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PostPosted: Fri Apr 03, 2009 11:19 pm 
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Yes, 150 ohms is a safer value for the power tubes not to over-cook themselves....

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PostPosted: Sat Apr 04, 2009 3:11 am 
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yeah was meaning a 150r...id take it for sure as i cant find the value here only been able to get a 220...


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PostPosted: Sat Apr 04, 2009 9:59 am 
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All, I haven't read the entire thread, but I too had a muddy tone that was boomy with HB's but ok with sinlgle coils, from a stock sIII I built in December.

I started by changing the power section cathode bypass cap from 220 to 50uF/50v. That tightened it up a bit. Then after reading some posts on this forum, I check that plate dissipation and current through my JJ tubes using a 120 ohm resistor (actually measured 123) and it was at about 43ma per tube and 14 watts PD; way too high. I located two power resitors (totaling 150 ohms) and installed them to test. I'm amazed at the clarity and how articulate the amp became. Therefore, I changed backed to the original 220uF cathode bypass cap and all is good. The tone is magnificant, and now the tubes are running at about 39ma with 13W PD.

So, use that for what's it worth and see if you get the same results.

Also, coco being the gentleman that he is, has mailed me a 150ohm/5W, keeping his word.

I'm couldn't be more pleased with this amp. It rocks. :D

Just FYI - I'm playing through a 2x12 W* bomb - a 30w alnico blue dog and a 50w ceramic silver bell.


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PostPosted: Sat Apr 04, 2009 1:06 pm 
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Great, I was planning on using a 150r 5w since its all I have in my spare parts stash. I am building the plexi with mostly spare parts (not including the board/trannies) which were so graciously provided by Stephen. I did think that the 150 would be safer for the PD on the power tubes anyway. I guess I'll try it out before I change anything.

Speaker wise- I listened to the speaker comparisons for all of the 18watt models in the "Clippage" section. Usually my favorites were the Greenbacks or the TTA... how does the TT San Rafael sound? Stephen said it's their answer to the Greenback... but does anyone have any experience using one? I'd love to hear one if someone has a link.


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PostPosted: Sat Apr 04, 2009 1:47 pm 
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elegy wrote:
update....i put an 2200uf in the cathode power and it helped to tighten it up very much....now if i could get back some sparkle and more mids variations on the mid knob it would be cool.

For more sparkle, place a film cap of around 0.1uF or 0.68uF cap across your 2200uF cathode cap. Maybe an orange drop would would work even better here, as they tend to be quite bright sounding. For the mid control, try replacing the pot with a 50k, instead of the usual 25k.

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PostPosted: Sun Jul 22, 2018 10:03 pm 
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SPAM!!


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