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Re: [Amps] IM distortion and such

To: "Joe Isabella" <>,"Gary Smith" <>, <>,<>
Subject: Re: [Amps] IM distortion and such
From: "Cecil Acuff" <>
Date: Mon, 26 Jun 2006 11:37:50 -0500
List-post: <>
I would bet with the collective wisdom of this group two or three amp 
designs fitting the power levels and complexity generally agreed upon could 
be created and posted in an FAQ or Projects section of the Amps list.  It 
would need to include details...such as how to make various parts or where 
to buy various parts.  i.e....winding toroids and which core to use.  What 
surplus parts would be best suited for use in a particular design and where 
to get them.

Personally I would love to build an amp from scratch...haven't done that 
since high school when I built a dual 813 amp from hamfest parts for use 
with my Heath HW-101.  My Dad folded me up a galvanized steel chassis with 
an aluminum front panel at the local Jr. College VoTech where he taught.  He 
passed away a few years back...wish I still had that amp....or even pictures 
of it.  Would have been a lot easier if I had known more about tubes and 
picked a simple triode. The 813's were big, new and cheap with sockets back 
in 1974.....Looked impressive but didn't make a whole lot of power...think I 
got around 450 watts DC out using variable caps and a roller inductor from a 
Collins KWS-1.

My interests would be a basic manual tuned amp with a 2kw PEP output 
capability with the ability to switch it to a lower plate voltage to allow 
it to loaf along at say 1kw PEP or 600 to 800 watts CW out all day long. 
Based on a single tube or maybe a pair of tubes.  Cheap tubes allowing 
retubing of the amp for a few hundred dollars...less if possible.  Something 
fairly bulletproof, buildable with surplus parts such as transformers and 
variable caps so one does not have to buy high dollar new for everything. 
Stabile and clean output a must...

1.5 to 50 Mhz.....

Total parts bill of less than 1K including tubes desirable.

A 1K PEP output solid state auto band switching black box would  also be 
nice....that would communicate with my FT-1000D....

That didn't cost 3K+

Oh well one can dream....

Bet this group could do to save the competitiveness for the 
contesting though and be an AMPS team to get it done....


----- Original Message ----- 
From: "Joe Isabella" <>
To: "Gary Smith" <>; <>; 
Sent: Monday, June 26, 2006 10:40 AM
Subject: Re: [Amps] IM distortion and such

> Since when does management listen to engineers??  They listen to the 
> mighty $$$$.  Just like the Space Shuttle Challenger disaster chain of 
> events, the engineers said "NO!!", but management said "We'll lose 
> millions!!", so they launched with frozen O-rings.  We lost more than 
> millions...
> If you want a "perfect" amp, build it yourself.  Better yet, let's all do 
> that, swap hardware, and see how perfect they are!!  Bet you a cup of 
> coffee none of 'em are...
> :-)
> Joe, N3JI
> ----- Original Message ----
> From: Gary Smith <>
> To:;
> Sent: Monday, June 26, 2006 10:26:10 AM
> Subject: Re: [Amps] IM distortion and such
> Coming from Mr Matney, a most excellent point of view.  Particularly where
> one could be sued into bankruptcy and then oblivion.
> Gary...wa6fgi
> ----- Original Message ----- 
> From: "Will Matney" <>
> To: <>
> Sent: Sunday, June 25, 2006 5:39 PM
> Subject: Re: [Amps] IM distortion and such
>> It's according to what kind of audio amp. Guitar amps are designed to
>> purposely introduce distortion. That's where the squeal of the electric
>> guitar comes from. The bands actually prefer this. However, if one is an
>> engineer, and you have a maximum rating curve, it is a liability to ever
>> go outside the curve into the over load region. That's like saying I'll
>> put my stamp on this bridge which I know is going to deflect more than
>> allowable published tolerances, and that I think it can get by with the
>> added stress, even though I am over the maximum curves for tensile and
>> yield strength. Then an automobile drives over it and falls in the river.
>> Who's liable? Whether electrical or mechanical engineering, an engineer
>> should always look at this. Though running a tube out of spec probably
>> wont kill anyone, the manufacturer better be ready to replace tubes or 
>> the
>> entire amp if the customer is dissatisfied as a suit will sure follow if
>> they don't. If ran in spec, one has nothing to worr
>> y about, and has published data to fall back on. This from an engineers
>> point of view.
>> Best,
>> Will
>> *********** REPLY SEPARATOR  ***********
>> On 6/25/06 at 4:00 PM k7fm wrote:
>>>Tom said:
>>>"I think you are really saying an engineer shouldn't ever
>>>design outside what is actually published on a spec sheet
>>>that only covers a limited number of situations under any
>>>condition, even if the component manufacturer, field
>>>history, or direct testing show otherwise."
>>>It might be easier to grasp what Tom is saying if you think of audio
>>>amplifiers.  Assume a tube manufacturer specifies a tube for audio
>>>distortion.  However, the manufacturer of the audio amplifier is looking
>>>minimum distortion.  If he finds that running the tube outside of the
>>>specified by the tube manufacturer gives consistently lower distortion,
>>>it would be good engineering to do so.   In some cases, tubes might be
>>>selected for those parameters that met the goals of the engineer.  In 
>>>cases, the plate dissipation might be exceeded to get closer to class A.
>>>Colin  K7FM
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