Hi Gidu,
I still don't know why, but I implemented your mods (100R to ground on heating and a 3k res at input) and they appear to work.
The amp turned dead quiet, unless there is music, no hum or buzz. Very briefly during warm up a little hum, but gone after a minute.
Had to use the Chinese preamp tubes, because my Russian military tubes are rubbish. I have been told that they don't like AC heating. Then don't sell them as per 6sl7 spec, people!
Will see if I can find some decent Tungsol or EH!
Thanks your hints!
Cheers
I still don't know why, but I implemented your mods (100R to ground on heating and a 3k res at input) and they appear to work.
The amp turned dead quiet, unless there is music, no hum or buzz. Very briefly during warm up a little hum, but gone after a minute.
Had to use the Chinese preamp tubes, because my Russian military tubes are rubbish. I have been told that they don't like AC heating. Then don't sell them as per 6sl7 spec, people!
Will see if I can find some decent Tungsol or EH!
Thanks your hints!
Cheers
Hi DirkLeh !
I am glad to see that your buzz problem is solved !
As for me, i just replaced the ON/OFF switch by the Lorlin rotary switch i just got and it's perfect after having expanded the mounting hole ...
I also made some changes and improvements in the wiring (see pictures below).
But after I replaced the tubes, one of two EL34H Electro-Harmonix has failed ! Too bad ! So I replaced the Chinese EL34B waiting to order more.
Gidu
I am glad to see that your buzz problem is solved !
As for me, i just replaced the ON/OFF switch by the Lorlin rotary switch i just got and it's perfect after having expanded the mounting hole ...
I also made some changes and improvements in the wiring (see pictures below).
But after I replaced the tubes, one of two EL34H Electro-Harmonix has failed ! Too bad ! So I replaced the Chinese EL34B waiting to order more.
Gidu
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Hi!
Here are some pictures of my A9 BOYUU now fully operational:
The new tube 6CA7 EH instead of the Chinese EL34B :
And my actual hifi system (the CD player is fully diy, and the headphone too, but it is not visible on the picture ... see my signature !). The music player is based on MusicBee :
Gidu
Here are some pictures of my A9 BOYUU now fully operational:
The new tube 6CA7 EH instead of the Chinese EL34B :
And my actual hifi system (the CD player is fully diy, and the headphone too, but it is not visible on the picture ... see my signature !). The music player is based on MusicBee :
Gidu
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Yes, exactly ! Look here : Lecteur CD audio DiY Sorry, it's in French ...
But, there is no DAC Embedded.
Gidu
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Hi!
Here is my last mod : I have set up a 470 microfarads / 40 Volts capacitor in parallel to the cathode resistor of each 6N9PJ tube.
It is strange that this capacitor is not present on the original schematic, because almost all of the schematics that I found on internet show that capacitor ...
The listening benefits are very sensitive : the input stage has a higher gain and the frequency response seems more linear to me, including bottom spectrum with substantially low frequencies.
Here are pictures of the mod :
And here are all mods that i done :
Gidu
Here is my last mod : I have set up a 470 microfarads / 40 Volts capacitor in parallel to the cathode resistor of each 6N9PJ tube.
It is strange that this capacitor is not present on the original schematic, because almost all of the schematics that I found on internet show that capacitor ...
The listening benefits are very sensitive : the input stage has a higher gain and the frequency response seems more linear to me, including bottom spectrum with substantially low frequencies.
Here are pictures of the mod :
And here are all mods that i done :
Gidu
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YESTERDAY BUILD 2X17W
An externally hosted image should be here but it was not working when we last tested it.
MU is 70 for valve Driver ,att 5HZ -01 Db , use the calculator , i have done the amp , besides the 3,3k on Driver i use 5,6k for EL34 , B1 for one chanell draws about 47 DC mA , cathode 23,7v , on PSU I Used 2x100k Resistors paralell to capacitors, for soft turn on. (bleed R), Com for the output transformators are isolated (hum problems), finaly avoid ground loops , i mean the shield cable has to ground only att one side otherwise it makes hum.
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bypassed capacitotr on driver i used 80uf ( CALCULATOR ) ,the driver data Mu Gain is:70 , Besides 3,3k on driver i use 5,6k for EL34 , I DONT Earth the COM of my output transformator ( Avoid HUM) , on PSU I put parallel with capacitors 2x100k (soft run), then to avoid ground loops i use 27R 5W end 0,1 uf , ground to chassis (safety and hum ), for Shield Cables , ground only one side , not both ends of shield, the B volt , one chanell Draws about 47ma / 325v , catode (el34) 23,7v , the artificial tap att 6,3v with 2X100ohm 1w, ( eatch one draws 39ma) and 3w for the EL34 heaters
Hi !
This calculator is very interesting, but what's the downside of having a higher value than that indicated by the calculator for decoupling capacitor resistance cathode of 6SL7, ie 470 microfarads instead of 80 microfarads ?
Gidu
What would be the required voltage rating of the caps for this application? With two 1000uF in reverse series, this can become quite bulky in the enclosure!
Thanks!
