Dennis Had Inspire Amps

[Bombadil]

Originally Posted by zip

I only see a few comments on the Hot Rod versions. Is

Does the term "Hot Rod" actually mean anything anymore? I believe a Hot Rod KT88 amp produces 12 wpc. My non-Hot Rod KT88 produces 17 wpc.

[FloridaBoy]

Originally Posted by BearCityUSA

Give me a few days to put something together. Getting ready for vacation next week so pretty busy wrangling up stuff for the trip. The visit was eventful. I'm still getting my mind around it all. As I have said before, make the trip if you can. In the mean time I will attempt to be a surrogate.

Oh yeah, we want the story...but it can wait until you return from vacation.

[Musica Amantem]

Originally Posted by Analog Addict

If you don't get back to RTP by Sept, I will be in Asheville for a conference 9/8-9 10, and would be happy to bring my PSE 45 along for a demo. I'm hoping my PSE 71-A will also be ready by then....

I was curious about your interest in the 71-A output tube for your PSE project, so I did some research:

The type 71A vacuum tube was a power amplifier triode intended for use in the final audio stage of battery- or alternating current-operated receivers. It began life, under the old style of tube designation, as the UX-171 and was announced by the Radio Corporation of America (RCA) in May 1926. Operated at its published conditions, it was able to supply nearly 800 milliwatts of audio power, a reasonable amount for a single tube. It was superseded in November 1926 by the improved UX-171A, which featured a lower filament current.

"The UX-171 and 171A were first issued with the “globe” style bulb, similar in appearance to an old-style light bulb. In the early 1930s, the bulb was changed to the “ST” shape (also known as the “coke-bottle” shape), and given the new designation of 71A.

Radio engineers used it extensively in broadcast band radio receiver designs. The 71A provided more audio power than the UX-112A, and the tube was less expensive than the UX-210 or UX-250 tubes. The 71A's only real competition, for design purposes, was the UX-245 power triode.

Today, the 71A has a small following amongst high-end amplifier builders and hobbyists. It was a high-production tube and is relatively easy to find from various tube suppliers (and on eBay)".

What differences do you expect relative to the gorgeous PSE 45? Thanks for your inputs.

Edit: Excuse my old memory, because now I think I may have poised this same question in the past?

[Analog Addict]

Originally Posted by Musica Amantem

I was curious about your interest in the 71-A output tube for your PSE project, so I did some research:

The type 71A vacuum tube was a power amplifier triode intended for use in the final audio stage of battery- or alternating current-operated receivers. It began life, under the old style of tube designation, as the UX-171 and was announced by the Radio Corporation of America (RCA) in May 1926. Operated at its published conditions, it was able to supply nearly 800 milliwatts of audio power, a reasonable amount for a single tube. It was superseded in November 1926 by the improved UX-171A, which featured a lower filament current.

"The UX-171 and 171A were first issued with the “globe” style bulb, similar in appearance to an old-style light bulb. In the early 1930s, the bulb was changed to the “ST” shape (also known as the “coke-bottle” shape), and given the new designation of 71A.

Radio engineers used it extensively in broadcast band radio receiver designs. The 71A provided more audio power than the UX-112A, and the tube was less expensive than the UX-210 or UX-250 tubes. The 71A's only real competition, for design purposes, was the UX-245 power triode.

Today, the 71A has a small following amongst high-end amplifier builders and hobbyists. It was a high-production tube and is relatively easy to find from various tube suppliers (and on eBay)".

What differences do you expect relative to the gorgeous PSE 45? Thanks for your inputs.

Edit: Excuse my old memory, because now I think I may have poised this same question in the past?

Well, them I'll prolly wind up giving you the same answer. Some time ago, I heard a bit of wisdom from a old tube amp builder (NOT Dennis) about SET amps. Essentially he said the sweetness of the sound is inversely proportional to the power output of the tube. So far, I have found this to be true.

I have listened to a 300B amp - Dennis' own personal set of the Cary 300 mono blocks, a 2A3 I built myself, several 45 amps I've built or rebuilt myself, and lastly the PSE 45. Frankly, I wasn't really impressed with the Cary amps, as I already had heard Dennis' new offerings by then. The 2A3 amp is sweeter than the 300B, but is not as lush and sweet as the 45 amps. The PSE 45 takes the sweet sound of the 45 tube and adds authority without sacrificing anything. What I was told, and if my experience continues to follow as it has, the 71-A should be the sweetest of them all. But at a mere 0.8 watts per tube, and my recent PSE experience, I decided to go with three 71-A tubes per side, resulting in power output in the 2-2.5 WPC range. I'm hoping it will be like a single tube 45 amp, but even sweeter.

I have all the iron in the car, and after I get off of work tomorrow, I'm stopping by the Shop to meet up with Tony and lay out the chassis. I have the last misc parts coming in the mail shortly, so hopefully I can get the build started soon....

I'll also drop a thread on AK about the progress of the build. I will try and leave this forum more or less unadulterated....

[Coltrane1]

Originally Posted by pstrisik

Yes, mine is called a KT150. Dennis designed it with that tube in mind. I have since had the upgrade to IIPS.

I've never been able to warm up to the KT150 tubes though. They seem a bit sharp to me. I can't recall if I've tried them with the IIPS mod though, so probably worth another listen.

