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Inspire by Dennis Had Enjoying Vacuum Tube Audio

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  #4161  
Old 09-26-2017, 09:23 PM
CoGT3 CoGT3 is offline
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AA, speaking of the regularly scheduled programming, how's the 45 PSE holding up?
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  #4162  
Old 09-29-2017, 09:21 PM
Comzee Comzee is offline
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Has anybody ever tried or considered the EL156?
I see there's adapters online to convert 10pin -> 8pin to make them work like kt88.
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  #4163  
Old 10-10-2017, 12:14 AM
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Originally Posted by CoGT3 View Post
AA, speaking of the regularly scheduled programming, how's the 45 PSE holding up?
Great. Had a couple of AK buddies in tonight, and one of them couldn't believe that I can power four stacks of Altecs with it. I haven't spoken with Dennis recently, but last I heard there was some kind of hangup with his chassis supplier, so things may have slowed down at the shop. Meanwhile, I'm hoping that Straitwire will layout and cut the chassis for my 3 tube per channel 71-A PSE soon...
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  #4164  
Old 10-14-2017, 09:55 AM
Rosco65 Rosco65 is offline
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Great. Had a couple of AK buddies in tonight, and one of them couldn't believe that I can power four stacks of Altecs with it. I haven't spoken with Dennis recently, but last I heard there was some kind of hangup with his chassis supplier, so things may have slowed down at the shop. Meanwhile, I'm hoping that Straitwire will layout and cut the chassis for my 3 tube per channel 71-A PSE soon...
How do you like the Altecs with the Inspire? I have some Altec components that need to find their way into a new application (4 x 414A, 2 x 802D, 2 x 32A). The 414’s have limited LF output on their best day, so I am confronted with the need to either get the most bass I can out of them or accept the inevitability supplementing with active bass (probably the direction I will go). Compounding the challenge is my limited available space.

A poster on another forum started a long thread on crossover modifications to a 9844B monitor. He ended up with a slightly modified N800F crossover (using a 806 driver) with the A19 contour network added. He runs them in 2.5 way configuration, with the second 414 brought in with a single inductor at 200hz or so. This thread inspired me to try the 414’s in an OB configuration. The second driver should offset some baffle loss (to a point) and keeping it out of the midrange will help keep the point source aspect of the main 414A. I can then cross over the 802D with the HF portion of Joe Esmilla’s 3Khz crossover/eq. A single 414A would run full range with the second 414A brought in as a bass Adder below 200hz or so. I expect the size of the baffle to be similar to a Magnepan SMGA. Impedance should remain no lower than 12 ohms or so, since the 414A is actually more like a 25 ohm driver over most of its range.
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  #4165  
Old 10-17-2017, 10:30 PM
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A dual woofer OB design would never work with Inspire amps....

Untitled by Analog Addict, on Flickr

Untitled by Analog Addict, on Flickr

Untitled by Analog Addict, on Flickr

Dennis actually set these up as a true dual woofer design with the woofers running in parallel. The extra driver adds approx 3db spl. The quality of the Altec woofers is ahem...better than the drivers we were using, and they still sounded fantastic with any Inspire amp. Given that the sensitivity of the Altec woofers is probably 6-8 db better than the ones we used, I think even a 45 SET amp should work extremely well in this application

Last edited by Analog Addict; 10-17-2017 at 10:37 PM.
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  #4166  
Old 10-18-2017, 07:26 AM
david45 david45 is offline
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Analog Addict,

Thanks for posting pictures of these OB speakers. Considering the extra woofer and the 3db boost in terms of sensitivity, just how efficient are they and how low can they play?

Not that I'm in the market for new speakers, but I have been using a pair of open-baffle speakers designed by Danny Ritchie of GR Research for a few months now along with dual servo subwoofers (also OB) and I am now considering getting a new amplifier and pre. They mesure at 93.5 db all the way down to about 80 hertz and provided they are being used with the OB subwoofers, they can be high-passed anywhere from 80 to 200hz ideally with a cap in between the pre and the amplifier.

