Thats a weird glich, no wonder no one was responding......
okay, well I am currently constructing an EL84 SE amplifier, and I am using an LM317 as a CCS for biasing each tube (one LM317 per channel) and I wanted to know what would happen if I didn't bypass them with capacitors, I have seen several CCS bias designs that do not use bypass capacitors (none of them SE), and I wanted to know what the DIY Audio community thought.
-Moose
okay, well I am currently constructing an EL84 SE amplifier, and I am using an LM317 as a CCS for biasing each tube (one LM317 per channel) and I wanted to know what would happen if I didn't bypass them with capacitors, I have seen several CCS bias designs that do not use bypass capacitors (none of them SE), and I wanted to know what the DIY Audio community thought.
-Moose
I have seen several CCS bias designs that do not use bypass capacitors
Please post some schematics or links.
The design I am making is this
I have mostly seen non-bypassed designs on Push-pull stuff, but I did not know if it would carry over, here are some designs that do not include it
http://www.diyparadise.com/buildel84b.html
and
http://www.diyaudio.com/forums/showthread.php?s=&threadid=72536&highlight=baby+huey
I have mostly seen non-bypassed designs on Push-pull stuff, but I did not know if it would carry over, here are some designs that do not include it
http://www.diyparadise.com/buildel84b.html
and
http://www.diyaudio.com/forums/showthread.php?s=&threadid=72536&highlight=baby+huey
In the case of Baby-Huey:
On general schematic is drawn a "bias block". On the second page we notice the bias block in detail. It has the actual CCS (the 2 tranzistors + rezistors) and the bypass capacitors (4700uF+470uF+1uF) parallel for good frequence response. This is a good practice.
In your case you have to bypass the LM317 based CCS in a similar way
On general schematic is drawn a "bias block". On the second page we notice the bias block in detail. It has the actual CCS (the 2 tranzistors + rezistors) and the bypass capacitors (4700uF+470uF+1uF) parallel for good frequence response. This is a good practice.
In your case you have to bypass the LM317 based CCS in a similar way
The case of Simple EL84 is a litle special. We have an auto phase invering final stage. We notice one valve grid is grounded. In this case the CCS must be NOT bypassed. The signal for the lefthand pentode is applied on grid and for the righthand pentode is applied in cathode. Search the net for "long tail pair" for more details. http://www.aikenamps.com/LongTailPairDesign.htm
I have just built a El84SE using an LM317 in lieu of the cathode bias resistor.
The voltages are correct, but the amp is mute...any idea?
Pin 1(adj) is grounded; 23.2 ohms from Pin 2 (Vout) to ground; Pin 3(Vin) is tied to the El84 cathode.
I have read in this thread that the LM317 needed to be bypassed, what is the cap value and do I connect it from Vin (pin 3) to ground?
Your help is much appreciated.
The voltages are correct, but the amp is mute...any idea?
Pin 1(adj) is grounded; 23.2 ohms from Pin 2 (Vout) to ground; Pin 3(Vin) is tied to the El84 cathode.
I have read in this thread that the LM317 needed to be bypassed, what is the cap value and do I connect it from Vin (pin 3) to ground?
Your help is much appreciated.
kooltubes said:I have just built a El84SE using an LM317 in lieu of the cathode bias resistor.
The voltages are correct, but the amp is mute...any idea?
Pin 1(adj) is grounded; 23.2 ohms from Pin 2 (Vout) to ground; Pin 3(Vin) is tied to the El84 cathode.
I have read in this thread that the LM317 needed to be bypassed, what is the cap value and do I connect it from Vin (pin 3) to ground?
Your help is much appreciated.
Your ccs is correct, you also have 50ma .As to the bypass caps. U can try it out any value from 47 -470 . U may also want to try higher current, its sound sweeter. Try 12R its tasty.
Thanks SINGLEENDED.
Amp works fine. I have used different cap values but 100mf sounds better to my ears.
I have also added 22mf betwwen Vout (pin 2) to ground, the soundstage seems to be scaled down.
I am confused about your suggestions to run the El84 at 104ma using a 12R resistor
Amp works fine. I have used different cap values but 100mf sounds better to my ears.
I have also added 22mf betwwen Vout (pin 2) to ground, the soundstage seems to be scaled down.
I am confused about your suggestions to run the El84 at 104ma using a 12R resistor
kooltubes said:Thanks SINGLEENDED.
Amp works fine. I have used different cap values but 100mf sounds better to my ears.
I have also added 22mf betwwen Vout (pin 2) to ground, the soundstage seems to be scaled down.
I am confused about your suggestions to run the El84 at 104ma using a 12R resistor
When u feed more current . First the vocal sound thicker. Than u have better soundstage. Get rid of the 22mf in pin 2 not required it will create different sound, best if we do not use caps at all but cant help it as we need it here & there .I have tried it with value from 65 - 100ma and i think it sound best at 100ma.
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