Dennis Had Inspire Amps
 

Is it permissible to discuss these amps in this section? Dennis is the man behind most, if not all, of the Cary tube products.

He is building single ended 12watt stereo power amps at reasonable prices. I'm seriously considering one:

He just released this one with KT150 tubes!

http://img20.imageshack.us/img20/4294/1d93.jpg

Sure! :thumbsup:

But we don't post links to eBay, sorry. :o

Ok, sorry. And thanks for removing it for me. I'll only mention though, that eBay is currently the only way to order them (new) and directly from Dennis. Easy to find there if anyone is so inclined.

I'm particularly intriqued by his use of the KT150, the brand new TungSol "buck rogers" tube. In corresponding with him, he detailed some differences between the KT120 and the KT150/KT88 which he favors. Mostly about hard vs. soft clipping and more that was above my head!

In conrad-johnson forum discussions, there was wondering and speculation about whether the KT150 could be a drop in replacement for the KT120/6550 that CJ most often uses these days. I asked Dennis about the tube swaps possible with his amps and the following are possible with varying resulting output power, no need for biasing at all, only sometimes the need to change the rectifier tube to go with the chosen power tube:

• 5 watts per channel - 6V6 output tubes and 5Y3 rectifier tube
• 7 watts per channel - 6L6, KT66, 5881 output and 5U4 rectifier
• 10 watts output - KT88, EL34, 6550, KT99, and KT120 output and 5U4/274B rectifier
• 12 watts output - KT-88, KT-120, KT-150 and 5AR4 rectifier

Peter,
Love the amp. I've always wanted to try a SET tube amp but I own Vandersteens and they are only 85 db efficient. I emailed Dennis and he thinks the KT150s will drive the Treos but I'm struggling to see how 12 watts can do it. I'm still tempted and may go for it just to prove it one way or the other. Keep us posted on your progress.

Cool bit of kit, thanks for sharing Peter

I will. I ordered one - in Jaguar Carnival Red :yes:. He's making them to order at this point. So, it will be a couple of weeks, at least, until shipping. There's nothing but skepticism all around. I'm getting doubts in the AR forum at ClassicSpeakersPages.net as well. My AR 2ax speakers are about 87db, though 8 ohms which helps. Even if there's not enough for higher volumes, if I can get sound that wows me at lower volumes, I will either go the way of finding or building 93db+ speakers or finding some Cary CAD508AE monoblocs for that single ended design of Dennis' with clearly enough power.

Fun exploration in any case!

As always, it depends on your room setup and listening habits. I found my lower power limit to be 25 Watts/ch into 93dB/Watt 8 ohm speakers, but then I like to listen quite loud and my room is not terribly small. Those 25 Watt tube amps sounded incredibly sweet, too.

I think classical music at anything beyond low levels probably won't work great with 87dB/Watt and 12 Watts -- but other music (with a greatly reduced crest factor, like most pop/rock) might be just fine at moderate levels or even a bit beyond. Anyways, that amp with single ended KT150 and a 6H30pi driver looks like fun! I love my gear stocked with KT120 and 6H30pi, and I bet the KT150 is indeed better.

I'm sorry, but I can't see them driving Vandersteens. I like the Vandersteens, and the amp looks very interesting. I just can't see them dancing together.

Can someone post Dennis's email address please? I have a few questions for him. Thanks!

I would like Dennis' email also. I've been corresponding with him through the ebay system which is cumbersome.

I've only corresponded thru eBay as well.

No way 15 watts is adequate for the Vandy's. You will get sound, but not the satisfying low end that could be achieved with proper amping. I love SET's and a great OTL amp sound, but you will want a speaker in the 96db or better to wring the full measure from a low power amp.

I can't disagree, however, Dennis was adamant that it would be a great pairing. He also said a good friend who is a Vandersteen dealer remarked that the KT-150 amp would be a good match. I know, it defies everything I "know" about audio. I'm still curious though.

