6P3S-E Cathode Resistors
I have just about completed assembling parts for an SSE build later this year. My main components are;
Hammond 374BX power transformer,
James 6123HS output transformers (5K),
Hammond 193J choke and
40uF/440v motor run cap.
From forum postings and using a 5AR4 rectifier, I hope to achieve a B+ of about 450v. I have some Russian 6P3S-E's that I thought would be a good place to start. From the forum it is evident that a higher rated cathode resistor, eg 750-820R, would be more suited to these valves. Would this be a sensible choice and is that B+(450v) okay?
In future I would like to move on to using new Tung-Sol 6L6GC-STR's, which would possibly be happier with the standard 560R cathode resistors.
Not being an experienced builder and wishing to keep things relatively simple, any advice would be appreciated.
Lastly, a big thumbs up for Digikey. I e-mailed my order for the majority of the items on the SSE PCB parts list last Sunday evening and in less than 2.5 days my parcel arrived. That's what I call great service.
Still running the Frugel Horn Mk3s? :)
Your choice of trafos is the same as what I am planning - may I ask where did you get the James 6123HS?
I'm a noob - so somebody else will have to answer your cathode resistor question.:)
820 is a safe place to start. It should be cold enough for any tube. I'd pick up a few other values, just you can play around with it. I don't know what the Tung-Sol reissues are like. I don't have any experience with those particular tubes.
Yes I still have the FH3's, they are great. I had a pair of Fostex 167E's so I purchased plans from Bob Brines and built his FT1600 MkII's. NICE.
I currently have a 0.75 Watt 'Darling' amplifier so I am trying George's SSE for a little more power. Should be good.
I see that you are also thinking along these lines.
There is plenty of good information on the forum and it helped greatly when putting my parts list together.
Thanks for the advice. I took a look at your website and the 'binding post' method for swapping cathode resistors would be the sort of solution that I would be looking for.
Could you please tell me how that works for you and possibly provide some additional information on the type of binding posts used?
About the James 6123HS output transformers, they came from a guy called Sandy in Taiwan via E-bay. This was quite a while ago and I'm not sure whether he is still trading.
2 cents more
I recently completed a tubelab simple SE and have been listening to 6P3S-E tubes. I like them very much; I can compare them to Groove Tubes KT66 (from china), and Groove Tubes KT88 with the heat sink (I think these are similar to the JJ). I've settled on the 6P3S-E as my current favorites.
my B+ is 455
plate voltage: 443
cathode resistors: 600 ohms 5 watt
cathode voltage left: 34.6 so 23.55 watts Pdiss
cathode voltage right: 35.8 so 24.29 watts Pdiss
These tubes sound darn near as good as the kt88's and consume a lot less power. I've got the amp plugged into a watt miser meter and with the 6P3S-E's I clock 107 watts; with the kt88's it burns up 150 watts !
Also noted with the watt miser is the fact that the 12AT7 I prefer, a nos sylvania 12at7a, uses more electricity than the 2nd best, a phillips jan 12at7wc. The 107 watt setup above is with the Sylvania 12at7a, with the Phillips I clock 89 watts.
Thanks for the information. The 6P3S-E seems like a good all-rounder. Glad that you are enjoying them.
I have just ordered a pair of Tung-Sol 6L6GC-STR tubes as users have posted that they also get close to the KT88's performance in the SSE.
What method do you use to change your cathode resistor values?
I think I will opt for a ON-OFF-ON DPDT switch to give three values for tube rolling.
rkinze (Russ) has posted helpful advice about switching and he has also included a spreadsheet to assist with the necessary resistor selection.
The forum is a great source of information.
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