Allan Songers SA-100 on the scope

[sfogg]

Rick,

"To further confuse you, the capacitor charging/discharging process is the same wether you are listening to music or square waves. "

Which might also shed light on the reason behind Craig's earlier statement of...

" It allows AC through it because it alternates and never completely charges the Capacitor to its limit before it switches this is why if your not getting good low end response after the coupling cap you increase its size so as to not allow the AC to charge it before switching or changing its polarity."

Which ties into the time constant (time it takes to 'fully' charge/discharge) information that both Rick and Ryan posted earlier.

Craig, when you increase the size of the cap what happens to its time constant?

Now consider what happens when you lower the frequency of a wave.... what other characteristic of the wave changes and in what way? If it helps think about it in sine waves or square waves, whichever you prefer.

How does that characteristic change in the wave tie into the discussion of the time it takes to 'fully' charge a capacitor?

Shawn

[maxg]

----------------

On 2/27/2004 9:24:57 AM paulparrot wrote:

Max,

I have lots of recordings with a greater than 40dB range. If you're concerned about the safety of your system, play it quieter than normal first time through, and then you'll know what you're facing.

A low watt SET amp isn't going to be damaged by playing it either. It'll clip like crazy, but that's nothing new. Plenty of low watt SET people have no idea when they're hearing clipping, and in that case ignorance is bliss.

----------------

I was more worried about the speakers than the amps. As DB said:

"This is what blows out tweeters if the amp power is sufficient."

Plus - I am now not sure if it said 40 dB range or 40 dB peak above the normal level - they certainly seem to imply this was a rare thing - not something you wouldbe expected to have "many recordings with greater range than this" to paraphrase what you said.

I'll re-read the thing first and then play it on the minimal volume to see what happens. Whatever the case I dont want to wake baby and wife...

[Parrot]

Max,

If you had a painfully low-watt amp, you wouldn't have to worry about blowing out speakers because it wouldn't have enough power to do it.

I doubt if you have anything to worry about, though, with your amp. But if things go badly and your speakers are ruined, you can always buy Klipsch!

[maxg]

Thanks Paul,

I'll have to take that under advisement - right now I am looking for ways to bring money in - not spend it.

Its been an expensive week - I just bought 2 plots of land on Naxos with money I dont have right now (and am about to buy a third), my builder confirmed yesterday we need to find another $100,000 for the houses we are building on Trikeri (another island), and the wife wants to invest in a friends medical clinic he is building on Santorini.

One day I will be rich - if I dont go bankrupt in the process.....right now I dont have funds for any new vinyl - let alone speakers.

[3dzapper]

"One day I will be rich - if I dont go bankrupt in the process.....right now I dont have funds for any new vinyl - let alone speakers."

Good one Max! LMAO!!

My favorite saying is: " All my money is tied up in debt these days!" Actually all my assets are in real estate too. The only problem with land is that it doesn't have an ATM.

Rick

[mike stehr]

"A low watt SET amp isn't going to be damaged by playing it either. It'll clip like crazy, but that's nothing new. Plenty of low watt SET people have no idea when they're hearing clipping, and in that case ignorance is bliss."

Ya know Paula, yer about a narrow-minded motherf*cker, ya know that?

I jack-off on your stereo.

[3dzapper]

Mike,

I hate to say it but i agree with Paul on this one but not for the same reason as his assumption.

One of the benefits claimed for SET is it's "gracefull" clipping. A soft cutoff of the extreme dynamics of the passage.

If I had a room as big as Paul's i would need a lot more power than the paltry 15watts/channel or so watts I usually listen on too.

Rick

[mobile homeless]

Rick, I agree and disagree. I agree that SET has some of the most benign clipping characteristics of any of the tube amps, up until a point. But then, all tube amps have better clipping characteristics than SS.

On the other hand, I think that a good SET amp can have some of the best MICRO dynamics of any amplifier topology I have owned. This is one of the strengths of a well designed SET amp. A snare drum wack can sound almost "jump out of your skin" startling with a good SET. The sounds of plucked strings can be tantalizingly real, ditto with the human voice, as I have heard no better.

Still, your point is well taken in a large room with massive amounts of air to move. SET does not do the best at loading a very large space with complex large scale music.

kh

[Parrot]

The inadequacies of low-watt amps are more readily apparent in a larger room, true, but even in a modest room can't cut it except under certain circumstances, like with low volume and a cocktail lounge singer with quiet piano accompaniment. If that is the way you like your music, super!

But, and this is a big but, if distortion, clipping, and mush aren't noticeable to you, enjoy yourself and play any type of music you choose, way louder on your amp than it was ever designed to be driven. You don't have to please anyone but yourself.

It's weird that the low-watt SET-cultists can't understand the simple facts of the matter, that Klipsch recommends 20 watts minimum for all of their Heritage series. But heck, when you're dealing with MAGIC, who cares about physics.

[ben.]

It's...

[Painful Reality]

Not really as a brick wall has some useful purpose.

[Parrot]

Yes, brick wall is a decent visual analogy to what low-watt SET does to the signal. When an amp is called on to do more than it was designed to do, the loudest portions of the signal can't get loud enough to reproduce accurately, and the loudest portions are then less loud than they should be. So you end up with the loudest portions clipping, getting flattened out and compressed, and being no louder than the quieter portions. Kind of like running it through a limiter. Exactly what you don't want for high fidelity.

