------------------------------
On: Fri, 8 Oct 2004 15:36:35 -0500 (CDT) Sean Jewett <[EMAIL PROTECTED]>
Quoted and wondered:
amplifier using 6550's as the output tubes. As I remember, I used a Starved Pentode circuit for the front end input amplifier which then drove a dual Triode Long-Tailed Pair which drove the output 6550's which were biased AB1 for an output of 100 watts, flat and stable from 5 cps to 100 kcps (cps= old speak for Hertz).
Which begs the question, what were you doing that you needed that range?! Better yet, did you have anything that would take advantage of that range?
Sorry Sean;
I should have been more clear. It was mostly because I wanted to see what could be achieved.
A friend and I set the amplifier on a small table in a room, empty otherwise except for an old up-right piano, with the intention of making power and band width tests. He had just finished what he referred to as his "Big Mouth" speaker. This was a 3/4 inch plywood box, on the front face of which he mounted 16 nine inch round speakers. The box was internally braced and stuffed with insulation to avoid both high and low frequency resonances. It sat at the outside wall of the room.
He also had two fairly hi-power "Tweeters" mounted on top of the box.
I started at 5 cycles and slowly swept the frequency upward. When I hit the resonance of the room, I increased the power and the piano started "walking" across the room. Much fun was had by all involved.
Later my friend took the Amplifier, Turntable, Pre-Amp and "Big Mouth" with a small motor generator in the back of his pickup to Huntington Beach where he later told me "Couples were dancing to the music from the "Big Mouth a half mile away".
This was in the 50's. None of this equipment was in any unusual. There were many outrageous designs in the magazines from many years before. There was an exponential Audio Horn that drove an 8x8 foot hole in the back wall of the front room of a house and curved properly exponential (so that the Speaker would match the room impedance) 20 feet out into the back yard where it was driven by some monster Amplifier and speaker..
I'm guessing something in the circuitry helped keep it that flat, but given the inablity for most amplifier manufacturers to build something flat across that range, why did it not take off? The only thing I can think of that comes close to meeting those specs are my Magnaplanar speakers. The specs state they're +-3db from 30Hz to 17kHz. They sound great even if they're a bit ineffecient (IIRC, 87db 1w/1m). I happened upon a good deal, otherwise I'd not own a pair. To paraphrase Ferris Bueller, if you have the means and ways I'd highly recommend them, they're so choice.
Most Manufacturers could do as well except there is a limited market for such a beast. One application comes to mind and that is Core Loss testing of large samples of of Hi-Frequency Ferrite or Iron transformer material.
That bandwidth was for the amplifier only at the Primary of the Transformer when loaded with a resister. Actually the feed back could be either from the Primary or the Secondary of the Transformer. Depending on the application. The design of the feedback compensation was difficult. The Audio Transformer was of very high quality.
The Starved Pentode front end allowed a very high effective mu for the single tube while the Long Tailed Pair allowed phase inversion with essentially unity gain to drive the 6550's. When the feedback included the transformer in the loop, the band width had to be chopped off in the high end to maintain stability.
Snip:
My hearing was limited (30db down at 10khz) early in my youth by close proximity, while duck hunting, to fired shotguns. So these projects were for the thrill of seeing them perform as designed and not for the Hi-Fi aspect.
If some one really begs me hard I can unburden myself of my adventures with the Tube Computers.
I only hear muffled groans. Ah me! just as well,
Ernie 75 and still going on and on and on ..............
-- SuperMacs is sponsored by <http://lowendmac.com/> and...
Small Dog Electronics http://www.smalldog.com | Refurbished Drives | Service & Replacement Parts [EMAIL PROTECTED] | & CDRWs on Sale! |
Support Low End Mac <http://lowendmac.com/lists/support.html>
SuperMacs list info: <http://lowendmac.com/supermacs/list.shtml> --> AOL users, remove "mailto:"; Send list messages to: <mailto:[EMAIL PROTECTED]> To unsubscribe, email: <mailto:[EMAIL PROTECTED]> For digest mode, email: <mailto:[EMAIL PROTECTED]> Subscription questions: <mailto:[EMAIL PROTECTED]> Archive: <http://www.mail-archive.com/supermacs%40mail.maclaunch.com/>
---------------------------------------------------------------
The Think Different Store
http://www.ThinkDifferentStore.com ---------------------------------------------------------------
