Dennis Had Inspire Amps

[FloridaBoy]

Originally Posted by Bombadil

Replying to my own thread, am I going insane?

Before writing the above, I searched my tube cache for Golden Lion KT77s, as I thought I had some. But couldn't find them. I moved recently and packed up all of my tubes and tube gear about 3 months ago. Shortly after writing the above, I found my GL KT77s. At least I wasn't imaging that I had some.

So today I slapped them into the Inspire and compared them to the JJs. I don't fully trust such comparisons, as they are sighted comparisons with several minutes between listening sessions. Historically I have found such comparisons to be untrustworthy. I am a fan of double blind testing. But I would need two Inspire amps to pull that off.

In today's listening evaluations, it was my perception that the GL tubes brought out a bit more subtle detail and had a bit more definition in the lower bass region. That is, I think I could perceive a little more air on percussives, a little more "fingering" on background guitar, a little longer decay on piano. I noticed all of these things more in multiple songs than I did when playing the JJs. Whether I could pick out the differences in a double blind test, who knows? I've failed those before when I was confidant I would pass.

I found myself getting more into the music when using the GL. Ultimately that's how I decide what to use.

So the GL moved ahead of the JJ KT77 on my list of preferred tubes.

Insane? You are posting here.

I have GL's and JJ's and prefer the GL. Dennis likes the JJ's. Different systems different preferences.

[FloridaBoy]

I bought a couple of Duelund tinned-copper bypass caps and will solder them in the amp and preamp soon. I have not done this before.

[Bombadil]

Originally Posted by FloridaBoy

I have seen older Inspire amps with a triode/pentode switch. I wonder why that has gone the way of the dinosaur?

There are certainly a lot of tube amps on the market which have this feature.

[Simonatsea]

I too would like to see this option. I imagine there would be some give and take though. Dennis catches me as a purist, putting something in the circuit that might degrade may not sit well with him.
Haveing a pair of those mono’s pumping out 25 watts might come in handy from time to time. It would be nice to have that level of adabtability as we all know a stereo setup is a contantly evolving entity...

[Simonatsea]

Originally Posted by FloridaBoy

I bought a couple of Duelund tinned-copper bypass caps and will solder them in the amp and preamp soon. I have not done this before.

Love to hear how it worked out. You might need to install a “lift kit” however...

[FloridaBoy]

[IMG][/IMG]


Simon, the Duelund bypass caps are .01uf and physically small. No lift kit needed. The photo is an LP27a, not mine, with .22uf Auricaps paralleled with the Audyn coupling caps and a Jantzen, can't read the value, bypass cap on the electrolytic cap.

[Simonatsea]

This just in from Dennis, apparently he is watching us.... LOL

Dennis wrote:
I firmly believe that the option of triode/pentode or triode/ul switching option is market driven. When one truly looks at the huge disparity in plate resistance of a vacuum tube in the pentode, beam power and tetrode configuration vs triode it is amazing. A simple example is the 6L6. The plate resistance in the pentode mode is on the order of 35,000 ohms. The same mighty 6L6 wired in the triode mode the plate resistance is on the order of 1700 ohms. The difference is night and day. The plate resistance of the tube will determine the proper primary impedance and ratios of the output transformer in the tube amplifier. An example of the 6L6 wired pentode would operate properly with a primary impedance of 7000 ohms. Take the same 6L6 wired triode the impedance is now on the order of 4500 ohms. I prefer to use a 4300 ohm primary for the basic beam powered tubes wired as triodes. The ultimate sound quality of a high performance vacuum tube amplifier is so dependent on the proper impedance and ratios of primary to secondary windings of the output transformer.

Anyway … I could go on and on . but simply stated … the differences are much too great in the sonic results of a compromised, market driven triode/pentode/ul switch. Give me some time and I could really let you know what I think of the ultra-linear (ul) mode of degenerative negative feedback!!!!!!!!

[BearCityUSA]

Originally Posted by nhparrot

Let me know how those Russian 6f6s/6f6g sound after you get an try them. BTW try KT77's with your ProAc's. Dennis recommended I try them with mine and the midrange is glorious.

Been listening to the to the 6f6gs for a day now. Definite keepers. The bass is very strong. Not lacking anywhere as I can tell but this is my work system and I am not doing really critical listening. I have not done it yet but may turn down the subs. I switched out GL kt77s for this change up though this is not my Proac system (Omegas) at the moment. 24 watts to maybe 4-5 watts and I am thinking about turning down the subs. Go figure. Anyway, they are cheep (relatively). Give them a try.

