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Old 2nd April 2007, 10:41 PM   #1
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Question Urgent OT HELP needed ASAP please

Hi,

I've ordered a pair of Lundahl LL1663 OT's for a Claus Byrith 4-30 amp & they should be shipped tomorrow. ((so I really need a reply in less than 4 hours )) Please.

Byrith uses the LL1663 which has a 5K plate to plate resistance.

http://www.lundahl.se/pdfs/claus_byr...fier_30wpp.pdf

While I was researching another project I read that a 6.6K is the best match for the EL34 tubes. I re-read the Byrith article & found that he has the same opinion ((Top of page 13)) yet he uses the 5K OT!!!!!!!!!!

Lundahl's LL1682 model has a 5.5K impedence (t has a higher turns ratio though) so I'm confused
why didn't he use it??? http://www.kandkaudio.com/transformers.html

My silly question is obvious, which is best, the 5K 1663 or the 5.5K 1682--------just want to be sure-------

Thaaaaaanx
Tarek
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Old 2nd April 2007, 10:45 PM   #2
Tweeker is offline Tweeker  United States
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The difference between 5K and 5.5K is not huge. At 5K you will have slightly more power and slightly more distortion.
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Old 2nd April 2007, 10:51 PM   #3
Salas is online now Salas  Greece
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What is the lowest impedance your speakers may dip? The 1682 has a 5 Ohm secondary, if your speakers are 6 ohm lowest, bingo! You get a 6600 reflected primary with 1682. Nominal 8 ohm speakers are 6 Ohm lowest for DIN specification.
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Old 2nd April 2007, 11:01 PM   #4
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The only important difference is weather you have 8ohm or 4ohm nominal speakers. The 1663 has 8ohm secondary and the 1682 has 5ohm secondary.

Chris
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Old 2nd April 2007, 11:18 PM   #5
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Thanx guys for your prompt reply:

Salas, I realy overlooked the speaker impedance, I ve got Pro Ac
Tablette 50's @ 8ohm. I dont know their lowest impedence but I'm planning to build a pair higher efficiency speakers @ 8ohm as its more varsatile.

I've got one more question, will an 8K OT give less power & less distortion ? So in opinion which is better -instead of the ideal 6.6K- the 5K or the 8K

I also want to know Ur opinion about the quality of the Triode Electronics Dyna Clone Z565

These are (((probably))) my final questions then I can call the guy to ship !!!!!!

I'm waiting , Thaaaaaaaaanx
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Old 2nd April 2007, 11:44 PM   #6
Salas is online now Salas  Greece
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For 8 ohm speakers you get 6.6K primary from1682 5.5k/5 ohm tap (for 8 ohm speakers dipping to 6 Ohm as it is the norm). 6K6 is best as stated by Mullard for EL34.
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Old 3rd April 2007, 03:39 AM   #7
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Mullard was talking about cathode bias UL when giving 6.6k as the optimum load for EL34s in UL PP. Claus Byrith's version of the 5-20 uses fixed bias UL, which I understand is better suited to a lower impedance load. Claus seems to have overlooked this; however, since I've never seen any figures in a data sheet for EL34s in UL with fixed bias, that's probably not surprising.

So, it may well be that the 5k P-P impedance is actually better than 6.6k in this instance. In any case, UL is not very critical when it comes to load impedance - nowhere near as critical as pentode - so it really isn't a big deal.

I wouldn't worry about it!
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Old 3rd April 2007, 04:40 AM   #8
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I dont know how to thank you guys you really saved my
Ok, one more question ((that's for another 6L6 project.))and I'll end these OT/PT threads that I've been bombarding the forum with!!!!!!!!!!
Ignoring impedence ratios, WHICH are BETER QUALITY OT's, Lundahls or Audio Notes? --You can STOP reading here if U want--

Thanx

In his artickle Claus Byrith praised the Lundahls as the best OT's he heard-Page 13-, however he designed the so called 4-30 as a return of favour for Lundahl !!!
On the other hand Audio Note is a reputable company specialized in tube trannies.
Each talk about the special cores they use, winding technique and claim that they are one of the best -handfull- OT manufactures-Lundahl-or even the best of all - Audio Note. Really confusing.
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Old 3rd April 2007, 05:13 AM   #9
Tweeker is offline Tweeker  United States
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They have both been making output transformers from some time and think highly of their own product. Lundahl seems to be more forthcoming on their products specifications.


For PP output iron and no budget considerations, Id favor Lundahl's amorphous core offerings.
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Old 3rd April 2007, 08:45 AM   #10
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Valvomaniac, what makes you think your post is OT? It's no more so than lots of others.

Regarding Lundahl's products, I think they're reasonably priced for their high quality compared with some other brands.
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