MEQ-5 - Alternate psu

[Deepdark]

Hi guys

I just redraw the psu to incorporate more filtering stages. Is it possible to get another look at it, especially the heater elevation part. Thanks

 

[5v333]

im not very good with tube psus but i think your elevated dc will be about 116vdc

33k/(33k+66k)*350v

what i have read about elevated dc, your looking for something like 20-75vdc.

so you might wanna raise the 66k.

thats a lot of filtering by the way have a look at the dimensions of thoose highvoltage caps and see that they will fit in your case before you spend alot of money on them.

 

[Deepdark]

Thanks, i will give a look at the heater elevation. Yes, its plenty of filtering. But since i'm designing the board and using a 2u, it will not be a problem. I like having a lot of filtering and kill every bit of ripples.

 

[Deepdark]

Ok, I've recalculated my voltage divider. If I change my 66K for a 100K and my 33K for a 25K, then my Vout would be 70V. I guess it should be plenty allright. Maybe Ian or someone else could validate it?

 

[PRR]

> more filtering stages.

Why do you need 160dB of filtering?

47u-2K-47u-2K-47u-2K-47u gives 6uV ripple. If this feeds your first plate, the input ripple will be far below all other tube noises (random hiss and heater racket).

 

[Deepdark]

Thanks PRR. I tend to fear about hum so I exagerate things abit loool. I agree 3 stages would be plenty enought. I could have lowered 47 to 22uf, too. Thanks again. Also, is my revised value for the heater elevation ok?

 

[Deepdark]

Hey guys, why the original heater elevation is so high? 115V. Is it because they found this value to be optimal for noise performance?

 

[Deepdark]

Ok, one thing. The cathode of teh 6AQ5 is about 160v. It's near half the B+ supply (350v). Maximum Heater to cathode DC volts is about 100v. Plus the maximum output rms, let's say 20V x1.414 + 160v = 188.28V. To avoid exceeding it, we must drop it to, at least, 90v so I think it explain why the heater elevation must be around 115v. Someone can correct me? Thanks :0

 

[PRR]

> Plus the maximum output rms, let's say 20V x1.414

It "can" pull-up much more than that. It may not be "clean". But you don't want your heater insulation to go POP on an unexpected overload.

I suspect the datasheet value of V(hk) can be exceeded. But the datasheet number is conservative. Long-time running above that value may be serious; short peaks may not be.

 

[Deepdark]

Thanks. Should i stick to the 115v elevation or i could go lower and still be "safe"?

 

[PRR]

I would assume some dead-guy picked that range for a good reason.

 

[Deepdark]

I guest so lol. I can't ask the dead man but I will trust him. Thanks for the help. I'll stick to my first heater elevation setup, around 115-117v. Should be allright.