[Analog Addict]

Originally Posted by BearCityUSA

I wanted to check in here and follow up on my latest trip to Cary. As you may know, Dennis and I ordered Proac DT8s, two pair, that were sent to his shop, which is 4 hours from my house. A good excuse for a visit. Took a couple weeks to get free but I was able to get over there a week ago Wednesday. I got to see Dennis and Tony (Staitwire) and was hoping to meet up with Allan (Analog (Addict) but sadly he was working. Next time.

Went directly to the 'Toy Factory' to get the speakers. Tony was there. He was nice enough to carry them to the car. Thanks Tony. Also there was the new LP-3a with three gas regulators arrayed behind the usual 6sn7 complement. Black on black with glow tubes. I should have taken a picture.

That taken care of, Dennis had us over to his house to listen to his new Proacs. He got the rosewood, me the cherry btw. I think there is a pict here of his sitting just outside of his Tannoys. Dennis had a few Inspires amps for us to audition and Tony had one of his that had just been completely rewired with D’s latest 'Universal' circuit design. Also on deck was Allan's 71a PSE. We started with Dennis' Universal prototype, a triode strapped pentode with new custom opts. Analog posted picts a short time back. NOS GE 6f6g output tubes installed. I did not make note of the rectifier or driver tubes. Honestly, I was mostly focused on the Proacs. We listened to an acoustic guitar duo Dennis had seen there recently. Good stuff. I wish I could recall who they were. I find my visits with Dennis to be a bit of an overload. No way to absorb all the details. Anyway, the new circuit is quite nice. Sadly, as I reflect, I have still not heard the Triode Hot Rod so I cannot comment on any differences/similarities. As I said, I was focusing on the Proacs. Listening in the sweet spot. Off axis. Sounded good, really good. The 6f6s in triode push 2 watts as I understand. The SPL of these Proacs was impressive at rated 90db/ as I recall. The sound was full but mellow. Everything was present that was supposed to be. Crisp and clear. Dennis commented the 6f6 to be good for late night listening when the world is quieter. I see that.

Dennis had one of his new mono block prototypes there. A PSE version of the Universal if I understand correctly. We swapped out the right channel for this one. A bit more drive and control but hard for my ears to fully delineate with only one channel. Really nice amp though. Look forward to the finished products.

On to Tony's amp. Tony's was much the same. Possibly a little more refined sound. Discussion yielded that Tony had different coupling caps. I would also attribute it to the PST and many parts including said caps as having some serious playing time on them already. Years of playing time. For those of you with relatively new Inspire equipment, they truly do get better and better with playing time. Somewhere during auditioning these two amps we swapped in some KT-88s for 8 watts/ch. A bit more control and volume but I'm still not a fan of that tube. I have yet to hear a set up that I thought the kt-88s benefitted. Just one mans opinion. We ended with Soviet 6f6s tubes. A perfectly good version of the 6f6. I have 10 on order from the Ukraine I was so impressed.

Next up was Allan's PSE 71a, a true SET. Now that is a lot of glass. Beautiful work getting it all in. I would like to see the underside. Tony mentioned 100+ holes in the chassis. I don't have a lot of experience with Triodes but I can say this one does have that triode sublime magic that so many like. I get it. Intoxicating with a lot of tracks. I have heard Allan say he likes to have it sound like Diana Krall is sitting in his lap. This amp does provide that intimacy and seduction, especially with the female voice. A jazz track yielded some very realistic horns.

An aside. The preamp for all this was an Inspire LP-1 (small chassis) upgraded to the 3a circuit. Old school Inspire populated with 9 pin Soviet tubes. I felt like a real insider as Dennis mentioned it was just like mine. I also learned that they did powder coat some pearl white chassis back then. Not all were sprayed with a rattle can. I was told how to tell the difference. Since, I confirmed that my KT amp is a spray job and my LP is a PC job. The color difference is very subtle. In 4 years I had not noticed it before.

