thinking of something like this =>
http://www.national.com/images/pf/LM317/00906301.jpg
If I do use a similar circuit in the schematics, what goes to the heater pins? say for a 6922, pins 4 and 5 are the heater pins.
maybe the +V goes to pin4 and the ground goes to pin5?
also what happens to the regulated DC heater supply ground? would I be connecting it to the ground of the B+ supply?
Are there benefits to a regulated DC heater supply? Looking at the schematic above, the cost doesn't seem to be that much.
thanks for the help.
ps. Is the schematic I mentioned above suitable for a heater supply? if not, please point me to the right direction. Thanks again.
http://www.national.com/images/pf/LM317/00906301.jpg
If I do use a similar circuit in the schematics, what goes to the heater pins? say for a 6922, pins 4 and 5 are the heater pins.
maybe the +V goes to pin4 and the ground goes to pin5?
also what happens to the regulated DC heater supply ground? would I be connecting it to the ground of the B+ supply?
Are there benefits to a regulated DC heater supply? Looking at the schematic above, the cost doesn't seem to be that much.
thanks for the help.
ps. Is the schematic I mentioned above suitable for a heater supply? if not, please point me to the right direction. Thanks again.
Not sure I understood perfectly your Qs. But I am using LMs quite everywhere to heat tubes.
That circuit, yes it works, but you need to adjust the resistors R1 & R2 to give 6.3V out (or whatever V you need). I am sure you looked at the NS datasheet for details.
I refer the heaters to the cathode of the valve and not to the B+ ground. It will not make a great difference, you just need to be sure not to exceed the heater-cathode max V diff (apllicable if you are using SRPP etc...). The circuit needs only one connection to ground or cathode!
You want to install the LM on an heatsink and make sure it is not dissipating too much ... I mean it should not drop much more than 3V. So if you need 6.3V at the output you will need 9V or so at the input. Can your 6.3AC be rectified to give 9V? Probably not under load. Just give it a try.
Ciao
That circuit, yes it works, but you need to adjust the resistors R1 & R2 to give 6.3V out (or whatever V you need). I am sure you looked at the NS datasheet for details.
I refer the heaters to the cathode of the valve and not to the B+ ground. It will not make a great difference, you just need to be sure not to exceed the heater-cathode max V diff (apllicable if you are using SRPP etc...). The circuit needs only one connection to ground or cathode!
You want to install the LM on an heatsink and make sure it is not dissipating too much ... I mean it should not drop much more than 3V. So if you need 6.3V at the output you will need 9V or so at the input. Can your 6.3AC be rectified to give 9V? Probably not under load. Just give it a try.
Ciao
I use separate trannies (torroidal 12V for a number of reasons)
1) solder one leg of a 100R resistor to the first heater pin
2) solder one leg of a 100R resistor to the other heater pin
3) solder the remaining legs of the Rs togheter
4) connect that point (ie the center of the two Rs) to the tube cathode.
5) forget the ground connection you see on that LM circuit. The whole stuff is now referenced via the 2 R's to the cathode.
If you are using a double triode, just tie the heater to one cathode only and make sure the other cathode-to-heater voltage is not exceeding the max rating.
I hope it helps.
Ciao
Gianluca
1) solder one leg of a 100R resistor to the first heater pin
2) solder one leg of a 100R resistor to the other heater pin
3) solder the remaining legs of the Rs togheter
4) connect that point (ie the center of the two Rs) to the tube cathode.
5) forget the ground connection you see on that LM circuit. The whole stuff is now referenced via the 2 R's to the cathode.
If you are using a double triode, just tie the heater to one cathode only and make sure the other cathode-to-heater voltage is not exceeding the max rating.
I hope it helps.
Ciao
Gianluca
just remembered that...
I can I can combined secondary 2 and 3 to get 12.6 (xformer datasheet => http://euphoniaaudio.netfirms.com/ea/nfoscomm/catalog/pdf/928P.pdf)
which should be enough to feed an LM317 (possibly lm350 for higher current rating).
My question is : If I combined sec2 and 3, what would be their current rating?
