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

Choke question...

OK, so I'm planning to build one of these puppies, using the Antek AN3T275 and ss rectification. The Radio Daze 8H choke doesn't seem to be available anymore, and I've been trying to come up with an alternate power supply with reasonably-sized Hammond choke(s). I'm assuming (and this is question #1) that, since the grid current of a single 6LU8 is listed as 20ma in the RCA manual, the 75ma available in the 5H Hammond 156L choke should be sufficient, and I don't have to match the overall 108ma draw of the whole amp when using choke/cap filtration (which would mean using the giant-ish 157M or 159Q). Assuming it is, could someone pls. look at the attached 'possibilities' to see if they might work (one uses one choke, the other two)...also please shout if I've screwed something else up; PSUD2 is not my strength.... Thanks in advance for the help; this should be a fun build.

George
 

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Have fun, and Good Luck with your Build...Just be Sure to get a Good Sounding .33uf Cap for C1, it Really Matters...Forget the 1% Daytons...Lifeless...The Wima MKP 10's sound a Lot Better, they're a good Starting Point...
 
katabatic said:
OK, so I'm planning to build one of these puppies, using the Antek AN3T275 and ss rectification. The Radio Daze 8H choke doesn't seem to be available anymore, and I've been trying to come up with an alternate power supply with reasonably-sized Hammond choke(s). I'm assuming (and this is question #1) that, since the grid current of a single 6LU8 is listed as 20ma in the RCA manual, the 75ma available in the 5H Hammond 156L choke should be sufficient, and I don't have to match the overall 108ma draw of the whole amp when using choke/cap filtration (which would mean using the giant-ish 157M or 159Q). Assuming it is, could someone pls. look at the attached 'possibilities' to see if they might work (one uses one choke, the other two)...also please shout if I've screwed something else up; PSUD2 is not my strength.... Thanks in advance for the help; this should be a fun build.

George
Click to expand...

:)

Not sure where your getting this, or why:
"grid current of a single 6LU8 is listed as 20ma"

But if you take the cathode voltage on the output listed on the schematic
an divide it by the cathode resistor you get roughly 50ma per output tube.

So both tubes in an stereo amp will draw you 100ma, then throw in drivers
and you'll want chokes of at least 120ma to cover an whole stereo amp.

Have you tried to buy the Radio Daze 8H choke lately ? , I haven't but it is
still listed here.. http://www.radiodaze.com/category/241.aspx

Any other questions or in need of help, just ask, we'll get yu fixed up there.
 
Kegger-
Thanks for the advice - I was afraid I was way off base with my assumption, and I was... The bigger choke it is (I had seen the Radio Daze choke on their site but there's no magic button to order it, so I assumed it was no longer in stock.) I'll call or email them to check for sure.

George
 
sled108 said:
Have fun, and Good Luck with your Build...Just be Sure to get a Good Sounding .33uf Cap for C1, it Really Matters...Forget the 1% Daytons...Lifeless...The Wima MKP 10's sound a Lot Better, they're a good Starting Point...
Click to expand...

I suspect that you can probably also rule out Bennics, Jantzens, Solens, Audiocap Theta's, most Mundorfs, Auricaps, Clarity Caps, and Kimbers for having the similar sonic qualities. Which does make me wonder if a wima mkp 10 is a starting point, what is a step up from there and how do you decide aside from spending 50-200 in caps to decide by tossing various caps in there?
 
Hey now...The 'Big' Edcor OPT's are on their way...Has Anyone heard any Sonic differences in any of the 6LU8's out there?...I have RCA's, Sylvania and GE's, which all seem to sound Very Similar...I like the GE's because they are Clear Top and Really Glow Nice...But, other than that, I can hear no Sonic Difference between them. Have any of you found a Sweet Singer 6LU8?....Or, do they all Sound the Same?
 
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dnewma04 said:
I suspect that you can probably also rule out Bennics, Jantzens, Solens, Audiocap Theta's, most Mundorfs, Auricaps, Clarity Caps, and Kimbers for having the similar sonic qualities. Which does make me wonder if a wima mkp 10 is a starting point, what is a step up from there and how do you decide aside from spending 50-200 in caps to decide by tossing various caps in there?
Click to expand...


You are somewhat right here I believe... The MKPs are pretty much all the same.

