http://www.dreamtone.org/Calculate_Current_Form.htm
It's a sad day
PT Current Draw Page Gone
Moderators: pompeiisneaks, Colossal
PT Current Draw Page Gone
The transformer current draw page is gone.
http://www.dreamtone.org/Calculate_Current_Form.htm
It's a sad day
http://www.dreamtone.org/Calculate_Current_Form.htm
It's a sad day
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gui_tarzan
- Posts: 607
- Joined: Thu Jan 16, 2014 3:10 am
- Location: The 26th State
Re: PT Current Draw Page Gone
www.archive.org is your friend. The form won't run there but you can save it and modify it on your own system.
https://web.archive.org/web/20150215195 ... t_Form.htm
If you know someone that's good with web pages you can migrate this page to another server that has javascript and it should work. Just remove all the references to archive.org and the original web page, then set it up for yours.
https://web.archive.org/web/20150215195 ... t_Form.htm
If you know someone that's good with web pages you can migrate this page to another server that has javascript and it should work. Just remove all the references to archive.org and the original web page, then set it up for yours.
--Jim
"He's like a new set of strings, he just needs to be stretched a bit."
"He's like a new set of strings, he just needs to be stretched a bit."
Re: PT Current Draw Page Gone
Brilliant!gui_tarzan wrote:www.archive.org is your friend. The form won't run there but you can save it and modify it on your own system.
Re: PT Current Draw Page Gone
I will take a look and see if I can redo it this weekend and host it. If per tube consumption values are not stored on the page it will be great if someone can post a compiled table of these.
Niki
Niki
Re: PT Current Draw Page Gone
Unfortunately per tube values are not exposed, hence some data sheet crawling is under way. Yet again if someone already compiled these it would be great to share them.
Niki
Niki
Re: PT Current Draw Page Gone
Ok. I did a quick page with pretty much simulating the calculation from the old page which by itself should be taken with a (lot) grain of salt as the accuracy is kinda medium. This one allows for entering a Rload value in ohms to kinda do better estimation.
Pre valves are overestimated and 10% is added to the overall calculation just in case.
It will make more sense to add some data from the tubes data sheets and show it as reference, but it will take some time. Other improvements such as class of operation should be taken into account as the current one assumes class AB push pull(approximated) and obviously doesn't make a lot of sense with 3 power tubes.
Suggestions are welcome
Http://thesubjectmatter.com/calcptcurrent.html
Niki
Pre valves are overestimated and 10% is added to the overall calculation just in case.
It will make more sense to add some data from the tubes data sheets and show it as reference, but it will take some time. Other improvements such as class of operation should be taken into account as the current one assumes class AB push pull(approximated) and obviously doesn't make a lot of sense with 3 power tubes.
Suggestions are welcome
Http://thesubjectmatter.com/calcptcurrent.html
Niki
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martin manning
- Posts: 14308
- Joined: Sun Jul 06, 2008 12:43 am
- Location: 39°06' N 84°30' W
Re: PT Current Draw Page Gone
Looks good, and I agree including the expected load is necessary for a good estimate. Could you add (at the bottom of the page, say) the equations you are using to make the estimates? In general I like using on-line calculators where I know exactly what they are doing.
Re: PT Current Draw Page Gone
Thought about that, together with references to sources. Will do, once I find my fancy formula visualization font. 
Thanks for looking.
Niki
Thanks for looking.
Niki
Re: PT Current Draw Page Gone
Nice "lead dress" on your page! Bookmarked.
I build and repair tube amps. http://amps.monkeymatic.com
Works for me
I just tried the formula page and the voltages are what I've measured on the few amps I've built so far.
I like it, nice design.
This brings up a question I've had. On the design, see attached design data, are not the voltages on the preamp tubes too high for the 12AX7? By that I don't mean your calculations but rather the actual voltages on the anode is about what the calculations reached- 330 volts. Seemed too high and now I've substituted a 12AU7 in an attempt to reduce the gain. Too high for B+ ?
Well now forum system is telling me a .pdf extension type is not allowed; so no formula page at the moment...
silverfox.
I like it, nice design.
This brings up a question I've had. On the design, see attached design data, are not the voltages on the preamp tubes too high for the 12AX7? By that I don't mean your calculations but rather the actual voltages on the anode is about what the calculations reached- 330 volts. Seemed too high and now I've substituted a 12AU7 in an attempt to reduce the gain. Too high for B+ ?
Well now forum system is telling me a .pdf extension type is not allowed; so no formula page at the moment...
silverfox.
Re: PT Current Draw Page Gone
a Bridge rectifier option would be nice in addition to the full-wave.
<b>LF Audioservice</b>
Built:
Weber AB200
Weber 6S100
Hiwatt DR201
Fender 6G3 Deluxe
Built:
Weber AB200
Weber 6S100
Hiwatt DR201
Fender 6G3 Deluxe
Re: PT Current Draw Page Gone
Thanks for looking.
Now, I've used RCA 12AX7 datasheet found here - http://web.eecs.umich.edu/~mmccorq/dive ... /12ax7.pdf
Where the absolute max plate dissipation is 1.2W and plate voltage is stated as 330V.
