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Old 17th April 2012, 09:13 PM   #1
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Default replacing kt66 valves

Hi ,can anyone recomend replacement valvesmay be sels for my quad11 amps.There are a batch of new valves,genalex,harma,saratovs,valve art,tad,sovtec,
shuguang,jj.I read about the russian 6n3c but found it to actually be a 6l6.So far it looks like the jj kt66 may be selected.Anyone had experience
with any of the named valves.
solderon.
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Old 17th April 2012, 10:34 PM   #2
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The Shuguangs are the closest to the originals. China already produced KT66s for GEC in the '70s, sold under the GEC/Genalex/MOV brands.

Sovteks and Tung-Sol reissues have very similar internal structures to their 6L6 tubes...

Harma and Groove Tubes are in fact russian Saratovs, as are TAD, I think.
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Old 17th April 2012, 10:54 PM   #3
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Quote:
Originally Posted by Vincent77 View Post
China already produced KT66s for GEC in the '70s, sold under the GEC/Genalex/MOV brands.
WHAT??? I thought China was only making trouble in the seventies.
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Old 18th April 2012, 09:00 PM   #4
7N7 is offline 7N7  United Kingdom
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In my Croft-modified Quad IIs, I run Russian 5881s or 6L6GCs. I know that everyone says they are no good, but they sound fine, the heaters require only 0.9A as opposed to 1.3 for KT66 - always worthwhile giving the poor old Quad's mains transformers a break, as they get hot enough as it is.

And they are very cheap.

And when I first installed the valves, I checked the various voltages and they were exactly on spec.

P.
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Old 18th April 2012, 09:19 PM   #5
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Originally Posted by 7N7 View Post
... I run Russian 5881s or 6L6GCs...
A 5881 isn't a 6L6GC! The numbered equivalent to the 6L6GC is called 7581A.

Your Russian 5881's are looking like these?

Click the image to open in full size.

These are 6P3E-S's, made by Reflektor and often sold as 5881's, but they don't match the 5881's maximum ratings.

Best rfegards!
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Old 18th April 2012, 09:26 PM   #6
7N7 is offline 7N7  United Kingdom
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Hullo.

The amps are not with me at present but yes they do look like that as far as I recall.

I bought the 5881s and the 6L6GCs from the same supplier in the U.S.; I know that they are different - the internal structure is different. I really cannot say that there is an audible difference - there may be but as usual I cannot hear it!...

And I do like the blue glow.

As for the ratings, well that has not proved to be a problem in the Quad IIs - no red anodes at least.

All the best
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Last edited by 7N7; 18th April 2012 at 09:27 PM. Reason: Typo
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Old 18th April 2012, 09:26 PM   #7
adam2a3 is offline adam2a3  Greece
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Hi, I have the best results with USA made 5881 RCA or TUNGSOL. Better than 6L6GC.
In my Quad II clone I run a pair of RY50 (250V at g2 stabilized by VR105+VR150). I use an original Quad output transformer and get approx 18 Watts. No KT66's needed!
The most economic and fast solution is EL34's (connect pin 1 to pin 8 and trim the cathode resistor for correct bias). Acceptable sound.
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Old 18th April 2012, 09:45 PM   #8
7N7 is offline 7N7  United Kingdom
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Originally Posted by adam2a3 View Post
Hi, I have the best results with USA made 5881 RCA or TUNGSOL. Better than 6L6GC.
In my Quad II clone I run a pair of RY50 (250V at g2 stabilized by VR105+VR150). I use an original Quad output transformer and get approx 18 Watts. No KT66's needed!
The most economic and fast solution is EL34's (connect pin 1 to pin 8 and trim the cathode resistor for correct bias). Acceptable sound.
adam2a3
Yes but 1.5A each to light up EL34s!

P
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Last edited by 7N7; 18th April 2012 at 09:46 PM. Reason: Edit!
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Old 18th April 2012, 09:59 PM   #9
adam2a3 is offline adam2a3  Greece
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Quote:
Originally Posted by 7N7 View Post
Yes but 1.5A each to light up EL34s!

P
Yes, it can fry the transformer if mains voltage happens to be high, so 5881's USA is best of all.
RY50's can replace except KT66 the KT88 too! Only g2 needs some attention and filaments need 12V.
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Old 19th April 2012, 01:11 PM   #10
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Quote:
Originally Posted by Kay Pirinha View Post
A 5881 isn't a 6L6GC! The numbered equivalent to the 6L6GC is called 7581A.

---snip---

These are 6P3E-S's, made by Reflektor and often sold as 5881's, but they don't match the 5881's maximum ratings.

Best rfegards!
Although on paper, no, the maximum ratings on the 6P3S-e's are lower than the 5881 (not to mention a 6L6GC's ratings), I'm yet to see them fail (or even break a sweat) in any situation which calls for a 6L6GC or a 5881.

Incidentally, the tube marketed by Sovtek as a 5881 / 6L6WGC (to my knowledge) is in fact a rebranded 6P3S-e which is used by a few manufacturers as their stock "6L6GC" they ship with amps.

The Soviet's sure knew how to build a hefty tube when the task called for it, I'll give them that.

But that said - no these are not 5881's, they just happen to be happy in a 5881's place.
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