For the last few days, I have been using a Line Magnetic 210ia integrated with 300b tubes that I have here on loan and I really like how it sounds. It excels at mid-range and transparency along with very good tri-dimensionality so that is just about perfect for the kind of music I like listening late at night (small ensemble, girl and a guitar, anything with piano or close mic vocals, etc). The speakers are getting a full-range signal and yet the big meter on the front of the amplifier pretty much never indicates over 0.5 watt and maybe 1 watt if I'm really pushing it during the day (ambiance music while doing random stuff and not critical listening). My room isn't the smallest at roughly 3000ft3 but everything is set up in a near field arrangement and the listening position is at about 6 feet from the speakers only.

I am really surprised that a 300b amplifier with only 8 watts per channel can work so well in my system and it makes me wonder if a 45 PSE and its glorious 3.5 watts could be an even better fit especially if it is being hi-passed (?). Could it also benefit from the IIPS mod?
I realize that Dennis still isn't offering his own version of your amplifier and that you recommend speakers that are 100db efficient or even higher, but I am intrigued nevertheless.

It's been a few months since your first listening session of the kt77 PSE prototype in triode and I also wonder how things are evolving as this is also right up my alley especially if it can be dialed-in to provide a maximum of mid-range magic similar to a 2a3-300b-45 amplifier but at affordable output tube prices.

I am also considering a triode strapped amp built on the 45 chassis with 20 watts transformers and IIPS along with a pre just like Florida Boy and Musica Amantem.

Also in the cards would be to fly to North Carolina and stop by Cary for a listening session if that is a possibility that could help me make up my mind.

Cheers,

David


Quote:
Originally Posted by Analog Addict View Post
A dual woofer OB design would never work with Inspire amps....

Untitled by Analog Addict, on Flickr

Untitled by Analog Addict, on Flickr

Untitled by Analog Addict, on Flickr

Dennis actually set these up as a true dual woofer design with the woofers running in parallel. The extra driver adds approx 3db spl. The quality of the Altec woofers is ahem...better than the drivers we were using, and they still sounded fantastic with any Inspire amp. Given that the sensitivity of the Altec woofers is probably 6-8 db better than the ones we used, I think even a 45 SET amp should work extremely well in this application

Last edited by david45; 10-18-2017 at 11:10 PM.
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  #4167  
Old 10-18-2017, 10:44 PM
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Originally Posted by david45 View Post
Analog Addict,

Thanks for posting pictures of these OB speakers. Considering the extra woofer and the 3db boost in terms of sensitivity, just how efficient are they and how low can they play?
If I recall correctly, they are in the 92-94 db/w/m range and they go down to 40-45 Hz. I have never really found them lacking in the bass dept, although that may be a function of Dennis' listening room



Quote:
Originally Posted by david45 View Post
I am really surprised that a 300b amplifier with only 8 watts per channel can work so well in my system and it makes me wonder if a 45 PSE and its glorious 3.5 watts could be an even better fit especially if it is being hi-passed (?). Could it also benefit from the IIPS mod?
I realize that Denis still isn't offering his own version of your amplifier and that you recommend speakers that are 100db efficient or even higher, but I am intrigued nevertheless.
Considering that you say that the meter isn't going much over 1 watt, even a 2 watt 45 SET amp may drive your speakers without strain, but I really am now a believer in the extra depth, richness and oomph the 45 PSE configuration adds. The IIPS is basically a voltage regulation scheme, and if I understand correctly, really shines in beam tetrode or pentode power tube applications where the rock steady voltage benefits the conversion to single ended output. (Dennis may correct me on this one) I do use voltage regulation on the driver tubes, but the Glo tubes don't have enough current capacity to handle regulating the power tubes.

Don't get me wrong, the PSE45 sounds amazing on the Inspire OB speakers, but I tend to run extremely high efficiency speakers because I love the sound of 50 year and older Altecs or Khorns, and the horn taming effects of highly engineered toob amps. I've tried to foist a pair of A7s off on Dennis for as long as he wants them, but they are too big (and possibly too ugly) for his shop.