As I've said, I'm very skeptical, even for my 87db 8ohm AR's. But Dennis expresses great confidence. Either he is a wizard or is hyperbolic (he does come across this way in his expressiveness). He has such a track record with great design, that I'm giving the amp a chance. Either: 1) it is as he says and it will live happily with my current speakers, 2) it won't be powerful enough but I will get a good sense of single ended sound at lower volumes - enough to take a new path if I like it.

New path is either: 1) build or buy higher efficiency speakers (used vintage Klipsch or a single driver design) or 2) buy CAD-805AE's and be done with it! :thumbsup:

As an aside, I'm wondering what we call this amp. I don't think it is SET. The KT-150's are not triodes; they are described as beam tetrodes. Unless Dennis wires it in triode mode, if that's possible.

The KT-150 is a higher current tube, though I don't know what that translates into in practice. Can it mean that the 12watts it produces in this design is a beefier 12w than other SE designs? I suppose it is possible. My 70wpc C-J Pr11A certainly produces a beefier 70watts than the typical 70watt solid state amp. Why couldn't there be differences between tube designs in this dimension?

It will likely come down to room size. if you have a smaller listening room (Like mine) then maybe 15 watts can load it properly.

Hi Peter,
Do you have a delivery date for the amp or are you still waiting to hear from Dennis? I'm anxious to hear your first impressions.

You're right about the tube ... It's a tetrode. There is no doubt that this amp will not play as loud as a big SS amp but it's about the tone & emotional content according to Dennis. I don't doubt the sound is lovely but is it loud enough? I tend to turn it up the longer I listen. :)

I do know one thing, my 120 wpc tube amp sounds much larger than my 100 wpc SS amp.

Still waiting. I think Dennis is just getting busy. Word has gotten out and it doesn't take much to slow things down since he is building these by hand. On 12/4, he said he was fabricating six chassis (what's the plural of chassis?) and hasn't listed anything on eBay since, so I'm guessing that he is working on direct orders now. I will be away 12/31-1/10, so I probably won't have anything to post until I get back. Even if he ships this week, it will cut things very close, so it will be after vacation that I will be able to spend some time with it.

I'll contact him now and get the status and report back.

I just heard back from Dennis. My chassis is at the powder coater. So it will likely ship while I'm gone. I'll hope to have it here when I return home on 1/10. It may be that my request for custom color (Jaguar Carnival Red) will mean it will take longer at the powder coater.

Maybe someone else will have one sooner and can post impressions.

Pictures are required!

I love Jaguar Red...:D

Oh yes.... there will be pictures!

Peter, can't wait ... Have a great trip.

Had a great trip, thanks! Flying home tomorrow. Dennis said he would have the amp finished today and be listening to it. Here's a photo of the bare chasis painted Jag Red........ I love that he sends baby pictures! :yes:

.

http://img23.imageshack.us/img23/7555/w4w1.jpg

I bet they would 'sing' on my son's mighty Zu set up !

Ah, a Treo owner! That is next on the acquisition list!

That red is stunning!! Can't wait for the first impressions. I've read what I could find about the KT-150 in general. Most say it has all the virtues of the KT-120 but with a "sweeter" tube sound.

I think I mentioned that Dennis said a good friend and Vandersteen dealer thought these amps would pair well with the Treos. Well, I called him and he was gracious enough to talk with me about it. He has NOT heard the pairing but is a Cary dealer and knows Dennis' designs quite well. He admitted that if you want to play really loud with Treos, these low power SET designs would run out of gas but at normal listening levels was sure it would sound great.

One thing Dennis mentioned is that the tube type matters with respect to controlling the drivers in a speaker. I'll quote Dennis here ... "I will say DO NOT go for a 300B, 2A3 type of amplifier for your Treo's. These amps do not have the capability to control the drivers in the Vandys. That is the beauty of the beam tetrod/pentode vacuum tube in class A service with feedback. I have been at this for over 55 years and I love music so I can enjoy many types of reproduction but in my home and for serious listening there is nothing like single-ended tubes."

Keep us posted,
Wes

Treos are great. If you ever meet Richard, he's a hoot ... No nonsense kind of guy.