When learning I would visit Dennis ' house earlier in the week for a listening session I knew right off I was going on to have to compare the lightly broken in Proacs with his Tannoys. When else would I get the opportunity? I abruptly segwayed the conversation with an elephant in the room reference. Well, 2 elephants. Those Tannoys do have a presence. Dennis was nice enough to humor me but prefaced that the Tannoys are 5 times the price. I was playing with fire here. I have a new pair of dt8s out in the car, unboxed, and I am comparing them to the Tannoys at 5x$. Would I be going home with a touch of buyers remorse? The Tannoys were better no doubt. We didn't listen long but the quality of that sound reproduction was of a very high order. A detailed speaker to say the least. Clinical and precise. The only fault I could see was that they needed more room to breath. Sorry Dennis. IMHO those babies need a bigger listening room. I could draw up some plans for an addition if you want. Just kidding of course. In the end though, the Proacs were everything I could expect at around $3k and I was leave very excited to get mine home and hook them up.

On to the last amp of the day. Dennis' coppertone PSE v2 with the glow tubes. He said while hooking it up that he had not listened to it for a while. It was a bit dusty. I guess he has been focusing on his SET Hot Rod and Universal for a time. The output tubes were a quad of the USSR 6f6s (st shape btw) Again I do not recall the driver and rectifier. This was the first and only SEP amp we played. The others were all triode wired pentodes or Allan's true triode. With the 6f6s we would have a full 4 watts SEP. Tony remarked a few days ago here, "WOW". I think we were all a bit blown away. From realistic horns in the Jazz piece to... well to use a DH expression HOLY CRAP. Those horns were right there in the living room. Smiles all around. Maybe a jaw or two agape. Laughter. I might have had a tear. My plan is to have my Proacs driven by my PSE. Sadly it was time to go out to lunch. Session over. Damn good times though.

Always the question, Inspire SET or SEP? Of course system dependent, blah blah blah. In my mind though, at least for me, it comes down to the music you listen to and the time and way you listen to it. If predominantly you are sipping wine on a quiet evening and want it to feel like Billy Holiday is whispering in your ear the triode strapped Inspires are truly magical. Now if you are drinking several beers and throw in Gov't Mule's Telstar Sessions the SEPs will just knock your socks off. Truly sounds like you are in the studio like the engineer saying, "that was F___ING AWESOME". I suggest if you are like me and listen both ways you need both types.

One other aside. As we have concluded here, SPL measurements as stated by manufacturers are worthless. As I said the DT8s are rated 90db/1watt @ 1 meter. Primarily we were driving with tubes providing 2-5 watts. With all the listening we did we did not get above 1/3 volume except with Allan's 1.5 watts where we got to 12:00 on the dial, briefly. Nothing was earsplitting but to talk we did have to turn down the volume. These Proacs at 90db are much louder than other speakers I have at 96db rating and others higher. I don't care weather one is lowballing or the other over exaggerating. The problem is that it leaves us all with useless reference points. When I first saw the DT8s in the Proac website. I contacted Dennis to ask if my PSE would drive them figuring I would need the whole 24 watts with GL KT-77s to make them sing. Dennis assured they would be fine and made arrangements for his own pair. What better recommendation. After our session I am confident that 2 watts is plenty. Go figure. My reference points are worthless.

Enough for now. I will post more about the Proac DT8s over on the other AF thread devoted to Inspire-speaker pairings as I get them broken in.



Scott

Scott,

Sorry to be so late in responding to your post. I just got back from 18 days abroad. I'm glad you liked my amp. I've purposely been following a little different path than Dennis, but we really benefit from trading ideas and experiences. Mind you, Tony and I are basically his apprentices, and I would never begin to think I could ever come close to his depth of knowledge and experience. How am I ever going to get 50+ years of experience building toob amps?!?
But, since I don't know any better, I try stuff just to see if it will stick to the wall, and it gives him an idea, etc. I'm pretty well set for amps currently, although I think a Universal amp of some type is in my future, along with an amp built around the 8417 tube. As an aside, this was the pinnacle of tube development in the 60's and are very hard to find. I happen to have a stash of them for some other amps I've accumulated, and may siphon 2 or 4 off for this project. The KT series of 90 or above are essentially just bigger power versions of the 88s, no matter how much the manufactures will argue. The 8417 is a novel design, once described as a “cavity anode”.
Next up on the block is a preamp, perhaps based on the 26 or 01A tube. Yes, Dennis doesn't like these directly heated triodes, but I have a stash of both, and I need another preamp, especially one with a dedicated center channel. Lastly, I have fallen in love with the blue glow of the mercury filled half wave rectifiers.
Bought a pair of 816s and they will definitely be going into an amp in the near future...

[BearCityUSA]

It's official the, the Universal is on the market!!!

Check out Dennis' latest ebay listing.