The Red Light District - another PP EL84 amp

[SY]

Those probably have built in current limiters. Not a good choice.

The HLMP6000s are ideal and pretty inexpensive.

 

[Alastair E]

How about a constant voltage-sink with a MOSFET referenced to a zener, suitably decoupled, will give the advantage of trimming the bias current....

Just a madcap idea, I used this on an OTL to good effect...

 

[SY]

That will get you constant voltage, yes, the question is then, what happens after overload? The LEDs snap back nearly instantaneously. A MOSFET regulator bypassed with a cap? Perhaps not so instantaneously.

The screen regulator gives you idle current adjustment.

 

[JZatopa]

SY could you confirm I am using the right LEDs? I ordered some 630-hlmp-6000 but they are very small

 

[roren]

Hi,
I want to ask you who have buildt this RLD amp. And live in a 230-240V country:
What transformer did you use for the 12AT7 driver HT? I have searched the net
but all that I have find is big and expensive transformer.
Every tip is welcome.

Regards.
Rolf

 

[yagoolar]

I have built it. You may check here
http://www.indel.pl/sp_prod.htm or here http://www.indel.pl/e_tsl.htm
For mains xformer go to "transformatory sieciowe do wzmacniaczy lampowych" TSL (plural). For output - " transformatory głośnikowe"

 

[stajo]

Hi,
I want to ask you who have buildt this RLD amp. And live in a 230-240V country:
What transformer did you use for the 12AT7 driver HT? I have searched the net
but all that I have find is big and expensive transformer.
Every tip is welcome.

Regards.
Rolf

I once asked Sverbry to wind one on an EI-60 but they wouldnt deal with 0.1 mm thread on secondary. Primary 230 is 0,15 on EI-60 i beleave.

You could volt-double or ask them for an EI-78 (30 VA) easy giving over 300 VAC. Not expensive.

 

[stajo]

Svebry, sorry I misspelled

 

[roren]

yagoolar and stajo,
Thank you guys! Both tips is new to me. So I will check them out.

Thanks again.

 

[stajo]

If you go for Svebry we could ask them to wind up a few, I would be interested to. They are nice to deal with and gives good prices on series. It would be this one EI-78 Trafobyggsats - Svebry Electronics AB which I guess will have 0.20 on primary 230. Ask them to put a full bobin of 0.15 on the secondary. Their mashine fixes that. They can predict the secondary voltage on that.

 

[stajo]

SY could you confirm I am using the right LEDs? I ordered some 630-hlmp-6000 but they are very small

Its easy to get fooled by size and looks regarding LEDs. Heres some tiny HLMP-6300, max current 50 mAand nominal 10 mA and a big gang of HLMP-D150 with 30 mA as max current nominal 1 mA.

 

[SY]

Sorry, JZ, I didn't see this post before. Yes, the 6000s are tiny, yes, they work perfectly for this.

 

[stajo]

So Stuart, I dont remember if I have read or asked before but why did you stick with red models when putting them in series? Like the colour? All others have larger drop and you might getaway with fewer?

/Staffan

 

[SY]

Reds have the lowest AC impedance per volt of drop.

 

[stajo]

Now I know. Thank you!

 

[JZatopa]

SY thanks for letting me know, I put the project on the shelf but plan on getting back to it at some point.

 

[roren]

stajo,
You got a P.M.

 

[brianco]

Reds have the lowest AC impedance per volt of drop.

.also Bevois Valley is the old red-light district of Southampton.

 

[SY]

Indeed, that's what was told to me, along with its rather idiosyncratic pronunciation.

 

[fpitas]

According to the V vs I graphs in the datasheet, the standard red (vs. high-efficiency) has the best characteristics as a regulator:

http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&ved=0CE0QFjAA&url=http%3A%2F%2Fwww.avagotech.com%2Fpages%2Fen%2Fleds%2Fsubminiature_lamps%2Fdomed-resistor_led_series%2Fhlmp-6300-f0011%2F&ei=tDWiUof5IsbWoASygoL4Dg&usg=AFQjCNHOvwzMcg9W0cL9V7NhblLMAm5xDw&bvm=bv.57752919,d.cGU