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SE 6CB5 : @ 23 watts anode triode mode , LSES exp. update

24.140.192.106
Posted on December 7, 2016 at 19:48:55
deathtube 667



My LSES experiment with Edcor 2H/300ma/21 ohm chokes used for input service ended in failure.

I began to notice an odd buzz begin to develop in the L1 choke that sounded like frying bacon , so I pulled the plug on LCLC (L1=L2) LSES filters for fear of damaging a good part.

The 6CB5 finals were running at about 14 watts.

Returned to a flywheel filter: (1) LC section with 35mH/2A/.79 ohm input choke followed by (2) LCRC section for left/right finals and driver stages.

With is filter, I was able to run about 23 watts on the anode of 6CB5 in triode mode with no audible noise coming from the L1 choke.

Driver stage is ECC83 w/CCS plate load @ 1.5mA.

AC heating for all tubes.

Heyboer SE 14W 5K:8 OPT's.

The subjective sound is very powerful on Altec 811B+808-8A/414-8B.

dt 667







 

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LSES is an acronym for failure, posted on December 7, 2016 at 21:52:59
Triode_Kingdom
Audiophile

Posts: 10042
Location: Central Texas
Joined: September 24, 2006
 Glad you got it working. I'll bet it sounds superb with those horns. :)


 

RE: SE 6CB5 : @ 23 watts anode triode mode , LSES exp. update, posted on December 8, 2016 at 03:24:33
vinnie2
Audiophile

Posts: 4481
Location: North Carolina
Joined: September 28, 2013
 Nice breadboard!

 

RE: LSES is an acronym for failure, posted on December 8, 2016 at 05:56:09
rage
Audiophile

Posts: 793
Joined: December 17, 2010
 I bet that setup sounds good too. Laughed out loud at acronym for failure!


How do you like the Heyboer outputs?

Flywheel has worked well for me too.

 

RE: SE 6CB5 : @ 23 watts anode triode mode , LSES exp. update, posted on December 8, 2016 at 07:13:54
deathtube 667
 Vinnie2,

This is a very basic circuit compared to what you are doing with the ultrasonic DHT's, but the power output should be around 6 watts.

dt 667









 

RE: SE 6CB5 : @ 23 watts anode triode mode , LSES exp. update, posted on December 8, 2016 at 07:39:49
drlowmu
Manufacturer

Posts: 9730
Location: East of Kansas City
Joined: January 10, 2005
 Nice breadboard. There was nothing wrong with the filter, except, you needed to do a separate L1/C1/L2/C2 for each channel. That way, you are running with half the currents, and nothing gets stressed in L1.

A flywheel works because the typical Flywheel's 35 mHY L1 choke is usually rated a 2A., and it can absorb the high peak currents with a stereo load, on the less-than-critical-inductance choke input.

Many, 8 years ago, mis applied a LSES to a typical shared ( stereo ) supply. LSES was originally used in monoblock amps, to filter a single channel - with a TOTAL current draw of maybe 53 mA. Bumping filter current up to two channels, at 106 mA. or there abouts, is NOT an automatic possibility.

Even an inexpensive ( under $12.00 ) Triad C-40X ( 320 mHY at 10 Ohms ) will work with no problem, IF implemented as I suggest, for ONE channel's L1 only. A separate B+ filter ( and, for that matter - power transformer / rectifier tube ) will outperform shared parts sonically, in any decent amp.

Mikey Samra will confirm, a cheap 10 Ohm Triad C-40X is GOOD sounding .

In my latest ( 11-2016 built ) 2A3 amp, ( which I have been showing pictures of ), you will see FOUR chokes below deck, two for each channel. My L1s are only 210 mHY at 8 Ohms - filtering about a 55 mA. load, per channel. They run flawlessly that way, cool, no vibrations, etc etc.

Keep up the good work. Such a low DCR supply is AWESOME on ALTECS. have fun listening.

BTW, I have confirmed with DF, the LSES inventor, JUST last week, that when L1 equals L2, as in his LSES filter, the amp sounds the best to him.

Merry Christmas,

Jeff Medwin

 

RE: SE 6CB5 : @ 23 watts anode triode mode , LSES exp. update, posted on December 8, 2016 at 08:09:27
rage
Audiophile

Posts: 793
Joined: December 17, 2010
 "Even an inexpensive ( under $12.00 ) Triad C-40X ( 320 mHY at 10 Ohms ) will work with no problem, IF implemented as I suggest, for ONE channel's L1 only. A separate B+ filter ( and, for that matter - power transformer / rectifier tube ) will outperform shared parts sonically, in any decent amp."


No Jeff the Triad C-40x will not WORK at 53mA without buzzing!

It WILL work in a cap input supply. I've gone as low as 1uF before the Triad C40x.

Triad C40X will NOT work as "input choke" under any circumstances I've found.

Great choke for $12 though!

 

RE: SE 6CB5 : @ 23 watts anode triode mode , LSES exp. update, posted on December 8, 2016 at 11:10:15
drlowmu
Manufacturer

Posts: 9730
Location: East of Kansas City
Joined: January 10, 2005
 OK Rage,

In my November 2016 built JJ 2A3-40 amp, using about 55 mA per channel, I Thought I had used 320 mHY / 600 MA. Traid C-40 Xs, and had I had absolutely NO problem. But Rage, I was mistaken.

You MAY have been correct if you have direct experience. But I need to ask, was your Triad C-40X L1 choke just doing duty for one channel , not a shared channel supply, as you seem to indicate ??

