Klipschorn 2A3 amps versus 300B amps

[kilowattski]

I have surfaced from the forum archives and I can see the

collective experience base of the forum is vast but reaching consensus on even what is the best underwear may be difficult. With that said, I am soliciting opinions between 2A3 (Moondogs?) and 300B amplifiers to make my newly acquired 1983 Klipshorns (with stock cross-overs) sing.

Female soprano vocal opera, new age, jazz, soothing mediative electronic music (liquid mind), not terrible loud, same amplitude as loud conversation all from CDs (have not been afflicted by vinyl...yet). The sound of silence is as important as the sound of music, to me.

Also does anyone have vertical dispersion information for Klipshorns? I am told that the vertical dispersion lobe is small and I should not worry about reflections from the floor or ceiling, mostly just reflections from walls. I have marble floors and the room is 21' X 24' with the speakers against the 21' wall (tightly placed in the corners).

Thanks

Kilowattski

[3dzapper]

kilowattski,

2A3s

You will want to "deaden" your room no matter what you put in there besides an unpowered kareoke machine. Singing in the shower sounds good because the highly reflective surfaces redirect our voices back to our ears with white noise and decay. This is not a good envrionment for audio enjoyment. Some nice overstuffed furnature, wall treatments and drapes on the sliders and a carpet on the floor to absorb some reflections will IMHO be in order.

You are starting with a blank sheet and, working with SWMBO, can no doubt decorate your room in a manner pleasing to eye and ear.

Rick

edit:WHOA!!!! Happy new avatar. In the time it took me to write the above (and condense a tretice on tubes to a word) you became colorful!

[Erik Mandaville]

Yikes!

...some more tomorrow.

[Dflip]

I hate having to retype messages that get lost in never-neverland.

The general consensus is to go with the Moondogs. A 2A3 amp will give you more detail and richness for the type of music you listen to. I can't honestly remember too many people who have recommended a 300B amp over a 2A3, especially for the type of music you listen to. You don't need the extra 4.5 watts with your Khorns.

Contact Erik M. or Kelly (mobilehomeless) for recommendation regarding which upgrades you should perform to get those dogs to really sing. They both have made significant improvements over the stock versions.

I'm sure one of the experts will chime in with their comments.

[jt1stcav]

I've personally never heard either a 2A3 or a 300B yet, but I wanted to take a leap of faith on SET topology, and so I ordered a 300B SET power amp. The only reason I chose the 300B over the 2A3 is because of its 8 watts stereo as opposed to the 2A3s 3.5 watts per channel. Since I own less efficient Cornwalls (and I like my pipe organ music played a bit louder than you), I felt a little more comfortable having the extra few added watts of headroom, even though I know the 2A3 is generally acknowledged as being the better sounding tube.

If I owned Klipschorns, I'd also go for the 2A3.

[jazman]

kilowattski,

I have no desire to raise the rancor of my 300Bb SET brothers/sisters, but my vote is 2A3. I did a lot of research that ended with the 2A3 Moondogs as my choice. With an efficient speaker such as the Khorn, a 2A3 tube at 3.5 watts or a 45 tube with 1.8 watts can be "MAGICAL"!

Klipsch out.

[Painful Reality]

2A3 or 300B...

There is no real definitive answer. If you look at the linearity of the 2 tubes, the 300B is a clear winner but when you look on this question as a whole, things get more complicated.

It's somewhat easier to come up with a decent sounding amp with a 2A3 as they are easy to drive and they can be run pretty quietly with AC on the heater.

The 300B are tougher on driver requirement and cannot really be run quietly with AC on the heater. Thus DC on the heater is mandatory for a quiet operation. All this makes the design of a good 300B amp more difficult. Another problem with a 300B amp is the output transformer (aka OPT). It must be designed to handle 70 to 100 mA in standing current (depending of the chosen operating point of the 300B). This will require a huge air gap in the OPT core (unless one goes with a parallel feed configuration but that is another story). Having a huge air gap will drastically reduce the inductance of the primary winding of the OPT. The problem is that as a general rule (i.e. a bit simplist), the higher inductance in the primary winding, the better.

Soooo, a 300B amp can be extremely good but it will have to use a robust driver with a rather high current capacity and plenty of voltage swing. It will also have to come with excellent OPTs is you want to really "taste" the 300B. Such 300B amps do exist but are quite costly.

[Daddy Dee]

2A3 can't go wrong here.

[Erik Mandaville]

A 300B amp similar to what Jeff described can be found in the Welborne Labs DRD 300B monoblocks. The 2A3 version is AC heated, and was extremely quiet when it was here. Jack Eliano (the guy who designed the DRDs)prototype DRD was a 300B, and is a little different from that sold by Welborne Labs. It uses regulated DC on the filaments, and also uses solid state diode B+ (plate voltage) rectifiers. I have heard (well, at least read) some discussion of what was perceived to be perhaps not the best choice in using SS rectification, due to the more traumatic effect of SS diodes on downstream components than that achieved with a vacuum tube rectifier. However, the usual problems imposed by SS high voltage rectification is rather diminished by the circuit design. Without getting overly technical, SS rectification is fine in this amp, and is even preferred by Ron Welborne. Kevin Cutthroat has the 45 DRD with SS rectifiers, and likes it very, very much.

On top of that, the Welborne kits are really, really good kits. The DRDs do seem to need a bit of drive in front of them, and my feeling, based on my experiences with the 2A3 DRD and now my own amplifier (a parallel-feed version of the DRD)is that preamps with moderate gain and low output impedances (say, under 1 k ohm)might be more suitable.

[Erik Mandaville]

"The sound of silence is as important as the sound of music, to me."

