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SET amps.............


SWL

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I get more involvement with the music when listening to my 2A3 SET amp than all the other junk around here. But there is compromises. It falls short with some music I like at higher levels.

One can design a BR cabinet using a amplifier with lowish damping factor in mind.

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Things don't change much around here it seems!

Oh well...

Parrots may come and go, but the topics usually remain the same.

Scott (SWL), have you thought anymore on what SET amp you'd like to mate with your Peach and RB-75s?

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Things don't change much around here it seems!

Oh well...

Parrots may come and go, but the topics usually remain the same.

Scott (SWL), have you thought anymore on what SET amp you'd like to mate with your Peach and RB-75s?

I just got a pair of Heresy's (80's) to throw into the mix. So, I have gotten a few offers that are somewhat local that I can do some experimenting with the Peach/ Heresy/RB-75 configuration. I will take my time to find the "right" amp for this system.

PS........Traded the Mini Max for a nice pair of oiled walnut Heresy's.

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"Further, I didn't enjoy the 300SEI so much musically merely because it introduced frequency-response deviations and added lots of low-order harmonic distortion. Instead, the 300SEI's fundamental musical rightness overcame its limitations."Robert Harley

 

Kev--

That's the "thing" that is entirely impossible to express to people who don't hear, or care about that "thing." The so-called "musicality" simply can not be expressed in words to another person any more than trying to explain love or art or beauty, or the taste of chocolate really. The embodiment of it is not intellectual in any sense (frequency response chart deviations), it is purely in the experiential realm. I don't think anyone designing such amps isn't fully aware of the compromise being made, they just prefer this set of outcomes over others.

Mark - I hear you. The output impedance of an amplifier will have an effect on the sound but, much like wattage (specifically LOW watts), that why, IMO, speaker selection and system matching becomes even more crucial. So I can appreciate that , as an engineer ho designs amps, you would make this design choice to obtain a particular sound with a particular type of speaker. I'm not familiar with your amp, so I cannot comment on its performance on speakers with a less than optimal impedance plot (optimal referring here to the way it matches up with the pCats). If I'm off base on that, please feel free to castigate me in public view.

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In the interest of full disclosure I should also note that I am the owner of an amp which S'phile found to have up to three times the output impedance as the one originally cited by Dean. In that instance, although the issue of sound variance among loudspeakers was raised, much less was made out of the issue of a high output impedance. Oh...and I like it with my speakers. (For whatever THAT is worth). http://www.stereophile.com/tubepoweramps/601cary/index6.html

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What thread are you guys reading? Craig pointed out a couple of issues with the topology, I added something tongue-in-cheek, and followed up with a link supporting Craig's comments. Mark then accuses me of being "silly and disingenuous" and sets up the straw-man by claiming I said you guys "don't know what you're hearing" and that I've "ruled hearing out" as one of my guidelines. And of course, it is only those who use zero-feedback preamps and amplifiers who "actually listen". The only pseudo-personal attacks I see in this thread have come from your side of the house.

Because of the number of times I've said it, I find it hard to believe no one here has seen my comments regarding Rigma's 300B amps. Of course, all of the recordings were stellar, and we didn't listen to any Rock music or movies.:)

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This has been one of the best and well mannered SET threads on this forum ever. It is a nice change. I haven't taken offense to anything in this thread I ain't that thin skinned. I can find an amp I love from every topology from SS, PP, and SET. There is something to be admired from each topology. There is also complete junk in every topology because they aren't all created equal. Just because someone prefers one over the other it is their ears decision to make not ours be it tube solid state pp otl or set . To each his own.



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O.K., I guess I misunderstood. I'm glad you weren't slamming me, you know how sensitive I am.:)

Some of your comments do give the impression that you think those who don't appreciate the difference either don't get it or plain just can't hear it. I don't know, I guess it doesn't really matter much to me either way -- since it certainly doesn't apply to me.

