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Old 15th February 2005, 01:50 AM   #11
day is offline day  Thailand
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no! ti is 300b .. i love triod. i think tetrodes is not goog as triod
what do you think
sorry for bad ENG.
thank you.
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Old 15th February 2005, 05:42 AM   #12
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No need to apologise for your English, it's much better than my Thai

Pentodes and tetrodes can be very good, it's just that they tend to produce too much distortion and have too high an output impedance on their own - so they need some negative feedback to work well (preferably of the local kind). In any case, some tetrodes can make very nice triodes.
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Old 17th February 2005, 05:41 AM   #13
day is offline day  Thailand
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this is my RCA8121 it look nice . today i saw new tube 6C4 . IT can be preamplier and how dose it sound.
thak you
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Old 17th February 2005, 05:49 AM   #14
day is offline day  Thailand
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rca 6C4
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Old 17th February 2005, 07:20 AM   #15
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Isn't the 6C4 essentially half od a 12AU7/ECC82?

dave
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Old 17th February 2005, 08:52 AM   #16
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Whoa! It looks like you have about seventy 6C4s there, and I can see some other valves which I can't quite make out in the box at the top left of the picture.

Dave is right - the 6C4 is essentially half a 12AU7/ECC82/etc...

Why not try making a massively paralleled amp - maybe something along the lines of the Tim's Hept'AU7 <- why isn't this link working?
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Old 17th February 2005, 09:06 AM   #17
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Hept'AU7

Hept'AU7

Click the image to open in full size.

just testing
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Old 17th February 2005, 09:10 AM   #18
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The parser is choking on the ' in the URL -- not a legitimate character for a URL... i'm surprised the graphic worked. The working URL probably 404s since i took out the '

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Old 18th February 2005, 01:59 AM   #19
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Default Re: want to build SE450TL

Quote:
Originally posted by day
HI
I have 3 of 450TL. can i do SE amp? anybody have circuit
thank you


Sell to a licensed Amateur Radio Operator.
Ebay.
Or better still trade with a licensed Amateur Radio Operator
for some tubes that will fly much better in SE operation:

845
211
etc...

The voltages required are very high with the 450TL and the plate impedance is scary high too - makes for a tough xfmr match...

Not a project for someone who is not clear on the tube and working safely with LETHAL high voltages...

Makes a fine AM ham radio transmitter tube though!




_-_-bear

PS if you were in north america you'd have no trouble finding hams who want and use them class C... if they are good, don't waste them on lamps!
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Old 18th February 2005, 02:06 AM   #20
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Quote:
Originally posted by day
this is my RCA8121 it look nice . today i saw new tube 6C4 . IT can be preamplier and how dose it sound.
thak you

That is a 4CX250B

4 elements... 4CX----
CX = ceramic & metal

250watts of plate dissipation.

Useful for class C RF or Class AB modulator service.

Very high voltage ~2kv and up.

Not a very good audio tube, but usable in a stable circuit.
Eimac and RCA showed some applications as modulators.
High plate impedance makes it tough though.
FORCED AIR COOLING (noise)

NOT a preamplifier tube!!

Nice tube for RF, a pair will do ~1kW PEP as a linear - the tube is useful up into the VHF spectrum.

Again, sell or trade to a licensed ham radio operator!

_-_-bear
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