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The "$250" Amp? - 6LU8 Compactron SE, UL

Kegger, Wojek, and Nella came over Sunday for burgers and equipment swapping. Kegger brought over the $250.00 amp and WOW, was I impressed. My amp is a 6SN7 line stage and 25/300b amp running KR300B globe tubes. Wojek brought over his DIY Hagerman Cornet to compare to my DIY Octal Cornet. First, I drank too much gin so the next day I felt like crap, but we had a great time. Except for a little less bass slam, the $250 sounded better then my amp. Really clean, detailed, and flat across the entire spectrum. It really made my Jensen Imperials shine (they are loaded with EV woof, mid-horn, and tweet-horn). I really am impressed with this amp and I think it will make a fine addition to my system when I finally tri-amp my speakers. Of course it was the working prototype so I’ll have to make a work of art out of it, but I am looking forward to the build. I am also going to build one for my wife’s system. She said she does not want something from the Frankenstein movie, so I have to be conventional with that build. It was difficult to listen to my Octal Cornet as I still have a loud buzz in the left channel but what I heard; the Octal was much richer with the same detail as the Cornet. That buzz is driving me crazy and I would like to get the $250 back over here once I have it straitened out. So, to Kegger, Squidward, Wigwam, and PakProtector…..Great job!!! This is a winner. For a $250.00 amp, this thing sounds like ten times that much money. Cheers.
 
djnagle said:
For a $250.00 amp, this thing sounds like ten times that much money. Cheers.
Click to expand...

I think the real thanks does not go to me. I'm the guy who saw an old article in Nuts-n-Volts and showed it to Squidward and said "Could you show me how to build that, or build it for me?" and he and Kegger took it and ran with it, then others joined in with their expert advice and suggestions.

My value-add will be, I hope, to provide the repository for the build info and detailed steps so that non-soldering, non-electronics-knowing guys like me could build such an amp if they wish. I'm good with documentation and photographs and 'splainin' things because I have to have it 'splained' to me first.

I'm just thrilled to see it all being pushed forward and not stalling. For that, we must thank Kegger and Squidward, along with PakProtector and dnewma04, I think.

Hooray!
 
And not to forget Bricktop here, he put some technical testing hours in on this baby as well!
 
I wish I could take some credit for this one, the only thing I'm providing is potentially pre-drilled top plates and/or sockets for potential builders. Unless you count annoying Ed often as input, in which case, I provided nearly unlimited input. :)
 
dnewma04 said:
I wish I could take some credit for this one, the only thing I'm providing is potentially pre-drilled top plates and/or sockets for potential builders. Unless you count annoying Ed often as input, in which case, I provided nearly unlimited input. :)
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Yeah, he said something like that. :blah:
 
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golf claps, golf claps :yes:
 
I'm not going to be playing the home version of this game ( I have built a couple of small SE amps already), but I have been following the discussion. I can't help with a quantity build, but if anybody is short a part or two or wants to make something slightly different, let me know. But my supply of 6LU8s is reserved for a push-pull amp I'll be building...

George (TubeLab) has shown a very similar design on some OTHER audio board... using the electrically identical 6LR8. The socket is the only difference, 9 pin vs. 12. It has the further advantage of having a pinout that matches the dual triode 6GF7. There's also the slightly lower-powered 6KY8 that will plug in too. And there are the 21LR8, 21LU8, 15KY8, 13GF7 if you happen to have an odd voltage transformer already...
 
Hey guys! I'm in San Diego now (I've got about 12 hours of sleep total in three days :drool:), and it looks like this project has stirred up some serious interest! The channel I built is still on the bench at home, I haven't touched it since talking to Kegger about it. I was planning to rig another channel up and give them a listen, but I got busy before the trip. If it sounds anything like that 6JM6 amp (and it should), it should be sweet. I'll also do a full measurement freq response / distortion sweep if anyone is interested. And then, I'll give pentode a shot like Doug mentioned with regulated g2 and some more feedback probably.:scratch2:
 
First post here and first on AK in quite a while. Hats off to all you guys who have been putting this together. I know several folks who would be really interested in an amp like this -- myself included.

I just wanted to pass along that AES has the 6LU8s for $ $4.58. I just bought a bunch myself.

Looking forward to the next steps.

-- Jim
 
nother build

Just so this thread doesn't go stagnent while materials are being finalized.

Here is the next installment I've been fevorishly working on to bang it out.
(it's going much slower then I'd hoped with how I'm laying this one out)

It's the 6LR8 version (same as 6LU8 but in a 9 pin socket instead of the 12)
I'm doing this to test the 6LR8 and am building it a bit bigger using a pair of
tubes for each channel in paralell for more power.

Plus you can just pull 1 tube from each channel and run normal, as has been
mentioned the triode 6GF7 can pop in as well (if the circuit is optimized) I am
wiring in a large filament tranny so multiple or single rectifiers can be used to
hopefully help altering voltages. (some sort of first cap alterations by switch)

This will be a traveling test bed as all connections can easily be modified, can
even morf into a push pull version. I'll be doing a combo cathode and fixed bias
using one of the VTA boards basically just for bias and signal input as I have it.

------------

The original amp is working very well and the schem on the first page is finalized,
it will be traveling to the local SMAC meet this saturday for a larger audition. :smoke:

But here are a couple pics of the latest 6LR8 test subject now under construction.:scratch2:
 

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hey-Hey!!!,
I got a chance to hear the amp today at the SMAC meet. It was...errr..under less than ideal conditions...:) Lots of background noise...and the like. Still, it did quite well. Metalica to Bela Fleck/Edgar Mayer did not offend my ears...:)
cheers,
Douglas
 
PakProtector said:
hey-Hey!!!,
I got a chance to hear the amp today at the SMAC meet. It was...errr..under less than ideal conditions...:) Lots of background noise...and the like. Still, it did quite well. Metalica to Bela Fleck/Edgar Mayer did not offend my ears...:)
cheers,
Douglas
Click to expand...

I'm sorry I was not there myself. I have been forced to seek new accommodations on short notice. Very soon I will be settled in the new digs.
 
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Ok, I don't make much of a cheerleader (not so pretty) but, nice! job guys. This little amp in a bottle sounded (way) pretty good. The mule amp and it's designers/builders would be more than welcome over to my place for some serious listening, hint, hint, and some not too serious beer tasting. (just had to put some bait on the hook). That would include whoever wants to get a listen. Keg? Squid? Wig? could we make it this weekend, maybe?

I have the Coincident 94db, 14ohm and two way Linn Sara (?db), 4ohm speakers to try.

Happy (mini-amp) Listening! :beatnik:
 
The speakers got setup for the little amp gave us great bass and while people where there we’d
had to turn up the volume I see more then what the speakers truly were meant to shine at, after
many people left and there were just the 5 or so of us and the volume turned down I thought that
those tweeters sounded excellent an the whole speaker was impressive, perfect for that intimate
listening experience. (I believe they were Altec Bolero)

It’s truly tough at quite a few of these get together’s during the “high tide” time of the event to do
a “real world” setting an really evaluate the system or piece but I’m usually one of the last to leave
most of these things (usually one of the last to show up as well) so quite often I'd get to hear that
system the way it was meant to be played, while most of the time the systems do sound very good
during the meet it is quite often better in the lower noise floor setting as was the case here to.

(But the beer/food and conversations are a true high point as well)
Thanks to Ross for the invite to set the little guy up and the great spread!

-----

Rob no problem we can get the amp at your place for a test run, looking forward to it!

-----

Wiggy I was quite bummed you could not make it, I hope all is well with you and the family!
 
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