My heater voltage checks out fine. I think the output cap theory is correct. I will first go to a regulated B+ supply, and if I still have a problem I will reduce the capacitance.
1uF is the max recommended for coupling cap. Somewhere George(Tubelab) wrote a terrific post on why that is. IIRC it had to do with the corner frequency, saturation of the cap itself and time it takes to "recover" if I am describing it correctly. Also I think he went into why guitar amps tend to be 0.22uF or less and why hi-fi amps tend to be between 0.22 and 1.0uF.
I will try and dig it up...
JACKPOT!!!
I will try and dig it up...
JACKPOT!!!
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Thank You for all the help. I think the post is in:
http://www.diyaudio.com/forums/tubelab/177194-tubelab-se-coupling-capacitors.html
I will now reduce my output cap to 1uF. I expect all will be well.
http://www.diyaudio.com/forums/tubelab/177194-tubelab-se-coupling-capacitors.html
I will now reduce my output cap to 1uF. I expect all will be well.
All is well 1uF reduced the fluctuations to less than 0.2 mv under the high load impedance of my volt meter. I have also learned a new word "bias drift". Tubes are different but cool.😛
Indeed, after starting this hobby about 5 years ago I am still a complete noob but know enough to be dangerous!!!
Someone here has a cool signature..."Real amps glow in the dark"...
Someone here has a cool signature..."Real amps glow in the dark"...
Alright, I'm going to change my input tubes from 6CG7's to 6DJ8's, I need a little more gain.
The manual shows the R10 value but that looks to be in the output section.
If I look at the input section the only value that looks to change would be the R3 & R4 but the voltage suggested for R3 & R4 is at 150V.
I am running @ 290V w/ 7.3 mA to my 6CG7's, @ 300V the chart shows 8mA to the 6DJ8 but that is set by R10 which is in the output section.
Will my higher voltage (290 vs 150) @ the R3&4 change the values needed for R3&4?
Should I just plug them in and hope for the best?
There doesn't seem to be much listed for changes in the input tubes.
The short of it is that I want to run a 6DJ8 @ 290V on the input of my glassware Aikido 9-Pin All in One.
Thanks
The manual shows the R10 value but that looks to be in the output section.
If I look at the input section the only value that looks to change would be the R3 & R4 but the voltage suggested for R3 & R4 is at 150V.
I am running @ 290V w/ 7.3 mA to my 6CG7's, @ 300V the chart shows 8mA to the 6DJ8 but that is set by R10 which is in the output section.
Will my higher voltage (290 vs 150) @ the R3&4 change the values needed for R3&4?
Should I just plug them in and hope for the best?
There doesn't seem to be much listed for changes in the input tubes.
The short of it is that I want to run a 6DJ8 @ 290V on the input of my glassware Aikido 9-Pin All in One.
Thanks
SO.....for 6CG7 R10 @ 300V it shows about 83kR & 6DJ8 @ 300V it shows 87kR.
Since I'm mixing tubes should I just shoot for half?.....Say about 84.5kR?
Or does R10 only have something to do with the output tube (which is staying 6CG7) and I should leave it alone?
Since I'm mixing tubes should I just shoot for half?.....Say about 84.5kR?
Or does R10 only have something to do with the output tube (which is staying 6CG7) and I should leave it alone?
also you may want to consider 6n1p for the higher voltage... you must pay attention to the plate to cathode voltage very carefully for 6dj8 especially at higher voltages.
OK well.... I have already removed my 870R R3&R4 resistors and destroyed 2 of them in the process.
I will swap them out for my 470's that I have pulled or should I go 1k instead?
BTW my loaded B+ is 284V.
I will swap them out for my 470's that I have pulled or should I go 1k instead?
BTW my loaded B+ is 284V.
The manual shows Cathode R value for 6DJ8 between 100-330R but it doesn't say which R it is.
Pin 8 & 3 are cathode correct? That would mean R3&4 are the cathode resistors correct?
Should I go for somewhere around 200R then for R3&4?
Pin 8 & 3 are cathode correct? That would mean R3&4 are the cathode resistors correct?
Should I go for somewhere around 200R then for R3&4?
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The current by measuring the voltage across the cathode resistors. I=V/R
R=340
V=?
I= let's assume 10 ma
So you want about 3.4v dropped across the cathode resistor.
R=340
V=?
I= let's assume 10 ma
So you want about 3.4v dropped across the cathode resistor.
check out this post for an explanation of heater to cathode voltage.
But with 300v b+ and heaters at b+/4 or 75v above ground you will probably be OK.
You might want to consider trying to drop b+ to 250 or so.
But with 300v b+ and heaters at b+/4 or 75v above ground you will probably be OK.
You might want to consider trying to drop b+ to 250 or so.
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