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Old 26th December 2010, 06:17 PM   #8001
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Quote:
Originally Posted by simon7000 View Post
Gosh darn golly, I saw that exact circuit in a 60's home electronic organ circuit!
Cool.

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Pain in the "A" to fix as by the 80's the PNP germanium output transistors were getting pretty scarce. The output choke was "fist" size, the heatsinks the 6 x 4 12 fin design and the output transistors were TO3's. The earlier version used a modified all copper TO5 which took a bolt into the top to attach to a heatsink. The drivers were TO5 cased. Put out almost 10 watts at 5% THD!
For the headphone amp I'm able to rather better than that, using modern, high gain silicon devices.

I'll let you know how the scaled up power amp version fares.

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So what was the patent claim?
Transistorized power amplifiers suitable for driving loud speakers are known. A variety of configurations may be used for such amplifiers, such as complementary symmetry transistors (one PNP and one NPN transistor or one P-channel and one N-channel FET) connected as push-pull emitter followers or push-pull common emitter stages; or like conductivity type transistors (both PNP or NPN transistors or both P-channel or N-channel FETS) may be used in a push-pull configuration, with one of the transistors being operated as an emitter follower and the other of the transistors being operated as a common emitter stage.

While these systems provide a way to power a loud speaker system, several problems are associated with each of the prior art systems. For example, when a common emitter stage is used in a push-pull configuration in conjunction with an emitter follower stage, the gain characteristics of the two stages forming the push-pull circuit are inherently unequal. Consequently, feedback circuitry must be employed to compensate for such differences, and to reduce the distortion caused by such differences. Such feedback circuitry usually takes the form of an external feedback loop, such as collector to base feedback. Similarly, feedback must be employed when two complementary symmetry stages are connected in a common emitter configuration to reduce distortion inherent in common emitter stages. Such feedback increases the complexity of the amplifier, and reduces its stability.

Another problem associated with the prior art transistor amplifiers arises in the coupling of the loud speaker system to the output of the amplifier. Direct coupling to the amplifier is advantageous from a simplicity and low-frequency response standpoint, but such direct coupling results in a direct current path through the loud speaker which can cause excessive direct current to flow through the voice coil of the loud speaker. Such direct current can adversely bias or saturate the voice coil of the loud speaker and result in distortion. Consequently, in order to avoid such a direct current flow, the prior art amplifiers utilize coupling capacitors in series with the loud speaker to block such direct current flow, or employ a split power supply that maintains the potential difference between the terminals of the amplifier to which the loud speaker is connected at substantially the same potential.

The use of capacitor coupling has the disadvantage that unless a very large capacitor is used, an attenuation of low frequencies results. Furthermore, the use of a capacitor in series with the loud speaker can produce a loud pop in the speaker during the time the capacitor is being charged after the unit is turned on. The use of a split power supply requires precise balancing of the amplifier, and usually requires a balance control to maintain the output terminals of the amplifier at the same potential. Furthermore, failure of a component in the output or balancing circuits of the amplifier can cause substantial direct current to flow through the speaker. In addition both solutions significantly increase the cost of the amplifier.


se
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Old 26th December 2010, 06:58 PM   #8002
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Originally Posted by john curl View Post
You should of seen me in them 50 years ago. I looked great!
The reason for the tights is to be able to properly see your legs, which is the tool you are refining, and still keep them warm. This is important.
Oh I get it. Otherwise you couldn't see the forest for the tree?
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Old 26th December 2010, 06:59 PM   #8003
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Originally Posted by john curl View Post
Poor design, just the same.
Because...?
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Old 26th December 2010, 07:08 PM   #8004
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Oh I get it. Otherwise you couldn't see the forest for the tree?
Now THAT was funny.

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Old 26th December 2010, 07:13 PM   #8005
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What's wrong isn't the amplifier, it's the paradigm behind the system design. Given the ability of human hearing and memory, it is not possible for todays concepts of what high fidelity means in the sense of duplicating the sound of live acoustic instruments through recordings to convince the human brain it is experiencing the same stimulus.
Reproduced music cannot reconstruct truly and fully live music. Agreed.
So?
Is there a design concept for audio amplifiers you offer, or is it hat, according to you, all amplifiers are futile?
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Old 26th December 2010, 07:15 PM   #8006
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Unfortunately, Soundminded, the detailed commentary that I put forth this morning, discussing our differences, has disappeared, and I am reduced to just a few words, that sometimes pass on to be be seen by everyone else. I would have thought you more refined when it came to the Arts, but I must have been wrong.

