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

http://www.diyaudio.com/forums/tubes-valves/183193-tonys-6lu8-push-pull-power-amp-build.html

all irons used in this amp was handbuilt by me...
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Richard (and anyone else still viewing this thread),

I finally got back to this project. Richard, your advice was perfect and solved my main problem. I had other problems as well, but minor in comparison. I still have a humming problem, but am slowly tracking it down. I would upload a photo, but the unit would look as before.

This was a very good learning process for me and I want to thank all that contributed and answered my questions. How does the unit sound? OK. Nothing like a Class D amp board-----especially when you apply the cost.....but cost was not the reason for building this, the main reason was to do something from the past.

Mike
 
"Nothing like a Class D amp board" I'm with you on that. I am starting to hear very good chip amps, but I still like the looks of tubes and the warmer sound they produce. I can get that sound by using a tube preamp into a class D though.
 
Just finished this amp. Thought I would post a few pics. I designed a different power supply for it,one I use for my guitar amps. No chokes. Changed a few resistor values but nothing drastic.Super quiet. Nice little amp.
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Hi
I have built this amp a few years ago and really enjoy the sound. Lately my 6LR8 (not 6LU8) socket seem to have gone bad with some contacts. Where could I buy good quality 9 pin socket ? I believe these needs to be Noval type, the one I used were Chinese from e-bay.
Thanks for the help,
Isophon
 
Long dead time in this thread. I was going to build an ECL86 then decided that I didn't want t to spend that kind of money for a non-directed noob first build. I settled on S,unkeyworks (?) build of a 6MB8, as her example is very well documented. I then stumbled across projects using ECLL80 and ECLL800 tubes with ore power.

With the bit in my mouth I have ventured forward with the 6MB8 as far as purchasing tubes and the complete BOM.

Still looked for a follow on project and discovered compactron tubes!

Right now I am checking g out my transformers to see if they are sufficiently beefy enough to handle the6lu8s. If so, I will build out the 6bm8 as a prototype,and when satisfied,maybe moving on to this project. It will be I threshing if anyone is still following this thread.
Roger
 
RogerA said:
Long dead time in this thread. I was going to build an ECL86 then decided that I didn't want t to spend that kind of money for a non-directed noob first build. I settled on S,unkeyworks (?) build of a 6MB8, as her example is very well documented. I then stumbled across projects using ECLL80 and ECLL800 tubes with ore power.

With the bit in my mouth I have ventured forward with the 6MB8 as far as purchasing tubes and the complete BOM.

Still looked for a follow on project and discovered compactron tubes!

Right now I am checking g out my transformers to see if they are sufficiently beefy enough to handle the6lu8s. If so, I will build out the 6bm8 as a prototype,and when satisfied,maybe moving on to this project. It will be I threshing if anyone is still following this thread.
Roger
Click to expand...
Welcome to AK! Perhaps you haven't noticed but Stephe just started a series on her YouTube channel building an amp using 6LU8s.

https://www.youtube.com/c/SkunkieDesignsElectronics/videos

I'd suggest that you start a new thread specifically about your build over on the Tube Forum. It will get much more attention over there. For some reason there are very few threads about DIY builds from scratch on this forum. The focus here seems to be on repairs to a wide variety of equipment and, in terms of amps, it's mostly SS oriented.
 
RogerA said:
Long dead time in this thread. I was going to build an ECL86 then decided that I didn't want t to spend that kind of money for a non-directed noob first build. I settled on S,unkeyworks (?) build of a 6MB8, as her example is very well documented. I then stumbled across projects using ECLL80 and ECLL800 tubes with ore power.

With the bit in my mouth I have ventured forward with the 6MB8 as far as purchasing tubes and the complete BOM.

Still looked for a follow on project and discovered compactron tubes!

Right now I am checking g out my transformers to see if they are sufficiently beefy enough to handle the6lu8s. If so, I will build out the 6bm8 as a prototype,and when satisfied,maybe moving on to this project. It will be I threshing if anyone is still following this thread.
Roger
Click to expand...
There are lots if choises of cheap compactron tubes. I built one using 6LR8's for 5.5wpc. I built mine Ultra Linear. It could have been configured straight pentode or triode strapped using 5 different sweep tubes. If I hadnt splurged on the chassis, It would have come in just shy if $200 at the time. I'm building a passive preamp with a phono stage to match it at the moment.
 

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The power tyranny for my 6mb8 amp will not work f9r the spud amp project.

I will complete the 6m 8 first, and then decide whether to go forward with the spud.

Awaiting a variac and isolation transformer before building. I do not think I could resist poweri g up if I had something wired up!

Roger
 
Well I went ahead and built it! I followed the Skunkie Designs video series and schematic. My thoughts post build are that this is much better than I expected. It drives my Advent Graduates, and my Polk 50 monitors very well. Neither of those have bass below about 50-60Hz, so I cannot comment on bass power, but to my ears, Santana's Black Magic Woman has a great bass rift at the end, lots of dynamics, detailed percussion, guitar, and organ. I was not expecting this amp to be capable of powering the Polk Monitor 50's at 89dB sensitivity, but did a great job of it.

As far as any regrets, I wish I had bought a more powerful power transformer. The one I got delivers 104mA, andI think the amp is drawing just about that. It gets hot to the touch, but reaches a thermal equilibrium after a while and gets no hottoer, so no runaway. I suspect that I will upgrade the tranny at some point. The pair of tubes I got were not well matched and the sound stage is a little lopsided, hard to tell how much is due to tube and how much due to speaker placement as even with my Sony AVR it is a little off center, but not by this much. I have a spare 6LU8 I purchased,and will try to see how well it is matched.

dand of course pics. My amp, and my listening space with the 6LU8 in the center on the console. The Advent Graduates are a recent refoam.
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