[Hammarlund] Old Hammarlunds - audio output power

[Carl]

----- Original Message ----- 
From: "Richard Knoppow" <1oldlens1 at ix.netcom.com>
To: <kgordon2006 at frontier.com>; <Hammarlund at mailman.qth.net>
Sent: Friday, April 15, 2011 5:50 PM
Subject: Re: [Hammarlund] Old Hammarlunds - audio output power


>
> ----- Original Message ----- 
> From: "Kenneth G. Gordon" <kgordon2006 at frontier.com>
> To: <Hammarlund at mailman.qth.net>
> Sent: Sunday, May 15, 2011 12:52 PM
> Subject: Re: [Hammarlund] Old Hammarlunds - audio output
> power
>
>
>> On 14 Apr 2011 at 17:37, Carl wrote:
>>
>>> The military and commercial enviroment some of those sets
>>> were
>>> initially used in might have needed that much power.
>>>
>>> We are listening to AM, not a symphony or some wailing
>>> opera
>>> screecher.
>>
>> Actually, those receivers came with a phono input, so
>> maybe some of them,
>> at least, were used for listening to a symphony. :-)
>>
>> What was that very rare Hammurlund in the wooden cabinet?
>> The SP-155,
>> or something?
>>
>> Maybe Hammarlund just figured that once that 14 watt audio
>> stage was in
>> their receivers, they might as well leave it there.
>>
>> Ken W7EKB
>
>    At the time the Super-Pro was first put on the market
> many "deluxe" radio receivers had fairly high power,
> push-pull audio. It was sort of a horsepower race, plus the
> Super-Pro was a very high performance receiver for broadcast
> use and quite high fidelity. Remember, this was before TV or
> FM and the main source of entertainment broadcasting was AM
> radio. Also, many listened to short wave station which could
> sometimes deliver good quality audio. The push-pull stage in
> the Super-Pro and in other receivers of the time also had
> the advantage of lower distortion and much better low
> frequency responce than the usual single-ended output stage.
> Actually, despite its being overkill for communications use
> I found the low distortion of the Super-Pro reduced the
> effects of noise and QRM due probably to its lower IM and
> harmonic distortion. This can make a surprizing difference
> even for CW.
>     BTW, I strongly disagree with Carl about "headroom" or
> the ability of an amplifier, or whole system to deal with
> peaks. While this is of little relevance when the sources
> are highly processed to eliminate peaks it cerainly makes a
> difference for high fidelity reproduction. I mis-spent a
> large part of my life in professional audio and know how
> much difference good peak handling can make to the sound
> even though the peaks may be short. Certainly even one watt
> on a high efficiency loudspeaker can make a very loud sound
> but many high quality systems trade efficiency for bandwidth
> and are far from efficient plus the peak to average ratio of
> unprocessed music, or even speech is surprizingly large.
> Even if only twenty db the peaks for a 1 watt average will
> be 100 watts (db power ratio).
>     Typical medium high efficiency speakers will be around
> 94db SPL at one meter from 1 watt. 94db is _very_ loud. If a
> speaker system does not need to reproduce low frequencies
> (say below 250 hz) it can be made to have very high
> efficiency especially if using horn loaded compression
> drivers of the sort used for public address applications.
> Because these have high conversion efficiency and are also
> quite directional they will produce ear-splitting levels
> from a watt at a few feet.
>     On an old-fashioned horn loaded movie theater speaker a
> couple of watts will be quite sufficient. Typically old
> style theater amplifiers were around 10 watts for smaller
> theaters but then the dynamic range of old photographic
> sound traces was rather limited.
>
>
> --
> Richard Knoppow
> Los Angeles
> WB6KBL
> dickburk at ix.netcom.com
>

Disagree all you want but its completely irrelevant to the discussion of 
Super Pro audio and ham user requirements where 2W into any half efficient 
speaker is sufficient to fill a room. A radios audio output is specified at 
a certain THD or other distortion term at its maximum rated output which 
includes peaks. When the desired peaks for comfortable listening are only 2W 
or so the rest is wasted heat and overkill if the capability is 14W.

A single ended 6AQ5 can provide excellent over the air quality when the 
circuit is designed for it. Its when the range is restricted to 
communications audio and the output transformer has insufficient iron for 
the lows that it gets a bad reputation. Any Hammarlund using a 6AQ5 are 
excellent examples of barely adequate to poor audio. Include Collins and 
many others.

Carl