Originally I was planning to slightly under heat the tubes in my 6CG7 and EL84 PP amp using a 12v AC supply, but I've been advised that I'd be much better off using a 6.3v DC supply instead.
Given that throwing another 12v AC toroid into the chassis is no drama, has anyone got a childs play circuit for giving a smooth 6.3v DC supply capable of feeding the heaters of 4EL84's and 2 6CG7's.
Rather have it regulated with a bit of spare current capacity so that a change in draw won't cause the voltage to droop than do it unregulated with a Pi filter.
Looking for cheap simple and pretty idiot proof.
An old HiFi World DIY supplement for their phono stage uses a bridge rectifier feeding a 4700uF cap into a 78S05 regulator with a pair of 1N4001's under its ground terminal outputting into a 100u cap.
This arrangement is only feeding a trio of ECC83's and a pair of 6922.s though.
Given that throwing another 12v AC toroid into the chassis is no drama, has anyone got a childs play circuit for giving a smooth 6.3v DC supply capable of feeding the heaters of 4EL84's and 2 6CG7's.
Rather have it regulated with a bit of spare current capacity so that a change in draw won't cause the voltage to droop than do it unregulated with a Pi filter.
Looking for cheap simple and pretty idiot proof.
An old HiFi World DIY supplement for their phono stage uses a bridge rectifier feeding a 4700uF cap into a 78S05 regulator with a pair of 1N4001's under its ground terminal outputting into a 100u cap.
This arrangement is only feeding a trio of ECC83's and a pair of 6922.s though.
check out the application notes for the LM3705. They show a current enhanced option using a basic transistor (can't remember which) to carry the main current.
There is an NJR 2396 6.3V fixed regulator that Mouser sells if you want something simpler. Current capability is not a problem if you split the load and use several of them, running them off of the same filter cap.
hey-Hey!!!,
The heaters are not going to change load demand. I'd suggest a full bridge and an LC-RC filter. You won't need much inductance, and 16V caps are available in low-esr in 15,000 uF about the size of my thumb.
cheers,
Douglas
You can use a CRC filter to make 12,6 volt and put two tubes in series.
EDIT:
12AC -> Bridge -> C (10000uf) -> R (adjust this one so you get 12,6VDC, use ohm's law) C- (10000uf) to one of the heater pins of a tube, then from the other heater pin to the heater pin of an other tube and then from the heater pin left to ground.
I'm a newbie myself so correct me if I''m wrong.
EDIT:
12AC -> Bridge -> C (10000uf) -> R (adjust this one so you get 12,6VDC, use ohm's law) C- (10000uf) to one of the heater pins of a tube, then from the other heater pin to the heater pin of an other tube and then from the heater pin left to ground.
I'm a newbie myself so correct me if I''m wrong.
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12V AC - bridge rectifier - 4700µF 16-25V capacitor - 100nF 63V capacitor - LM317 regulator - 2k resistor adjust-output - 10k variable resistor adjust-ground.
Bandsnatcher...............as far as I understand you will get some change due to electron emission in times of higher usage
something to do with cooling via electron emission
but don't ask me about it too much as it's just something I have heard of.
something to do with cooling via electron emission
but don't ask me about it too much as it's just something I have heard of.
One "DOWN" and dirty, completely idiot proof and relatively cheap way to go would be look on Epay for a 12.6V "Laptop" powersupply. Wire the heaters of the PP pairs in Series and the 2 CG7's in series. Parallel the 3 pairs and put an input jack on the chassis.
Here's one
You can put the supply far enough away from the chassis so there is no noise. That one in the link is 4Amps plenty of power for the filaments.
Here's one
You can put the supply far enough away from the chassis so there is no noise. That one in the link is 4Amps plenty of power for the filaments.
why DC Drew?
are you having issues with noise? I just completed my EL36/6CM5 p-p last night (well, almost completed... one channel still needs to be tweeked...)
It uses a 24VAC transformer feeding the output tubes (4 x 6.3 @ 1.2A) and the voltage amps (6J7) + phase splitters (6J5) (4 x 6.3 @ 0.3A) as two series chains.
At the moment it is running bare - I will probably virtual centre-tap it later on, but so far no noise issues and it has made dealing with the 1.2A heater current in the EL36 a non-issue.
JMTCW...
are you having issues with noise? I just completed my EL36/6CM5 p-p last night (well, almost completed... one channel still needs to be tweeked...)
It uses a 24VAC transformer feeding the output tubes (4 x 6.3 @ 1.2A) and the voltage amps (6J7) + phase splitters (6J5) (4 x 6.3 @ 0.3A) as two series chains.
At the moment it is running bare - I will probably virtual centre-tap it later on, but so far no noise issues and it has made dealing with the 1.2A heater current in the EL36 a non-issue.
JMTCW...
Not yet, still at the getting bits together stage. Had been advised not to AC heat the 6CG7's. Happy to go with the original AC heated design and take my chances with a retrofit later on if needed...
You've talked me into it, will series the heaters and run off the 12v AC supply first up and we'll see how things go...
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