Quote:
Originally Posted by david45 View Post
It's been a few months since your first listening session of the kt77 PSE prototype in triode and I also wonder how things are evolving as this is also right up my alley especially if it can be dialed-in to provide a maximum of mid-range magic similar to a 2a3-300b-45 amplifier but at affordable output tube prices.
Heh, the problem with me commenting on the KT77 PSE prototype is that nothing ever seems to stay around the shop long enuff for me to really get familiar with the sound. Either it gets sold off, or it gets reworked to something else. I have heard a number of similar amps since then, and they are always very impressive, but to my ears they just don't have quite the same magic in the mid range, the honey that just drips out of the speakers when all is in alignment. In my mind, the magic really lives inside the tube, and the real art to amp designing and building is to figure out the best way to let the magic shine through. Dennis and I are in basic agreement in that the amplifier circuit/signal path should generally be made as simple as possible with a minimum number of high quality components. The complicated part of any design and build is getting the power supply as robust and clean as possible. Then with no limitations on them created by current or voltage fluctuations, or noise/distortion getting in the way, you just stand back and let the tubes do their thing.

Dennis is pragmatically handicapped by the fact that he builds in much greater volume than I do, so he has to use tubes that are one, consistent in their sound and build quality, and two, are available in enough quantity that he doesn't spend all his time trying to chase down enough tubes to properly outfit the number of amps that roll off the line. So that being said, I also have a love affair with old dusty triodes, so much so that I am going with this cockamamie 71-A build I've been planning.


Quote:
Originally Posted by david45 View Post
I am also considering a triode strapped amp built on the 45 chassis with 20 watts transformers and IIPS along with a pre just like Florida Boy and Musica Amantem.

Also in the cards would be to fly to North Carolina and stop by Cary for a listening session if that is a possibility that could help me make up my mind.

Cheers,

David
By all means, you should come to Cary NC and really see what all the fuss is about. A trip to the shop would be like a pilgrimage to Mecca for anyone who has ever heard an Inspire amp and loved the sound. If you manage to schedule a visit, I would be happy to take the PSE 45 over to the shop and let you have a listen to it as well. The Inspire speakers are also well worth hearing.

And for anyone who hasn't figgered it out, I was being sarcastic about the OB design not working with Inspire amps. Dennis would have never put the Inspire logo on the speakers if they didn't live up to his exacting quality and performance standards.

Oh yeah, before I forget, a certain radioman731 has put a brand new 2A3 amp up on E-bay for one lucky discerning consumer. Get it while it's hot!!!

Last edited by Analog Addict; 10-18-2017 at 10:56 PM.
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  #4168  
Old 10-19-2017, 10:03 AM
Musica Amantem Musica Amantem is offline
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I believe, based on my own experience with the KT-88 Triode-strapped Inspire amp (20 watt trannies and long chassis), that the Gold Lion KT-77 works wonders because it is a distant relative of the EL34 Pentode, the only tube which can be strapped in Triode mode naturally, given its internal configuration. A quote from Steve Deckert (Decware):

"... [I]In a pentode such as the EL34 where the screens are not tied together internally, it is possible to wire it as a "true triode". It is the only pentode I know of that is. The other ones have internal connections on the screens that can't be changed so you end up with a ´Pseudo triode´"

Although one would think using EL34 would theoretically beat the KT-77, hands-on experience from others have testified to the contrary, making that special combination of KT-77 (a "hybrid" between the EL34 and the KT-88) the best approach short of a real Triode. The cited KT-88 is really an excellent tube in the Inspire, on its own merits (again, referring to the Triode-strapped mode), so best-of-both-worlds, as they say.

Mind you, I have NEVER heard a 45, 300B or 2A3, so I cannot judge the midrange quality in my amp relative to those others, but at least I get to use different tubes and cheaper replacements with an outstanding midrange and highs, along with some higher SPLs. With a sub crossed anywhere between 50 and 100 Hz (in my case), these also have outstanding bass. Just my $0.02, YMMV.