Mundorf tube-caps are different I believe...also rated at a bit higher voltage. I've used their 20uf, 30uf and 47uf very successfully. They are also quite a bit smaller than Solen.

I really like nice GE oilers or ASC... however space is an issue. I wonder if anyone around here as experimented with those Chinese obligattos?
 
Hi,
I am going through this wonderful thread. I am willing to try this Tube amp. Does someone has PCB for this? Is this final schematic?
attachment.php

I can get to make some good quality PCBs for this project.

Regards,
Sachin
 
That is the final schematic, and all the needed info is on the first page post number 5.

--

No I do not believe a circuit board has been made for this amp, should be pretty easy.
(and some may interested in them, if so keep that to PM's)
 
You're the Man, Kegger...The Edcor GXE15-16-10K's have made the Compactron Amp into a 'Mighty Compactron Amp'...The OPT's are so much more Open and Crisp that I put MKP10 1uF's bridged with .01's in C1...Wow, this Baby has Bottom now!. I've also done a bit on the Power side so it's running as Hot as the Hammond PT can, 333V B+...It's hitting C1 with 165V now...I'm working on a nice 'Tubes a Glowing' shot of It that I will post as soon as get a Good One...
 
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I've just got a Pair of NOS Sylvania 6LU8's, Chrome Top, with Halos...I'm A-B 'ng them with the GE Clear Tops...So far, it seems that that GE's have a bit more Punch. But, they both Sound Great...And, from what I've been able to find about TV Sweep Tubes...Is, that when these were made, they were the Best Tubes that they could Make at that Time. TV tubes lived a Hard Life, so they had to be Strong, and Work just Right...And, so These did...The Last, and Quite possibly, the Pinnacle of Consumer Tubedom....Any Thoughts?..
 
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Yah your pretty much on with all of that.
I do tend to favor the Sylvania 6LU8/6LR8 myself.

I personally think these may be the best of the triode/pentode combination
tubes to use for this type of amp, an better than many of the usual suspect
audio tubes or at least as good, for the combo tubes I think they have there
"output" tube portion as being the highest wattage plate rating as well.

As beefy as they are I wouldn't hesitate to now after experimenting with them
run them at a solid 18w of plate dissipation in circuit an still expect to live long.
 
Most of your compactron based were, to try an keep pace with SS that was
trying to replace them, so yah there is some great tech in a lot of these and
had to be very rugged so they were overbuilt for there environment, now we
using them in audio which is much less demanding both stress an performance
wise that there just loafing along doing what we ask them to do.

It's that way with a lot of TV tubes, let alone the last of the compactron tech.
Quite a few TV based tubes make exceptional Audio tubes, both small an large.
 
Well a few that come off the top of my head are.

6EJ7 (GREAT SMALL SIGNAL/DRIVER TUBE)

8608 "FAMILY" (HIGH PERFORMANCE HIGH TRANSCON TUBES, DRIVER/SMALL OUTPUT)

6EB8/6GN8 (TRIODE/PENTODE, SIGNAL, GOOD FRONT END/DRIVER, 6JT8 BIG BROTHER)

6BK7/6BZ7/6BQ7 (VERY NICE AND CHEAP DUAL TRIODE DRIVER TUBES, PRE 6DJ8 TUBE)

EL500/6GB5 (TOTALLY SWEET OUTPUT TUBE)

6AV5 (TOTALLY SWEET OUTPUT TUBE)

6HB6 (9PIN POWER PENTODE FOR OUTPUTS, VERY VERY EASY TO DRIVE)

6JC5/6JB5/6HE5 here is a link to a post I made about these.
http://www.audiokarma.org/forums/showpost.php?p=4774570&postcount=26

For rectifiers those TV damper diodes are pretty killer and very cheap, think 6AX4 ect.

----- All but those 8608 family type of tubes are very inexpensive and easy to source.

I've used All of these with good results, so this isn't just "second hand net info" there.

The 6BG6G is the TV tube equivalent to the 6L6, with a top cap and ST shape as well.
 
Yeah, it would seem that those 6JC5's are a Great Deal...But, which are the Sweetest, and the most Powerful of them all?
 
Oh, I mean of the 6LU8 Type....
What has the Most Power, with at least as Good of a Tone as a 6LU8?
 
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