6550/KT88 SET amp aka "Uber Beam Machine"

jrebman · « **Reply #60 on:** 7 Dec 2007, 04:56 am »

Josh,

Can you give the voltages dimensions, or price of the transformer you're talking about so I can figure out which one it is? The page you gave renders very oddly with my scrreen reader and it is somewhat difficult to tell which transformer is which.

The PCR300, from what I can tell is a big filament transformer, but the one I think you're talking about (CG316 ?) ($245 ?) has a 115 vac primary, secondary taps of 5xx, 2xx, 75 and two 6.3 vct secondaries -- 1 at 6 amps, the other at 1 amp. Is this the one?

Don't see a 5v tap either.

Thanks,

Jim

JoshK · « **Reply #61 on:** 7 Dec 2007, 12:39 pm »

I'm talking about the PCR300. They have it mismarked. The primary listing they give are the secondaries. The primary is 117V. They confirmed this for me.

JoshK · « **Reply #62 on:** 7 Dec 2007, 02:06 pm »

Broskie mentioned he is starting a sale this weekend for Aikido hardware. If you want to build the Aikido version, or want to compare, this would be a good time to purchase.

SET Man · « **Reply #63 on:** 7 Dec 2007, 11:44 pm »

Quote from: JoshK on 5 Dec 2007, 05:12 pm

Buddy,

Thanks for the props. When I get it done, I'll have to come over to compare on your single driver speaks. I'm long overdue to pay you a visit anyhow.

Hey!

Yes, Josh you are very welcome to stop by my place.

Like I said I do have a bit of fascination about this type of amp for some time now but never got to hear it. So, if you are coming with your SE KT88 amp you will be doing me a favor by satisfy my curiosity with this type of amp.

Now if your amp sound better than my current amps than I think I will have to build one!

Take care,
Buddy

JoshK · « **Reply #64 on:** 8 Dec 2007, 01:48 am »

Will do Buddy.

Here is my first shot at sketching the layout, or at least a good part of it.

jrebman · « **Reply #65 on:** 8 Dec 2007, 04:15 pm »

Josh,

Do you have any details on the Aikido hardware sale? I don't see anything on the tubecad site.

I subscribe to the announcement list, but sometimes it doesn't get delivered, and I think this is what happened this time.

Thanks,

Jim

JoshK · « **Reply #66 on:** 8 Dec 2007, 05:11 pm »

He had just sent me an email regarding my order for a stereo board and mentioned that he was going to have a sale starting this weekend. Maybe he hasn't finished the site update and stuff yet.

jrebman · « **Reply #67 on:** 8 Dec 2007, 05:16 pm »

Thank you.

-- Jim

slbender · « **Reply #68 on:** 8 Dec 2007, 07:10 pm »

Hi Josh -

You know its really not all about the power. Around ten years ago, I made a SET Amp with the UBT-1 OP transformer, it has three EL-84 type tubes (in reality 10BQ5's) triode mode, in parallel in each channel, driven by a single 12AX7. Its totally been my fav amp and someone offered to buy it from me several times. Nice, rich, detailed sound, clear and transparent, despite my using ordinary polyester caps for coupling. The power supply has about 180 Volts on the OP tubes Plates, and around 5,000uF. in four cap banks and the input section of the HV PS for both channels. Its output is around 4-5 wpc. So stable, I haven't needed to change the bias setting in ten years. Tried several different input tubes, personally, I really like the smooth plate Telefunkens' the best..

Current amp I'm working on for nearly the past year is a bit more high-end and sophisticated.. I recall talking with you about the 5687's at Sands Point, listening to those Horns of Richards'. The current amp uses 5687's instead of the 12AX7, and paralleled 5687's for the OP tubes. Plate voltage is around 265 Volts, and 10 mA per triode; six triodes per channel.. It only has two cap banks, one for each channel; about 1,200 uF. total in the HV power supply one for each channel; and another 1,400 uF. in the input section. The power output is probably around 3 wpc, but preliminary listening, with average 86dB speakers reveal its' even more detailed and of higher clarity, due to the Polypropylene coupling caps. So its not the amp to play the 1812 Overature on inefficient speakers; or really wide range material above 80dB.

While it is not finished yet, but I'm already starting on a higher power version, likely it will use a Cathode Follower to drive a 6AR6/6098/6384 getting into the 8-9 Watt range.

I tried to attach a photo of the 5687 based SET, but I can't seem to do it since I switched to the Mac for email and internet browsing.

I might be interested in using that stereo input board in one of the units, some URL details for that item?

Tnx,

-Steven L. Bender

Quote from: JoshK on 8 Dec 2007, 05:11 pm

He had just sent me an email regarding my order for a stereo board and mentioned that he was going to have a sale starting this weekend. Maybe he hasn't finished the site update and stuff yet.

