I bought a TVA-10 a couple of years ago, soon after I renewed my interest in tubes. It was a bit lack lustre in performance, which is down to its age - I could see the cap for bias adjustment was bulging, and the output tubes are probably ripe for replacement.
I confess I am in awe of this amp, and hence it has been gathering dust so I can acquire more skills, renovating some old Quad 2’s, for example.
For safety’s sake I do intend to replace the electrolytics - they are getting on for 50 years old now. I have been considering some minor mods to improve ruggedness, and was wondering what others think.
I am very keen on Patrick Turner’s writings, and he uses a simple warning system to monitor cathode current balance in tube pairs. If there is a significant difference, then a run away tube is suspected, and power is disconnected. I planned to fit that monitoring, with some sort of bias balance circuit between the channels. Then I can just use closely matched pairs of tubes, which feels more of a realistic goal than having 4 tubes that need to stay in alignment for their lifetime.
At the risk of incurring the wrath of Tim, is that gilding the lily?
I confess I am in awe of this amp, and hence it has been gathering dust so I can acquire more skills, renovating some old Quad 2’s, for example.
For safety’s sake I do intend to replace the electrolytics - they are getting on for 50 years old now. I have been considering some minor mods to improve ruggedness, and was wondering what others think.
I am very keen on Patrick Turner’s writings, and he uses a simple warning system to monitor cathode current balance in tube pairs. If there is a significant difference, then a run away tube is suspected, and power is disconnected. I planned to fit that monitoring, with some sort of bias balance circuit between the channels. Then I can just use closely matched pairs of tubes, which feels more of a realistic goal than having 4 tubes that need to stay in alignment for their lifetime.
At the risk of incurring the wrath of Tim, is that gilding the lily?
20ufd/120vac film caps is what i used to replace the old swollen cap...if i can find 22ufd/630vdc caps that will fit,i will use them in place of the ecaps used in this amp..
i also reduced the grid leaks to the power tubes from 470k to half of that...
yes a matched quad is a must when using in this amp...years ago I purchased a quad of JJ6L6GC's and i was amazed to find out that they indeed biased exactly the same up to the first decimal digit....i hope the quad JJEL34's i got from the same vendor biased the same...
i also reduced the grid leaks to the power tubes from 470k to half of that...
yes a matched quad is a must when using in this amp...years ago I purchased a quad of JJ6L6GC's and i was amazed to find out that they indeed biased exactly the same up to the first decimal digit....i hope the quad JJEL34's i got from the same vendor biased the same...
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