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Old 6th March 2004, 01:54 AM   #21
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Quote:
Originally posted by fscarpa58
2W for 20k e 30k res

for the other ( 200, 1meg, 270k) also 0.2 W.

I like the topology very much but, in this case,
and with 6N1P, we need 300 V to have it working properly.

Owing to the constrain due to the rigid connection
between plate of 1th tube and grid of the 2nd, the working
point is not very good, that is high distortion
( 0.4% at 5Vrms out) and not very great max swing.

However it works and maybe you will like its
sound.


If you don't need gain the CF is advisable.

Federico
Thanks Federico! Will give you updates soon.
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Old 6th March 2004, 02:52 AM   #22
AKSA is offline AKSA  Australia
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Federico,

I agree with your comment about the poor operating point of the direct coupled CF. It does not sound so good.

However, the configuration has a huge advantage.

If the output is taken from the plate of the first tube, not from the cathode of the second, and if the plate resistor is made equal to the cathode resistor, then we have perfect current balance as long as the plate is held at half B+.

This means that the current draw of the two triodes will add to a constant; viz, perfect current balance. This makes power supply design very easy, and improves the bass performance a great deal because there is no voltage sag on the B+.

In 1999, John Broskie of Tubecad.com came up with this approach; I think it is very clever.

Cheers,

Hugh
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Old 6th March 2004, 02:37 PM   #23
trancy is offline trancy  Slovenia
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Quote:
Originally posted by fscarpa58
However

this has about 25 db of gain.

I really do not like it.

federico, are those (in post #16) values for ecc88, or some other tube? if its not, could you recalculate for me....


i'll be grateful
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Old 8th March 2004, 08:44 AM   #24
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Hi trancy

You have to decide.

post #16 is addressed to JojoD.
The cir has high gain, 150 V B+ supply,
it is tuned for 20k load, and uses 6n1p.

I post a message for you a few days ago.
It was a 3db gain with 100V B+, uses 6DJ8/Ecc88
and was tuned for 4.7k load.

let me know.

Federico
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Old 8th March 2004, 08:48 AM   #25
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Quote:
In 1999, John Broskie of Tubecad.com came up with this approach; I think it is very clever.
Hi Hugh

I agree with you, and I also consider
Broskie idea a very good one.

Federico
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Old 8th March 2004, 08:59 AM   #26
trancy is offline trancy  Slovenia
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Quote:
Originally posted by fscarpa58
Hi trancy

You have to decide.

post #16 is addressed to JojoD.
The cir has high gain, 150 V B+ supply,
it is tuned for 20k load, and uses 6n1p.

I post a message for you a few days ago.
It was a 3db gain with 100V B+, uses 6DJ8/Ecc88
and was tuned for 4.7k load.

let me know.

Federico
sorry for inconvenience federico,

I"ll try to make CF on 100V B+ with ECC88 from your schematic, and also I want to try on 150V B+ with same sch.(if I"m correct, higher B+ is better for sound quality)...

........


is there any simple formula to recalculate values, or its nessesary to have some tube related sw?

I really dont want to bother you federico, but...you know....I dont know anything about tubes...this is my first one....practicly I am a tube virgin....ohhhhh yeaaahhh....
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Old 8th March 2004, 09:25 AM   #27
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Trancy

Quote:
I really dont want to bother you federico
I am happy to help you.

But I need clear data to work on.

1) type of circuit
2) tube
3) gain
4) B+
5) load

If you only want that I recalculate values for circuit of
post #8, here is the pic.

Federico
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Old 8th March 2004, 10:00 AM   #28
trancy is offline trancy  Slovenia
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great...thanks federico.....

thats all I want this moment....i will report you, how its work....
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Old 8th March 2004, 10:49 AM   #29
trancy is offline trancy  Slovenia
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federico,

those values of resistors, is enough for 14K resistor to be 1/4W, and for 200E 1W ?
Is it O.K., if I use 14,7K instead 14 and for 180 ohms instead 200 ohm....?

its hard to find exact values ( I have 14,7K and 180 E)...


thanks


ciao
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Old 9th March 2004, 11:18 AM   #30
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Quote:
Is it O.K., if I use 14,7K instead 14 and for 180 ohms instead 200 ohm....?
Yes , it's o.k.



Quote:
is enough for 14K resistor to be 1/4W, and for 200E 1W
No, actual static dissipation of the 14.7k res. is a bit less
of 0.5 W so I advice you to use at least 2W to 4W res.

the 200R res dissipates less of 10 mW so you can safely
use 0.1W res

Federico
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