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Old 13th February 2006, 03:47 PM   #1
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Default 6922 .2 sections in parallel

(sorry for my english)
Hi, I am a total newbie with tubes:
I have a simple preamp with one Sovtek6922 anode output
( half one channel- half the other channel)
210 Volt ; anode resistor= 15Kohm ; cathode resistor=330 ohm
Cathode bypass= 220 microF
Now I want experimentate the sound of 2 sections in parallel ( each channel) at the same "work-point". I expect 1/2 Zout .
What is the correct values for resistors and cap?
Thanks advanced for your time
Cheers,
Inertial
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Old 13th February 2006, 07:28 PM   #2
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TubeCad results suggest that you could removed the resistors and capacitor from one side of your dual triode then jump pin 1 to 6, 2 to 7, and 3 to 8, and have safe operating conditions without changing actual values of the remaining components.

1/2 the z out @ 1.35 K, bias @ -2.65 volts, gain 29.6

dr._sleep
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Old 14th February 2006, 10:42 AM   #3
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Thank you dr._sleep for the help!
Cathode and anode resistors remain the same. Now I am quiete.
Many thanks again.
Cheers,
Inertial
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Old 14th February 2006, 11:29 AM   #4
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incorrect
you need to half anode and cathode resistor,if you want same transfer characteristic
if you don't want same transfer cc... , it's another story
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Old 14th February 2006, 03:29 PM   #5
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Oh, Thanks Choky!
Yes , maybe my bad english have caused mistake.
Yes I want exactly the same behaviour for the "double" that
I haved before with "single". Istinctivally I also have thinked
for Half-values of the two resistors .
I can go with safety!
Many thanks again Mr Choky!
Cheers,
Inertial

P.S.: Double values for the capacitor of cathode bypass?
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Old 14th February 2006, 10:29 PM   #6
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Quote:
Originally posted by inertial
Oh,

P.S.: Double values for the capacitor of cathode bypass?

yup!
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Old 15th February 2006, 05:05 AM   #7
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Thought I'd offer the easiest way to go parallel:

"TubeCad results suggest that you could remove the resistors and capacitor from one side of your dual triode then jump pin 1 to 6, 2 to 7, and 3 to 8, and have safe operating conditions without changing actual values of the remaining components."

"incorrect says chokey
you need to half anode and cathode resistor,if you want same transfer characteristic
if you don't want same transfer cc... , it's another story"

If you keep the same B+ and half the anode and cathode resistors you will excede the recomended plate voltage for a 6922.

If my suggestion sounds crappy then change all components as others have suggested.

Sorry,
dr._sleep
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Old 15th February 2006, 09:30 AM   #8
Zen Mod is offline Zen Mod  Serbia
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do your homework without tube cad
every program is effective exactly as guiding hand is capable

I repeat-if goal is double S,half Ri, lowered noise and same transfer characteristic ,then you must halve both resistors;
in that conditions both triode systems will see same voltage and current as in previous -one triode- stage.
I have no doubt in your good will , but this is simply incorrect;

if you keep same resistors as for one triode,transfer characteristic will change;
depending of actuall circuit-maybe to worse,maybe to better....
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Old 29th May 2006, 03:09 AM   #9
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Hi Inertial,
Any update ?
Did you make any changes ? If so what were the results ?
Cheers.
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Old 29th May 2006, 08:57 AM   #10
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Unfortunately I am now total absorbed by speakers and room
development.
The guy that normaly help me with tubes ( 66 years old) is total
dedicated with a phono preamp. I must have a lot of patience

Cheers,
Inertial
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