Hi all
Regarding this 01A schematic https://vinylsavor.blogspot.com/2013/10/ux201a-sound-processor-part-1-circuit.html
What is the Watt rating on the 22R resistor?
Thanks
Regarding this 01A schematic https://vinylsavor.blogspot.com/2013/10/ux201a-sound-processor-part-1-circuit.html
What is the Watt rating on the 22R resistor?
Thanks
What's the tube current? 80mA?
It's I^2*R, makes 0.08 * 0.08 * 22; about
I'd also look at the 500R resistor, iirc the heater current is 250mA so that R dissipates 0.25 * 0.25 * 500 would be a tad over 30W ....
I'd go for a separate 5V supply.
Jan
It's I^2*R, makes 0.08 * 0.08 * 22; about
I'd also look at the 500R resistor, iirc the heater current is 250mA so that R dissipates 0.25 * 0.25 * 500 would be a tad over 30W ....
I'd go for a separate 5V supply.
Jan
Ohm's law.
The filament current is 0.25A.
P=I*I*R
P=1.325W use at least 3-5W resistor.
BTW the dissipation on 500R is more critic, 31.25W.
I'm not sure, that this preamp is the best solution.
The filament current is 0.25A.
P=I*I*R
P=1.325W use at least 3-5W resistor.
BTW the dissipation on 500R is more critic, 31.25W.
I'm not sure, that this preamp is the best solution.
Yes, I disregarded the heater current through the 22R. But you disregarded the anode current through the 22R, so it will even be a bit more.
But the elephant in the room is the 500R. I fully agree this is a horrible preamp circuit. It needs a separate 5V heter supply.
Jan
Hi Jan,
Aside from the 31.25W thru the 500R resistor, and given the objective of the schematic is to "apply the unique distortion characteristics of the 01A tube to the signal" , why do you think this is a horrible schematic?
Aside from the 31.25W thru the 500R resistor, and given the objective of the schematic is to "apply the unique distortion characteristics of the 01A tube to the signal" , why do you think this is a horrible schematic?
Topical 01a anode current is 2..5mA, so negligible vs. 250mA filament current (which is deviating even few ten mA from tube to tube) if the filament bias resistor dissipation is the problem.
No more reasons aside from what you mention, especially the 30+ watt dropping R for the heater.
If you like some form of distortion, that's your personal preference and not subject to discussion; there probably are people that retouche their copy of the Mona Lisa because they like blue more. Personal preference.
But the 30W drop loss is just horrible circuit design.
I know Thomas; I'm sure he is well aware of the issues and I assume this is a principle circuit not meant to be copied 1:1 without some thinking.
Jan
Thomas build this solution more than ten years ago as "sound processor".
Use NP-8 10k:600 line transformer for 10k Ri tube.
Not sure, that nowadays it's the best solution to built linear preamplifier.
Use NP-8 10k:600 line transformer for 10k Ri tube.
Not sure, that nowadays it's the best solution to built linear preamplifier.
Thanks Jan.
TBH, I've never heard the unique distortion characteristics of an 01A tube, so I'm not 100% sure it's for me, however , given the application (one of several selectable input tubes for a bass guitar amp) , and the fact that I have some beautiful looking UX201A , I thought I'd better check on the schematic details before I go ahead and try this out.
Btw, what kind of resistors for the 500R and 22R, thick film non inductive?
Cheers
Thanks euro.
Re the PSU.
For a single 01A, it's 250ma @ 150V
Is there any info detailing power supply, and transformer, or any advise..
Re the PSU.
For a single 01A, it's 250ma @ 150V
Is there any info detailing power supply, and transformer, or any advise..
Check Thomas' article: "In the next articles the circuit and assembly of the power supply will be covered. Stay tuned!"
https://vinylsavor.blogspot.com/2013/11/ux201a-sound-processor-part-3-psu.html
Note that if you derive the heater from the 150V supply that supply gets much bigger than it should be to support the anode current.
Jan
https://vinylsavor.blogspot.com/2013/11/ux201a-sound-processor-part-3-psu.html
Note that if you derive the heater from the 150V supply that supply gets much bigger than it should be to support the anode current.
Jan
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Thanks everyone...I guess it depends on the VA rating of the transformer and the rated current of the secondary winding of the transformer, as to how much the B+ will drop from no load on the power supply, to the 150VDC @250ma (for a single 01A tube)
I wonder if there is a way to increase (and control, eg pot/switch) the harmonic distortion of this preamp
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As drawn the circuit you have in your first post is unworkable and has probably lost something from the original. The Heater is 5 Volt 0.25 Amp. The Heater is also the Cathode. Here is a more workable circuit, the heater supply is a simple AC transformer giving 5 Volts, the circuitry for the B+ HT 120 Volts DC is not shown:
PS The resistance of the heater is about 5 / 0.25 which is 20 Ohms so the 22 on your circuit might just have been a label to say the heater was 22 Ohms, just a thought.
The datasheet for this tube:
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Yes with the 100uF capacitor in parallel with the 500R resistor there will be more distortion and more gain. Are you building or renovating this?
Thanks guys. The application is an input stage for a bass guitar amp.
So I was wondering if I could somehow amplify the natural and unique distortion characteristics of the 01A tube.
In my application, gain takes 2nd place to tone (unique natural distortion characteristics etc) , and linear and undistorted comes last place.
So I was wondering if I could somehow amplify the natural and unique distortion characteristics of the 01A tube.
In my application, gain takes 2nd place to tone (unique natural distortion characteristics etc) , and linear and undistorted comes last place.
Sorry if this is a dubm question. What is the watt rating of the 500R cathode resistor?