Newest clem

sweet & juicy SE amp for 1626 Darlings and the 6L6 family

Newest clem

Postby justinsweber » Wed Jun 12, 2013 1:13 am

The newest clem is taking some of the improvements and moving them up a bit more... Im using Transcendar iron 5k, 8ohm ultra linear, a Transcendar 5H 300ma 60ohm is the choke, in stead of the 100ohm resister in the power supply I bought a 2nd 5H choke... Seems I have a high iron diet. The power transformer is a sp one I had designed at edcor... you now can get the same transformer without the design charge. its 330-0-330 @ 325ma 2 6.3v @4amps, 2 5v @ 4amps. Ill parallel the 6.3s so I can light up KT120 without a problem. The rectifier is a 5U4GB... should light everything up :-). The cathode resisters were out of stock at mouser.. for ~.50 more you can get 1% wire-wound which is what I chose. Coupling caps are Wimas bigger units. The power supply is spec'd at 100uf @ 450v if I remember correctly... I went to looking at found a 180uf @ 500v (Mouser part # 647-LGN2H181MELA50). I always use a 3" chassis and with short standoffs they clear... I am hoping that the additional 320uf of cap will be worth while.

Any thoughts/ feedback re using the 5H choke instead of the 100ohm 3watt resistor? Ive been told that mirrly increasing the cathode current does not equal more power, just more linearity... Is this true? If so, how do I get more B+?

Hope everyone likes... Im going to build one right after with same chokes and power, just with edcor CXSE iron I got used.
Thanx.
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Last edited by justinsweber on Thu Jun 13, 2013 12:15 am, edited 1 time in total.
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Re: Newest clem

Postby Geek » Wed Jun 12, 2013 4:26 pm

Careful with that last photo.... the amp will fall and smash the tubes! =:o

The inter-shield idea is nice :))
-= Gregg =-
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Re: Newest clem

Postby justinsweber » Thu Jun 13, 2013 12:16 am

ok, tried to fix the pic.
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Re: Newest clem

Postby Geek » Thu Jun 13, 2013 2:16 am

Lookin' snazzy!

justinsweber wrote:Any thoughts/ feedback re using the 5H choke instead of the 100ohm 3watt resistor?


Well, a 5H choke at 120Hz has a reactance of about 3.77K, so you'll have less likelyhood of hum with really sensitive speakers. Just choose a choke with about 100 ohms of DCR so the voltages stay put.


Ive been told that mirrly increasing the cathode current does not equal more power, just more linearity... Is this true? If so, how do I get more B+?


In a class-A amplifier, more bias = more undistorted power. But you don't want to go too hot without far bigger iron on that thing (as in CXSE). Otherwise the THD reduction you gain in the tubes will be returned back and then some by core saturation.

Cheers!
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Re: Newest clem

Postby justinsweber » Thu Jun 13, 2013 10:40 am

I can order a 10H 200ma @ 100ohms. for $30. Would this be a better choice for the 100ohm 3watt?


(I curently own 2 5H 300ma @ 60ohm chokes)... which is what I was going to use.
1 for the choke and 1 for the 100ohm resistor. Im happy order 1 more choke...

Would it be wise to order 1 10H @200ma and use as the 100ohm or use as the primary choke?
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Re: Newest clem

Postby Geek » Thu Jun 13, 2013 6:01 pm

If you have room for one and can orient it so it doesn't induce rubbish, iron will always beat a resistor for PSU duty.

Your minimum choke value in henries is given by B+ V/I mA according to the Morgan Jones rule-of-thumb. So what B+ do you have and how many mA is it drawing?
(measuring via the power cathode resistors is fine since they take the most juice).

Any larger of a choke is a waste.

Cheers!
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and then there were 2.

Postby justinsweber » Fri Jun 28, 2013 7:38 am

So in building 1 clem... you get to thinking... there should be a sibling... Same 17x12x3 chassis, bigger caps, and a but load of chokes... 2 for a total of 15H without an changes to voltage... The super ST35 transformer came in ... 2 6.3v @4 amps and 2 5v @4amps, still 330-0-330 but instead of 170ma its 325ma.... Bad Ass! Thinking GZ37 for rectifier or 5u4. The Edcor XPWR247 is the transformer... $103 each. ~ 11lbs.

The 1st amp has all the mods done and is awaiting time for me to complete.
The 2nd is the one I will keep uses Edcor for power and CXSEs for output... ~11lbs each... so are at ~30lbs before chokes and ~38 with chokes but not chassis.

I hope we all get to building this summer. (Having built a all the amps but the Eico the 1626 is my favorite.)
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Re: Newest clem

Postby justinsweber » Mon Jul 01, 2013 3:29 pm

[img][img]All done... Major assit form TIm Meza... wiring skills fair and away beyond my own.
Noise floor is stupic low... not worth measuring... (15H of choke... way over kill witout any side effects... The next amp is built and will do the same, but moving forward it will be a 5H 200ma 50DCR thats used). RMS is 8 watts with KT120, 7watts with EL34s and 7watts (7 and change) with KT88s.
The Amp has backup diodes encase the tube rectifer goes south. Able to run any 5v rectifer as its on its own 4amp winding. The 6.3v heater is made up from 2 6.3v @ 4amp... So I have nearly 50% current head room... Any tube, any time :-). The Cliping is still curious/ amazing to me... It reaches clipping and the output dosnt fall, just begins to distort. Seems there is a 1/4" more chassis space for larger caps (already 380uf over). All in all, great amp... plan a several day burn in... then Raython 6SL7, GE5U4, and new Tungsol 6550 or Tungsol 6l6STR. [/img][/img]
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Re: Newest clem

Postby justinsweber » Mon Jul 01, 2013 3:33 pm

underside wired up
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