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OLD THREAD DAC End by Andrea Ciuffoli

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#1,422
Problematic I/V stage PCB

Hi quanghao,

I looked at ksnider1's I/V stage PCB that's clean with crispy copper traces and examined mine that arrived this morning. Why is mine so dirty and masked by something unknown, and the ground plane near R32/R33 is extremely deformed and distorted?

😱 😕
 

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#1,427
erwincantona said:
Just sharing

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


My friend uses Nelson Pass D-1 (replacement for Supply + IV Stage) for my DAC End 2.
But it hasn't worked well. He said the problem is on D-1.
(He'll find what really happened later)
Sound output ( Right and Left channel) isn't at the same level.
Click to expand...

After replacing IRF610, previous problem is gone...
now DAC sings equal volume at right & left channel

After 1 hours play few songs, the result (compare with just DAC+Salas Shunt):

soundtage get wider
thick vocal
low and high get more extend

But..... voice sounds a little bit stiff. Need more time to break in?
 
#1,428
Nice. Seems D1's I/V is an alternative to the tube I/V.

Thanks. Would like to hear further progress.


erwincantona said:
After replacing IRF610, previous problem is gone...
now DAC sings equal volume at right & left channel

After 1 hours play few songs, the result (compare with just DAC+Salas Shunt):

soundtage get wider
thick vocal
low and high get more extend

But..... voice sounds a little bit stiff. Need more time to break in?
Click to expand...
 
#1,430
I have altered my unit so that it is now using Welborne's PS10 power supply. It is regulated and uses no electrolytics. 267 volts to I/V board with 105V on the plates. I have listened for a couple of hours and believe the DAC has more punch and dynamics. Could me my head playing tricks but I am going to keep it this way for now.

Enjoy

Bob
 
#1,432
fredlock said:
Hi CustomHT,

I have the same transformer as yours, R80-36. I haven't connected yet since I'm still waiting for parts that I ordered.

This is how I will connect it

You have 2 center tap 3.15V/3A per winding, Gray, Black Gray

You have 1 center tap 2.5V/3A per winding, Blue, Brown, Blue

To make it 8.15V for the heater filament, you only need the 2 Blue wires, ignore the Brown wire just insulate the end of it. That gives you 5Vac/3A. Then connect one of the blue wires, to whichever 3.15V center tap you want to use, to Gray wire and the black wire will be 0V reference. Measure it with the voltmeter and if you don't get 8.15V, you might want to reverse the connection of black and Gray, as what housing had mention earlier. It might be out of phase. You were also asking if you can parallel the 3.15V winding. I think you can but this will become 6A which I don't recommend.

In regards to the 260Vac, I think you can parallel the winding to achieve the maximum current rating, tie up Green and Green wire and orange will be your 0V reference.

Let's consult with the veterans here. Guys, correct me if I'm wrong. I'm just trying to help CustomHT. I know he asked this question like 3 times already and nobody had given him a detailed answer of the transformer connection.

Thanks,
Fred
Click to expand...


Thanks for you advice..

I've managed to get the 9v input right now, but I'm thinking I may have something wrong on the 260Vac side (maby in the IV power supply?) as I've tried both green / orange and violet / orange which both show required voltages when not connected to the IV stage power supply. Once connected to the power supply the r-core trannie starts humming and the power supply is not outputing any voltage, so turned it off quickly..

Any suggestions?
 
#1,436
adamus said:
you cant parallel the 260, it is centre tapped, not dual secondaries. You are just shorting it. HOpefully the secondary survived, just connect one of the 260v and the CT as 0.
Click to expand...

I thought I had been using the CT? or am I getting confused?
The trannie is 260v (green) 230V (violet) 0v (Orange) 230V (violet) 260v (green).. I had been using the green and the orange wire for 260V?
Is this wrong?

Cheers in advance.
 
#1,439
CustomHT,

I don't have the regulator board, I have the HV shunt supply PCBs only.

Don't populate the 4 HV rectifiers and the 4 snubber capacitors on your board. Instead solder the center tap to a plate-thru' via connected to the -ve pole of C5 (100uF/450V) and the rectified HV to a plate-thru' via connected to the +ve pole of C5.

In such case, you can use the full 200mA capacity of the transformer.
 
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