I DID have 320 mHY / 600 mA. chokes in my newest build for L1, but instead of Triads, they were the same-rating Stancor C-2708s in there, ( NLA ) and Jeffrey confused the two chokes. My mistake. Thanks for pointing this out to me.

I think Mikey Samra used the C-40X in some duty other than as L1, and he told me how much he liked it.

Jeff

 

RE: SE 6CB5 : @ 23 watts anode triode mode , LSES exp. update, posted on December 8, 2016 at 11:20:05
rage
Audiophile

Posts: 793
Joined: December 17, 2010
 yes I ran the C40x first in my 2a3 amp, one PER channel not shared supply.

so dual LCLC.

input choke was C40x, second choke was your Heyboer 7 ohm model

they feed per channel 2a3 at 43mA and 12ax7 at 1/2mA.


They buzzed pretty good. Had to take them out and replace with Triad .035h and went flywheel.


If C40X worked I would use them for both positions and do the LSES that way rather than acquiring those Stancore chokes.

 

RE: SE 6CB5 : @ 23 watts anode triode mode , LSES exp. update, posted on December 8, 2016 at 13:23:47
JKT
Audiophile

Posts: 612
Location: Midwest
Joined: November 26, 2002
 Something to consider: all rectifiers have a small amount of "dead time" during each AC cycle. When that occurs the input choke will produce a high voltage spike caused by its collapsing magnetic field. With repetition (120 times/sec.) this can breakdown the insulation in the choke and cause failure. Much of the literature from the "Golden Age" shows that designers applied snubbing circuits to the choke to control this phenomenon. M. Jones 4th ed. shows a variation of this usage. A small cap before the choke will help maintain voltage though the rectifiers "dead time" and prevent this.

In the old days of automotive Battery/Coil ignition systems when the points opened the collapsing magnetic field of the primary winding in the ign. coil would generate an inductive "kick" in the same manner and would quickly burn-up the points through arcing if not for the condenser. Back in the day I had a Honda motorcycle that had a penchant for trashing condensers. When the cap failed the points soon followed. A PITA when out on the highway touring.


"It is better to remain silent and thought a fool, then speak and remove all doubt." A. Lincoln

 

RE: LSES is an acronym for failure or redemption ..., posted on December 8, 2016 at 14:24:19
deathtube 667



Someday I will build an LSES filter that will not buzz or make other hideous noises.



 

The 6CB5 must be VERY easy to drive if 12AX7 sounds good into it, posted on December 9, 2016 at 02:15:36
Timbo in Oz
Audiophile

Posts: 23221
Location: Canberra - in the ACT - SE Australia
Joined: January 30, 2002
 Myself, I wouldn't use a 12AX7 as a driver, anywhere.




Warmest

Tim Bailey

Skeptical Measurer & Audio Scrounger


 

RE: The 6CB5 must be VERY easy to drive if 12AX7 sounds good into it, posted on December 9, 2016 at 04:44:53
PakProtector
Audiophile

Posts: 12363
Joined: May 14, 2002
 As pentode it is quite easy. As triode, the g1-g2 capacitance( effectively the g1-plate) is comparable to a 2A3. There is plenty of anecdotal evidence from a fan or two that this high-gain triode can work 'the best'. IMO, they're smoaking crack and subjective...LOL
cheers,
Douglas

Friend, I would not hurt thee for the world...but thou art standing where I am about to shoot.

 

RE: LSES is an acronym for failure or redemption ..., posted on December 9, 2016 at 11:18:50
Eli Duttman
Audiophile

Posts: 10455
Location: Monroe Township, NJ
Joined: March 31, 2000
 "Someday I will build an LSES filter that will not buzz or make other hideous noises."

Rant on Get the Physics right! Rant off

A good PSU has a LOW impedance and plenty of current in reserve. There are several ways to achieve the requisite characteristics. Which of the choices gets selected is matter of costs, personal preferences, etc.


Eli D.

 

RE: nope ... , posted on December 9, 2016 at 11:29:12
deathtube 667



The most popular SE triode mode 6CB5 circuit features a 6N7 driver stage (cap or IT coupled stages) and the designer uses a tube preamp.

I have tried 6SN7, 6SL7 and ECC83 (all using CCS plate loads) cap coupled to triode mode 6CB5.

6CB5 is about as difficult to drive as a 2A3.

I tried ECC83 because I wanted a low current driver for the LSES experiment.

Not saying it is the best driver stage option or best sounding.

Didn't get any typical measurements (THD%, bandwidth, power output) to see how this circuit is performing, so I might change things up a bit with driver stages and biasing.

Work in progress.

dt 667







 

RE: SE 6CB5 : @ 23 watts anode triode mode , LSES exp. update, posted on December 9, 2016 at 13:44:35
Michael Samra
Dealer

Posts: 36118
Location: saginaw michigan
Joined: January 30, 2005
 In the MAC mono amps that run tube rectification are absolutely fantastic.
I have used them in place of the 150 ohm resistor coming off the 5U4 to the reservoir cap.I also use the .5hy at 30 ohms and those are very nice as well.
"For every complex problem there is an answer that is clear, simple, and wrong" H. L. Mencken

 

RE: SE 6CB5 : @ 23 watts anode triode mode , LSES exp. update, posted on December 11, 2016 at 05:36:19
hifipaul
Audiophile

Posts: 735
Location: NY
Joined: December 22, 2008
Have you considered fixed bias for the 6cb5s?

 

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