If could please have a look at the datasheet I mentioned above to see how sec2 and 3 are combined.
Thanks again for the help
I can I can combined secondary 2 and 3 to get 12.6 (xformer datasheet => http://euphoniaaudio.netfirms.com/ea/nfoscomm/catalog/pdf/928P.pdf)
which should be enough to feed an LM317 (possibly lm350 for higher current rating).
My question is : If I combined sec2 and 3, what would be their current rating?
If could please have a look at the datasheet I mentioned above to see how sec2 and 3 are combined.
Thanks again for the help
Gluca said:
steps 1 to 5 is somewhat clear. with step 4, the combined end of the 100ohm resistors is connected to the 6922 cathode (using 6922 as an example)?
Also where/how do I connect transformer output? I would assume it goes to the LM regulator but how is the LM regulator connected to the heater pins?
also, would it be same steps if I decided to use the heater supply secondary instead of a separate transformer?
what capacitor values do you use for the LM circuit?
thanks again for the help
Sec2 and sec3 are rated at 1.5A. If you series connect them you can get 1.5A out of them (and 6.3+12.6V).
Sec3 is rated for 12.6V that, once rectifed, will give you 16V or so: it is too much for the LM and you need to drop the extra voltage through a resistor or use an heavy heatsink under the LM. So you can use sec3 (forget its CT).
You need to connect Vout (the upper leg of the regulator in your first jpg) to first pin of the heater and the lower leg to the other pin. Order doesnt matter. Combined end of the 100R resistor tied to the cathode.
I do use LM1084adj and 10 or 22uF electrolytic for local bypass. Diodes are followed by 10000uF, 1.5uH, 10000uF.
Ciao
Gianluca
Sec3 is rated for 12.6V that, once rectifed, will give you 16V or so: it is too much for the LM and you need to drop the extra voltage through a resistor or use an heavy heatsink under the LM. So you can use sec3 (forget its CT).
You need to connect Vout (the upper leg of the regulator in your first jpg) to first pin of the heater and the lower leg to the other pin. Order doesnt matter. Combined end of the 100R resistor tied to the cathode.
I do use LM1084adj and 10 or 22uF electrolytic for local bypass. Diodes are followed by 10000uF, 1.5uH, 10000uF.
Ciao
Gianluca
OH well! Doing so the heater will stay at a voltage close to the voltage of the cathode and will not float around.
You want to use 100R resitors or bigger as they are in parallel to the heater but only a little current (coming from you regulated supply) will flow through them as their resistance is much bigger than the heater resistance. Most of the current will go into the heater.
Keep in mind the whole stuff will cost you > 20 euros (not including the trafo you have already in your hands): rectifiers, large can C, inductors, PCB, heatsink, LM, resistors. And you are populating the amp with more compenents and increasing the probability to have something going wrong.
The advantages (for a indirectly heated valve) are often questionable. If you do not have any issues with hum (coming from heaters) ... well ... it's up to you ... just experiment and have fun.
Ciao
Gianluca
You want to use 100R resitors or bigger as they are in parallel to the heater but only a little current (coming from you regulated supply) will flow through them as their resistance is much bigger than the heater resistance. Most of the current will go into the heater.
Keep in mind the whole stuff will cost you > 20 euros (not including the trafo you have already in your hands): rectifiers, large can C, inductors, PCB, heatsink, LM, resistors. And you are populating the amp with more compenents and increasing the probability to have something going wrong.
The advantages (for a indirectly heated valve) are often questionable. If you do not have any issues with hum (coming from heaters) ... well ... it's up to you ... just experiment and have fun.
Ciao
Gianluca
8V??? What the heck?! What tube is it?
You can parallel connect as many tube as you need to the regulated 6.3Vdc as long as the current they are drawing (tube1+tube2) is within the max ratings of the tranny and LM.
So you need 1 regulated supply for the 6.3 tubes and an othone for the +8V tubes. You need to reference to ground or to the cathode ONLY one heater ... the other tube's heater will take the reference via the regulated supply.
