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HQ-IV tube output balance DAC

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#24
I think my past among the first ones has been lost somewhere.

So adding me once more and would he good to review the whole thread to make sure no one else is lost

1. adeveza :1PCB
2. apnneto :1PCB
3. goldkenn: 1PCB
4. AR2: 2 PCB
5. Brooksl2: 1PCB
6. mvictor69: 1PCB
7. jonwhitear: 1PCB
8. rredline : 1PCB
9.aradan 2x sets of dac and psu
____________________
Total : 11

Sent from my ONE A2003 using Tapatalk
 
#28
Hello Quang Hao,
What is the gain of the tube stage and can it be modified, lets say to 5-6. I want to use 1 Ohm to ground from balanced outputs of dac and use (beyer dynamic 370 215) step-up transformer 1:30, and 5-6 gain in tube stage.
Thanks and best regards
Arda
 
#29
Quanghao please add a muting relay with switch on delay (and fast turn off) to avoid burnt woofers and/or a defective power amp. At least do it to avoid annoying switch on and switch off bumps in case one switches the wrong device off first which is the DAC + output stage.....

Also please change LM317 for filament power to a modern LDO regulator (way less energy thrown away as useless heat !! ). There is really no excuse to use LM317 for filament power nowadays. It needs minimum 3V over itself to function properly which gives insane levels of dissipated power and a very large heatsink. You see, useless heat = shorter life. So you will need 6.3V + 3V = 9.3V at the input of a LM317 as an absolute minimum. Add ripple voltage and a safety margin (LM317 needs at least 3V differential voltage) to that and multiply the total voltage with the current to see how much power the reg needs to dissipate.

With 2 x ECC88 you will need to supply 0.73 A. This, combined with the high input voltage of at least 11V, is asking for trouble and not proper designing.

Transformer voltage should be tuned to the voltage of LDO regs if you go that way. A 6V transformer works OK with LT1764 regs that only need 0.34 V over themselves to function properly.
 
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#30
Correction:

jean-paul said:
...and multiply the total voltage over the regulator with the current to see how much power the reg needs to dissipate.
Click to expand...

I understand "inexpensive", I don't understand leaving out necessary options or component choice for LM317 and a more expensive heatsink. Using tubes/valves to make an output stage wil result in high costs anyway so why not make it a complete well-thought-out design ? For a few $ more it is protected against destroying speakers that cost way more than that...Please think of the design ending up in a home with untrained users. Please avoid possible user errors, certainly when daddy uses a solid state power amp. He will thank you for that 🙂
 
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#31
Ardahan said:
Hello Quang Hao,
What is the gain of the tube stage and can it be modified, lets say to 5-6. I want to use 1 Ohm to ground from balanced outputs of dac and use (beyer dynamic 370 215) step-up transformer 1:30, and 5-6 gain in tube stage.
Thanks and best regards
Arda
Click to expand...

in this IV tube , so you can use R IV = 47 R to 100. the gain can go up to 2 vrms .

but i test many times, i see ES9018 with this IV is not good when use i-out.
the Bass is heavy.

better fỏ sound, and i love, i not use R IV. and tube IV not need preamli after DAC

thanks
 
#35
That B+ volage will be at the output when switching the device on. That is why I advise you to use a muting relay with a two color LED and let it mute the outputs for the time the valves/tubes need to settle. Flashing red LED when muted and green LED when unmuted.

LT1084 is a good choice but it still needs at least 1V differential. You can get better LDO regs for this purpose as mentioned before. Please think of standard transformer voltages which will likely be 6V AC.....so the lower the drop out voltage the more likely it will be you can use 6V transformers (and not 9V !)
 
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#36
jean-paul said:
That B+ volage will be at the output when switching the device on. That is why I advise you to use a muting relay with a two color LED and let it mute the outputs for the time the valves/tubes need to settle.
Click to expand...

yes yes, i always have relay for slow turn on out put with deign Tube.

but in this case i use UPC 1237 for it!

thanks your advance
quanghao
 

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#38
Hi Quanghao,

1 board for me, please

1. adeveza :1PCB
2. apnneto :1PCB
3. goldkenn: 1PCB
4. AR2: 2 PCB
5. Brooksl2: 1PCB
6. mvictor69: 1PCB
7. jonwhitear: 1PCB
8. rredline : 1PCB
9.aradan 2x sets of dac and psu
10.vasillis 2x dac+ psu
11. Ardahan: 1 PCB
12. frankwilker: 1 PCB

thank you
 
#39
Hi Quanghao,

3 boards for me, not 1, please update as follow

1. adeveza :1PCB
2. apnneto :1PCB
3. goldkenn: 3 PCB
4. AR2: 2 PCB
5. Brooksl2: 1PCB
6. mvictor69: 1PCB
7. jonwhitear: 1PCB
8. rredline : 1PCB
9.aradan 2x sets of dac and psu
10.vasillis 2x dac+ psu
11. Ardahan: 1 PCB
12. frankwilker: 1 PCB

thank you
 
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