[Amps] Advice

[Carl]

That would be true if the only criteria is filament emission.

However, a single 8877 is loafing at 1500W and is not really a good example.

Now, if you want to compare a 3-500Z at 900W to a pair at 1200W I suspect 
the answer will be that a pair will be holding at that power level a lot 
longer.

You can see similar in a 30L1 that has had the 811A's replaced by 572B's. 
Power remains the same but life becomes almost infinite.......at least with 
USA tubes.

Carl
KM1H



----- Original Message ----- 
From: "Jim Barber" <audioguy at charter.net>
Cc: <amps at contesting.com>
Sent: Saturday, December 05, 2009 1:28 PM
Subject: Re: [Amps] Advice


> Here's a question from another angle:
>
> Say I use two 8877's instead of one (with proper cooling and whatever
> else is required) and run 1500W PEP output SSB, would the two tube
> version run more hours than the single tube before output started to
> degrade?
>
> My guess is "probably not". Takers?
>
> Thanks,
> Jim, N7CXI
>
> Bill, W6WRT wrote:
>> ORIGINAL MESSAGE:
>>
>> On Fri, 4 Dec 2009 17:07:47 +0000 (UTC), Paul Decker <kg7hf at comcast.net> 
>> wrote:
>>
>>> One possible advantage of two tubes over a single tube is the blower and 
>>> airflow.  Sometimes using two smaller tubes will require less airflow 
>>> and have less backpressure than a single tube.
>>
>> REPLY:
>>
>> Excellent point. It is a well known law of geometry that multiple small 
>> objects
>> have larger surface area than a single object of the same total volume. 
>> It
>> stands to reason that two smaller tubes will cool better than one large 
>> one,
>> other factors being equal. Thanks.
>>
>> 73, Bill W6WRT
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