ecc88 tube pover supply-rect.

[marijan]

I`m planing to build this 6dj8/ecc88 based J.J.Curcio linestage. I`d like to use tube rectified PS and crcrc or lcrc filtering. I have acces to AZ11, GZ32, 5Y3 tube rectifiers to achive 250V B+. What woud be your choice or recomendation?

P.S. Stupid quest. I supouse but, I have a choke, 120 ohm mesured. Is there any possibility to determine tha H value, since there is no marks on it. 3inch W, 1inch D, 2,2inch H are aprox. dimen.

Thanks

[Geek]

Originally posted by marijan
P.S. Stupid quest. I supouse but, I have a choke, 120 ohm mesured. Is there any possibility to determine tha H value, since there is no marks on it. 3inch W, 1inch D, 2,2inch H are aprox. dimen.

It would be irresponsible of me to venture such a guess.....

Oh well

Best guess is 10 Henries at approximately 100mA - your description matches a Thordarsen I used in a project

<<edit>>

Oooops, forgot part

What woud be your choice or recomendation?

Unless you're a puratin for a tube supply, solid-state PS and tube preamps are, IMO, a match made in heaven for their low-Z power rails which reduces cross-channel and motorboating.

[marijan]

Frend of mine made this pre. using ss rectifiers (ecl82 regulated) and a version with az11 crcrc filter PS. I certanly prefered AZ11 instade of SS. That`s why I m going that way. But as I sad, I can use a few diferent tube rectifiers and I wondered which one of those would be prefred in such design based on sonic advantages, long live duration, good reputation, reliability....

Thank`s for your guess about choke.

[analog_sa]

Hi Marijan

Given your choice i'd go for the AZ11. In the past i've used an AZ1 in a preamp and liked it a lot. The GZ32 is nothing special and best left for Quad II enthusiasts. If i were you i'd sell the GZ32 and buy either mercury or damper diodes.

[marijan]

I bought two AZ1`s yesterdaj. It`t look similar (data) to AZ11. My transformer is 2x280V 125mA, but I don`t know what is a voltage drop on AZ1. I need cca 350V after rectifier tube. What voltage will I get after AZ1 using this transformer?
Thank`s

[Miles Prower]

P.S. Stupid quest. I supouse but, I have a choke, 120 ohm mesured. Is there any possibility to determine tha H value, since there is no marks on it. 3inch W, 1inch D, 2,2inch H are aprox. dimen.


Yes. I've had that same problem from time to time. What I would do is connect it to a variac, then carefully bring up the current until it hits a couple hundred milliamps. Then measure the voltage. Then:

Z= V/I (Magnitude, ohms)

Z= sqrt(R^2 + X(l)^2)

Since you know Z and R, simply solve for X(l), then figure from X(l)= wL

(Where w= 2 * pi * f)

To see what current will max it out, increase the current until you hear it begin to hum, then back off quickly. That'll give you a good idea what current will saturate the core.

You should also keep in mind that these iron core coils show a wide variety of inductances, depending on the current. That's why an RLC bridge will show a hundred henries or so (very small sense voltage, typically 1.0V(p) ), even if it's rated for a more likely 8 -- 10H.

So, if you know what current it'll operate with, and it doesn't saturate, then go with that current and measure the voltage needed to draw that.

[marijan]

Thanks Miles. I`ll have to employe a frend with variac and much more expirience than mine, to do that safely I supouse.

Again if someone please can assist me. What would be aproksimate voltages behind AZ11 or GZ32 rectifier, when 280-0-280 125mA transformer is used? Or another way, what kind of secondaries I`ll need to achive 350 V aprox. after rectifier. Filter has a drop of cca. 100VDC (from 350 to 250). That is B+ I need. Do I realy need those 125mA or (if I have to order new transformer) can I take let say 100mA or lover. 88`s will need cca 60mA for boath chanals.

[Miles Prower]

That xfmr ought to work just fine for the voltages you need. That should give you 396V of no-load DC into a capacitor input filter. Given the diode forward voltage, voltage averaging from the filter, and xfmr loading, you can count on 330 -- 350V(dc), or so. That will get you right where you want to be. Here is a good discussion of what you might want to consider in the way of diodes.

If your demand is going to be 100mA, then the 280-0-280 @ 125mA should be OK.

[marijan]

Winding for heaters is 2x3,15 VAC (center tap). What is usualy a beter solution: bridge, cap, rails on the tube and center tap on the star ground point or bridge, cap, rails on the tube and conection of either neg. or. pos. poole of the cap to star ground point - leaving center tap on the air.