[Swan] Swan 1200W amp question

[John P.]

Hi,

  I have a 1200W that I love.

  On the 1200W the bias is fixed and thus the idling current is about 100 to 120ma.  I put a voltage doubler on the bias power supply and made it an adjustable bias.  I run at a max idle of 80ma - That is only about 70 watts total or 17.5 per tube.

  I use an MFJ 971 tuner on the input.  I really give me more by tuning the input.  BTW, I drive it with an SB-101.

  As far as tubes,  the amplifier uses 6LQ6's.  You can also use, 6MJ6, 6ME6, & 6JE6C tubes.  They are all 99.9% identical.

  I recapped the amp earlier this year.  The original filter had a net of 52.5uf and my recapped one now has 115uf.  It is not for more output but for a stiffer supply and better linearity.

  For best linearity, use a scope to look at a trapezoid pattern.




--- On Thu, 11/27/08, Paul Cleven <pdcleven at charter.net> wrote:

> From: Paul Cleven <pdcleven at charter.net>
> Subject: Re: [Swan] Swan 1200W amp question
> To: "Discussion of equipment manufactured by Swan" <swan at mailman.qth.net>
> Cc: "Gil Woodside" <wa1lad at cox.net>
> Date: Thursday, November 27, 2008, 12:55 PM
> Hi Gil;
> 
> I really enjoy using my 1200X with my 300B.
> The 1200 series can be driven with less than 100watts. 
> The nature of a linear amplifier is that there is a maximum
> drive level that allows the amp to stay in its linear range.
>  This implies that that the amplifier, driven correctly,
> will reproduce the transceivers signal without adding
> spurious signals.  Overdriving is the big problem.
> 
> The 1200x is looking for a 12V switching current in
> transmit.  I don' know what modern transceivers provide
> for outboard switching.
> 
> Also these amps don't have adjustable tuned inputs so
> the solid state stuff may not like driving into this load. 
> Back in the day tube rigs didn't mind driving a 5:1 swr
> as long as that voltages produced didn't cause arcing in
> the final stage.
> 
> Paul
> N9XZ
> ---- Gil Woodside <wa1lad at cox.net> wrote: 
> 
> =============
> Hi All.
> 
> A friend of mine just aquired a Swan 1200W amp. I have a
> couple of questions about it. I'm not an amplifier user
> so I couldn't answer his questions. 
> 
> 1. Can it be used with a solid state radio (ie-IC706,
> TS140, FT840) ?
> 
> 2. Can it be driven with less than the 100-120 watts the
> manual states without damage to the amp? 
> 
> Thanks, 73
> Gil/WA1LAD
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