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Old 19th Oct 2019, 5:22 pm   #1
sparkymike
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Default Quad valve query

Can a Quad amplifier run on 6L6GC valves in place of the KT66 ?
If so, what modifications are needed, if any ?
Mike.
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Old 19th Oct 2019, 5:31 pm   #2
Herald1360
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Default Re: Quad valve query

Yes.


A search in this forum will turn up a fair bit of info, a good starting point may be here?


https://www.vintage-radio.net/forum/...ad.php?t=77741
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Old 19th Oct 2019, 5:56 pm   #3
RojDW48
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Default Re: Quad valve query

I always liked the sound of the 6V6GT, beloved of Decca and Tripletone back in the day, and popped my Tripletone ones in a Quad 2 for fun and it sounded fine. 6L6 should be OK too I would expect.
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Old 20th Oct 2019, 8:50 am   #4
sparkymike
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Default Re: Quad valve query

The RCA 6L6GC black plate's are the best sounding ones in my opinion, but now getting up to similar prices of KT66's. I have a copious supply of these, as I own a couple of Fender twin amps and these have four in each amp.
Mike.
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Old 20th Oct 2019, 2:22 pm   #5
analogadikt
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Default Re: Quad valve query

Quote:
Originally Posted by RojDW48 View Post
I always liked the sound of the 6V6GT, beloved of Decca and Tripletone back in the day, and popped my Tripletone ones in a Quad 2 for fun and it sounded fine. 6L6 should be OK too I would expect.
This is the first time am hearing or reading about KT66s being subed by 6V6 GTs. Is the pinout and voltage ratings same for both these valves?

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Old 20th Oct 2019, 3:23 pm   #6
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Default Re: Quad valve query

The pinouts of the 6V6 and the 6L6 and the KT66 are all the same. But the ratings of the 6V6 are substantially lower than the other two valves. I would expect their lifetime, even in a Quad II, which doesn't work KT66s hard, would be short.

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Old 20th Oct 2019, 6:35 pm   #7
Herald1360
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Default Re: Quad valve query

Downsizing to 6V6 should at least involve some rebiassing, I would think. The output loading would be rather less than ideal, too.
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Old 20th Oct 2019, 10:29 pm   #8
Synchrodyne
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Default Re: Quad valve query

Quad did cover the alternative use of the 5883 and 6L6G in its Quad II instructions, as shown here:

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The 6L6G was specified to be used in matched pairs. I imagine that this may have been because of its lower maximum anode dissipation as compared with the KT66.

I recall that back in the early 1980s, the then NZ agents for Quad put a 6L6G pair in one of my Quad II amplifiers when they were serviced. As I recall – and as expected – in normal use I couldn’t tell the difference between that and the other one which retained its KT66s. Perhaps there would have been a difference when driven to clipping, but I didn’t go there.


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Old 20th Oct 2019, 10:52 pm   #9
turretslug
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Default Re: Quad valve query

I'm assuming that Quad meant that the 5881 (a widespread industrial-series 6L6 derivative) could be substituted, rather than the 5883 (a somewhat specialist waveguide-mounted X-band T/B switch....)
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