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#26 pre amp
#26 pre amp
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Old 30th March 2013, 02:07 PM   #3081
merlin el mago is offline merlin el mago
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Quote:
Originally Posted by stajo View Post
I didnt find any suggested value in the sheets. Try 50 k. You might need to up the B+ to compensate for the fall over the anode resistor.
Can't compensate B+ the VR150?
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Old 30th March 2013, 02:08 PM   #3082
stajo is offline stajo  Sweden
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#26 pre amp
Quote:
Originally Posted by Magz View Post
Simple. R+C across transformer secondary.
Click the image to open in full size.
As a zobel?
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Old 30th March 2013, 02:12 PM   #3083
stajo is offline stajo  Sweden
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#26 pre amp
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Originally Posted by merlin el mago View Post
Can't compensate B+ the VR150?
Then I suggest OPT, choke or gyrator. Resistor voltage drop will skate you our of the loadline.
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Old 30th March 2013, 02:14 PM   #3084
Magz is offline Magz  United States
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Originally Posted by stajo View Post
Click the image to open in full size.
As a zobel?
Yes.
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Old 30th March 2013, 02:15 PM   #3085
merlin el mago is offline merlin el mago
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Gyrator like Iko used? It seems to complicated for me, could you please post a schematic how can be used with VR150?
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Last edited by merlin el mago; 30th March 2013 at 02:19 PM.
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Old 30th March 2013, 02:21 PM   #3086
Magz is offline Magz  United States
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Quote:
Originally Posted by stajo View Post
Then I suggest OPT, choke or gyrator. Resistor voltage drop will skate you our of the loadline.

In my mind, 150v is far too low a B+, because it doesn't allow you to use a proper load on the 26. Even if you want to use an active load such as a CCS or a gyrator, these work best with 70-100V headroom. If you want to operate at ~150V on the tube, I suggest having 220V B+ at least.

I would suggest increasing the B+ and using a VR150 and VR75 in series to get 225V, followed by a CCS set to 6-7mA. Alternatively you could also use a resistor or go back to your transformer load.
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Old 30th March 2013, 02:22 PM   #3087
iko is offline iko  Canada
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#26 pre amp
The only way you could possibly have a circuit from a 150V DC supply would be to have a low DCR anode choke of 150H up and output the anode signal with a capacitor.
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Old 30th March 2013, 02:23 PM   #3088
merlin el mago is offline merlin el mago
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Thanks guys, I supposed be more easy change OPT to output cap, I left the OPT
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Old 30th March 2013, 02:24 PM   #3089
iko is offline iko  Canada
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#26 pre amp
Quote:
Originally Posted by Magz View Post
B+ and using a VR150 and VR75 in series to get 225V, followed by a CCS set to 6-7mA.
It's what I have, a VR150 in series with a VR75 for B+. Gyrator as load, and I end up with 150V DC on the plate of the 26.
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Old 30th March 2013, 02:26 PM   #3090
merlin el mago is offline merlin el mago
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What about the SQ with that configuration?
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