Again, I didn't say "doesn't measure good", but "measures badly". No, I don't believe you need +/-3dB in a room and .0001% distortion for something to sound great -- not by a long shot. I do believe the ears are easily fooled, so we need the basic measurements. We were poking each other in the eye over the output impedance issue, so "measurements" in this case was for the most part (from my side) related to what happens to the FR of a zero-feedback amp under different types of loads. I was basically trying to back up Craig's statement about how these amps track impedance, and that a speaker's high sensitivity rating doesn't automatically make it a great candidate for SET -- my emphasis was really on what happens on the speaker end of things. Most manufacturers of zero-feedback amps recommend speakers with a "benign load", or "stable impedance". Now, it simply seems to me that if you want the best out of these amps -- don't use a speaker that's going to cause the amp to swing its response back and forth by 10dB. A room may or may not swamp these differences, never-the-less, I don't see how adding to the already existing frequency response abberations can be constituted as "an improvement." Finally, the old Klipsch networks swing the speaker from 5 to 40 ohms, and even a dolt like me knows what's happening with the sound in this situation. I don't think you can build a case that shows how a high output impedance doesn't have a profound effect on the measured HF response, and of course what is actually heard. Finally, if it measures "bad" and it sounds good, it's probably not the best idea to assume that it won't sound better if you fix a few things. The ideal situation for these amps is better for the sound than the haphazard combination. Just my opinion.

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Finally, the old Klipsch networks swing the speaker from 5 to 40 ohms, and even a dolt like me knows what's happening with the sound in this situation. I don't think you can build a case that shows how a high output impedance doesn't have a profound effect on the measured HF response, and of course what is actually heard.

Dean,

Can you elaborate on what this swing in impedance would do to the sound? I am still using the old Klipsch type 'A', with the added inductor that you suggested on my Khorns with Altec Midrange. What type of crossover would you suggest to be optimum for my situation. The below picture is one you created for b-amping (which I still have not got around to yet) - But to just to refresh your memory on what type of crossover I have been using. I did end up popping for the V-caps on them

Bi-ampingaModifiedTypeA.jpg?t=1204490777

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"It's only a Red Herring if you like or build amplifiers with limited bandwidth and can't deliver flat response except with a dummy resistor."

Now maybe you should aplologize to Mark for this comment, Mr. Sensitive.......

Ouch! Yeah, but that was after he'd already "insulted" me.:) Man, I didn't mean it as slam but it sure sounds like one! Sorry Mark!!

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Wow Kevin, that drawing is really old. I might change that 2uF to 1.5uF or even 1uF -- I'd have to go back and run the numbers.

With the autoformer, the impedance will be all over the place, and would probably look similar to the Klipsch curve. You probably have a good bump somewhere in your midrange response.

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Wow Kevin, that drawing is really old. I might change that 2uF to 1.5uF or even 1uF -- I'd have to go back and run the numbers.

With the autoformer, the impedance will be all over the place, and would probably look similar to the Klipsch curve. You probably have a good bump somewhere in your midrange response.

Dean,

I will pay you for your time, if you can rig up a better design for me. I can assemble it, but I don't know beans about how to design one!

Thanks,

Kevin

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It's a double edged sword for SET guys; the only way to flatten the impedance with our speakers is with zobels and l-pads or by swamping the autoformer -- which uses up power. If you're only starting with a few watts ( or in your case, half of that). you don't have much power to give up. I mean, you do need some headroom. The question is probably best answered by someone who really understands amplifiers -- if I had to guess I would say you lose 3dB, which means the 3.5 watt amp becomes 1.75 watts and the 1.5 watt amp becomes .75 watts. The alternative is to do nothing and live with the FR abberations. If and when I go back to tubes, it will be 300B with a constant impedance filter.

I won't take any money for that. Really, you might try the DHA that Bruce is using -- I would just float common like the ALK so you can adjust the midrange level, and pick up a couple of attenuators from Al so you can dial the tweeters in where you like them.

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