Amp required for cornerhorns

[Mike Lindsey]

I can only add the first SET amp I ever heard was a Bottlehead 2A3 that Colin brought over, and I was very unimpressed with it when mated to my La Scala's. I much preferred my NOSValves modded Scott 299. Having said that, I later purchased a Korneff 45 (from the builder) which only had about 1.5w of power, and I was very impressed with it. I ended up sticking with my NOSValve VRD's though, mostly due to the extra oomph, but also because they are incredible amps in their own right.

Mike

[Plink]

Hi Rolly,

Personally, I would not use a SET with Klipschorns. I would suggest a low watt push pull amp using 2a3, 45, 6V6, 6L6G, 6L6GA, 6L6GAY, or EL84. First Watt is another good suggestion.

I love SET amps and do not subscribe to the misinformation brought forth in this thread on the topic (notice how tube fanatic's excellent post on Electra-print transformers went completey ignored...can you say agenda?). However, I just don't think they are a good match with Klipschorns. It is worth noting that many people think they work nicely with Klipschorns and equally valid.

Cheers.

PS. I once had a 300B SET built by James Burgess. I took that amp to my tech to measure the Magnequest outputs and while rolloff started around 16 khz, the measurement in the bass region was incredible...nearly flat down to 10 hz. AC heated amp with incredible presence...I changed the cathode bypass caps on the 300B tubes and ended up with a SET that had superior drive and PRaT than my mid level Naim combo! But a tiny bit of midrange presence was lost...I think. Why o why did I sell that amp.

[Marvel]

Plink,

My Welborne Labs Moondog 2A3 amps have Magnequest OPTs (they later used Electraprint), and the performance is wonderful on my LaScalas. What certainly may be of significance is my constant impedance crossovers I made for them. This would certainly be of benefit to Khorn owners as well, minimizing the interaction between the possible higher output impedance of the SETs.

Bruce

[Plink]

Bruce,

I bet your crossovers help a great deal. I am not saying a SET will not work. I just think a triode push pull or a carefully considered pentode push pull amp could work better. No doubt good output transformers (like on your amp) are mandatory, imo, for any configuration.

Were you able to listen to your LaScalas with the previous crossover with your Moondogs?

Cheers, P

[Marvel]

Were you able to listen to your LaScalas with the previous crossover with your Moondogs?

THey came with type AL crossovers, and I didn't have the Moondogs yet and powered them with a SS amp. John Albright graciously loaned me a set of ALKs Univiversals that he wasn't using, until I could get something of my own. I built a set of his DHA2 crossovers, and then got the 2A3s. I never swapped the ALs back in to try. The caps needed to be replaced on them and I didn't like them anyway.

If I had the time or money, I would love to try some SETH 2A3 P-P monoblocks. I do have a Dynaco ST70 that I'm putting the second front end into, but I may adjust the PS and try some 6L6s in it. I had replaced the original front end with a Curcio Audio board, and although it was better than the stock board, I decided to try something else. I picked up one of Roy Motttram's boards (VTA70), and just haven't gotten around to finishing it.

Bruce

[NOSValves]

Were you able to listen to your LaScalas with the previous crossover with your Moondogs?

THey came with type AL crossovers, and I didn't have the Moondogs yet and powered them with a SS amp. John Albright graciously loaned me a set of ALKs Univiversals that he wasn't using, until I could get something of my own. I built a set of his DHA2 crossovers, and then got the 2A3s. I never swapped the ALs back in to try. The caps needed to be replaced on them and I didn't like them anyway.

If I had the time or money, I would love to try some SETH 2A3 P-P monoblocks. I do have a Dynaco ST70 that I'm putting the second front end into, but I may adjust the PS and try some 6L6s in it. I had replaced the original front end with a Curcio Audio board, and although it was better than the stock board, I decided to try something else. I picked up one of Roy Motttram's boards (VTA70), and just haven't gotten around to finishing it.

Bruce

What made you decide on the VTA board? Is it the high gain or low gain version?