My list of things to try is still growing but our Alaska summer visitors are still coming and going!

Hey pstrisik! How's summer Alaskan style?

Funny story...today I'm eyeing a CJ P11A on our friendly USA AM...not being familiar with the amp I google it and what comes up? Your ad from '14 located at AC....I said, hmmmm...that user name looks familiar! Nice buy too...how'd you like that amp? Is it fair to say you sold the CJ P11A b/c you prefer the Inspire amps?

[pstrisik]

Originally Posted by Coltrane1

Hey pstrisik! How's summer Alaskan style?

Funny story...today I'm eyeing a CJ P11A on our friendly USA AM...not being familiar with the amp I google it and what comes up? Your ad from '14 located at AC....I said, hmmmm...that user name looks familiar! Nice buy too...how'd you like that amp? Is it fair to say you sold the CJ P11A b/c you prefer the Inspire amps?

Wow! That 11A was a sweet amp. I should have kept it. It is hard to compare with the Inspires as I had not yet found Omega speakers when I had it (and a number of other pieces). I would love to see how it performs with my current setup.

I also didn't know anything about tubes. I was limited to swapping KT120's and 6550's. I realize now there were some others I could have tried. The CJ had manual bias, so a few in that class would have worked.

It was 70wpc if I recall correctly. Push pull with two KT120/6550's per channel. I sold it and tried newer and more powerful CJ monoblocs. I was stumbling around back then. My speakers were classic AR 2ax 2-way large monitors. I still have them, but they require more than the 10-12 watts I'd be providing with the Inspire (or the 8wpc my Pass ACA monos would offer).

Without the tube cage on it, it was really beautiful. That row of transformers behind the tubes and the gold anodized front and top plates really made for a stunning classic look.

Oh well! What is it going for these days? IIRC, it was about $1600 a few years ago.

Edit: I googled and see one for a bit over $1900. States it has the teflon cap upgrade. If that's the one, and you want one of these, I would grab it now. I've not seen them with the upgraded caps much at all. By reputation, that brings it into another league altogether! How it would compare with the Inspires? You have the potential to let us know! I suspect that the Inspires are easily as least as good as the CJ unless the speaker's sensitivity requires more power than they can offer.

Oh! The summer here is glorious! It's a bit past 6pm and the light feels like mid afternoon. With apparent climate warming, we are seeing an earlier start to summer than we are used to and temps in the 70's are no longer unusual. Enjoying it immensely. It is an amnesia drug for the last winter we endured. If it weren't for that, many less would live here! Maybe fiddling while Rome burns

[Musica Amantem]

Originally Posted by Analog Addict

Well, them I'll prolly wind up giving you the same answer. Some time ago, I heard a bit of wisdom from a old tube amp builder (NOT Dennis) about SET amps. Essentially he said the sweetness of the sound is inversely proportional to the power output of the tube. So far, I have found this to be true.

I have listened to a 300B amp - Dennis' own personal set of the Cary 300 mono blocks, a 2A3 I built myself, several 45 amps I've built or rebuilt myself, and lastly the PSE 45. Frankly, I wasn't really impressed with the Cary amps, as I already had heard Dennis' new offerings by then. The 2A3 amp is sweeter than the 300B, but is not as lush and sweet as the 45 amps. The PSE 45 takes the sweet sound of the 45 tube and adds authority without sacrificing anything. What I was told, and if my experience continues to follow as it has, the 71-A should be the sweetest of them all. But at a mere 0.8 watts per tube, and my recent PSE experience, I decided to go with three 71-A tubes per side, resulting in power output in the 2-2.5 WPC range. I'm hoping it will be like a single tube 45 amp, but even sweeter.

I have all the iron in the car, and after I get off of work tomorrow, I'm stopping by the Shop to meet up with Tony and lay out the chassis. I have the last misc parts coming in the mail shortly, so hopefully I can get the build started soon....

I'll also drop a thread on AK about the progress of the build. I will try and leave this forum more or less unadulterated....

Quite interesting! I had not read about it so this is all new for me. Thanks for the insights and good luck with that build.

[Bombadil]

The C-J P11a is spec'ed at 70wpc, but only hits that mark into 4 ohms. I've seen two sets of benchmarks on them and they only do 50 wpc into 8 ohms. They are always shown as 70wpc in used ads and in comments, but they aren't.

[pstrisik]

Originally Posted by Bombadil

The C-J P11a is spec'ed at 70wpc, but only hits that mark into 4 ohms. I've seen two sets of benchmarks on them and they only do 50 wpc into 8 ohms. They are always shown as 70wpc in used ads and in comments, but they aren't.

Conrad-Johnson lists the following specs:

Specifications:

Power Output * Ultralinear Operation: 70 watts per channel RMS at 4, 8, or16 ohms both channels driven from 30Hz to 15kHz with no more than 1% THD or IMD.

[Bombadil]

Originally Posted by pstrisik

Conrad-Johnson lists the following specs:

Specifications:

Power Output * Ultralinear Operation: 70 watts per channel RMS at 4, 8, or16 ohms both channels driven from 30Hz to 15kHz with no more than 1% THD or IMD.

I know that is what they claim, but they don't meet those specs. They are far from the only manufacturer to fail to meet their tube amp specs. It is pretty common.