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What can you build with a 50mA 5k SE output transformer?

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Posted on February 15, 2017 at 06:54:57
vbenonisen
 I need recommendations for an output tube that works well with up to 50mA with 5K single ended output transformers. The 45 and the EL84 is an obvious choice but what else? Is there something exotic, strange or unusual that would work well with these parameters?

 

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RE: What can you build with a 50mA 5k SE output transformer?, posted on February 17, 2017 at 19:29:36
hifipaul
Audiophile

Posts: 735
Location: NY
Joined: December 22, 2008
6CK4 is an IDHT, simple to implement an will net you ~2 watts. Triode strapped 6L6s (6bg6g, 807, 6V6s, 6ar6s...) will work within that range.

50s are not that expensive when compared to their sound quality.

Given their low bias rating I'll guess that they are smallish xfmrs; making the 6ck4 or 6v6 the best bet.

 

RE: What can you build with a 50mA 5k SE output transformer?, posted on February 21, 2017 at 04:46:04
PakProtector
Audiophile

Posts: 12363
Joined: May 14, 2002
 6CK4 and its cousin 6AH4 should be on the list for sure. Y'all can go out an hoard all you want, I have a decent stash of each already...heh-heh-heh.
cheers,
Douglas

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

 

or go totally nutsy..., posted on February 21, 2017 at 04:48:48
PakProtector
Audiophile

Posts: 12363
Joined: May 14, 2002
 and get a tetrode like the 4-65 and use its g2 as anode. Check it for dissipation ratings, but IIRC it is 10 or 15W. The larger 4-125 is sporting a 20W g2...LOL
cheers,
Douglas

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

 

RE: What can you build with a 50mA 5k SE output transformer?, posted on February 17, 2017 at 01:55:31
91derlust
Audiophile

Posts: 1101
Joined: December 25, 2014
 300B at between 300 - 350 Volts plate to cathode (running at 50mA).

91.

"Confusion of goals and perfection of means seems to characterise our age." Albert Einstein

 

RE: What can you build with a 50mA 5k SE output transformer?, posted on February 17, 2017 at 03:02:39
vbenonisen
 I have a pair of old 300B tubes. Maybe that's an idea. I've read that 300B tubes doesn't sound good with low current and low voltage but who knows. Anyway how many watts can you expect with 50mA?

 

RE: What can you build with a 50mA 5k SE output transformer?, posted on February 17, 2017 at 02:18:59
fred76
Audiophile

Posts: 1586
Location: Manila
Joined: February 28, 2004
 +1

That operating point/range sounds good to me, albeit at lower power. The 300B would last longer too..

 

Go DH...:), posted on February 16, 2017 at 03:40:07
PakProtector
Audiophile

Posts: 12363
Joined: May 14, 2002
 Type 2E24 will work with this load. As Andy suggests, run filament bias. Schade plate-to-grid with a pentode driver.
cheers,
Douglas

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

 

RE: What can you build with a 50mA 5k SE output transformer?, posted on February 15, 2017 at 18:54:00
hennfarm
Audiophile

Posts: 535
Location: Oregon
Joined: October 8, 2008
 6JT8

 

We275a Asano amp., posted on February 15, 2017 at 09:10:39
Wojciech
Audiophile

Posts: 4124
Joined: June 23, 2009
 nt.

 

RE: What can you build with a 50mA 5k SE output transformer?, posted on February 15, 2017 at 07:02:08
Stuben
Audiophile

Posts: 669
Location: Guber Ohio
Joined: December 30, 2005
 I use a Lundahl LL1663 for my 50 monoblocks.... If you want to dive into the world of valves on the rare side...I've picked up 5 RCA balloon 50s over the last decade to support...If I had it to do again, I would have gone with the 2a3...the sound is glorious though...

Stuben

 

RE: What can you build with a 50mA 5k SE output transformer?, posted on February 15, 2017 at 08:57:08
vbenonisen
 The 50 would have been something yes. But oh so expensive and difficult to get hold of. How many watts do you get out of it?

 

RE: What can you build with a 50mA 5k SE output transformer?, posted on February 15, 2017 at 12:37:02
Stuben
Audiophile

Posts: 669
Location: Guber Ohio
Joined: December 30, 2005
 I'm running them as delicate as reasonable ...about 4-5 watts of very big sound. I have had difficulty driving them. I have a prototype EL84 line stage that is getting the job done finally. The monos are IT coupled 417a-50 output.

I was working out of town years ago and had some spare cash...now I'm very happy with the results less the expense.

Stuben

 

4P1L in filament bias, posted on February 15, 2017 at 08:04:56
andy evans
Audiophile

Posts: 4378
Joined: October 20, 2000



I'd suggest using a 4P1L. Just 2 stages - no preamp needed with 2v in and sensitive speakers. Mu of 4P1L is around 11. Much more than 45. Also filament bias is an advantage - no cathode bypass caps.

The 01A Gen 2 preamp design is the best sound I've built or heard for an input stage. Good combination.

 

RE: 4P1L in filament bias, posted on February 15, 2017 at 09:02:38
vbenonisen
 Yes, 4P1L is a great alternative, but isn't one tube per channel too little to drive a normal loudspeaker (Let's say a Audio Note AN-J for the sake of argument).

 

RE: 4P1L in filament bias, posted on February 15, 2017 at 16:07:08
andy evans
Audiophile

Posts: 4378
Joined: October 20, 2000
 I use a pair, which is the equivalent to a 2a3, with a 70mA OPT. A single is equivalent to a 45. You can use three in parallel - just wire the filaments in series, then in parallel between the tubes. For 3 you really need a 100mA OPT.

But if you want some volume at 50mA, you need a higher plate voltage. 4P1L is rated 250v a-k though you could probably push it a little.

 

RE: 4P1L in filament bias, posted on February 15, 2017 at 11:48:34
Eli Duttman
Audiophile

Posts: 10455
Location: Monroe Township, NJ
Joined: March 31, 2000
 Apply Paul Joppa's 102 dB. rule to the claimed 93 dB. sensitivity and you get 8 W.

A look at a chart of 300B operating conditions
http://tdsl.duncanamps.com/dcigna/tubes/sheets/misc/4300b-2h.gif
suggests that 450 V. on the plate and -103 V. on the grid will work with your "iron". Don't expect lengthy service life under that sort of regime.


Eli D.

 

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