Finally got the last touch for my ‘69 clone!

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SpiderWars

SpiderWars

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A set of Sylvania 6CA7s. I bought a quad a long time ago but one tube ran way, way hotter than the other three and just wasn’t compatible. So I finally bought another matched pair and they are within 10mA of a pair of the others so…close enough.

Definitely has a slightly different midrange. Not scooped but definitely less mids at certain frequencies. It also gives it a little more lean/muscular tone. Tighter. But if you remember from the EL34/6CA7 Shootout that Friedman/Thorn did it’s not a night/day difference. But enough of a difference.

The hope is that these will last the rest of my days. I swear this thing does not break a sweat running it cranked/variac’d.

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NICE SPIDER.......:2thumbsup:LUV me some Sylvania 6CA7's! I run them in my 72 and 68 plexi! The last pair in my 68 were 15 years old and still biasing ok but weren't sounding like they used to so I recently installed another matched Quad where just one tube reads about 10ma higher than the other three but oh well. I went on a Sylvania kick years ago and picked up quite a few, enough to last how much I play now.

FWIW the EH6ca7's are fairly close sounding to Sylvania's and the EH's are beam forming element tubes( a 6l6 with an EL34 pinout) just like the real 6ca7's were.
 
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Nice! Looks great.

Funny thing about matching tubes; I've found that when they are mismatched like yours, ie lowest at 30ma and highest at 40, I hear better tone vs 4 matched within 2ma of each other. Go figure.
 
Racerxrated said:
Nice! Looks great.

Funny thing about matching tubes; I've found that when they are mismatched like yours, ie lowest at 30ma and highest at 40, I hear better tone vs 4 matched within 2ma of each other. Go figure.
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I think I totally agree with that statement..................The tone is in the mismatch.........................................:yes::2thumbsup:
 
What filtering are you running on your 69? I see you have dual 100uf ARS in it...... Is your PI 100 or 200uf?
 
Congrats. Those tubes are indeed special. To my ear they occupy a space that sounds like a 50% EL34, 25% 6L6 and 25% 6550 blend.
 
harddriver said:
What filtering are you running on your 69? I see you have dual 100uf ARS in it...... Is your PI 100 or 200uf?
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It's 100uF. There is a 330k (or 390k) resistor from that lug to the other lug with an 82k resistor to ground. The filament center tap is connected to that second lug. I have dual 100uFs in the main first filter stack too. The screen stack is typical 50+50 cans.

I shouldn't really call it a '69 clone. It just started out as a '69 variant Ed-spec inspired amp. Stout filtering, oversized OT (it's too fat too mount '69 style* so it's '68 style), 500+ volt Super Bass laydown PT.

* - \:D/
 
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SpiderWars said:
It's 100uF. There is a 330k (or 390k) resistor from that lug to the other lug with an 82k resistor to ground. The filament center tap is connected to that second lug. I have dual 100uFs in the main first filter stack too. The screen stack is typical 50+50 cans.

\:D/
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Are you running some type of elevated heaters off that second lug, sounds like a voltage divider setup on that 100UF for just that very purpose?
 
SpiderWars said:
Yes, exactly.
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Ahhh.... HAH! Very NICE! I usually tap mine at the screens filter caps as it was recommended to me to tap it there.

Is there a benefit to tapping the B+ at the PI besides convenience?
 
harddriver said:
Ahhh.... HAH! Very NICE! I usually tap mine at the screens filter caps as it was recommended to me to tap it there.

Is there a benefit to tapping the B+ at the PI besides convenience?
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Just convenience. You can also use dual 100s for the screens but then only use one side of each for the screens. Then use the unused lug on the grounded can for the heater center tap connection. I saw that in a Friedman-modded Marshall. I think the resistors were 470k/100k.
 
SpiderWars said:
Just convenience. You can also use dual 100s for the screens but then only use one side of each for the screens. Then use the unused lug on the grounded can for the heater center tap connection. I saw that in a Friedman-modded Marshall. I think the resistors were 470k/100k.
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Good info to know and keep in the bag of tricks! Thanks Spider!:2thumbsup:
 
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