Basic Stamp - Bias Tubes
ElvisTheDJ
Posts: 2
Hello all,
I'm reallly enjoying learning my new Basic Stamp.· Sadly, the BOE wasn't available to purchase in town (I wanted instant gratification, couldn't wait for shipping [noparse];)[/noparse]· so I got the homework board from RadioShack.·
Anyway, I'm the type of person who doesn't really commit to learning something until I actually have a purpose for it.· (I didn't by this thing just so I could learn to turn LED's off and on).· I would like to integrate the stamp into my tube amplifier.
Goal One:
Biasing the tubes:
There are two "ports" in the front of my amp to measure the tube bias voltage.· It is supposed to be 1.56 volts and should be biased once a month to preserve the tube life.· It would be nice if I had a microcontroller that would be able to do this for me.· The way this is currently done is by measuring the voltage with a multimeter and then adjusting a pot with a screwdriver to get the correct voltage.· At first I thought I wanted to maintain the original design and simply use the stamp to actually measure voltage and rotate the pot accordingly, however after some thought I bet a digital resistor is the best way to go.
My question is, what parts will I need for this project (I'm not looking for a complete schematic, just what in addition to the stamp as far as how it will measure the current.. can I accomplish that with what I have already, or do I need to buy something additional?)
Goal Two:
Biasing the tubes is really the point of the project, but it seems like I could take the integration of old/new technology to a higher level by attaching an lcd and getting some info about the amp (for instance, displaying the bias voltage and maybe sound levels coming into the amp.
If anybody can point me to a thread or other source that might have some relevant information I would be greatful.
Thank you for reading!
Kris
I'm reallly enjoying learning my new Basic Stamp.· Sadly, the BOE wasn't available to purchase in town (I wanted instant gratification, couldn't wait for shipping [noparse];)[/noparse]· so I got the homework board from RadioShack.·
Anyway, I'm the type of person who doesn't really commit to learning something until I actually have a purpose for it.· (I didn't by this thing just so I could learn to turn LED's off and on).· I would like to integrate the stamp into my tube amplifier.
Goal One:
Biasing the tubes:
There are two "ports" in the front of my amp to measure the tube bias voltage.· It is supposed to be 1.56 volts and should be biased once a month to preserve the tube life.· It would be nice if I had a microcontroller that would be able to do this for me.· The way this is currently done is by measuring the voltage with a multimeter and then adjusting a pot with a screwdriver to get the correct voltage.· At first I thought I wanted to maintain the original design and simply use the stamp to actually measure voltage and rotate the pot accordingly, however after some thought I bet a digital resistor is the best way to go.
My question is, what parts will I need for this project (I'm not looking for a complete schematic, just what in addition to the stamp as far as how it will measure the current.. can I accomplish that with what I have already, or do I need to buy something additional?)
Goal Two:
Biasing the tubes is really the point of the project, but it seems like I could take the integration of old/new technology to a higher level by attaching an lcd and getting some info about the amp (for instance, displaying the bias voltage and maybe sound levels coming into the amp.
If anybody can point me to a thread or other source that might have some relevant information I would be greatful.
Thank you for reading!
Kris
Comments
How much do you find your bias drifts in a month? I usually set and forget, or if I'm feeling motivated I'll check it after the tube has burned in for a while. What kind of tubes are you biasing? Triodes I'm guessing, but what kind? One feature that would be neat is you could have settings to run the tube hot if you wanted some distortion or greater volume, and a setting for max tube life, and one for "normal".
Current sensors: Look at what Allegro has in the way of Hall Effect sensors. This will work through an ADC for measuring current. You will need an ADC to measure the bias voltage too.
For a musician friend of mine who didn't want to drag a voltmeter around I made a little baiser circuit that used a comparator to light an LED. When the bias was right, the LED goes off. If it drifts much it would come back on. Simple.
Be careful using a Stamp in a tube circuit. That B+ voltage could be a bugger and ruin the Stamp easy.
Jonathan
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www.madlabs.info - Home of the Hydrogen Fuel Cell Robot
Thanks for the reply! I'm actually working on a dynaco st70 (2x7199 and 4x el34's), so distortion isn't really anything desirable in my case. I will definitely be cautious about power. My stamp is too young to die [noparse]:)[/noparse]
I'll start reading up on your advice.
Thanks again!
After a quick search I found one on Jack's website:
http://www.tech-diy.com/MCTracer_no_pix_files/MCTracer_opto_ver_feb6_04.htm
Hope this helps,
Martin
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StampPlot - GUI and Plotting, and XBee Wireless Adapters
Southern Illinois University Carbondale, Electronic Systems Technologies