[erik2A3]

Bruce:

As a fellow Moondog owner (with ElectraPrint OPTs, by the way), I have built a couple of parafeed amps, one of which was by the same person who designed the Seth 2a3 in push pull. Bottlehead, formerly Electronic Tonalities, was among those in part responsible for rejuvinating the parallel-feed (aka shunt-feed) output topology. They are fast sounding amplifiers, and I thought nothing could sound as good as my then-and-still-beloved Moondogs. The ouput transformers on the Welborne amps are enormous because they have to be; they are simultaneously dealiing with power supply and music sginal components. Parallel-feed amps separate the two, and instead use a large choke on the output tube plate (as in plate choke). And this in turn allows for a much smaller output transformer for coupling with the loudspeaker. There is of course a smallish value, high quality capacitor that fugures into the parafeed equation. Many people love the Bottlehead amplifiers, though.

If one is using large, airgapped OPTs, another option is direct coupling where even the finest (taste dependent), most expensive capacitor would not only not be an improvement, but not even needed.. You can do this both between sections of the 6SN7, as well as between the voltage gain stage and the 2A3 -- though both of these, particulalrly the latter, require some circuit modification. I also got some pretty good sounding results by paralleling the two input stage sections on the Moondog, and this circuit in conjunction with dedicated 5 volt filament transformers sounded truly even better and more lively to me than the 2a3 version. In other words, I optimized the same circuit to be used with 300Bs and it was really fantastic sounding! The Moth si2A3 I bought as a box of parts and a schematic (it also uses very fine ElectraPrint OPTs) uses a paralled 6SL7 direct coupled to the 2A3, and is very nearly on par in terms of perceived frequency response. I still really like and use my Moondogs often, and they are wonderful and rich sounding with solo classical guitar.

Totally agree with you on the 6L6! The Baldwin organ amp I rebuilt (now residing under another forum member's roof) is just a great amp, period. It sounds good with all types and genres of music. With our La Scalas, I really think on par with the Transcendent OTLs, with which I have much personal experience. But my moods change, which is why it's so great to have some different options. Another possible thing to try with the Moondog, which I have in fact done, is the so-called Ultrapath output connection ( a term coined by Jack E. at Electra Print). Like parafeed, it also has its roots that go back to the very early decades of tube audio design. I tied my brain in knots tracing current paths of a combined ultrapath-parafeed amp, and though I'm still not sure what I actually ended up with, boy was it good sounding. So many good sounding ideas. Ultrapth is a breeze to do, though.... BTW: LeoK hasn't posted here for a long while, but he also had Moondogs. However, he went to the effort to incorporate the parafeed output stage into the venerable old Moondogs, and loved it.. I guess Bottlehead still sells the MagneQuest parafeed OPTs....maybe not. It's been years since I've looked there. Though I preferred the EP OPT in the Moodnog, the MQ parafeed tranny, particulalrly the cobalt version, was killer. Erik

[erik2A3]

Apologies for lack of paragraph breaks in comments above. Someone kindly explained how to make them, but I've completely forgotten.

[Marvel]

What made you decide on the VTA board? Is it the high gain or low gain version?

Craig,

I picked the low gain version. I admit it was partly the price, partly the quality of the board itself. Partly just to try something different. I didn't want to use an SS parts on it (like the constant current source boards). IIRC, you modded one of the VTA boards in some way, but I don't think you every posted what you did. I thought about one of Shannon Park's boards, too.

I should get plenty of gain out of my Merlin to handle driving the front end.

Bruce

[Marvel]

Apologies for lack of paragraph breaks in comments above. Someone kindly explained how to make them, but I've completely forgotten.

Erik,

I assume it's Safari... You can put in a break (put in a less than, greater than pair with a BR in the middle, with no spaces), OR you can use the paragraph tag, but to do that correctly, you should use a new paragraph and then an end paragraph (less than, greater than pair with a p in the middle to open, and less than, greater than pair with a /p between to close).

It's easier to do than to explain.

