SET shortlist to drive tweeters in active system


I'm building a DIY 4-way active system and thinking an SET for the tweeters might be a great choice. But wanted to get input from knowledgeable users.

The 20 to 600Hz range will be handled by active subs plus 10" drivers with their own 700W class D amp.
I'm still undecided about the midrange driver, but likely to be driven by my McIntosh MC275. It will be a 6.5 or 8" cone, though.

The top end will be through a Beyma TPL-150H, a pro ribbon with a horn playing from 2 to 23 kHz, spec'd as 102 dB (@1W, 1m) and a pretty constant impedance of 4.9 to 5 ohm.
I'm thinking it looks like a great place to use a SET, right? Which amps should I include in my shortlist?
Looking for SET holographic magic with dynamics.
The signal will come from a balanced IC, so XLR input would be preferred.
Reliability is a must, and the more the better. I will import this into Argentina, so sending the unit to the manufacturer would be difficult.
Price range: under 4k.

I'm surprised I'm not getting any reply. Maybe I asked a stupid question? If so, would appreciate learning how it was so. Wouldn't be the first time, though :-)
Lewinskih01- I think what has me baffled is why you would want to use an SET on the tweeters in a 3 way. The vast majority of the musical information is conveyed by the midrange and that is where SETs really deliver their magic. Also, I believe that one of the knocks on SETs (I don't know if it's true) is that they are bandwidth limited, which again would argue against using them at either extreme in a 3 way.
I don't see it mentioned but you will probably need some kind of external active crossover to get decent sound.

To me it just seems unnecessarily complex and violates the KISS prime directive. I'd bet you could get better sound any way by equalizing the active subs and simply using the MC275 for the rest of frequencies.
Fair enough.
Maybe I was jumping to conclusions.

My 4-way would be divided as follows:
20 to 80 Hz by active subs
80 to 600 Hz by two 10" midbass woofers per side, driven by class-D amp.
600 to 2500 Hz by a midrange. Was assuming my MC275 for this. Most midranges are somewhere in the 94 to 100dB sensitivity and 4 ohms.
2.5 to 23kHz by the TPL-150H at 102dB sensitivity.

Do you think I'm better off using SET in the midrange and having the MC275 do the higher frequencies?
A number of people who choose this approach will often use a 45,2A3 or 300b. Some opt for 300b SET midrange and say a 45 SET on the tweeter. I find that high quality SETs(300b.45 or 2A3) have very natural extended high frequency sound. I agree SS is more likely to provide a hyper extended sound if that's your desire. There are certain clichés concerning SETs that don't bear out once you've heard a good example of them. You could just as easily say SS presents a tipped up upper frequency(not true for all of course) clichés are easy.

Would a SET be the very best choice for bass/subwoofer duty? No they wouldn't be. Midrange and upper frequency they'd be my first choice. Depends on what sound quality objectives you have, as is always the case. When I use the premium level 300b tubes(currently using the Elrog 300b, there are other fine choices also) the upper frequency information and air are superb and just sound natural/right. Best of success to you on your project.

I didn't wanted to go there to avoid complicating the thread as my setup is rather unusual. My only source is a very optimized PC running, among other things, Acourate for digital room correction. It can also perform digital crossovers, linearize drivers and time align the different channels. This will feed an 8-channel DAC that in turn will feed the amps driving the speaker drivers directly.

I realize this is not for everyone. Not sure KISS is too applicable. Passive crossovers are used to make a speaker easy to use, not for their better performance.
Hello Charles1dad.

Thanks for the input. I was actually hoping you would chime in.
I like the sound of tubes for the midrange and treble. Hyper extension is not a need for me - and anyway can't hear close to 20kHz. Imaging, air and spaciousness are highly desired.

Could you suggest a couple good amp options using 300b and 45 tubes? Those Elrog 300b sure look nice, but beyond my current budget.
Hi Lew,
Do you have a price target for the amplifiers. For a niche segment(SETs) there are many choices and directions to go. New or used?
Initially I said 4k, but in reality that would be the utmost I could do. I would be much happier if they were 2k. Too many things changing in my system now.

Used would work, provided I can have the manufacturer or service turn it to 220V.
Up to 4K used can get you a very good 300b SET. Coincident,Allnic,Wavelength, Sophia Electric, Audio Note Kit etc. Definitely 45 and 2A3 SETs as well but I'm not as familiar with them as the 300b amps. What ever you choose be sure the builder emphasized quality output transformers and stout power supplies. These are fundamental keys to high grade SET amplifiers. Saving a few bucks by compromising these areas is a poor decision IMO.

After looking into the suggested brands they all seem to be beyond my budget. I'm part way through the "greatest bargain in SET amps these day" thread and the Dynamo 34SE has me intrigued. How do you think it would do in light of my McIntosh MC275? The EL34-based amps weren't in your listed suggestions.

I could have one Dynamo driving ribbon tweeters and MC275 driving midrange, or even two Dynamos one for L and one for R and have each drive tweeter on one channel and midrange on the other channel. And do without my MC275. And of course keep everything below 500Hz to the class D amp.

Hi Lew,
You asked about SET(single ended triode) which would use a DHT tube, The Dynanco is actually a SEP(single ended pentode tube). I haven't heard the Dynaco however professional reviews have been raves(6 Moons review is very detailed). Dynaco owners on this site are very happy with it. I believe for your application it could be really quite good. I'm not familiar enough with either the Dynaco or MAC amp to offer a comparison opinion.

Hi Lewinskih01, for a top tweeter amp you want extension and Class A. I would look at some of Nelson Pass Aleph's or a small class a kit, if your up to doing a chassis and power supply this maybe nice.

Cheers George
I'll look into the Pass Aleph. Hadn't thought about it. I confess I like tubes though. But I'la look into user feedback.
DIY is certainly an alternative for me. But I'm very hesitant to go with a cheap alternative I never heard of.

BTW, Charles: thanks for the input. I hadn't realized it was a SEP. Dynamo looks like a viable option. I know price does not equate to sound, but honestly down deep I'm struggling with replacing the Mac with two Dynamos plus Hypex.
I understand your dilemma when it comes to performance versus price. You would naturally expect a linear relationship between the two but in reality this isn't the case in a number of situations. It honestly would not surprise me if you preferred the sound of the pure and simple Dynamo compared to the MAC amplifier.
Lewinskih01 This would be a great amp for your tweeters, Pure Class A, 8 x output devices, doubles it's wattage to 4 ohms. Just came up on Ebay, could go cheap, and it's in the US.

Cheers George