In reality - it will be much lower (with bias point centered around 1mA, see http://www.aikenamps.com/index.php/desi ... amplifiers.
Now, using other preamp tubes such as 12AT7, 12AU7, 12AY7, 12BZ7, 12AV7 will definitely change the overall picture, but not significantly. Plus, using other type phase inverter, or cathode follower post PI, will change it even more significantly.
At the end of the day the power section is the biggest concern as far as current draw goes and putting like 10-15% above what power section draws in most cases will land you in the ballpark of what your PT should be rated for.
Another point is that different screen grid arrangements, will eventually render different current draw.
With all these factored in, the page will end up like a web version of (LT)Spice
I am not saying it is impossible to design the page so you have more configuration options (and I am all open to listen for what will work for you all), but:
- it will definitely bring up the assumptions level
- will take more time & testing - I am OK to do it (after all this fine community is driven by its members contributions)
As at the moment, I think that it will make more sense to prepare "datasheet" type database to be displayed when a particular tube is selected, as whatever calculations are performed on this particular subject- they are always approximate and datasheet should be referenced.
Niki
EDIT: Meanwhile, the formulae has been added. Just click "Show formulas" for an immediate math experience ...
Did not manage to find the fancy font, so it is rather ordinary still.
Now, I've used RCA 12AX7 datasheet found here - http://web.eecs.umich.edu/~mmccorq/dive ... /12ax7.pdf
Where the absolute max plate dissipation is 1.2W and plate voltage is stated as 330V.
In reality - it will be much lower (with bias point centered around 1mA, see http://www.aikenamps.com/index.php/desi ... amplifiers.
Now, using other preamp tubes such as 12AT7, 12AU7, 12AY7, 12BZ7, 12AV7 will definitely change the overall picture, but not significantly. Plus, using other type phase inverter, or cathode follower post PI, will change it even more significantly.
At the end of the day the power section is the biggest concern as far as current draw goes and putting like 10-15% above what power section draws in most cases will land you in the ballpark of what your PT should be rated for.
Another point is that different screen grid arrangements, will eventually render different current draw.
With all these factored in, the page will end up like a web version of (LT)Spice
I am not saying it is impossible to design the page so you have more configuration options (and I am all open to listen for what will work for you all), but:
- it will definitely bring up the assumptions level
- will take more time & testing - I am OK to do it (after all this fine community is driven by its members contributions)
As at the moment, I think that it will make more sense to prepare "datasheet" type database to be displayed when a particular tube is selected, as whatever calculations are performed on this particular subject- they are always approximate and datasheet should be referenced.
Niki
EDIT: Meanwhile, the formulae has been added. Just click "Show formulas" for an immediate math experience ...
Did not manage to find the fancy font, so it is rather ordinary still.-
martin manning
- Posts: 14308
- Joined: Sun Jul 06, 2008 12:43 am
- Location: 39°06' N 84°30' W
Re: PT Current Draw Page Gone
Niki, looks like something is not quite right here. If I specify Rload at 6608 ohms on your page, I agree with your result. However, if the Rload input is zero, and it is estimated at 6608 ohms, a different result is returned. Note I haven't included preamp tube current (quantity 1) in my calculation, so your result should be ~125 mA.
You do not have the required permissions to view the files attached to this post.
Re: PT Current Draw Page Gone
Hi Martin,
This is rightfully noticed. And it is because different formulas are used when the Rload is filled and when it is not.
(1) When it is filled, I am using power output estimation formula from Merlins page (towards the bottom) http://www.valvewizard.co.uk/pp.html . Admittedly for a push pull stage. Then P is divided by DC for current draw calculation.
(2)When it is not filled - the Rload is estimated as per SE output stage (again pretty much standard and can be seen at Merlin's page - http://www.valvewizard.co.uk/se.html). The current draw though is estimated by dividing a single power tube max dissipation (multiplied by the number of power tubes selected) by the DC voltage calculation.
This is the way the old page did the calculation (presumably - as the calculations are very close - within 1 mA or so - maybe different rounding has been used) .
Both formulas are listed and I can either make it a bit more clear in the description or change the approach and always use Merlins PP output power estimation calculation as a basis.
Hope this makes sense FWIW.
Niki
This is rightfully noticed. And it is because different formulas are used when the Rload is filled and when it is not.
(1) When it is filled, I am using power output estimation formula from Merlins page (towards the bottom) http://www.valvewizard.co.uk/pp.html . Admittedly for a push pull stage. Then P is divided by DC for current draw calculation.
(2)When it is not filled - the Rload is estimated as per SE output stage (again pretty much standard and can be seen at Merlin's page - http://www.valvewizard.co.uk/se.html). The current draw though is estimated by dividing a single power tube max dissipation (multiplied by the number of power tubes selected) by the DC voltage calculation.
This is the way the old page did the calculation (presumably - as the calculations are very close - within 1 mA or so - maybe different rounding has been used) .
Both formulas are listed and I can either make it a bit more clear in the description or change the approach and always use Merlins PP output power estimation calculation as a basis.
Hope this makes sense FWIW.
Niki