JoshK · « **Reply #69 on:** 8 Dec 2007, 07:35 pm »

Hi Steve,

Thanks for your comments. I would agree with you that it isn't all about the power, but this project was attempt to design a slightly higher powered SET amp that didn't use uber expensive tubes/parts and didn't cost an arm and a leg. I think EL84s sound devine. They are up there among my favorite tubes I've heard with 45's & 6V6s. But then I haven't heard a plethora of SET amps.

My problem is I like music that is more complex than jazz, and much wider range. Progressive metal and large scale classical are among my staples and when I put on some metal it isn't typically at 80dbs. I also tend to listen to classical at realistic sound levels. But I listen to a lot of music that is about the same complexity as jazz (indie rock & pop).

When we were at sand points I remember clipping the 45 amp and a 2a3 SET amp (not the white PP2A3) quite a number of times. Especially when I played my selections. And those were on supposedly 100db Avangarde Duo's. For simpler music the 45 amp was the best of the ones I listened to critically. There were a number of amps where I was too busy talking or there was far too much background chatter.

Dmason I think wanted an amp to end all amps, that could hang on drunken rockin out nights as well as have the inner detail to float his boat (my words). I want a reasonable cost moderate powered SET amp to try out in a multiamped system that can play full scale music balls to the wall and still whipe the floors with the typical commercial stuff. Maybe that is an impossible dream, but I think it might just be reachable.

The good thing about DIY is that if this doesn't reach all of my goals, I'll keep it for the less complex music or whatever it does do well and build something else for the other situations. And I can afford to do that since I am not paying retail prices to go through gear to float my boat.

I went out to Nathan L's place in conneticut this summer (along with Jonathan Weiss and some other local triode heads). His OB Fertin's with his DIY 45 amps were angelic on intimate music selections. I've never heard a better reproductive of "feeling of jazz". No offense to anyone in our Rave, as we've heard great systems, but this had the je ne se quoi. The reach out a touch you feeling and I hate that song (which is why I don't mind playing it to death on auditions). Unfortunately, when I put in my Tool cd (one of my favorites still after being a fan for over a decade) when Nathan slipped out to pick up the pizza it fell apart, even with the helper woofers (powered by SS amps).

This tells me that those that like flea powered amps don't listen to the same music that I do. That is fine. I even think there is a place for those amps in my listening habits, just not the primary amp.

poseidonsvoice · « **Reply #70 on:** 8 Dec 2007, 07:56 pm »

Quote

Dmason I think wanted an amp to end all amps, that could hang on drunken rockin out nights as well as have the inner detail to float his boat (my words). I want a reasonable cost moderate powered SET amp to try out in a multiamped system that can play full scale music balls to the wall and still whipe the floors with the typical commercial stuff. Maybe that is an impossible dream, but I think it might just be reachable.

Josh,

There are a few amps that are like this. They are all expensive to build. The ones that immediately come to mind are Lynn Olson's Karna (which you already know) and Kevin Carter's 3 stage designs using either push pull parallel 6550's or just push pull "super" 300B's. Or even Allen Wright's DPA designs. Those guys have the inner detail & grunt. But be ready to pay out $$$.

The amp you are building is probably just a stepping stone. Sooner or later, you will own/build a 3 stage push pull Class A 300B amplifier using octal input and driver stages (or DHT) and lots and lots and lots of iron.

However if you are only looking for SET and not push pull you are looking at an 845 right in the eye. That includes playing with a minimum 1000V B+ to get at least 15 watts out of it.

Best of luck in taming the disease

Solid state would be so much cheaper...but certainly not as much fun! I love both types though. DIY for me is like a buffet line. No use discriminating as I've heard excellent examples in both genres.

Anand.

JoshK · « **Reply #71 on:** 8 Dec 2007, 08:02 pm »

I already have all the iron for the Karna, or all but one pair of chokes. That is an uber expensive project. I've been buying the iron, here and there for over a year including tubes probably 2 years. This project was to set a solid base for a medium powered SET to compare to. I also have a 6v6 PP console pull amp that has had a bit of rebuilding and I will use to try out tricks on.

I have read a lot of stuff and now is the time for me to correlate it with my own experience. The point about little watts being enough was something I also had to experience for myself (it wasn't for me) to know.

JoshK · « **Reply #72 on:** 10 Dec 2007, 04:16 pm »

Homework...

1) If you guys want to arm yourself with the tools to design a SE output stage, read Blog 122 from tubecad.com. It is less than 1,000 words so it isn't too much reading. Obtain KT88/6550 triode curves from the internet and work out operating points yourself for this amp. Then you can share your results with the class. (hint: there is more than 1 right answer and more than 1 way to go about it, but Broskie's method works well and is straight forward).

2) Go to http://www.basaudio.net/diymag.htm, and download the 2005 christmas edition webzine and 2006 Q1 webzine. In these two editions is the articles (part I & II) of "Designing a PSU with Duncan amp's PSUDII". Having completed #1 you will now have an appropriate B+ and current rating (add ~50mA for front end) needed for the PSU. Download PSUDII from duncanamps.com and model a PSU for this amp. Share with the class.