Last edited by john curl; 26th December 2010 at 07:45 PM.
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Old 26th December 2010, 07:17 PM   #8007
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Here's an unexpected answer to Joshua's question. If you walked into a room and a sound system was playing music and you didn't know what amplifier was installed, could you correctly guess which one it is? I'd have thought the answer was no. But in 2007 I went to the VTV show in central NJ which wasn't far from my home. I heard a whole building of vacuum tube amplifiers. Then late in my visit, I heard a setup with a solid state amplifier, probably the only one at the show that day. I guessed it correctly immediately. I was reminded why I was glad to see the end of vacuum tube amplifiers and why I never turned back. Perhaps todays seemingly universally shrill loudspeakers benefit from the peculiar coloration (electrical waveform distortion) that an output impedence matching transformer imparts to high frequencies. I know it did not benefit the dull sounding bookshelf speakers of the 1960s. I only learned recently on another blog site that the reason the AR3 LvR demonstrations I heard worked as well as they did, surprisingly well in fact, was that Roy Allison had turned up the treble control on the PAS3 preamp to compensate for AR3s rolled off high end and possibly the Dynaco Stero 70s coloration. You had your choice then, dull high ends from bookshelf speakers or harsh ones from large horn speakers like A7.

Hearing memory is I think better than you'd imagine, better than a what I've read would have me believe. For example, you can usually immediately identify someone you knew for a long time but hadn't seen or heard form in decades if you get a surprise phone call from them. You can also usually tell if someone you don't know has even a slight cold or sinus condition by the sound of their voice alone. While hearing can't improve with age, it can only deteriorate (mine still tests very good) I think you can train yourself to become a much better listener. You can make yourself aware of many details of sound you overlooked in the past. It's too bad I can't hear those LvR demos again. I wonder how convincing they'd sound to me now. If you can find it, watch PBS's documentary about Steinway pianos called "Note By Note." Notice how carefully prospective buyers listen to and compare the sound of different Steinway pianos. Each of them sounds different and each performing artist is looking for a particular sound that suits their performing style best. It is too bad our recording technology can't really reproduce the sound of any of them. That is still beyond the state of the art. Improving a preamplifer to get from 99.997% perfection to 99.998% perfection will not close the gap.
This definitely doesn't answer my question.
Here we go again:
Reproduced music cannot reconstruct truly and fully live music. Agreed.
So?
Is there a design concept for audio amplifiers you offer, or is it hat, according to you, all amplifiers are futile?
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Old 26th December 2010, 07:17 PM   #8008
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Hi Joshua, thanks for your input. I know that you can tell the difference in amps and preamps, just from your responses over time.
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Old 26th December 2010, 07:50 PM   #8009
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Originally Posted by Joshua_G View Post
This definitely doesn't answer my question.
Here we go again:
Reproduced music cannot reconstruct truly and fully live music. Agreed.
So?
Is there a design concept for audio amplifiers you offer, or is it hat, according to you, all amplifiers are futile?
How many audio amplifier designs exist? 10,000? 20,000? 50,000? 100,000? Why would one more matter when there are so many out there which perform just fine? I built my first audio amplifier when I was 10 years old. Not from a kit but from the schematic in the back of an RCA tube manual. I used old radio parts I found. I didn't even have the right amplifier tube. I needed a 50EH5 but used a 50C5 instead. I bought an aluminum chasis at Lafayette radio for about $3. I found a tool and die set and punched to tube holes, drilled out the screw holes for the tube sockets. I was amazed when I hooked it up to a crystal phono cartridge and a table radio speaker and it worked. I've seen, heard, built, owned countless units. My professor Paul Chirlian wrote the book. One more amplifier or preamplifier won't slove anything. The whole approach needs to be rethought.

As for "Reproduced music cannot reconstruct truly and fully live music" I consider that a temporary situation, a problem that will be eventually solved. But not yet, not by the people working on it now, at least the ones I'm aware of. They aren't up to it, it's beyond their capabilities. A discussion looking for the holy grail in one more preamplifier, one more amplifier, one more speaker system, one more wire or cartridge is proof. You can hit your head against those walls all you want, they won't fall over.
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Old 26th December 2010, 08:08 PM   #8010
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Originally Posted by john curl View Post
Simon, please, what does this submission of circuits relate to wearing ballet tights? Does anyone know WHY dancers wear tights? Do you also know that we wear a matching pair of shorts over the tights for modesty sake, AND we wore a DANCE BELT that puts a Jock Strap to shame in elastic strength and containment.
I was a swim team parent for a while, it's amazing how many 8-12 yr olds are embarrased to wear a Speedo in public.
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