I believe you told that mine had the Magnequest OPTs in it.

Bruce

[erik2A3]

Bruce:

I mentioned at your request a number of times since you received the amplifiers that they had Magnequuest output transformers. I found them a little on the warm side of neutral compared to EP in the same circuit, but there were other differences in terms of parts selection that influence final voicing, too. Like virtually every word mentioned above in this thread reagrding the 'better' or 'worse' aspect of equipment performance, it's essentially what one prefers to dine upon at a buffet of many offerings -- and then feel the need, for some reason, to defend our choices. I'm speaking in general terms, here, and not referring to any specific element of this thread. BTW: you can identify your OPTs by the color coding on the primary and secodnary winding -- it's different from what EP uses. Hey, don't your crossovers just use a simple swamping resistor across the autoformer? That's been used on Lowthers for many years to help calm some pretty drastic impedance swings. For some odd reason I often prefer the Lowther horns without them because they sound more lively. Others differ on that opinion -- the audio buffet personal preference syndrome at work again.... Safari must be the issue with my paragraph break situation.

[Marvel]

Erik,

...a number of times, yes. I just know it's great iron. THe EPs could be even better, but as you point out, it becomes more personal preference. I would still like to put in the grid chokes, but finances aren't where they should be right now.

And yes again about the crossover. Pretty much a swamping resistor. I didn't add the light bulb for the tweeter protection, especially since I added Bob's tweeters.

Bruce

[Ski Bum]

At the end of the measurements section well known audio pimp Robert Harley wrote the following...

At some point, I believe that engineers will simply say , and walk out of the room, no matter what the PC answer is.

My observation: If you want soft clipping, buy a SET (personally, I don't want clipping at all, and I don't have to put up with clipping).

If you like listening to even-order harmonics that aren't in the source material, you can buy a synthesizer that does that (such as an Aphex Aural Exciter), or you can buy a SET.

If you want a reverb unit, you can buy a reverb unit, or you can buy a high-output-impedance SET.

If you want EQ, you can buy an active digital crossover, or an EQ unit, or if you like the "canned EQ" that a SET brings (i.e., high and low end roll-off), you can buy a SET.

If you want all of these "features" at once, then buy a SET: it might be cheaper (...or it might not be...). It also glows in the dark, heats the room, and gives you something to do (rolling tubes) when you are looking for something to do with your spare time...

...but please don't call it "high fidelity", because it isn't...it's a sound synthesizer/processor that has a small amount of forward loop gain.

Chris

Yep, that's SET in a nutshell! Thanks for this concise description, Chris.

Strangely, I completely agree with this, yet I'm still one of those folks who use SET w/ Heritage...it may not be 'hi-fi' by strict definition, but the presentation has a knack for piercing whatever perceptual filters I have to the point that it's near impossible not to feel connected to the music. The SETs keep me happy about 85% of the time, and for those other times I have proper amps waiting in the wings.

I actually got into SET amps after hearing a Pass amp, simply because SET is a much more affordable way to get into class A.

All this discussion of SETs and Pass' approach to SS class A has me wondering if anyone has tried one of Peter Walker's 'current dumping' amps. Class A output/zero crossover distortion? Check. Low parts count? Check. Long term reliability? Check. Plenty of power and able to drive any load? Check. Seems to me that those old designs achieved what Nelson Pass is trying to do in much more elegant fashion.

Has anyone here used a Quad 405 or 909 with their Klipsch?

[erik2A3]

Bruce

Thanks for posting a copy of the schematic for your crossovers. I recall it now from years back, and it always looked like an interesting design. I prefer the tweeter on its own branch the way its done above, and soit seems there is an actual bandpass on the sqauwker. Great! Listening to our Heresies right now with Moondogs. This combination has always had amazing synergy, with the slightly brighter Heresies giving a verynnice balance to the warmer, but very rich and complex tonal quality of the Moondogs.

Maybe I'll seriously try that crossover in the La scalas. It really does look like an excellent design. Erik