Other than keep improving the source side on my gear, a technologically ever-evolving field, the best upgrade after the Inspire Lp-27a and HO amp is definitely a finer set of loudspeakers, which would ultimately do justice to that amplification and sourcing setup gem.

Last edited by Musica Amantem; 10-19-2017 at 10:21 AM.
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  #4169  
Old 10-19-2017, 10:51 AM
PHC1 PHC1 is offline
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Late in joining this thread and trying to catch up. How many models of amplifiers is Dennis Had building these days? Is the only way to buy through EBay? Thanks
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  #4170  
Old 10-19-2017, 02:09 PM
david45 david45 is offline
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I might just have to take you up on that generous offer!!

Quote:
Originally Posted by Analog Addict View Post
By all means, you should come to Cary NC and really see what all the fuss is about. A trip to the shop would be like a pilgrimage to Mecca for anyone who has ever heard an Inspire amp and loved the sound. If you manage to schedule a visit, I would be happy to take the PSE 45 over to the shop and let you have a listen to it as well. The Inspire speakers are also well worth hearing.
Great news! This should give me a good idea of what to expect with my current speakers in terms of overall volume and offer similar presentation.

Quote:
Originally Posted by Analog Addict View Post
If I recall correctly, they are in the 92-94 db/w/m range and they go down to 40-45 Hz. I have never really found them lacking in the bass dept, although that may be a function of Dennis' listening room
I'm not too sure just how much headroom is needed for most people but considering the type of music I usually listen to and that I am not really into classical music all that much, a PSE45 could be just the ticket...

Quote:
Originally Posted by Analog Addict View Post
Considering that you say that the meter isn't going much over 1 watt, even a 2 watt 45 SET amp may drive your speakers without strain, but I really am now a believer in the extra depth, richness and oomph the 45 PSE configuration adds.
I actually love how VOTT speakers look!! But their size certainly doesn't make them very room friendly
How about a pair of Model 19? Perhaps that could do it for him?

Quote:
Originally Posted by Analog Addict View Post
Don't get me wrong, the PSE45 sounds amazing on the Inspire OB speakers, but I tend to run extremely high efficiency speakers because I love the sound of 50 year and older Altecs or Khorns, and the horn taming effects of highly engineered toob amps. I've tried to foist a pair of A7s off on Dennis for as long as he wants them, but they are too big (and possibly too ugly) for his shop.
My pilgrimage to Mecca would most like have to be scheduled sometimes mid-December if it can fit your schedule as well as Dennis'. I recall someone commenting that Dennis loves a challenge so I'll try to convince him to go with an all out assault to get as close as possible to your PSE45 but using KT77 output tubes or any other affordable tube that fits the application. And depending on the end result, I might just have to bring the amp back with me to Montreal!

Quote:
Originally Posted by Analog Addict View Post
Heh, the problem with me commenting on the KT77 PSE prototype is that nothing ever seems to stay around the shop long enuff for me to really get familiar with the sound. Either it gets sold off, or it gets reworked to something else. I have heard a number of similar amps since then, and they are always very impressive, but to my ears they just don't have quite the same magic in the mid range, the honey that just drips out of the speakers when all is in alignment. In my mind, the magic really lives inside the tube, and the real art to amp designing and building is to figure out the best way to let the magic shine through.
This is making a lot of sense as to why Dennis still hasn't built his own version of your amplifier. Hopefully your 71-A build with 3 output tubes per side can be finished in time for my visit!!

Quote:
Originally Posted by Analog Addict View Post
Dennis is pragmatically handicapped by the fact that he builds in much greater volume than I do, so he has to use tubes that are one, consistent in their sound and build quality, and two, are available in enough quantity that he doesn't spend all his time trying to chase down enough tubes to properly outfit the number of amps that roll off the line. So that being said, I also have a love affair with old dusty triodes, so much so that I am going with this cockamamie 71-A build I've been planning.

Last edited by david45; 10-20-2017 at 10:11 AM.
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