Improving the Aikido line stage...

[Craig405]

Hi,

I have just read this thread and the recent trouble sunrise had with his heaters concerned me. I am running 12AX7's/12AT's and 12AU's and should get around 130V on cathodes of upper tubes, this is too much for a heater at only 6.3V.
How should i float my heaters?

Heaters are run from 6.3V DC and My HT is 370V before voltage regulators and 265V after.
Do i just run a divider down? is it better from unregulated or regulated supply?

BTW
I also get uneven division of voltage in My CF and SRPP stage and it is due to dodgy tubes containing 2 dissimilar triodes, mine are as dodgy as they come

Cheers
Craig

 

[sparkle]

To float heaters just pull the voltage divider from the last capacitor at Your high voltage. Calculate the voltage divider so that at top You have Your high voltage (where the divider is connected) and in the middle (between two resistors of the voltage divider) You have the voltage You need to float the heaters. If Your voltage between the cathode and heaters is,say 100V - You can float Your heaters arround 50-55V.
So - if the upper resistor is R1 and lower resistor is R2 than Your voltage could be calculated with 55V=(R2/(R1+R2))*Uht. Uht is Your high voltage (265V). So lets say that You want to drop on those resistors 5mA. Than Your R1+R2 is arround 53k. With that You can calculate R2 and find the closest values of R1 and R2 so that You have some current flowing through them and also some nice values that You can buy in stores. Hope this helps and hope that I have written everything correctly- not much sleep last night

 

[Craig405]

Dont worry that made perfect sense thanks . One thing though where do i connect the divider to, do i make it my heater ground?

Thanks
Craig

 

[sparkle]

hi,
maybe this helps.... best is case with the transformer (in my opinion)
regards
daniel

p.s. do not connect heater circuitry to the ground (they are floating on the voltage that You set in point A)

 

[Morgan L]

Missprint on heater balancing resistors? Says 100k. I guess you
meant 100 ohms? (normal choice) Also, there might be a point in
bypassing the lower of the (B+ to GND) voltage divider resistors
with a cap. Some small-signal valves have a spec. max impedance
between heater and cathode, usually 20k, if memory serves. Use
at least a 1uF cap, IMO.

Morgan

 

[Craig405]

Thanks for the diagram, will this work?

 

[sparkle]

Missprint on heater balancing resistors? Says 100k. I guess you
meant 100 ohms? (normal choice) Also, there might be a point in
bypassing the lower of the (B+ to GND) voltage divider resistors
with a cap. Some small-signal valves have a spec. max impedance
between heater and cathode, usually 20k, if memory serves. Use
at least a 1uF cap, IMO.

Morgan

thanks..... no sleep last night i guess

 

[Craig405]

Will that circuit i posted work to float my heaters on 74V DC(2 posts before this one)?
I dont wanna fry my transformer and rectifiers

P.s. the 1 ohm resistors are supposed to be heaters in //

Cheers
Craig

 

[sparkle]

You can do that but I would connect middle point between 80k and 20k on the center tap of You mains transformer (I see that You have a center tap).
Sorry for the long waiting but I didn't have internet for two weeks in my new appartement. My hifi is not working cause it has nowhere to be set to work - everything regarding aikido and other projects has stopped. But - the good news I have few 6n6p tubes waiting to be installed and some sneeky ideas what to put for the first stage....

Best regards
sunny

 

[Bas Horneman]

some sneeky ideas what to put for the first stage

Aaaah...you've made me curious now..

 

[sparkle]

don't worry - i will post as soon as I put it/hear it

 

[jsn]

The extreme solution of course is to have a small filament transformer for each filament and reference it to it's tube's cathode. Probably way too much trouble with DC heaters, but hey, nothing exceeds like excess.

jsn

http://boozhoundlabs.com

 

[joe3rp]

aikido with cathode resistor bypass caps?

Will the aikido still be an "aikido" if the cathode resistors to ground are bypassed with capacitors? This is to remove the local feedback.

Has anyone tried it? How will it affect sound and performance?

 

[sparkle]

DON'T DO IT - Aikido is not Aikido if You put those cap's. Read carefully all the articles on www.tubecad.com regarding Aikido preamplifier and You will se in one (or more of them) that Mr. Broskie strictly mentioned not to do it.....
regards

BAS... i am sorry for keep You waiting -but because of my appartement problems (I have moved in a new one) I have no time to work on my aikido so - You will know when I finish it --- You will be the first to know --- if this satisfy YOu (kidding, just kidding).... I am sorry too that I have no time now for my major and only hobby for now..... well things are going to be better.

 

[HiFiNutNut]

dave dove,

Hi I have taken everything you said and have ordered the 6n1p and 5687.

Is yours using the same schematic as per JB's article with added protection resistors only? Are you running on 220VDC B+?

I need to work out a PSU so if you could tell me how much current these tubes draw it would be a great help.

Regards,
Bill

 

[dave dove]

hi bill

well i hope you're not disappointed
otherwise my name will be mud in these parts
and holidays in australia will be out....

i don't know how much current it draws
i always mean to keep notes
but i'm more of a -wonder if this will work- kind of guy
and i only threw it together one evening in a fit of boredom
i was very surprised how good it is

i'll measure the current later tonight - hopefully
and let you know

my power supply is nowhere near as fancy as most on this thread
just LCLC hammonds and it does sound pretty good
but i've just made it redundant......

http://www.diyaudio.com/forums/showthread.php?s=&threadid=65708

have fun
speak to you later

dave dove

 

[dave dove]

bill

mine runs at 210V
total current @20mA
sorry for the delay

dave dove

 

[HiFiNutNut]

Dave,

Your name is now shining in the Aussieland. Make sure you book your next holiday here and I will be "up the ramp" (a slang I learnt in a pub in East London, which means - God knows what the Dockland men say. If I am not wrong, "buy the next round of drinks", that is.)

Regards,
Bill

 

[dave dove]

bill

does that mean you've built it?
or just happy that i could be a***d to pull mine apart for you?

see you down the pub later mate

dave dove

 

[HiFiNutNut]

Thanks Dave,

I have ordered the 4 tubes. Bas said he was going to send me 2 boards. I will need to knock out the PSU using the PSUII based on your figures (20mA in total for 2 channels - that is lower than I expected) and the tube datasheets. I have ordered 2 x 200uF Solen PP from www.solen.ca (I have not heard from them since I made the credit card payment a week ago!) to be used as the last caps in the PSU. It will probably take me another month or two to finish it. I wish I could knock it out in one evening like what you did. I have another project that I have to finish first - building a pair of 400W SS mono blocks. Hey, don't tell anyone that I told you that. They will kick me out of the tube forum.

Regards,
Bill