help with voltage reg ala Sbench,but pass tubes s11e12

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vegard
Posts: 4
Joined: Thu Jun 03, 2010 10:04 am

help with voltage reg ala Sbench,but pass tubes s11e12

Post by vegard »

I built S bench ,voltage regulator as described in his article.I ommitted the negative supply, and placed a 0d3 between cathode of error amplifier and ground.
the regulator worked well.
I then changed the error amp tube to 12by7a.This worked well to.
Then I changed the passtube.Two s11e12 instead of pl519.
with a load of about 70-80 ma the voltage out is as wanted, but when I increase current draw to 190 ma the outputvoltage drops to 330 ca.attached is a schematic values in open field is with 70-80ma drawn.
The enclosed values is with 190 ma drawn.
What did I do wrong ?
How doI correct it ?

Vegard
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s11e12regulator.JPG
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sbench
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Post by sbench »

Hi,
My first comment would be the pass tube want more than the G2 voltage you provided them in order to provide the current output you want. The "107 volt" G2 supply looks to be too low, so that when you attempt to draw the required current you can't get enough output.

Hope that helps.

Regards,
Stephie
vegard
Posts: 4
Joined: Thu Jun 03, 2010 10:04 am

Post by vegard »

Stephie !
Swaped in one 0D3 : rising vg2-k in the pass tubes.
I have to change some resistorvalues but output voltage could be turned up over 480 v with full load (225 ma in my case)

I buildt your voltage reg to do meassurements on 13e1, last year.
The voltage regulator is now in the psu of two 13e1se monoblocks.
The drawing in my post has one fault :11 ohm resistors in the pass tube cathodes was forgotten.

I was surprised that I had to rise g2.13e1 is running very well with g2-k voltages as low as 100 v.
The voltage va-k in the pass tubes is about 100 v at 450 v out, vg2-k is 155v,
should I worry about vg2 at higher potensial versus cathode than the anode versus cathode ?

Ps Thank you so much
pps running 13e1 as beam tetrode with plate to grid feedback.the voltage reg supply is performing better than a lc-lc I compared it with.
I did not expect such differences soundwise that I experienced.

Best regards Vegard
vegard
Posts: 4
Joined: Thu Jun 03, 2010 10:04 am

Post by vegard »

Because I´m curious:
would it be worth the effort to build a shunt reg ala the one used in the t-rex amplifier, and compare performance with the one above in my amplifier circuit (attched)
13e1 is run as tetrode at about 160 ma, v-ak 460v,vg2-k 100-120 v
opt is 2600/8.E282f pentode coupled ,g2 107v vak140v 20-24ma.
degree of feedback between 10-16%.I have not nailed the ca values yet.

as is amp is quiet enough (400microvolt noise on output)makes about 30w
with thd at 1 khz between 1.3 and 2,6 % a tad below clipping.
(depends on degree of feedback)

If worthwhile : do I have to alter something in the shunt reg circuit of the
t rex (exept changing some resistorvalues to compensate for my higher v+ ?
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sbench
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Post by sbench »

Shunt regulators almost always sound better than series regulators for whatever reason. As to whether it's practical and or worthwhile? Good question. They throw out a lot of heat, thus become impractical at some point. Not sure what the T-rex shunt reg looks like, but if its higher voltage you're moding for and roughly the same current, your power dissipation in the shunt element will, of course, be higher. That may take it outside the range of the devices used.

Warmest Regards,
Stephie <3
vegard
Posts: 4
Joined: Thu Jun 03, 2010 10:04 am

Post by vegard »

http://www.enjoythemusic.com/magazine/e ... x/fig2.gif

Here is the schematic of the shunt reg used in T-Rex .One such common for the channels(300b se )voltage is lower but current channel l+r should be the same as in one of my monoblocks.
Yes I understand that this reg ulator is ac-shunting.thought it might do well in tetrode/pentode anode supply

As for the heat:It has been about 20 degrees celcius below zero since primo november here in Norway ....
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