Poobah,
As I understand it, the hotter heater can act like a weak cathode to the cooler cathode which then acts like the plate of a diode. It’s not a good diode because the heater insulation is in series, but that insulation can vary, especially if there is any breach or crack. The relative work functions of the inner un-coated surface of the cathode and the tungsten heater wire must determine how much weak current can flow. So you simply elevate the heater slightly (only slightly) above the cathode to reverse bias that weak diode, shutting off any noisy currents.
As I understand it, the hotter heater can act like a weak cathode to the cooler cathode which then acts like the plate of a diode. It’s not a good diode because the heater insulation is in series, but that insulation can vary, especially if there is any breach or crack. The relative work functions of the inner un-coated surface of the cathode and the tungsten heater wire must determine how much weak current can flow. So you simply elevate the heater slightly (only slightly) above the cathode to reverse bias that weak diode, shutting off any noisy currents.
Looks nice. Should have good hum rejection. And you should'nt have to worry about transformer induced hum, with your separate PS chassis. Minor refinement: If the blk/red twisted pair is your heater supply, I'd separate that from the other wiring as much as practical, until it enters the board. Tips from Morgan Jones - You'll get nicer twisting if you take two wires and clamp one end in a vise, stretch both out and twist until the length starts to pull in. A variable speed drill works well here. Solid core is good for twisted pairs too.
Sheldon
Sheldon
Thanks Brian,
I see what you're saying(
)... seems like it might be a good topic for another time and place. Seems like a contest between space charges and the temperatures of emission for the respective metals involved.
cm_ls1,
I'll defer to Brian and Sheldon on this as they have actually designed and built tube stuff, whereas I just fix music amps now and then (but these evil guys have me convinced that I should design a tube amp for the HiFi). Let's just say that the heater to cathode voltage should be well within the manufacture's specs... following the instructions sometimes gives good results.
Tell us what tubes you are using... so we can gawk at the specs.
I see what you're saying(
)... seems like it might be a good topic for another time and place. Seems like a contest between space charges and the temperatures of emission for the respective metals involved.cm_ls1,
I'll defer to Brian and Sheldon on this as they have actually designed and built tube stuff, whereas I just fix music amps now and then (but these evil guys have me convinced that I should design a tube amp for the HiFi). Let's just say that the heater to cathode voltage should be well within the manufacture's specs... following the instructions sometimes gives good results.
Tell us what tubes you are using... so we can gawk at the specs.
poobah said:I'll defer to Brian and Sheldon on this as they have actually designed and built tube stuff
On Brian you are right. But it would be a stretch to say that I design stuff. I read as much as I can, take a tested design and build something. I may play with a few variations that are well within the design limitations (at least I hope they are), but that's about it. I'd have a long way to go before I can design from first principles.
Sheldon
poobah said:Well,
I'm getting the itch to try some HiFi with tubes. I have yet to fully master the math for P-P output stages yet. The SE stuff is pretty simple though...
Some good stuff here: http://members.aol.com/sbench102/composit.html In fact, his whole site is full of interesting and practical stuff.
poobah said:Am I missing something here?
Shouldn't that Aikido board have a place to land a bypassed divider for heater bias?
He's got space on the board for individual caps to the return leg of the heater supply. It'd be nice to have the divider on the board, but pretty easy to put in in the power supply side too. Just connect the bias leg to H-.
Sheldon
ok ive powered her on ... no smoke but only one centre tube and one end tube litup ...
so i checked the jumpers for the heaters and discovered i had connected 6.3v tubes (assuming 12v ps) :duh: , i needed to use the jumpers for 6.3v tubes (assuming 6.3v heater power)
SOOOOO ... anyway the tubes all light up .... and we have music ... woooT
i just grounded the centre of the heater and it is causing a slight hum , barely audible ( once i reference the heaters i should be sweet).
the sound from mid - highs ... is magical , very very happy ...
but the bass is a bit subdued compared to not using the preamp at all , im using a .47uf auricap output caps , and a 100k pot ... any reason my bass is lacking ? what component would cause this ..?
thank guys overall im rapt , its sounds great and im sure these two minor hiccups will be fixed...
