Dennis Had Inspire Amps

[Blackcat]

@Johnnyprod... I have the 300PSE and no worries it can ROCK. Given that in my system I use the 300PSE to drive Celestion AXI-2050 that can take up to 300 watts to ear splitting levels (Wife is a head banger, god help me).

[Analog Addict]

Dennis finished up a couple of amps last weekend. First up is an incredibly clean 2A3, the first one of these Dennis has built in quite awhile. Featuring 4 mighty watts per channel, this amp is perhaps the cleanest one I can remember on the distortion analyzer, with the 2nd harmonic down almost -60db. Dennis has this one at his home and says it "sounds like a 40 watter!"

It's awaiting a front panel, but is otherwise complete. It's set up for both 6SN7s and 6SL7s, but Dennis likes the 6SN7 better. Supplied 2A3s will be a new manufactured pair, since Dennis borrowed the old stock RCAs currently playing from me, and I ain't coughing those up....

Untitled by analog addict, on Flickr

Untitled by analog addict, on Flickr

Untitled by analog addict, on Flickr


Price is $2700 plus shipping...

Also, as a last minute thought, he brought out this KT-170 firebottle. Featuring the TOTL KT-170, this amp puts out a powerful 12 wpc. Driven by a pair of 6SN7s, I don't have the distortion numbers or additional pix, but I can get them if someone is interested.

Untitled by analog addict, on Flickr

Price is $2500 plus shipping


PM me if interested...

[timeout59]

The 2A3 is something I'm interested in to add to my Inspire amp collection. I've been comparing my new 300B-v to the integrated PP KT-66 amp I've enjoyed for over two years. Was thinking it was a toss up as to which I liked better. However last couple days did some level match testing, plus some listening at higher than normal levels, and pretty sure I'll be selling the the KT-66. Then I could buy this 2A3, or if it's gone by then, ask Dennis to make me one?

I'd love to post the details of these listening impressions, and how I'm able to use the 4v XLR output from my DAC, but it would be a long post and not sure everyone would be interested.

[Analog Addict]

Originally Posted by Johnnyprod

Thank you for your impressions! Sounds like both Dennis and Don nailed it with their respective amps ( not surprising ). That’s my only hesitation with 300b amps and the types of music I listen to. It would be great when I put on Coltrane , Davis , Norah Jones , cannonball adderly etc but maybe less so with eagles , rush, stones , who , zeppelin

The PSE 300b can easily drive my Vandersteen 3As, which supposedly require 100 wpc minimum to drive. (Click images for video/audio)

Here's a taste of the Chairman of the Board...

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And here's a little dance music with a thumping bass line.

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The PSE 300b's VR tubes might wink at you a little, but the amp itself doesn't blink at anything you might feed it. We were also playing the 1812 with cannon fire, and again, like butter....

[BlackBess]

Well isn’t that a kick in the pants. After posting a question earlier in May about an Inspire 2a3 amp with no response I chose a different path. Perry Board answered my inquiries & agreed to build one for me with some “custom” features. But that’s something not relevant to this thread. What I would like to know if I can get a question answered is if Mr. Had still sends any information out with amps currently. My 6FLV-v came with 3 pages of information, the 300PSE, maybe I lost it. I could easily figure out where to put the 9-pin tube, 4 spots for 4 pin tubes, check. But the octals, 5 holes to stick 3 different kinds of tubes. Even someone like me got that right the first time. But the ad I responded to said the amp would “auto-bias for plug & play tube rolling”. Which tubes? The VR tubes, the rectifier? How about a 6SL7 instead of the 6SN7. What about a 5670 or even a 6H3n-EB in lieu of the WE396a? I know some parts get very hot & not to get it wet but I could use additional guidance. So as they say, inquiring minds want to know.

[BlackBess]

With egg on my face, I’ll just say that while I was busy ranting Mr. Had had already reached out to me to answer some questions with more grace & kindness than I deserve. He is sharing his skills to make people’s lives better. Thank you sir but you might regret one of your suggestions. I might just take you up on your offer.

[Analog Addict]

So Dennis said it would be OK to detail the build of this unit here, so I will proceed. Maybe not everyone is aware of how much work goes into building an Inspire amp, or a one off like this prototype. Now Dennis has the benefit of all new parts, and enough in the way of resources so that he doesn't have to do everything himself, but given my meager resources and the desire not to lean on him as much as I can, this is going to be a completely from scratch build.

So how does one of these amps start out? - Basically with an idea.

