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Old 5th September 2006, 10:55 PM   #1
Jaime is offline Jaime  Uruguay
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Default Direct heating triodes are really better?

The direct heating triodes are really better?.
There are some Web where explains this?

I feel very intrigued by the FI 421A
http://www.6moons.com/audioreviews/fi6/421A.html

best regards Jaime
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Old 6th September 2006, 10:34 PM   #2
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Jaime

No reason. On the contrary, there is a varying potential difference between parts of the filament and the control grid, so what is the actual bias? - etc. It is sometimes a little intriguing how, years after some developments have taken place and had been universally accepted as improvements, some visionaries would suddenly pop up and cause doubt as to which direction in audio is actually forward.

The F1 421A certainly looks neat, but I find the description too loaded with typical promotional fodder to mean much. (I mean: "When simple is best, that's the only ticket to bliss in valve land." Please!) Or simply swapping 6SL7s with 6SN7s?? I personally have a problem with exorbitant costing flea-power amplifiers - I built enough of them myself, and never found a good reason for using multibuck ultra-scarce tubage. Unless for collector's value, of course ...... But it is your money.

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Old 7th September 2006, 12:53 PM   #3
amperex is offline amperex  United States
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Usually older direct heater tride power tubes are better. It is the low plate resistance that is desireable in home entertainment amps.
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Old 7th September 2006, 01:45 PM   #4
Giaime is offline Giaime  Italy
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Quote:
Originally posted by amperex
It is the low plate resistance that is desireable in home entertainment amps.
Now tell me between trioded EL36 and 2A3 (absolutely the same dynamic characteristics) which is better.


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Old 7th September 2006, 10:16 PM   #5
Jaime is offline Jaime  Uruguay
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Amperex:

Plate resistance 6AS7G : 280 ohms
Plate resistance 421A : 330 ohms
Plate resistance 2A3 : 800 ohms

You said : 6AS7G and 421A are better than 2A3 ?
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Old 7th September 2006, 11:35 PM   #6
kmtang is offline kmtang  Canada
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Hearing is believing.

If you don't believe it, try it out yourself.

I won't say which one is better. It is up to you to decide.

Johnny
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Old 8th September 2006, 12:40 AM   #7
SY is offline SY  United States
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Or (as I've found), there's no consistent sonic advantage of one over another as a general case. But a DH tube certainly is more of a pain in the posterior to set up and run correctly, which may be its real attraction.
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Old 8th September 2006, 12:56 AM   #8
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"Better" is too subjective in audio. Kmtang and the correct answer
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Old 8th September 2006, 03:22 AM   #9
vax9000 is offline vax9000  United States
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I believe DHT is better. the low impedance and high linearity combined, is better. 6AS7 has very bad linearity.

My theory:
DHT are old; thus primitive tech; thus big distance between cathode and grill; thus better linearity.
newer diode's problem, newer tech; thus closer cathode and grill (for higher amplify factor); thus worse linearity.
If we can move the grill of new triode away from its cathode, we may get a triode that is better than those old DHT.
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Old 8th September 2006, 03:50 AM   #10
rdf is offline rdf  Canada
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Quote:
Originally posted by vax9000
6AS7 has very bad linearity.

How so?
Attached Images
File Type: png 6as7g.png (18.7 KB, 368 views)
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