P.S. this weekend I played a bit more with PSUDII and PSU variations depending on front ends in use. However, I can't pin anything down without the PTx in hand to measure it's impedance, since it does matter.

JoshK · « **Reply #73 on:** 10 Dec 2007, 04:29 pm »

6550's datasheet....
http://datasheets.electron-tube.net/sheets/135/6/6550A.pdf
Top of page 5 is the triode curves.

KT88's datasheet (should be similar)...
http://datasheets.electron-tube.net/sheets/084/k/KT88.pdf
page 7 is triode curves.

Dmason · « **Reply #74 on:** 10 Dec 2007, 06:17 pm »

Josh,

Ya gotta love Fedex. Like friendly aliens they look the same whether in Lima Ohio, or Lima Peru. A knock at my door awhile ago, and I have my new Hashimoto irons now. These are beautiful and are every bit as nicely finished as Floobydust indicated. Big, heavy, slabs of metallic candy. Color me stoked. And my next door neighbor right now is an electrical engineer that would love to get in on cobbling up something new.

Apparently Robert Simpson has read this thread and was impressed with the level of information, and all that. All he added was in the form of a glowing recommendation to anyone contemplating something like this. He feels that his single ended amp for home audio, using the new production TungSol 6550 sounds fantastic any way you strap it, and well worth some nice transformers. He used some ancient rewound Western Electric's that he poached from a theater that was being torn down.

JoshK · « **Reply #75 on:** 10 Dec 2007, 06:37 pm »

So you went with the Hashimotos then? Good for you. A bit more expensive but probably worth the price to not have to say "what if?"

Dmason · « **Reply #76 on:** 10 Dec 2007, 06:59 pm »

Not all that much more however. Asikura san is worth dealing with. You wind up with friends in Japan with this stuff. Kevin, if you are reading. Asikura san has been reading some of this stuff..the decision was made after some contemplation, part of it was the fact that this will likely be my last tube amp, part was that single ended, outputs become pretty important, although Roger Modjeski might argue that one, but also part of the decision was made by what Robert said, that using the TungSols you get a big bold and powerful sound with bucketloads of single ended charm, and that considering it would be a relatively powerful amp, that even moreso than even good iron was in order. It was a "rational" decision. I once heard a Sun Audio 300B with huge Tamura magnetics, and I think I know the sort of sound Robert is going on about.

Also, as both Robert and Bruce, here with me now, are Canadian, I have to say I just heard on the news that Conrad Black is going to prison.

Conrad Black is in jail, and I am not. Way to go Conrad.

DaveC113 · « **Reply #77 on:** 10 Dec 2007, 09:06 pm »

Quote from: Dmason on 10 Dec 2007, 06:59 pm

Not all that much more however.

Did you find a deal? They are about 2.5x the price of the James transformers when I checked...

I found this website: http://timebanditaudio.com/Hudgins300B/Hudgins300B.html

In which I found this:

I am unable to hear an appreciable difference between
the James 6123HS output transformers and the Hashimoto H-20-3.5U.

I choose to believe this because I can't afford the Hashimotos

Josh,

Last day of school is the 19th, no more homework before then

Dave

Dmason · « **Reply #78 on:** 10 Dec 2007, 09:28 pm »

Dave

The James are the bargain deal no doubt, and I do not doubt that someone cannot hear a difference, but I will bet money that I can. If I can correctly identify key signature of a given tune, I can hear these types of differences. Two people here concluded on Hashimotos based on experience, maybe Floobydust could comment as well, on the matter. I got them because I wanted them. The fit and finish of them is astounding. The paint comes off the James ones really easy, and the Hashi's have some sort of acrylic finish. They are works of art.

Still they are keepers. Depends on your value system. I would never spend 50K on a damn car, preferring to buy older cars that I like, for peanuts, but lots of people who earn less than I do, especially in California that would consider an expensive are mandatory. You are a lucky student if you can contemplate such esoteric treats as audio iron imports.

jrebman · « **Reply #79 on:** 10 Dec 2007, 09:43 pm »

Dan,

I too have decided that I'm pulling out all the stops on this one as this design/build process, while a lot of fun, is also an order or two of magnitude more challenging for me, and can be very frustrating at times.

Dave, maybe you can help me with interpretation of graphs and software that won't work for me, and together we can come up with an optimum set of operating points and a suitably excellent PS together. Mike's dad has a machine shop, so top plates should be no problem either.

Dan, any more physical descriptive information like weight, size, appearance?

The other two big-buck options I'm considering are MQ and possibly one of Jack's Partial Stranded Silver secondary SE OPTs. Oops, then there's Onetics too. I'll almost certainly have Jack make the PT for me.

Josh, got a 9 pin stereo board and kit (6CG7/6922) and a pair of the octal mono boards for a headamp project. Thanks for the heads-up on the sale.

-- Jim