With a fresh head and a new set of eyes I found my first wiring problem.
I don't know why I didnt check myself, because it did seem a different pinout to a normal ECC83.
JJ ECC803S / 12AX7
Should be 1 and 6 cathodes
3 and 8 anodes.
Pretty sure the ECC803s' ive been using will be damaged now, but they are easliy replaceable. I hope there is no other damage done.
At least we have progress!
Charlie
OK, what if there was a -55V supply to feed the cathodes of the input stage 12AX7? If I figure on 0.6 mA per triode, and use a 47k resistor for the tail resistor, do you think that arrangement would compromise the performance of the input stage by orders of magnitude compared to the CCS in the tail?
I know the CCS would be a better solution, just looking for something easy and super-reliable to start with, and this post gave me the idea...
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Everything seems to up and running. However i think there is a slight issue with one of the ccs' as I cant match the anodes.
As for the bias, one is pulling about 74mA, and the other about 82mA. What will be the best solution to match these? Should I be looking to change the screen resistors so both sides match up?
Cheers
Ahh sweet music.
It's all up and running, still needs a few tweaks - need to lower the HT a little more as the el84s are running at about 40mA (too high?) and a little hum, think heater wiring maybe seeing as im using a choke for the HT.
Im not sure I can drag it away from my record player at the moment though...
As for the sound. It would be unfair to judge it against my other BH, becasue this one uses better transformers but I am very impressed. The sound is very detailed and clean. And the dynamics are far superior! I love it! As for the RLD bias, it looks like my amp has neons. Very cool.
Many thanks to all for helping me, ill post a picture here soon.
Cheers
Charlie
It's all up and running, still needs a few tweaks - need to lower the HT a little more as the el84s are running at about 40mA (too high?) and a little hum, think heater wiring maybe seeing as im using a choke for the HT.
Im not sure I can drag it away from my record player at the moment though...
As for the sound. It would be unfair to judge it against my other BH, becasue this one uses better transformers but I am very impressed. The sound is very detailed and clean. And the dynamics are far superior! I love it! As for the RLD bias, it looks like my amp has neons. Very cool.
Many thanks to all for helping me, ill post a picture here soon.
Cheers
Charlie
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a growing family
Hi Rongon,
Hard to beat the simplicity of a resistor.
Can't see any point in deliberately increasing the resistance and then supplying the negative voltage to compensate. Others more knowledgable might disagree. No harm in trying out your idea to hear the difference.
In the past I've played about with cathode resistor substitutes. I started with ordinary diodes, led's. an LM314 regulator and finally Gingertubes ccs. To my ears Gingertubes ccs made the most noticeable difference even though I used non exotic caps.
The thrill of building your own gear is you get to tweak