 2, If you like you can write please!
thank you.

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Old 2nd March 2010, 08:08 AM   #983
Ferrari is offline Ferrari  Netherlands
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Old 2nd March 2010, 09:01 AM   #984
adamus is online now adamus  United Kingdom
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Quote:
Originally Posted by apelizzo View Post
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.
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
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Old 2nd March 2010, 10:58 AM   #985
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*******( ( ( ( E182CC MICROPHONICS ) ) ) )*****

Quote:
Originally Posted by adamus View Post

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
hahaha, I like it, yes it's true. Russian stuff!!
I will try Mrs JAN 5687WB first and if it doesn't work... surgery time.

Last edited by apelizzo; 2nd March 2010 at 11:05 AM.
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Old 2nd March 2010, 11:41 AM   #986
adamus is online now adamus  United Kingdom
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Default **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.


Click the image to open in full size.
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.

Last edited by adamus; 2nd March 2010 at 12:04 PM.
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Old 2nd March 2010, 12:24 PM   #987
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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?
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Old 2nd March 2010, 12:30 PM   #988
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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!

Last edited by adamus; 2nd March 2010 at 12:44 PM.
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Old 2nd March 2010, 05:14 PM   #989
toufu is offline toufu  United States
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Old 2nd March 2010, 09:16 PM   #990
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