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Original Burnedfingers 26th March 2006 08:28 PM

Kitparts line stage
 
I have a kitparts line stage that is supposed to be a copy of a Jadus line stage. A quick check of the schematic will prove that it is a distant ripoff but no where close to being a Jadus.
Anyway it has provisions for 12VDC heater supplies for each side. Note, the ground of the heater is shared with all other grounds.

I need a 12 VDC supply for each side and was wondering if a LM317 should be used or a 7815 regulator. I have a dual supply in which to feed the regulators.

There are three 12AX7's per side.

All suggestions will be welcome.

Eli Duttman 26th March 2006 08:40 PM

JMO, a 7812 in each channel is FINE. A 450 mA. draw through a well heatsinked 7812 should be problem free. Use 7058s for a nice LOW cost NOS option. The triodes in the 7058 are identical to those in the 12AX7, but the tube pins out like a 6922. Intended for automotive service, the 7058 works correctly when anything between 12 and 14 V. energizes the heater.

Original Burnedfingers 26th March 2006 10:36 PM

I was thinking about using a 7815. I thought supply,cap, regulator,cap,resistor,and cap for a final of 12VDC.

anatech 27th March 2006 06:13 PM

Hi Joe,
I am curious why you would use the second R-C in the heater string. The higher regulator voltage may reduce it's temperature (the IC regulator) but will increase the chance of drop out. Why not then use the R-C ahead of the regulator and go with a 317 or 7812 type?

-Chris

Original Burnedfingers 27th March 2006 10:08 PM

Chris,
I have to use what I have.. I am 317 poor at the moment. To be perfectly honest I cannot remember the formula for figuring the resistors R1 and R2. Some people are telling me that a 7815 sounds better than a 317 also.

I figured use what I have and tweek it to get my 12.6 volts.


supply, cap, cap, resistor, regulator, cap, resistor, and cap for a final of 12VDC.

Supply,24VDC, cap .01, cap 4700, resistor 12 ohms, regulator, cap 470mfd, resistor 5 ohms, cap 220 mfd. This should let me end up with 12 volts with a 450mA load I think.

anatech 28th March 2006 02:13 PM

Hi Joe,
Fair enough. The mark of a good experimenter is to adapt what he has to what he needs.

Consider allowing some resistance between your 4,700 uF caps and the rectifiers. That will reduce the current peaks and cut down on some diode switching noise (a good thing). Your transformer may run cooler if the resistance is high enough. It's a good place to bleed off some voltage too.

With all your filtering, especially after the regulator, I strongly doubt there will be an audible difference in your regulator. Use whatever puts out the volts you want.

-Chris

audiohead 28th March 2006 03:20 PM

Hi Joe:
LM-317 : Vo = 1.25 X (1+R2/R1). Where R2 is connected from Adj pin to ground.

You can also use 7812, lift the ground lead of the regulator , insert a diode (1N-400X) in series with the ground lead, connect anode to the regulator ground lead and the cathode to ground. The regulator output voltage would 12.6 V.
Art

Original Burnedfingers 28th March 2006 11:58 PM

Quote:

Hi Joe,
Fair enough. The mark of a good experimenter is to adapt what he has to what he needs.

Chris

Who said I was good? Just lucky sometimes. I will move the 12 ohm resistor's position to right after the rectifier. This will give me supply, resistor, cap, cap, regulator, cap, resistor, cap, output.
This should allow current limiting and noise removal?

Hi Art,

Thanks for the formula. I will put it away for safe keeping and use it with the next batch of LM317's I buy. Now that I have the formula I will try it for future applications.

anatech 30th March 2006 01:50 AM

Hi Joe,
Quote:

Who said I was good?
See, now you just let the secret out. Everyone was convinced! I tell ya!

Try it and see. Make sure you have at least 3 VDC above the regulated output voltage at minimum line voltage, at the lowest point in the ripple to feed the regulator. Add some for safety and tired caps.

-Chris

Original Burnedfingers 30th March 2006 11:02 AM

Thanks Chris:D


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