We liked the new GK6'er so much that it seems a natural next step to see what a similar unit with twice the output wattage might sound like. A great example is the 300b-v and the PSE 300b. The b-v is a great amp, but the PSE does everything the b-v does, and at twice the power output. Anyone who's heard both has no illusions of which one is the top dog.


That being said, I decided to put off another amp design, and use an old dusty blank chassis that I had sitting around for this project. One advantage of this chassis is that at 19", it's longer than anything Dennis currently uses, giving me more room to play.

Untitled by analog addict, on Flickr


The down side is that the corners were unwelded, giving the chassis a lot of flex. Considering the weight of all the iron that was going to be sitting on top of it, I decided to get it welded up for the added strength.


Untitled by analog addict, on Flickr

Untitled by analog addict, on Flickr


So $40 later, I've got this on my hands. Not entirely what I was expecting. This was the worst of it, with a big divot on the seam and a bulging blob on the corner. Apparently there must have been a residue from the protective plastic sheet that caused the weld to flow poorly. After he did two joints, he realized sanding the surface before welding removed the coating. Sigh....

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However, I knew that I could cover all of this up with some JB Weld, and a bunch of elbow grease (Hard work for you non-US slang speakers) and a file.


Untitled by analog addict, on Flickr

Untitled by analog addict, on Flickr

Not perfect, but since Dennis has talked me into powder coating rather than painting, that should cover the remaining small defects pretty well.



Since I want to have all (hopefully) the holes drilled before powder coating, I started on the layout. Now, forgive me if I can't post the circuit schematic, but I can post the power supply since nothing is proprietary on it.


Untitled by analog addict, on Flickr

Now realize that I over engineer my power supplies because I want the cleanest DCV I can produce. In fact Dennis just admitted to me the other day that he has also moved to two choke PS designs instead of one choke. It really does make a difference. My philosophy is to put a lot of effort into the PS, and correspondingly, make the signal circuit as simple as possible. In addition, all the extra capacitance acts as a "current reservoir" for moments of high current demand. As far as I'm concerned, there's no such thing as too much clean power....

Anyway, here's the current layout as it stands.

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The oil filled cap will be the first stage of the PS. I like the oil caps because they have a lot of storage capacity, and seem to provide a smoother sound. However, because of their size, they can't be used in space limited designs. I have the dimensions of the power transformer (PT) and output transformers(OPT) laid out in rectangles for space considerations. I will most likely put the two stand alone filament transformers for the rectifiers on top between the oil cap and the OPTs.

The rectifiers will go in front of the PT, indicated by the 4 pin sockets and the plate caps.


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The three voltage rectifier tubes will go next where the octal sockets sit. I'm using one 0C3 and two 0A3s,
giving me purple and orange to go with the blue glow of the rectifier.


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Since this amp is going to light up like the Las Vegas Strip, I'm calling this the Vegas Power Supply.

Also, notice the two switches and two (red and green) lamps. Because the Hg rectifiers need a short period of pre heating to allow for the liquid Hg to vaporize, I'm using separate switches and lamps for the filament and high voltage, kinda like in my last phono pre amp build. I have them laid out so that I can try to ensure that they will have enough room in the chassis so I'm not crowding anything.

Lastly, you'll see the four 9 pin sockets for the quad of 6GK6s and the single center socket for the 5670/396a driver.

I'm heading over to the shop today, so I'm hoping to have some additional progress soon. I love building these beauties, and I hope the final produce will reflect that. More soon....

[Jefffeith]

I joined the Inspire family!

Question, can the Ruby 5U4GC rectifier tube be switched to something else in the future? They are not easy to find.

https://speakerprojects.files.wordpr...5/img_8240.jpg

[cgn-dt-n]

Hello Analog Addict,
Nice project. Sounds exciting.
I think it's a good idea to have a PSE circuit around the 6GK6 tubes. The mercury rectifiers are awesome. This gives a light like in a gloomy pub with neon advertising signs.

I don't think any of the people here doubt that it takes a lot of work and time from the idea to the planning, construction, discarding, sound optimization to the finished product until the final result is satisfactory.

I don't speak slang, but I come from a metalworking background and can think with the rest.... It's possible to mess up more beautifully.... But the color obscures everything.

[Analog Addict]

Originally Posted by Jefffeith

I joined the Inspire family!

Question, can the Ruby 5U4GC rectifier tube be switched to something else in the future? They are not easy to find.

https://speakerprojects.files.wordpr...5/img_8240.jpg

So you're the fellow that wound up with this amp?...

5U4GC isn't really a tube designation as far as I know. You can use any 5U4, along with a 5Y3, 5R4, and 274B.

DO NOT use a 5AR4, as this could damage your amp.