Hello all,
Quick question. Took my Decware SE84CSEX apart a while back to rebuild on a larger chassis due to hum, started listening to cans, and never rebuilt it.
It's time to get it functional again ( wife's orders ).
On some other projects I have used the new Amtrans carbon resistors and I really like them. I decided to use them for the shared cathode resistor on the EL84 output tube ( 100 ohm ), but its not available in sufficient wattage, so I decided to parallel four 2 watt 390 ohm resistors which nets me 97.5 ohms on the cathode. Didn't think twice about it until after they were in house. Since I have very limited experience doing this stuff, I was wondering if that 100 ohm value needs to be closely adhered to, or the slight additional current the 97.5 ohms will draw is insignificant. ( Using 6n14n-ev, which are pretty robust tubes ).
So to you guys who have been doing this awhile, is 2.5 ohms under target OK in this application, or should I go back to my original 5 watt 100 ohm Kiwame ?
As always, many thanks in advance
Cheers, Crazy Bill
Quick question. Took my Decware SE84CSEX apart a while back to rebuild on a larger chassis due to hum, started listening to cans, and never rebuilt it.
It's time to get it functional again ( wife's orders ).
On some other projects I have used the new Amtrans carbon resistors and I really like them. I decided to use them for the shared cathode resistor on the EL84 output tube ( 100 ohm ), but its not available in sufficient wattage, so I decided to parallel four 2 watt 390 ohm resistors which nets me 97.5 ohms on the cathode. Didn't think twice about it until after they were in house. Since I have very limited experience doing this stuff, I was wondering if that 100 ohm value needs to be closely adhered to, or the slight additional current the 97.5 ohms will draw is insignificant. ( Using 6n14n-ev, which are pretty robust tubes ).
So to you guys who have been doing this awhile, is 2.5 ohms under target OK in this application, or should I go back to my original 5 watt 100 ohm Kiwame ?
As always, many thanks in advance
Cheers, Crazy Bill
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Actually I like to hit them a little harder, ala Decware and Eddie Vaughan's Carina. Bias is 9 volts, and they're right at their listed max. for plate dissipation, which is why I noted I used the Russian milspec tube, which is noted for being able to take some punishment. I'ver got 20 pr in house. I know I'll probably shorten lifespan a bit, but I'm worried about a catastophic failure.
Thanks for your help,
Crazy Bill
Thanks for your help,
Crazy Bill
From c 2.5% variation in cathode resistor value ??? That will be lost in the wash, other factors swamp it.
Personally I wouldn't think twice about such variation, wouldn't expect any notable change in bias or audible effect - but then personally I wouldn't really expect an audible effect from changing cathode resistor manufacturer/type either
FWIW 5W rating of the original part appears a bit OTT from what you posted.... probably dissipates somewhat less than 1W in use....? Who knows, perhaps it covers fault conditions, but hard to see that IMO and in case it helps.
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