Ciao
Gianluca
You can parallel connect as many tube as you need to the regulated 6.3Vdc as long as the current they are drawing (tube1+tube2) is within the max ratings of the tranny and LM.
So you need 1 regulated supply for the 6.3 tubes and an othone for the +8V tubes. You need to reference to ground or to the cathode ONLY one heater ... the other tube's heater will take the reference via the regulated supply.
Ciao
Gianluca
6922 is a double triode. Heaters at pins 4 and 5. Cathodes at pins 3 and 8. You have 2*6922 (that is 4 triodes).
You can connect pins 4 (both 6922) to Vout from you regulated DC supply and pins 5 (both 6922) to the leg labelled ground in the first LM pic you attached. That leg will not be connect to ground any more as said. This way the heaters will be in parallel. They will require 300+300 mA so your tranny (1.5A) is fine.
Grab 2 100R resistors and tie them to pin 4 and 5 of the first 6922 as described in the prev posts. Connect their combined end to pin 3 or pin 8 of first 6922. Forget the other cathode and the other valve. The heater of both the valves will be at the first tube's cathode voltage due to the 100R resistors.
Again you must be sure your 6922 are not wired as SRPP or stacked one above the other as the max heater-to-cathode Vdiff is 90V. Any schematic of your amp?
Gianluca
You can connect pins 4 (both 6922) to Vout from you regulated DC supply and pins 5 (both 6922) to the leg labelled ground in the first LM pic you attached. That leg will not be connect to ground any more as said. This way the heaters will be in parallel. They will require 300+300 mA so your tranny (1.5A) is fine.
Grab 2 100R resistors and tie them to pin 4 and 5 of the first 6922 as described in the prev posts. Connect their combined end to pin 3 or pin 8 of first 6922. Forget the other cathode and the other valve. The heater of both the valves will be at the first tube's cathode voltage due to the 100R resistors.
Again you must be sure your 6922 are not wired as SRPP or stacked one above the other as the max heater-to-cathode Vdiff is 90V. Any schematic of your amp?
Gianluca
Gluca said:
are you saying that the 2nd 6922's heater pins are not connected?
would it be the same procedure for my other 2 tubes which are 8FQ7 which uses 8+V heater supply?
I'll be having 2 regulators: 1 giving 6.3V and another giving out 8+V.
it'll be the aikido amp designed by john broskie (tubecad.com - blog64)
http://www.tubecad.com/2006/04/27/aikido_high_impedance_headphone_amplifier.png
Shoog said:
I was using 6922 as an example to make things clearer as it is the only dual triode tube where I have a copy of the datasheet already.
yes it could be a waste of time but it's my time after all.
and oh it's my money as well. (!!!) But thanks for the advice
Shoog said it's a waste of time because AC heaters sound better than DC, but that's highly subjective. I prefer AC heating myself.
Having said that, you'll be dissipating more heat via the power transistors for the filaments, you'll need higher voltage to feed them, you won't have line regulation when wall voltage drops, you don't have current limiting (which is better I think).
Having said that, you'll be dissipating more heat via the power transistors for the filaments, you'll need higher voltage to feed them, you won't have line regulation when wall voltage drops, you don't have current limiting (which is better I think).
"Shoog said it's a waste of time because AC heaters sound better than DC, but that's highly subjective. I prefer AC heating myself."
I do think that there is enough opinion out there that AC sounds better, to think it a highly questionable exercise to go DC. Having said that I have just been on a thread where a poor first time diyer has spend week tracking down a circuit hum, which turned out to be from the heaters. This was with a 5687, which I personally have found to benefit from DC heaters. There are no hard and fast rules, but I certainly think that AC is better whenever it can be used.
Shoog
I do think that there is enough opinion out there that AC sounds better, to think it a highly questionable exercise to go DC. Having said that I have just been on a thread where a poor first time diyer has spend week tracking down a circuit hum, which turned out to be from the heaters. This was with a 5687, which I personally have found to benefit from DC heaters. There are no hard and fast rules, but I certainly think that AC is better whenever it can be used.
Shoog
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