Lundahl LL1540 for SY's heretical?

Andypairo · 24th May 2006, 07:00 AM

Hi,
I was wondering is the Lundahl LL1540 can be a good choice for SY's Heretical line stage.

http://www.lundahl.se/pdfs/datash/1540.pdf

It can be configured as 1:1 or 1:2 to give some boost (if needed), what do you think about it (electrically and soundwise)?

Cheers

Andrea

Andypairo · 25th May 2006, 06:30 AM

Another thing,
how does it compare to the Jensen and the Cinemag trafos suggested for this amp?

Cheers

Andrea

SY · 25th May 2006, 10:57 AM

I haven't personally used it (I've only tried Jensen, Cinemag, and Ampex), but I would have no hesitation using the Lundahl. Their transformers are superb up and down the line.

Andypairo · 25th May 2006, 08:13 PM

Hi,
thanks for the reply.
I have another question: in case I need to use them as step-up (1:2) the source would see 1/4 of the input impedance (roughly equivalent to the potmeter paralleled to the 15K resistor in your schematics.
Do I need to adapt these values to keep the impedance at about 10k?

Is there a particular reason to use a 100K pot with a paralleled resistor instead of a lower value pot?

I ask because I have on hand a motorized 50k blue velvet and a 20k black velvet...

Cheers

Andrea

SY · 25th May 2006, 08:17 PM

Lundahl does spec a higher load than Jensen, so if you use their network and a 50k pot, you should be fine.

mark_titano · 6th October 2006, 12:20 PM

Another lundahl transformer for the heretical...

http://www.lundahl.se/pdfs/datash/1545a.pdf

Can I use it without any changes in the schematic if I'd choose R4B / R4U : L4B / L4U connection?

Thaks SY

Mark

SY · 6th October 2006, 12:43 PM

That connection is (according to the sheet) optimized for 10k:10k, so should work fine with no changes with no gain at stepup. Check square wave resonse to see if you have to load the secondary with a Zobel to get rid of any ringing.

Eusebius · 6th October 2006, 03:01 PM

I've used the LL1540 as an output to a balanced 12b4 line stage, and it sounds fine in parafeed - doesn't overload to my ears. I don't think it likes many volts of signal through it, though, so a low mu valve might be required. A friend put it on the scope with a 3A5 driving it (higher mu) and found that it was overloading.

mark_titano · 6th October 2006, 07:33 PM

Thanks Stuart.

I'll try to assemble it as soon as possible.

Just another question ( a bit OT, sorry): I've read the DiyAudioMag article about the heretical line stage and, in the last schematics, I can't see how you feed the opamp. I suppose using the +/-12V supply...I'm right?

Mark

SY · 6th October 2006, 07:45 PM

You're right.

24th May 2006, 07:00 AM	#1
Andypairo diyAudio Member Join Date: Sep 2002 Location: near Milano , Italy	Lundahl LL1540 for SY's heretical? Hi, I was wondering is the Lundahl LL1540 can be a good choice for SY's Heretical line stage. http://www.lundahl.se/pdfs/datash/1540.pdf It can be configured as 1:1 or 1:2 to give some boost (if needed), what do you think about it (electrically and soundwise)? Cheers Andrea __________________ I don't believe in audiophile components - except when I can get them at frugal-phile(tm) prices

25th May 2006, 06:30 AM	#2
Andypairo diyAudio Member Join Date: Sep 2002 Location: near Milano , Italy	Another thing, how does it compare to the Jensen and the Cinemag trafos suggested for this amp? Cheers Andrea __________________ I don't believe in audiophile components - except when I can get them at frugal-phile(tm) prices

25th May 2006, 10:57 AM	#3
SY diyAudio Moderator Join Date: Oct 2002 Location: Chicagoland Blog Entries: 1	I haven't personally used it (I've only tried Jensen, Cinemag, and Ampex), but I would have no hesitation using the Lundahl. Their transformers are superb up and down the line. __________________ If there's a sucker born every minute, where do the rest of them come from?

25th May 2006, 08:13 PM	#4
Andypairo diyAudio Member Join Date: Sep 2002 Location: near Milano , Italy	Hi, thanks for the reply. I have another question: in case I need to use them as step-up (1:2) the source would see 1/4 of the input impedance (roughly equivalent to the potmeter paralleled to the 15K resistor in your schematics. Do I need to adapt these values to keep the impedance at about 10k? Is there a particular reason to use a 100K pot with a paralleled resistor instead of a lower value pot? I ask because I have on hand a motorized 50k blue velvet and a 20k black velvet... Cheers Andrea __________________ I don't believe in audiophile components - except when I can get them at frugal-phile(tm) prices

25th May 2006, 08:17 PM	#5
SY diyAudio Moderator Join Date: Oct 2002 Location: Chicagoland Blog Entries: 1	Lundahl does spec a higher load than Jensen, so if you use their network and a 50k pot, you should be fine. __________________ If there's a sucker born every minute, where do the rest of them come from?


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6th October 2006, 12:20 PM	#6
mark_titano diyAudio Member Join Date: Oct 2004	Another lundahl transformer for the heretical... http://www.lundahl.se/pdfs/datash/1545a.pdf Can I use it without any changes in the schematic if I'd choose R4B / R4U : L4B / L4U connection? Thaks SY Mark

6th October 2006, 12:43 PM	#7
SY diyAudio Moderator Join Date: Oct 2002 Location: Chicagoland Blog Entries: 1	That connection is (according to the sheet) optimized for 10k:10k, so should work fine with no changes with no gain at stepup. Check square wave resonse to see if you have to load the secondary with a Zobel to get rid of any ringing. __________________ If there's a sucker born every minute, where do the rest of them come from?

6th October 2006, 03:01 PM	#8
Eusebius diyAudio Member Join Date: May 2006	I've used the LL1540 as an output to a balanced 12b4 line stage, and it sounds fine in parafeed - doesn't overload to my ears. I don't think it likes many volts of signal through it, though, so a low mu valve might be required. A friend put it on the scope with a 3A5 driving it (higher mu) and found that it was overloading.

6th October 2006, 07:33 PM	#9
mark_titano diyAudio Member Join Date: Oct 2004	Thanks Stuart. I'll try to assemble it as soon as possible. Just another question ( a bit OT, sorry): I've read the DiyAudioMag article about the heretical line stage and, in the last schematics, I can't see how you feed the opamp. I suppose using the +/-12V supply...I'm right? Mark

6th October 2006, 07:45 PM	#10
SY diyAudio Moderator Join Date: Oct 2002 Location: Chicagoland Blog Entries: 1	You're right. __________________ If there's a sucker born every minute, where do the rest of them come from?

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