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alejo 23rd August 2004 02:30 PM

need 13fd7 curves
Hello, I interesting to buil a little SE amp around a disimilar triode 13fd7.
In Duncanamps page find datashet for this double triode but not find curves, I need this for desing.
The 6V version of this triode name is 6fd7.

Plese, if you now where I can find this.....

PrairiePete 24th August 2004 01:57 AM

I think the closest you are going to get, is the 6em7. Triode 1 is identical. Judging by other circuits (6em7), run triode 2 as per the manual for a 6fd7. In this case 150v, -17.5v at 40ma.

fdegrove 24th August 2004 03:41 AM


Maybe this will help:


I haven't checked if any of the references have a published datasheet showing curves.
Seeing what the tubes were designed for, I doubt any of them will.
I recall having had to plot the curves ourselves when trying to decide which of those disimilar triodes was best suited for a headphone amp....


EC8010 24th August 2004 08:27 AM

Aaargh! I looked up that reference, Frank, and it had 6ES8 as a replcement for 6DJ8! Now we know where all that trouble started.

(For those of you who didn't know, 6ES8/ECC189 is a variable-mu double triode, whereas 6DJ8/ECC88 is constant, so if you try to use 6ES8/ECC189 for audio, you can count on increased distortion.)

fdegrove 24th August 2004 08:15 PM



Now we know where all that trouble started.
Oh dear...
I doubt they were the cause of the confusion. Many publicized documents list it as being a substitute anyway.

What caused the troubles is some greedy vendors rebranding their stock of ECC189s turning them into fake ECC88s IMO.

Either way, it's generally good practice to know that most so called substitutes will "work" in most circuits although far from optimally in quite a lot of cases.
For a finely tuned audio circuit it would be good practice to carefully check with the datasheets first.


Tom Bavis 24th August 2004 11:51 PM

For what it's worth, the 6DE7 (10DE7, 13DE7) DOES have curves at Frank's place (though the smaller triode has lower gain), and it's pin-compatible with the 6FD7. So you could start with that one, and if you need the gain, drop in the 6FD7. They all are probably close to 6EM7 / 6FG7 / 6FM7 etc.

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