DRDs are extremely quiet SET amplifiers, with very, very low residual noise and hum. It's one of the main reasons I prefer the design with my Klipschorns, and our listening habits and preferences are quite similar.

[leok]

Something you might consider is a good 300B amp configured for 4 Ohm output. This will give you 4 Watts into 8 Ohms, but with reduced interaction between the amp and speaker. It will also load the 300B at a higher impedance which will probably improve linearity. Go with a parallel feed version and you get around the transformer difficulties.

All of that would require some customization of an existing design. I don't know if you're interested in that approach.

Otherwise, I certainly enjoy my 2A3 SET

Leo

[Erik Mandaville]

I'm glad Leo contributed. He has done more work on the Moondog in terms of modifications than any of us. I have very recently added the 2A3 grid chokes that were formerly in the Horus amps I built; and as they performed there, they are working really well in the Moondogs. These are MagneQuest chokes which, although small, are kind of expensive. For those with Moondog schematics, the grid resistor I'm referring to is R9 -- 221K.

[Randy Bey]

I have the Welborne Labs 300B Laurel II's with all the tweaks and I can say I like them a lot.

At another house I've listened to a different 300B (which I didn't care for that much), a Moondog 2A3 (which I loved) and a DRD 45, which seemed even a bit more musical (in the good sense of the word) than the 2A3.

Nonetheless, nothing seems able to pry these Laurels from my hands.

And a 300B (even a 45) is way powerful enough for khorns.

You will want to put several throw rugs down on the floor, you'll be spiking around 5-6K without them.

You will want to encourage wall reflections around the speakers, for 4-5 feet either side.

You will want to discourage wall reflections from the rear as much as possible.

Put your listening position where you can sit and turn your head to either speaker and be looking directly at the tweeter/squawker.

Enjoy, I know you will.

[Colin]

Well, I think there is a definitive answer, I dont think most loudspeakers are sensitive enough to take advantage of the flea-powered 2A3 tube, except classic Klipsch corner Khorns, and especially with your music tastes

[Cut-Throat]

Randy,

When you heard my 45, it was tapped for 16 Ohms! It's even better now!

Sometime when you get a chance, stop over and listen to my Belles (now that they are in a proper listening arrangement - In front of the listener, instead of behind) Also have my Rel Strata Sub Hooked up which made a big difference. And the 45 amps being tapped for 8 Ohms ! I am also listening to pair of NOS National Union 45 Tubes that have a little more of that 45 Magic.

Also I built another Set of Type 'A's, with Original Klipch Oils on the Tweeter. So everything here is humming along pretty well, since you were here last. I have never heard the Belles sound better!

[maxg]

Cut-throat,

I swear that REL was made with Klipsch Heritage in mind. I adored mine with the Heresy's. nice to hear it does the business with the larger heritage too...

[Cut-Throat]

max,

Yup the Rel Strata helped out my monitor speakers quite a bit before the Klispch Belles moved in also!

When I first saw the physical size of the Belles, I just didn't think that the Sub Woofer was going to add anything. But there were some missing bass notes. And as you probably have discovered, even Piano music has a certain depth and substance with the Rel, that is missing without it. The Sub adds a texture and foundation to even the high frequencies. Hard to describe easy to hear!

[sunnysal]

I would never argue with Jeff, he knows his tube amps!

You will find strong proponents of both tube types here and on AA, I settled on 2A3 becuase in my room, with my music, with my system, they sounded best...to me.

I strongly suggest you make an effort to hear both types in your system, or at least try to audition them side by side at a dealer, that way you can get a grip on the differences and try to extrapolate those into your system.

If this will be your first SET I also suggest you get an firm idea if they will produce enough volume in your system/room before making the investment, I found SET did not give me the power I wanted and moved to PP DHT for a few more watts.

best of luck, tony

[Erik Mandaville]

Kilowatt:

What you get in the Welborne kits for the money is superb. Parts qaulity (passives and active alike)are excellent, and the overall quality of construction amazing for the price. I've built both Moondogs and DRDs, and each had fantastic attention to detail. You will end up with a very professional looking product. The solder terminal strips on the Moondogs were attached to the chassis plate with epoxy (I submitted a mild complaint about that, since the epoxy on mine was either old, incorrectly mixed, or a combination of both. The terminals on the DRDs use machine screws and are far more solid.

Another nice feature of the DRD is the so-called Ultrapath connection, which provides power supply decoupling. Leo and I both employed that modification into our Moondogs, and like the results.

That rectifier question is really personal. Both do the job of rectifying AC, and as Kevin has pointed out, sounds good in his amps. Still, if you're interested in trying different 5 volt rectifiers, you obviously can't do that with SS diodes. Different rectifiers can provide the opportunity to experiment with increases or decreases in plate voltages, and I used a 5Y3 on the Moondogs with good results. It provides a little more flexibility. Also, your power transformer will run a little cooler, because of the lack of the current draw that would otherwise be imposed by the tube diode heaters (but it doesn't get overly warm, anyway!).

For experimenting with different OPT taps, you could use plastic wire nuts for configuring the secondary winding for 4 ohms or 8 ohms, to see what sounds best in your system. Once you know what you prefer, those can be soldered onto the terminal strips as indicated in the very clearly done instruction manual.

Gosh, they are great kits! I'd love to build a 45 DRD amp!

[leok]

kilowattski,

Tony's idea of PP is influenced by the fact that his PP amp is one of the best around. I wouldn't expect the kind of low level detail that Tony hears is present with just any feedback class A/B tube design. Tony's PP amp uses the 2A3 and is primarily Class A and has no feedback, and finally, is designed and built by Jean-Francois Lessard. All of that matters.

Jeff, Tony .. correct me if I'm being misleading here.

Leo