I met Richard in December. I had a great time with him. We spent the evening with his Model 7's. What a genius!

I love his speakers with Cary gear!

That's my guess with the AR2ax'. Should sound great at moderate volumes. I don't expect to rock the house though, particularly since my room is ~20 x 26. Everything I've heard though is that SE designs allow for more satisfying listening at lower levels than PP. With my PP setup I try to keep it under 80db.

Dennis commented to me about these pentodes. Quoting him,

The hard clipping of the KT120s would create harshness. Softer clipping of the KT150s would sound "sweeter" - both assuming they are driven to some clipping which is probably a safe assumption in a 12wpc design.

Hi Everyone,

I received the amp Wednesday, set it up Thursday eve and have been playing since. This is what I wrote to Dennis:

The reference to tubes is the choice of 6N30 or 6H1P for input and 5AR4 or 274B for rectifier. 12 wpc with the 5AR4 and 10 wpc with the 274B, but the 274B is just nicer in sound. Impressive looking tube, too!

We need pics, Peter!

OK, I'll upload some tonight. They won't be as nice as the ones Dennis took though. But you'll see it in the wild. http://fc00.deviantart.net/fs14/f/20...d_by_sml_e.gif

So Peter,
The $24000 question is ... Can 12 watts get the job done? Is it everything you hoped for sonically? I'm dying to hear SET!!

Also, does Dennis offer satisfaction guaranteed or is it yours to keep?

Congrats,
Wes

Here's a few shots......

First is the SLP-05, then the new Inspire KT150, then one of the restored AR2ax'. My conrad-johnson Premier 11A is below the Inspire. The big tube on the right is the 274B rectifier. KT150's are the twin spaceships. :D


http://img11.imageshack.us/img11/2949/l32f.jpg

http://img541.imageshack.us/img541/6541/dqn9.jpg

http://img542.imageshack.us/img542/2789/myus.jpg

I'm actually running it at 10watts with the 274B. It is enough power. I'm in a large room and sitting about 10 feet back. Listening ~80db.

Going by his eBay listings, I don't think Dennis is taking returns. You'd have to ask him though to be sure.

Tonight I swapped a couple of tubes in the SLP-05. I was running Sylvania Chrome Domes in sockets 1,2,4,5 and RCA grey glass in 3,6. The RCA's softened things nicely with the conrad johnson. When I swapped in Chrome Domes to 3,6 in place of the RCA's, the sound clicked more in to place. The detail and air is back without adding any edge. I am liking this amp more and more!

Hi Peter,

Any more observations now that you're getting to know the Inspire a little better? Are you able to rock out without losing the SET characteristic sound? Would you recommend low power SET for 85 db speakers?

Thanks,
Wes

Wes,

I'm liking the amp more as I settle in with it. Tube changes, both in the amp and in my SLP-05 pre seem to make more of a difference in sound quality than when I have done the same with other amps.

I wouldn't say I can "rock out". I try to keep my listening to 80db. It seems to start to give up some steam at about 85db. This is in a room ~ 23'x26' and listening at ~10ft. So, in a smaller room with 85db speakers, you would probably get similar results. In a room as large as mine, I don't think less efficient speakers than my 87db AR2ax' would cut it.

Another discovery though... I played some vinyl and found some of the "vinyl magic" I have never really heard before.

Bottom line, if you want to go single ended at lower wattage, I would consider your speakers. I will likely be experimenting with higher sensitivity speakers such as the Omega line. In part to get the higher sensitivity, but I am also curious about full range drivers, ie, no crossover. Since single ended is a "purer" signal, ie, not split and reassembled as with push-pull, and with no feedback, the "purer" single driver design seems like a logical extension of the approach.

If I really wanted single ended but wanted to keep lower efficiency speakers or, wanted higher power, I would go for Dennis' CAD-805's. But, even used, we are talking $6000+ for the latest version.

Mine runs very hot. The chassis was hot to touch. This normal ? I am pairing with KEF LS50 in nearfield application but speaker wire around 6metres.

Regards,
Joe Ling

Are you referring to an Inspire amp?