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OLD THREAD DAC End by Andrea Ciuffoli

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A

audiodesign

Banned
Joined 2005
Here distortion spectrum and noise of the DAC End 2.

The 50Hz peak at -62dB is present because I still have no chassie.
 

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apelizzo

apelizzo

Member
Joined 2006
gabanyayaya said:
So that meant no new parts or value need to be added, just reroute the solder track according to 6H6P spec right....




But what about the voltage? Do I need to reduce to 150V-0 , 0.2mA and 9v-0, 1.5A since I'm going to use 6H6P not E182CC or 5687 (250V 50mA/9v 3A)...?
Click to expand...

You only need to reroute the socket. Leave everything else the same. Because you preparing the bed for the 6n6P I recommend you to try the 6n6T which is a Chinese copy of the Russian 6n6P. The letter "T' is important and stands for Top quality. The Chinese 6n6 (without "T") most of the time has mismatch units inside the single tube. But the 6n6T be confident that the two units inside are matched. The sound of the 6n6T I believe is the best, I don't mean is the best quality tube, just the sound.
 
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G

gabanyayaya

Member
Joined 2008
adamus said:
looking at the datasheet no changes necessary. the curves are very similar to the 5687. Just the appropriate rerouting needed.

I would say though many people prefer the 6n6p running at more than 8ma. I like at least 15
Click to expand...

In the data sheet 6H6P needs around 28mA but I've seen people use up to 100mA for B+. Wont this be a waste....? What exactly the suitable traffo for 6H6P?
 
A

adamus

Member
Joined 2008
just run it the same as the 5687, it will be fine.

With the B+ at 270 audiodesign has picked a reasonable operating point, so unless you want to seriously change things then i would do as apelizzo suggests, and stick with same components. same transformer.

heres the datasheet

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

apelizzo

Member
Joined 2006
gabanyayaya said:
In the data sheet 6H6P needs around 28mA but I've seen people use up to 100mA for B+. Wont this be a waste....? What exactly the suitable traffo for 6H6P?
Click to expand...

As I agree with adamus,
6n6p, 5687, E182CC are all very close. So you don't need to change anything on the board unless you want to change setup.
So the 6n6p can handle max 20mA per unit when units are both working. With 100mA definitely will destroy the tube. Using 7.5mA each tube is not a waste. Remember that DAC is a source of signal and you need to keep the noise figure as low as possible. Low current through the tube reduces the noise and you still have low impedence output because the nature of the tube. The noise is generated by the amount of electrons hitting the plate in the same way when rain falls on a metal roof. If the rain is heavy the roof is noisier. Sometimes it rains and you cannot hear it. The tube is a "musical instrument" the sound also depends on how the plate vibrates when electron hit the surface. Caracteristic of the sound also varies with the current. So you need to find the balance, by experimenting, between noise figure and sound performance and the "sound of the plate".
I hope it helps.
 
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G

gabanyayaya

Member
Joined 2008
adamus said:
just run it the same as the 5687, it will be fine.

With the B+ at 270 audiodesign has picked a reasonable operating point, so unless you want to seriously change things then i would do as apelizzo suggests, and stick with same components. same transformer.

heres the datasheet

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


apelizzo said:
As I agree with adamus,
6n6p, 5687, E182CC are all very close. So you don't need to change anything on the board unless you want to change setup.
So the 6n6p can handle max 20mA per unit when units are both working. With 100mA definitely will destroy the tube. Using 7.5mA each tube is not a waste. Remember that DAC is a source of signal and you need to keep the noise figure as low as possible. Low current through the tube reduces the noise and you still have low impedence output because the nature of the tube. The noise is generated by the amount of electrons hitting the plate in the same way when rain falls on a metal roof. If the rain is heavy the roof is noisier. Sometimes it rains and you cannot hear it. The tube is a "musical instrument" the sound also depends on how the plate vibrates when electron hit the surface. Caracteristic of the sound also varies with the current. So you need to find the balance, by experimenting, between noise figure and sound performance and the "sound of the plate".
I hope it helps.
Click to expand...


Duly noted

Thanks both of you guys for the advice:)
 
apelizzo

apelizzo

Member
Joined 2006
Adamus,
today i received the new 5687 tubes. The heater power supply is not strong enough and I experienced the relay chattering because the regulator has not enough headroom so it passes AC.

Could you please measure your bridge rectifier AC input and the bridge DC output before the 2 power resistors. I can't believe this bridge becomes so hot and with 9.3V AC in gives 10.18V DC output , only x1.1 with 1.4A load (1.55V voltage drop on each 2.2R)

I'm not happy about the E182CC microphonics and I would like to test the 5687 if I can get rid of the issue. Can you give me your feedback about this issue. Appreciated

Thanks
 
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A

adamus

Member
Joined 2008
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.
 
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A

adamus

Member
Joined 2008
vac = 8.9
vdc after rectifier = 9
v drop over the power resistors = 0.9v
v after resistors = 8.1v

I am just within the regulation limits for the regulator. 6.5v out and its not regulating. 6.3 and it is. For reliability i should really remoe the power resistors completely, my ac line has horrible variation on it.
AC ripple on heater supply = less than 1mv

and my recitifer is HOT HOT HOT, i never tchecked this comp for heat, its go to be the hottest part. operating temp is upto 150c though.
 
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F

flocchini

Member
Joined 2004
Power Supply

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...

I am at the point of testing my supplies.

Adamus:

Did you change each of the 2.2R resistors to 1R?

Is the problem that 9V is not enough at the input?

Thanks

Bob
 
A

adamus

Member
Joined 2008
I did indeed. I would test it, and if you are having trouble regulating then jumper them out, or use a smaller value (0.5ohms).
1r 3w is ok (they dissapate 0.75w)

There is a larger than expected drop through the bridge on both my build and apellizo's

IF you dont have a scope then you'll have to look for ac ripple with a dmm, but the relay buzzing or chattering is a good indication you are out of regulation. My reg needs 1.5v to drop to regulation, hence it slightly marginal.
 
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E

Ekkeri

Member
Joined 2008
apelizzo said:
The heater power supply is not strong enough and I experienced the relay chattering because the regulator has not enough headroom so it passes AC.
Click to expand...

adamus said:
I sorted my chattering by dropping the 2.2r to 1r, and the 1k to 700r.
Click to expand...

What kind of transformer do you have? 9VAC & 3A? What regulators? LM338 have >2V voltage drop, LT1084 & LT1085 have only ~1V? Just wondering if I need to order more resistors.. Still waiting for the parts. Thanks.. :smash:
 
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