Good Day all,
I am a newbee at building tube amp as well and the wonderful advice and ideas in this place is sure "goldmines" for me. Thank you.
I would like to find out do you mean by for example "then add the B+ when everything is warm to avoid cathode stripping. and "The plate B+ in amps. What does this B+ means or referring to.
The other question is the device know as 'Choke". In my faint memory, choke mean an inductor. and where do this device is place usually in a amplification circuit?.
Thank you in advance for your precious advises.
I am a newbee at building tube amp as well and the wonderful advice and ideas in this place is sure "goldmines" for me. Thank you.
I would like to find out do you mean by for example "then add the B+ when everything is warm to avoid cathode stripping. and "The plate B+ in amps. What does this B+ means or referring to.
The other question is the device know as 'Choke". In my faint memory, choke mean an inductor. and where do this device is place usually in a amplification circuit?.
Thank you in advance for your precious advises.
My 2 cents are:
The B+ is hi voltage supply that is applied to the output plate or anode.
The B+ name came from the first tubes equips(1920s??)where there were no power supply, just a Battery, hence the B+ name.
The choke may be inserted before a power tube to drive it or in a power supply;
You're gonna have to get used to some archaic terminology. "B+" referrs to what would now be "Vpp" -- the main DC rail. Back in the really olden times, you didn't have mains operated power supplies. You had batteries: "A" batteries supplied heater or more likely filament power. "B" batteries supplied the main DC rail voltages. "C" batteries were used for grid bias.
Two places: most commonly, in the power supply as part of the ripple filter: an LCR LPF. Chokes are also sometimes used as passive plate loads.
There was once a thread somewhere on the Audio Asylum about this , started by somebody who had experimented with heater and filament voltages and found that starving them a little would make improvements in noise and/or distortion numbers. He charted his results.
I looked for the thread yesterday but couldn't find it quickly - there're too many hits to make it a quick search.
At the time I gave it a try and found that the results were variable by tube type and also individual tube construction and also individual tube, to the degree that I gave it up thinking that if you had to retest for optimum level for every tube used, it would be better to spend the time learning about circuit details that had more benefit and were more dependable. For one thing , I remember that the level of noise went up and down as the voltage was changed , not a linear ramp in one direction or the other - meaning that there was a spot on lowest noise voltage for each and every heater that had to be tested to be determined. ChrisA's approach seems to be the most sensible if you are going to work with lowered fil/heater V as a general practice.
One other thing though. I do remember seeing it written somewhere - a data sheet, I believe - that low voltage was also to be avoided. They were specific about staying inside the bracketed range. I'm sorry, I don't remember what that tube sheet was.
Here's a post of some interest. In addition, you can turn up a ton of stuff if you search the AA's tube diy forum using "starved fil" or starved heat" in the exact match blank. A lot of opinion and BS there but there are a few knowledgable people's posts as well.
At anode currents of less than about 1mA reduced heater voltage nearly always reduces noise, but at higher current the opposite happens. This behavious is pretty darn consistent between different triodes. We're only talking a dB or two difference, though.
Hi all,
I had read from several places about tube amp running at ultra "ultralinear"mode and triode mode. I am confused even after reading so much on this topic. your precious experiences and knowledge is much appreciated.
I had read from several places about tube amp running at ultra "ultralinear"mode and triode mode. I am confused even after reading so much on this topic. your precious experiences and knowledge is much appreciated.
Reducing heater voltage a little will reduce the temperature of the cathode space charge so reducing noise - smoothed shot noise is really thermal noise in disguise. Beyond this point you start losing the space charge smoothing effect so shot noise increases. Where the balance lies will depend on anode current, as higher currents are already using up the space charge.
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