no smoke but only one centre tube and one end tube litup ... so i checked the jumpers for the heaters and discovered i had connected 6.3v tubes (assuming 12v ps) :duh: , i needed to use the jumpers for 6.3v tubes (assuming 6.3v heater power)
SOOOOO ... anyway the tubes all light up .... and we have music ... woooT
i just grounded the centre of the heater and it is causing a slight hum , barely audible ( once i reference the heaters i should be sweet).
the sound from mid - highs ... is magical , very very happy ...
but the bass is a bit subdued compared to not using the preamp at all , im using a .47uf auricap output caps , and a 100k pot ... any reason my bass is lacking ? what component would cause this ..?
thank guys overall im rapt , its sounds great and im sure these two minor hiccups will be fixed...
Yes Dr. Yaniger...
Why do you think there is a double "yet"?
I'm still working on getting my Tandoori chicken right! Dosas are down pat however and I will soon publish "Dosa for Dummies".
Other resources have been diverted to the alternative fuel production project.
Seriously... I'll catch up that Push-Pull stuff. The transition point from Class A to Class B and the shift in "apparent" primary impedance awaits a lucid moment.
I REALLY need to buy Morgan Jones book as it purported to be a better read than all sixteen pounds of RDH4.
Why do you think there is a double "yet"?
I'm still working on getting my Tandoori chicken right! Dosas are down pat however and I will soon publish "Dosa for Dummies".
Other resources have been diverted to the alternative fuel production project.
Seriously... I'll catch up that Push-Pull stuff. The transition point from Class A to Class B and the shift in "apparent" primary impedance awaits a lucid moment.
I REALLY need to buy Morgan Jones book as it purported to be a better read than all sixteen pounds of RDH4.
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An externally hosted image should be here but it was not working when we last tested it.
ok , a bit of an update ......
the generic transformer **** itself
, it was working fine for a week or two , and then one day i went to turn it on... nothing was happening , all of a sudden the mains trips and everything inj the house turns off.
I go flick the switch again , and come back to feel the transformer , and its boiiiiiling hot :| ,
i put another fuse in it 1amp , and that blows straight away ... looks like its toast , i was worried that the supplier would say i caused it ( which is understandable as its my first DIY) , who knows , but he didnt blink , staight away , "no worries mate" , hmmm maybe these chinese traffos have a high failure rate , i said to him how much more for the Hammond 370fx , so i got that instead.
The hammond is quite a beast standing nearly twice as tall as the generic , and its 150ma , intead of the generic 80ma , cant go wrong with a bit of overkill, so that worked out well.
and as for how i said the aikido is lacking a bit in the bass dept , i noticed the auricaps have orientation , and that black wire is recommended as in , and red as out when used in the signal path (i had them the other way) , after turning them over , i swear the bass has improved , YES ! , i didnt think these caps had polarity ... anyway , it sounds better , the mids and highs are the same , but the bass goes deeper and has mo authority ... hmmm im not complaining .
the hum has also further diminished ... ( maybe cause of the hammond traffo)
in any case , i think im done...
< face of the people that have heard it so far
the generic transformer **** itself
, it was working fine for a week or two , and then one day i went to turn it on... nothing was happening , all of a sudden the mains trips and everything inj the house turns off.I go flick the switch again , and come back to feel the transformer , and its boiiiiiling hot :| ,
i put another fuse in it 1amp , and that blows straight away ... looks like its toast , i was worried that the supplier would say i caused it ( which is understandable as its my first DIY) , who knows , but he didnt blink , staight away , "no worries mate" , hmmm maybe these chinese traffos have a high failure rate , i said to him how much more for the Hammond 370fx , so i got that instead.
The hammond is quite a beast standing nearly twice as tall as the generic
, and its 150ma , intead of the generic 80ma , cant go wrong with a bit of overkill, so that worked out well.and as for how i said the aikido is lacking a bit in the bass dept , i noticed the auricaps have orientation , and that black wire is recommended as in , and red as out when used in the signal path (i had them the other way) , after turning them over , i swear the bass has improved , YES ! , i didnt think these caps had polarity ... anyway , it sounds better , the mids and highs are the same , but the bass goes deeper and has mo authority ... hmmm im not complaining .
the hum has also further diminished ... ( maybe cause of the hammond traffo)
in any case , i think im done...
< face of the people that have heard it so far - Status
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