Good call!

The old axe analogy is also pretty good, in that low-watt SET chops off the loudest portions of the signal. But it's not as good of a comparison as the brick wall, because the signal isn't really chopped off, but just cut down in size.

That's why Klipsch, in all their Heritage literature, calls for at least 20 watt amplifiers. Of course they're assuming that people want to hear high fidelity and won't be satisfied with an amp that produces loud volumes no better than a clock radio! But, hey, call it MAGIC and there will always be someone willing to believe.

[jazman]

Why did PWK like a Brooks 2A3 amp so much? You're the one who proclaimed PWK as "my hero". What a never ending crock?

Klipsch out.

[coda]

Paul, don't believe anyone asserted that low-power SET is a full-range device, but why the clock radio analogy? You should know, by reading on this forum alone, the availability of low-power SET gear that offers plenty of dynamic headroom on reserve when required. And you should also have some idea by now that the SET "magic" (i.e. coherence) is attributed, in part, to smaller amounts of high-order harmonic distortion as there is no possibility of crossover distortion with this circuit.

Difficult to understand the bottleneck in your understanding the benefits of SET, aside that the 20-watt power requirement isn't to be found online. Does Klipsch still publish it?

[mace]

Well, I finally got my hands on a scope and 8 Ohm, 25W non-wound resistors (thanks Craig). I want to AC balance my Scott 299Arev2.

What do you guys recommend for a frequency generator? I was planning on using my Macintosh (computer, that is). Is that good enough? I'm assuming I don't have to worry about coupling when I AC balance this amp. I figured I'd just go straight from amp to scope.

Thanks,

mace

[Tom Mobley]

Ryan,

Thanks for posting that succinct procedure. That's really helpful.

I recently acquired an LK-72 off ebay, the guy said he'd been using it. When I fired it up one of the 7591 plates started glowing red. I pulled the bottom off and did the DVOM on the pins method, turned out the pot was all the way to one side, no wonder. Anyway, evened it out some and red plate cooled off immediately. The thing is the nastiest POS I've ever seen, must have been mounted in the smoke exhaust duct of a bar or something. I'll try the oscope method when it's ready, see how far off it is.

Tom

[3dzapper]

Tom,

On your Lk-72 a good mod is to remove the 7591 cathode resistors and the wires connecting the pairs of cathodes.

Then install four ten watt resistors, one to each cathode and a test jack to measure the individual tube bias. To bias the tubes adjust the bias pots to increase or decrease voltage and the balance control to even the voltage between the tubes in the pair until both tubes read 350mV. This allows a little mismatch in the tubes to be compensated for. if you like I can send you some pictures.

This is not my idea. I learned it from Craig and give him all due credit.

Rick

[Parrot]

----------------

On 2/27/2004 8:42:10 PM jazman wrote:

Why did PWK like a Brooks 2A3 amp so much? You're the one who proclaimed PWK as "my hero". What a never ending crock?

Klipsch out.

----------------

First, the Brook 2A3 amp was not a flea-powered amp. It was 10 watts. I think, not positive, that PWK used a Brook at his lab on the workbench. If so, this was probably a situation in which he didn't need to fill a large room with sound. Further, most of PWK's praise of the Brook was in the early years. The amp was from 1947. Later, as I recall, he used McIntosh. And probably other stuff that I don't remember right now. It was not a case of him recommending only Brook, or only single ended.

Are you sure I proclaimed him my hero? I doubt that. First, I never even met the guy. By accounts he sounds like an extraordinary man, though.

I'm not sure what you're referring to in your next statement. You will have to be a little less subtle.

[Parrot]

----------------

On 2/27/2004 9:44:31 PM Are Friends Electric wrote:

Paul, don't believe anyone asserted that low-power SET is a full-range device, but why the clock radio analogy? You should know, by reading on this forum alone, the availability of low-power SET gear that offers plenty of dynamic headroom on reserve when required. And you should also have some idea by now that the SET "magic" (i.e. coherence) is attributed, in part, to smaller amounts of high-order harmonic distortion as there is no possibility of crossover distortion with this circuit.

Difficult to understand the bottleneck in your understanding the benefits of SET, aside that the 20-watt power requirement isn't to be found online. Does Klipsch still publish it?

----------------

I say to each his own and live and let live.

Actually, there are a couple or three people here who do indeed believe that low-power SET is a "full-range device." The clock-radio analogy was for their benefit, to illustrate that just because something can play really loud does not mean it is playing high fidelity. I can play the clock radio loud enough that I want to run screaming from the room, my hands over my ears, dodging the plaster as it is shaken off the ceiling. That kind of nasty distortion is a lot more obvious than the compression and mush you get with SET distortion, true enough, but the point is the same. It's not how loud it gets because just about anything can play loud, it's the quality when played at loud levels that's important.

But heck, if someone enjoys a lot of distortion or a lot of limiting and mush, that's fine by me. Everyone has different tastes and different criteria. I do think it would be a disservice to newbies to just let these low-watt posts slide by without comment, though. I'm not trying or expecting to change anyone's mind who is sold on anything. But it's a good thing to make people aware of the limitations of low-watt amps. If they decide to go that route after they've been informed, that's entirely their decision and I wish them lots of enjoyment.