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HQ-IV tube output balance DAC

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quanghao

quanghao

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Joined 2009
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Ryssen

Ryssen

Member
Joined 2003
quanghao said:
Ryssen said:
The DAC is playing (AK4490) allthow the gain is a little to high...
But I must ask again the delay for the relay is waaay to long.....How long is it for you other that have built this?

Hi!

C9 late on duty close to the relay, avoiding audible speaker.

Closing time lag depends on the capacitor C9.

470uF: closing delay of about $ 30.

680uF: closing delay of about $ 45.

very good time for most of the pre tube.

thank you
Click to expand...

I´ve changed the UPC1237 to another one and c9 1uf and I get about 1 minute,all components seems right.
excxept I use +F and-F 6,3v instead of 12,6v does it matter for the upc 1237?
Click to expand...
 
Ryssen

Ryssen

Member
Joined 2003
Those of you who built the tube output board,what DAC are you using and how is your gain?
The reason I´m asking is I get a little noise (when music not playing) in my 6E6p -->SE EL36 amp and the gain is way to high,I use the Squeezebox Duet and its volume control.I can bearly touch the volume before it gets to high..
How have you managed this? :scratch:

Edit:I use ECC88 and 12BH7
 
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R

RollE2k

Member
Joined 2007
Ryssen: If you are using AK4490 as you told before that is the problem. Because all info i find by googling around is that AK4490 is a voltage output dac, not a current output as this this output stage is supposed to be used with. So your dac shouldn't even use a I/V stage, just a buffer, if anything.
 
M

mvictor69

Member
Joined 2015
I know it has been sometime, but I have managed to populate the boards. I stii have the same problem as PASSIVE420 with the Power supply. The lv is working, but the 12V I can get is in the edge of the trimmer (I am using the LT1764 regulator). For the HV parte the only output I can get is 154VDC, with 220VAC input. Also the trimmer doesn't seem to modify anything. Passive420 how did you manage with the power source? Thank you.
 
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M

mvictor69

Member
Joined 2015
mvictor69 said:
I know it has been sometime, but I have managed to populate the boards. I stii have the same problem as PASSIVE420 with the Power supply. The lv is working, but the 12V I can get is in the edge of the trimmer (I am using the LT1764 regulator). For the HV parte the only output I can get is 154VDC, with 220VAC input. Also the trimmer doesn't seem to modify anything. Passive420 how did you manage with the power source? Thank you.
Click to expand...

I cannot edit the post once more so I post again
I have solved the two problems
For the HV section I had a problem with LM 317. It was somehow out of order. Changed it and the HV part worked as expected.
For the LV part I had to change R13 from 220R to 10k and after this I could fix the LV output to 12V or any other value.
 
J

jonwhitear

Member
Joined 2014
I've just been troubleshooting a low filament voltage, and (quite separately) discovered that the left and right channel input labelling is inverted on different sides of the IV board, i.e. what's labelled left on the bottom is labelled right on the top. Just noting that here in case it catches anyone else out.
 
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