XPost: sci.electronics.design
On Fri, 28 Dec 2018 14:19:50 +0200, Tauno Voipio
wrote:
>On 28.12.18 10:45, upsidedown@downunder.com wrote:
>> On Thu, 27 Dec 2018 21:11:35 -0600, tubeguy@myshop.com wrote:
>>
>>> I'm not intending on building this, but it's interesting and makes me
>>> wonder if someone could use EIGHT 6L6 tubes, or TEN?
>>> (Of course adding more tubes mean bigger audio output transformers and
>>> heftier power supplies.
>>
>> Tubes may age at different rates, so the characteristics might be
>> quite different after a long time. It might not make sense to replace
>> a single (failed) tube and you may have to replace the whole set of
>> tubes with new tubes preferably from the same manufacturing batch.
>> This can be quite expensive :-)
>
>
>In the 1960's, I made a guitar amplifier with six EL500's. The tubes
>are not characterized for linear use, and they were not matched in
>any way. Each tube had an own cathode resistor, and there was no
>evidence of any overload from unbalanced operation.
>
>The tubes had a tendency of parasitic oscillation, so I added a
>ferrite bead on the control grids and an inductor-resistor parallel
>combination on each plate (for constructions, see nearest ham handbook).
Back in the late 60s early 70s, I had several (self refurbished)
mono-block power amps that used four 6L6 output tubes. I did not even
know about matching those tubes. I just put in any tube marked as a 6L6.
I recall having both the glass (GC) types mixed with the black metal
ones. I always had good sound and lots of power. I do recall that
replacing the metal cased ones with 6L6GC did increase my power though.
But until I could afford new tubes, I used what I had. And even with the
new tubes, I never matched them.
--- SoupGate-Win32 v1.05
* Origin: you cannot sedate... all the things you hate (1:229/2)
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