This from manual of operation
Many time ago when I started to select the audio tube with Avo plus other tester this test was very important; each tube under 10 Mohm was eliminated because this paramenter tend to go low with the use due a low quality of build: In the time of early Chinese tube this was a problem; less with the russian. But also with the Nos also Nib. Someone remember Gold Aero; some trouble with them in the lasts time.
And every time I found a hum ( signal and power tube) most of the tiem was the low insulation when used the ac filaments
The the elevation, in every case is done if you are close to the limit; I have some equiments running from 2000 with dc and ac filaments without any type of problem with the perfromance quite well.
Many time ago when I started to select the audio tube with Avo plus other tester this test was very important; each tube under 10 Mohm was eliminated because this paramenter tend to go low with the use due a low quality of build: In the time of early Chinese tube this was a problem; less with the russian. But also with the Nos also Nib. Someone remember Gold Aero; some trouble with them in the lasts time.
And every time I found a hum ( signal and power tube) most of the tiem was the low insulation when used the ac filaments
The the elevation, in every case is done if you are close to the limit; I have some equiments running from 2000 with dc and ac filaments without any type of problem with the perfromance quite well.
How did we forget that pile of observations?
http://tubebooks.org/technical_books_online.htm
http://tubebooks.org/Books/Atwood/RCA 1962 Electron Tube Design.pdf
CAUTION 86MB PDF file
For a sampler, here's 7 pages from that section. 600KB PDF
Returning to this thread. The amp for which I used the suggestions in this thread works nicely and am happy with the results.
Moving on, I am building a phono-stage and would like to elevate the heaters about 50V, I understand how to accomplish that but I'm wondering if I can just elevate the center tap of the remote heater transformer which would be easy since the while power supply will be there instead of the output of the DC boards (difficult as I forgot to plan for this
) with equal results?
I am using D3A and 5687 tubes.
Moving on, I am building a phono-stage and would like to elevate the heaters about 50V, I understand how to accomplish that but I'm wondering if I can just elevate the center tap of the remote heater transformer which would be easy since the while power supply will be there instead of the output of the DC boards (difficult as I forgot to plan for this
) with equal results?I am using D3A and 5687 tubes.
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yes, just elevate the c.t.
Whilst a few uF are enough to provide an RC filter to the heater elevation voltage divider, there maybe some further benefit in using larger capacitance to reduce possible common mode l.f. noise riding through on the heater supply transformer winding, especially if you are not using a CMC.
Whilst a few uF are enough to provide an RC filter to the heater elevation voltage divider, there maybe some further benefit in using larger capacitance to reduce possible common mode l.f. noise riding through on the heater supply transformer winding, especially if you are not using a CMC.
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I’ve seen audionote Japan use at least 100uF with a film cap in parallel. I’d expect law of diminishing returns beyond that.
Thanks, just to confirm we are on the same page - I can elevate the 6.3V transformer CT and that will elevate the output from the DC boards? The fact that I'm using regulated DC boards was sort of buried in my initial text.
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That's interesting. I built an identical phono stage and did not elevate the heaters and its been working fine for 7 years with daily use. I wanted to improve things with this pre-amp but longevity wasn't necessarily one of those things
Appreciate the help tremendously!