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Pictures of your Tube Amplifiers


henry4841

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17 minutes ago, seti said:

That is a crazy rare piece.... More info please. Is that his surround sound piece???

heh

 

It's the static display version.

A guy ditched on me at an audio meet and greet.

 

It used a couple of filament transformers to light up the heaters to the tubes for display.

Then it had a plastic hammond case inside mounted on the front, with a Velleman LED control PCB inside, and a couple 9-volt batteries. (with 2004 date codes)

 

There was a little switch on the back for the LED display.

The knobs on the front are fake...like cabinet knobs screwed in with Allen bolts.

The switches are real, but not connected to anything.

 

If anything, I scored two dozen fresh input jacks, and ten good tube sockets.

The wood chassis is actually solid Bubinga. 

I'm pondering the idea of using the aluminum chassis plate and Bubinga base for an amplifier project.

But maybe shorten the plate and base for a smaller profile.

 

Interesting piece for the Poverty Audio scrapyard...

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4 minutes ago, mike stehr said:

heh

 

It's the static display version.

A guy ditched on me at an audio meet and greet.

 

It used a couple of filament transformers to light up the heaters to the tubes for display.

Then it had a plastic hammond case inside mounted on the front, with a Velleman LED control PCB inside, and a couple 9-volt batteries. (with 2004 date codes)

 

There was a little switch on the back for the LED display.

The knobs on the front are fake...like cabinet knobs screwed in with Allen bolts.

The switches are real, but not connected to anything.

 

If anything, I scored two dozen fresh input jacks, and ten good tube sockets.

The wood chassis is actually solid Bubinga. 

I'm pondering the idea of using the aluminum chassis plate and Bubinga base for an amplifier project.

But maybe shorten the plate and base for a smaller profile.

 

Interesting piece for the Poverty Audio scrapyard...

 

 

That is funny. There was an article years ago with the Foxgate tube surround sound he built for his own use. It looked pretty close to that.

 

 

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And two more pictures. I have some more testing and listening to do but for the most part I am finished with it. I do have a bottom plate to cover the electronics from curious fingers made of plywood I am going to install when I am satisfied with what I have done. Could possible be in the garage section at a later date if there is any interest. 

P1040123.JPG

P1040115.JPG

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8 hours ago, CWelsh said:

@henry4841 Beautiful work! What are the details? How does it sound? Compared to the Little Sweeties?

I was planning on detailing the time and work I put into this amplifier at some date. The case is solid 7/8" cherry wood with dovetails joints I personally cut myself. Aluminum is 1/8" plate. The design is a proven one close to if not over 20 years old with hundreds made and tested. In other words a solid design that I designed to be conservatively biased and operated and not hot rodded to produce better numbers that shorten the life of the tubes. A tube is somewhat like an old type light bulb with a wattage rating that has nothing to do with the output to the speakers. The JJ KT-84's are rated at 42 watts and I am running the tubes at less than 30 watts which is below the 80% l like to run all my builds at meaning one should expect a long tube life. One of my personal EL-34 amplifiers, which was my build before this one, is one I played around with the many different tubes in the EL-34 family which includes but not limited to the 6L6's, EL-34's, KT-77's and KT-88 with some others I do not have in stock that can be used. After doing many hours of listening and biasing the tubes I have there is no doubt in my mind the KT-88's are the best sounding of the family. Big and expensive but worth the cost in my limited experience. I actually started this build with the intention of using some EL-34's and actually bought a new set of JJ EL-34's for this build but after listening to the differences between the KT-88's and EL-34's I decided to bias this amplifier for the KT-88's. I have not done an A/B comparison between this build and the Sweetie. The Sweetie is one of my favorite sounding amplifiers and it has a tone I love. The Sweetie is limited in it's power more in line of the Decware Zen which it should be compared to. A SE KT-88 makes much more power, this one depending on the set of tubes is capable of 7 or more watts. This is a big amplifier. Right now with the tubes I have in it the amplifier is putting out an average of 6 watts per channel. One channel slightly over and one slightly less than 6 watts. This is typical power one can expect from a properly designed SET amplifier in the family of the EL-34 tubes. And for that matter a SET 300B amplifier. The KT-88 is a big tube that handles higher voltages and more current than a 300B. In my opinion the sound can be compared to a SET 300B without the hassle of dealing with a directly heated cathode. In other words much easier to build a quite amplifier. I ran a distortion analysis on this amplifier and the sound floor is 70db down from the main signal. In other works quite with your ear against my 103db LaScala's. Comparing the KT-88 tube to an EL-34, the ones I own, the bass is way better with a more pleasant vocal sound as well. This amplifier is built with slightly over 3lb OPT's instead of the 1 or 2 lbs ones you usually see being used that are offered for sale in most amplifiers of this type. With larger OPT's the sound becomes cleaner and clearer to my old ears with still a lovely SET sound. The output tubes are biased at around 70ma of current equaling 140ma for a pair with a few more ma's from the rest of the circuits and I am using a Hammond PS rated for 201ma's so one can expect a long life from this amplifier. I did a lot of testing inside this amplifier to determine if the higher wattage parts are operating within their rating. Also did some comparison on the input tubes. I knew there is normally a 20% tolerance in tube manufacturing but did not realize this also is true with a dual triode input tube. In one tube there can be a difference of 20% or more in the voltage and current between the two sections. I had to go through 4 12AT-7's before finding one that was closely matched inside the tube. Yesterday I received two Psvane 12AT-7's from tubesandmore and one of them had a difference in plate voltage between the pair of triodes of 30v's. The other was matched much better with just a slight difference between the two. I am sure most never realize the imbalance in the dual triode preamp tube they now have in their amplifier. Chances are one will never notice the difference in volume between the two. Yes one channel will always be stronger than the other if you have a 20% imbalance between the channels. That and one channel is going to put out more power at clipping than the other. One will never know when changing dual triode input tubes unless one checks the two triodes on the bench. This is just one step I took when building this amplifier. Right now it has JJ KT-88's which sound really good. They are the less expensive KT-88's being offered now that are in stock. After a few hours listening with the Psvane 12AT-7 tube last night for a few hours I like the vocals this tube produces and I do not think I would change it. It is being very conservatively biased with balanced triodes so I would not consider changing it. 

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Here are some pictures in Arta distortion software of the SE KT-88 amplifier after replacing the Psvane 12AT-7 with an NOS GE 12AT7. The distortion at 1khz 1 watt was cut in more than half by just changing the input tube. Distortion numbers of .26% THD and .27% THD+N at 1 watt is something I am proud of seeing in this SET tube amplifier. Left and right shots of the screens. Notice the  2nd harmonics and touch of 3rd and not much of anything else of the fundamental signal of 1Khz. The 4th harmonic is 73db down from the fundamental which is basically not heard along with a 5th harmonic 80db down. Good looking distortion profile for a SET in my book. Just what I expected and desired when building this amplifier. Some SET 2nd harmonics and a touch of 3rd is exactly what many consider makes an amplifier sound best. Some big name SS amplifiers introduce or build their amplifiers to have exactly the same stats as a good SET amplifier. 

 

 

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P1040139.JPG

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23 hours ago, henry4841 said:

It appears the Chinese do not have the ability, at least Psvane, to produce really low noise, matched internally for dual triodes, tubes consistently as the giants in tube manufacturing era did years ago. 

 

 

 

I have a hunch most modern tubes especially rectifiers can't hold a candle to originals.

 

 

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